Anatomy and Physiology I with Lab (D312)
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Free Anatomy and Physiology I with Lab (D312) Questions
Which of the following best describes the role of an organ system in the human body?
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A collection of tissues that perform a single function
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A group of organs that collaborate to carry out specific physiological processes
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An individual organ that regulates homeostasis
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A network of cells that communicate with each other
Explanation
Correct Answer
B. A group of organs that collaborate to carry out specific physiological processes
Explanation
An organ system is a collection of organs that work together to perform a specific function in the body. For example, the digestive system includes the stomach, intestines, liver, and other organs that collaborate to process food, absorb nutrients, and eliminate waste. Organ systems are critical for carrying out complex physiological processes, like circulation, digestion, and respiration.
Why other options are wrong
A. A collection of tissues that perform a single function. This describes a tissue, not an organ system. Tissues are made up of similar cells that work together to perform a specific function.
C. An individual organ that regulates homeostasis. While individual organs like the kidneys or lungs play a role in maintaining homeostasis, an organ system involves multiple organs working together.
D. A network of cells that communicate with each other. This is more related to cellular communication or tissue-level functions, not to the collaboration of organs in an organ system.
If you were a doctor and a urinalysis came back with high levels of glucose, ketones, and an acidic pH, what diagnosis would you immediately look into?
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Kidney stones
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Diabetes
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Urinary tract infection
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Respiratory acidosis
Explanation
Correct Answer
B. Diabetes
Explanation
The presence of high levels of glucose and ketones in the urine, along with an acidic pH, suggests that the individual may have diabetes, particularly diabetic ketoacidosis (DKA). In this condition, the body is unable to use glucose effectively, leading to the production of ketones as an alternative energy source. The acidic pH occurs due to the accumulation of ketone bodies, which are acidic by nature.
Why other options are wrong
A. Kidney stones
This is incorrect because while kidney stones can cause pain and other urinary symptoms, they do not typically result in the presence of glucose or ketones in the urine, nor would they cause an acidic pH.
C. Urinary tract infection
This is incorrect because a urinary tract infection (UTI) would more likely result in the presence of bacteria or nitrites in the urine, rather than high levels of glucose or ketones. UTIs are typically associated with symptoms like pain or burning during urination.
D. Respiratory acidosis
This is incorrect because respiratory acidosis is related to the accumulation of carbon dioxide in the blood due to inadequate ventilation, which would not cause high levels of glucose or ketones in the urine.
Which of the following best describes the arrangement of phospholipids in the plasma membrane?
-
Phospholipids are arranged in a single layer with hydrophobic tails facing outward.
-
Phospholipids are arranged in a bilayer with hydrophilic heads facing inward and hydrophobic tails facing outward.
-
Phospholipids are arranged in a bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward.
-
Phospholipids are randomly distributed throughout the membrane without any specific arrangement.
Explanation
Correct Answer
C. Phospholipids are arranged in a bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward.
Explanation
The plasma membrane is composed of a phospholipid bilayer, where each phospholipid molecule has a hydrophilic (water-loving) head and hydrophobic (water-fearing) tails. The hydrophilic heads face the aqueous environments inside and outside the cell, while the hydrophobic tails are oriented inward, away from water. This arrangement allows the membrane to act as a selective barrier, controlling the movement of substances into and out of the cell.
Why other options are wrong
A. Phospholipids are arranged in a single layer with hydrophobic tails facing outward.
This is incorrect because phospholipids form a bilayer, not a single layer. In a bilayer, hydrophilic heads face outward, not hydrophobic tails, which are oriented toward the interior.
B. Phospholipids are arranged in a bilayer with hydrophilic heads facing inward and hydrophobic tails facing outward.
This is incorrect because it reverses the orientation of the hydrophilic heads and hydrophobic tails. The hydrophilic heads must face the aqueous environments, while the hydrophobic tails face inward, shielded from water.
D. Phospholipids are randomly distributed throughout the membrane without any specific arrangement.
This is incorrect because phospholipids are specifically arranged in a bilayer with a clear orientation of their hydrophilic heads and hydrophobic tails. This specific arrangement is crucial for the membrane's structural integrity and function.
Which statement accurately describes protons in relation to atomic structure?
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Protons are negatively charged particles that orbit the nucleus of an atom.
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Protons are neutral particles found in the nucleus that do not affect atomic mass.
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Protons are positively charged particles located in the nucleus, contributing to the atomic mass and determining the element's identity.
-
Protons are particles that can be found in the electron cloud surrounding the nucleus.
Explanation
Correct Answer
C. Protons are positively charged particles located in the nucleus, contributing to the atomic mass and determining the element's identity.
Explanation
Protons are subatomic particles with a positive charge (+1) and are found in the nucleus of an atom. They, along with neutrons, contribute to the atomic mass of an element. The number of protons uniquely identifies an element, known as the atomic number. For example, hydrogen has one proton, while carbon has six. Without protons, elements would not have distinct identities, as the number of protons dictates an atom’s chemical properties.
Why other options are wrong
A. Protons are negatively charged particles that orbit the nucleus of an atom.
This description applies to electrons, not protons. Electrons are negatively charged and move in orbitals around the nucleus, while protons are located within the nucleus and have a positive charge.
B. Protons are neutral particles found in the nucleus that do not affect atomic mass.
Protons are not neutral; they have a positive charge. Neutrons are the neutral subatomic particles found in the nucleus. Additionally, protons do contribute to atomic mass, as the mass number is the sum of protons and neutrons.
D. Protons are particles that can be found in the electron cloud surrounding the nucleus.
Protons are never found in the electron cloud. Only electrons exist in the electron cloud surrounding the nucleus, while protons remain within the nucleus.
Hydrophobic substances are
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Non-polar and soluble in water
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Polar and soluble in water
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Non-polar and insoluble in water
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Polar and insoluble in water
Explanation
Correct Answer
C. Non-polar and insoluble in water
Explanation
Hydrophobic substances are typically non-polar, meaning they do not have a charge that can interact with the polar water molecules. This makes them insoluble in water. Examples include oils and fats.
Why other options are wrong
A. Non-polar and soluble in water. This is incorrect because non-polar substances are not soluble in water, which is a polar solvent.
B. Polar and soluble in water. This is incorrect. Hydrophobic substances are non-polar, not polar. Polar substances tend to be hydrophilic (water-soluble).
D. Polar and insoluble in water. This is incorrect because polar substances are typically soluble in water, as water molecules can form hydrogen bonds with polar molecules.
Which of these definitions best describes phagocytosis?
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The actin-mediated process by which a cell engulfs a bacterium or other particle into a large membrane-bound vesicle, which moves into the interior of the cell and is destroyed by the lysosome.
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An active process that requires energy and allows large molecules or particles to move into cells that are needed for the cell to function.
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Intracellular vesicles move into the cell membrane, fuse with it, and release their contents into the extracellular fluid.
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Movement across an epithelium through the junctions between adjacent cells
Explanation
Correct Answer
A. The actin-mediated process by which a cell engulfs a bacterium or other particle into a large membrane-bound vesicle, which moves into the interior of the cell and is destroyed by the lysosome.
Explanation
Phagocytosis is a type of endocytosis where a cell engulfs large particles, such as bacteria, by extending its cell membrane around the particle. This process forms a vesicle (phagosome), which then fuses with a lysosome for digestion. Phagocytosis is critical for immune responses.
Why other options are wrong
B. An active process that requires energy and allows large molecules or particles to move into cells that are needed for the cell to function.
This is incorrect because while phagocytosis is an active process, this definition describes endocytosis in a more general sense. Phagocytosis specifically refers to the engulfing of large particles, not just any molecules.
C. Intracellular vesicles move into the cell membrane, fuse with it, and release their contents into the extracellular fluid.
This is incorrect. This describes exocytosis, the process where substances are expelled from the cell, not phagocytosis.
D. Movement across an epithelium through the junctions between adjacent cells
This is incorrect. This describes paracellular transport, which involves the movement of molecules through the gaps between cells, not phagocytosis.
Which of the following types of lipids is primarily responsible for forming the structural components of cell membranes?
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Triglycerides
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Phospholipids
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Steroids
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Waxes
Explanation
Correct Answer
B. Phospholipids
Explanation
Phospholipids are the primary structural components of cell membranes. They consist of a hydrophilic (water-attracting) phosphate head and two hydrophobic (water-repelling) fatty acid tails. This amphipathic nature allows them to form the bilayer structure of cell membranes, which regulates the movement of substances in and out of the cell while maintaining cellular integrity.
Why other options are wrong
A. Triglycerides. Triglycerides function mainly as long-term energy storage molecules rather than structural components of cell membranes. They consist of three fatty acid chains attached to a glycerol backbone and are stored in adipose tissue for energy reserves.
C. Steroids. While some steroids (such as cholesterol) are found in cell membranes and contribute to their fluidity, they are not the primary structural component. Steroids primarily function as signaling molecules and hormones (e.g., testosterone, estrogen, and cortisol).
D. Waxes. Waxes are primarily used for waterproofing and protection in plants and animals rather than forming cell membranes. They provide a protective barrier in leaves, fruits, and animal fur but do not contribute to the bilayer structure of cell membranes.
Which of the following describes the function of microfilaments?
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They are involved in muscle contraction and intracellular movement.
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They form centrioles and support the cell and give it shape.
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They link adjacent cells together by attaching to cell junctions called desmosomes.
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They resist tension forces acting on the cell.
Explanation
Correct Answer
A. They are involved in muscle contraction and intracellular movement.
Explanation
Microfilaments are the thinnest type of cytoskeletal filaments and are primarily composed of actin. They play a key role in muscle contraction, intracellular movement, and the overall shape and support of the cell. In muscle cells, microfilaments work together to enable contraction by interacting with myosin filaments. Additionally, they are involved in other dynamic processes like cell division and cell movement.
Why other options are wrong
B. They form centrioles and support the cell and give it shape.
This is incorrect. Microfilaments are not involved in forming centrioles, which are made of microtubules. Microfilaments contribute to cell shape and movement but do not play a direct role in centrioles, which are structures important in cell division.
C. They link adjacent cells together by attaching to cell junctions called desmosomes.
This is incorrect. Desmosomes are involved in cell-cell adhesion, but the linking of cells through desmosomes is primarily facilitated by intermediate filaments, not microfilaments.
D. They resist tension forces acting on the cell.
This is incorrect. While microfilaments help with cell movement and shape, it is intermediate filaments that are primarily responsible for providing mechanical strength and resistance to tension forces.
Facilitated diffusion is:
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An active process to get needed substances such as glucose into the cell
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A passive form of transport to move large, water-soluble compounds into the cell
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A passive form of transport to move large, water-soluble compounds into the cell
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An active transport process which moves substances down their concentration gradient
Explanation
Correct Answer
B. A passive form of transport to move large, water-soluble compounds into the cell
Explanation
Facilitated diffusion is a passive transport process where substances like glucose or ions move across the plasma membrane with the help of carrier proteins or channels, but without the need for energy. These substances move from an area of higher concentration to lower concentration, following the concentration gradient. This process does not require energy (ATP), which differentiates it from active transport. It helps larger or water-soluble molecules, which cannot easily pass through the lipid bilayer, to enter or exit the cell.
Why other options are wrong
A. An active process to get needed substances such as glucose into the cell
This is incorrect because facilitated diffusion is a passive process, not active. Active transport requires energy to move substances against their concentration gradient, but facilitated diffusion relies on the concentration gradient and does not use energy.
C. A passive form of transport that moves substances up their concentration gradient
This is incorrect because facilitated diffusion moves substances down their concentration gradient (from high to low concentration), not up. Moving substances against their concentration gradient requires active transport, not facilitated diffusion.
D. An active transport process which moves substances down their concentration gradient
This is incorrect because facilitated diffusion is passive, not active. Active transport would require energy (ATP) to move substances, while facilitated diffusion relies on the concentration gradient and does not require energy.
What is an atom?
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Is the fundamental unit of matter
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Is made of subatomic particles
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Is the smallest unit of an element capable of displaying all properties of the element.
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All of the above
Explanation
Correct Answer
D. All of the above
Explanation
An atom is the fundamental unit of matter, composed of subatomic particles such as protons, neutrons, and electrons. It is the smallest unit of an element that retains the chemical properties of that element. These atoms combine to form molecules, which make up the various substances found in the universe. All the listed statements correctly describe different aspects of an atom's definition.
Why other options are wrong
A. Is the fundamental unit of matter
While this is true, it does not fully capture all the aspects of what an atom is. It is not the complete definition because an atom is also composed of subatomic particles and displays the properties of the element it represents.
B. Is made of subatomic particles
Although this is accurate, it lacks the full context of the atom being the smallest unit of an element that maintains the element's properties.
C. Is the smallest unit of an element capable of displaying all properties of the element.
This is also correct, but it does not encompass the idea that atoms are made up of subatomic particles, which is part of the full definition.
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SCIE 1011 Anatomy & Physiology I with Lab (D312) – Comprehensive Study Guide
Table of Contents
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Introduction to Anatomy & Physiology
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Definitions & Key Concepts
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The Chemical Basis of Life
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Cellular Structure & Function
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Tissues & Integumentary System
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Skeletal System
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Muscular System
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Nervous System
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Special Senses
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Endocrine System
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Cardiovascular System
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Respiratory System
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Case Studies & Analysis
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Case Study 1: Osteoporosis & Bone Remodeling
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Case Study 2: Diabetes & Endocrine Dysfunction
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1. Introduction to Anatomy & Physiology (Expanded)
Anatomy is the study of the structure of body parts and their relationships to one another. It can be divided into:
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Gross anatomy: Study of large, visible structures (e.g., organs, muscles)
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Microscopic anatomy: Study of structures too small to be seen without magnification, including:
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Cytology (study of cells)
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Histology (study of tissues)
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Physiology is the study of how body parts function. Important subdivisions include:
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Cardiac physiology (heart function)
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Neurophysiology (nervous system function)
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Respiratory physiology (lung function)
Complementarity of Structure and Function: This fundamental principle states that what a structure can do depends on its specific form. For example:
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The thin, flat shape of red blood cells allows for efficient gas exchange
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The branching structure of neurons facilitates rapid communication
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Chemical Level:
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Atoms (e.g., carbon, hydrogen)
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Molecules (e.g., water, DNA)
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Example: Hydrogen bonds in water give it unique properties essential for life
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-
Cellular Level:
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Basic structural and functional units of life
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Specialized cells include:
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Erythrocytes (red blood cells) for oxygen transport
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Osteocytes (bone cells) for maintaining bone tissue
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-
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Tissue Level:
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Groups of similar cells performing specific functions
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Four primary types:
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Epithelial
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Connective
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Muscle
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Nervous
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-
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Organ Level:
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Discrete structures composed of at least two tissue types
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Example: The stomach contains:
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Epithelial tissue (lining)
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Muscle tissue (churning motion)
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Connective tissue (support)
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Nervous tissue (control)
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-
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Organ System Level:
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Groups of organs working together
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Example: Digestive system includes:
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Mouth → esophagus → stomach → intestines
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-
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Organismal Level:
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All systems functioning together
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Highest level of organization
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Homeostasis is the maintenance of relatively stable internal conditions despite external changes. It involves three key components:
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Receptor: Detects changes
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Control center: Determines set point
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Effector: Produces response
Negative Feedback Examples:
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Thermoregulation:
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Stimulus: Body temperature rises
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Response: Sweating, vasodilation
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Blood Glucose Regulation:
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Stimulus: High blood sugar
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Response: Insulin release
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Positive Feedback Examples:
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Blood Clotting:
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Platelet activation stimulates more platelet activation
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Childbirth:
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Oxytocin release strengthens contractions
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Homeostatic Imbalance leads to disease. Example:
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Diabetes mellitus results from failed glucose regulation
2. The Chemical Basis of Life (Expanded)
Atomic Structure:
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Protons (+), neutrons, electrons (-)
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Isotopes: Variants of elements with different neutron numbers
Chemical Bonds:
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Ionic Bonds:
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Electron transfer
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Example: NaCl (sodium chloride)
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Covalent Bonds:
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Electron sharing
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Example: H₂O (water)
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Hydrogen Bonds:
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Weak attractions between polar molecules
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Critical for DNA structure and protein folding
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Water Properties:
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High heat capacity - moderates temperature
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Universal solvent - dissolves polar substances
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Cushioning - protects organs
pH Scale:
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0-14 range
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Acidic <7, Neutral =7, Basic >7
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Buffers maintain stable pH (e.g., bicarbonate in blood)
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Carbohydrates:
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Monomers: Monosaccharides (glucose)
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Functions: Energy source (4 kcal/g)
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Examples: Starch, glycogen
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Lipids:
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Nonpolar molecules
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Functions:
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Energy storage (9 kcal/g)
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Cell membranes (phospholipids)
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-
Types:
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Triglycerides
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Phospholipids
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Steroids (cholesterol)
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-
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Proteins:
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Monomers: Amino acids (20 types)
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Structure levels:
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Primary (sequence)
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Secondary (α-helix, β-sheet)
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Tertiary (3D shape)
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Quaternary (multiple chains)
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-
Functions:
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Enzymes (catalysts)
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Structural (collagen)
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Transport (hemoglobin)
-
-
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Nucleic Acids:
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DNA: Double helix, stores genetic info
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RNA: Single strand, protein synthesis
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ATP: Energy currency of cells
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3. Cellular Structure & Function
Cell Theory:
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All organisms are composed of cells
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Cells are the basic unit of life
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New cells arise from existing cells
Organelles:
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Nucleus:
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Contains DNA
-
Surrounded by nuclear envelope
-
-
Mitochondria:
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Powerhouse of cell
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Site of ATP production
-
-
Endoplasmic Reticulum:
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Rough ER (protein synthesis)
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Smooth ER (lipid synthesis)
-
-
Golgi Apparatus:
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Modifies, sorts, packages proteins
-
-
Lysosomes:
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Digestive enzymes
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Cellular cleanup
-
Passive Transport (No energy):
-
Diffusion:
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Movement from high to low concentration
-
Example: Oxygen entering cells
-
-
Osmosis:
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Water movement across membrane
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Tonicity:
-
Isotonic: Equal concentration
-
Hypertonic: Higher solute outside
-
Hypotonic: Lower solute outside
-
-
Active Transport (Requires ATP):
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Sodium-Potassium Pump:
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3 Na+ out, 2 K+ in
-
Maintains membrane potential
-
-
Vesicular Transport:
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Endocytosis (into cell)
-
Exocytosis (out of cell)
-
-
Glycolysis:
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Occurs in cytoplasm
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Glucose → 2 pyruvate + 2 ATP
-
-
Citric Acid Cycle:
-
In mitochondria
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Produces NADH, FADH₂
-
-
Electron Transport Chain:
-
Generates 28-34 ATP
-
Oxygen is final electron acceptor
-
Additional Case Studies
Scenario: A 7-year-old presents with chronic lung infections and salty sweat. Genetic testing reveals CFTR gene mutation.
Analysis: This illustrates defective chloride ion transport due to faulty CFTR protein. Thick mucus results from improper water movement, demonstrating the critical role of membrane transport proteins in maintaining fluid balance.
A 58-year-old male smoker presents with crushing chest pain radiating to his left arm. ECG reveals ST-segment elevation in leads II, III, and aVF. Blood tests show elevated troponin and CK-MB levels. Coronary angiography confirms complete occlusion of the right coronary artery.
Analysis:
This acute myocardial infarction results from coronary artery blockage, causing cardiac ischemia. Deprived of oxygen, myocardial cells switch to anaerobic respiration, producing lactic acid and triggering pain. Prolonged ischemia leads to cellular necrosis, releasing cardiac enzymes. The case demonstrates the heart's absolute dependence on continuous aerobic ATP production through oxidative phosphorylation in mitochondria. It also highlights how atherosclerosis (exacerbated by smoking) disrupts the oxygen supply-demand balance, emphasizing the critical link between cardiovascular health and cellular metabolism. Immediate reperfusion therapy is crucial to restore aerobic respiration and minimize irreversible damage.
This guide systematically covers SCIE 1011 Anatomy & Physiology I, integrating foundational concepts with clinical applications. Use the case studies to apply theoretical knowledge to real-world scenarios.
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Q&A Section: SCIE 1011 Anatomy & Physiology I (D312)
Question 1:
A) All cells in the body perform the same function.
B) The function of a body part is unrelated to its structure.
C) The shape and organization of a structure determine its function.
D) Only organs, not cells or tissues, exhibit specialized functions.
Correct Answer:
C) The shape and organization of a structure determine its function.
Explanation:
The principle of complementarity of structure and function states that the form (structure) of a body part or organ is directly related to the job (function) it performs. For example, the thin walls of alveoli in the lungs allow for efficient gas exchange. This principle applies from the cellular level to entire organs, showing the body's intricate design-function relationship.
Why the Other Options Are Incorrect:
A) All cells in the body perform the same function
This is incorrect because the human body has highly specialized cells, each with different structures and functions—like neurons transmitting signals and muscle cells contracting. This diversity enables complex body systems to operate efficiently, reinforcing the concept of functional specialization, not uniformity.
B) The function of a body part is unrelated to its structure
This statement is the opposite of the principle of complementarity. In reality, structure and function are tightly linked; altering a structure (e.g., damaging a valve) affects its ability to perform its function (e.g., regulating blood flow). Thus, dismissing this relationship contradicts a core concept in anatomy and physiology.
D) Only organs, not cells or tissues, exhibit specialized functions
Incorrect. Cells and tissues also have specialized structures and functions, not just organs. For example, red blood cells have a biconcave shape to increase surface area for oxygen transport. This option overlooks the fact that specialization starts at the cellular level and builds up to form organs and systems.
Question 2:
A) It increases blood glucose levels by stimulating glycogen breakdown.
B) It signals cells to take up glucose, lowering blood sugar.
C) It triggers the release of glucagon from the pancreas.
D) It inhibits cellular respiration to conserve energy.
Insulin plays a key role in negative feedback regulation of blood glucose by signaling body cells—especially muscle and fat cells—to absorb glucose from the bloodstream. This reduces blood sugar levels to maintain homeostasis. Insulin also promotes the storage of glucose as glycogen in the liver, helping to keep glucose levels within a normal range after meals.
Why Other Options are Incorrect
A) It increases blood glucose levels by stimulating glycogen breakdown:
Option A describes the function of glucagon, not insulin. Glucagon is released when blood glucose is low and acts to increase glucose levels by promoting glycogen breakdown in the liver. In contrast, insulin works when blood glucose is high, promoting glucose uptake and storage, not breakdown. So, insulin lowers blood sugar, not increases it through glycogen breakdown.
C) It triggers the release of glucagon from the pancreas:
Insulin and glucagon have opposite roles in glucose regulation. When blood sugar is high, insulin is released; when it is low, glucagon is released. Insulin does not trigger the release of glucagon—rather, high insulin levels typically suppress glucagon secretion. Therefore, insulin reduces glucose, while glucagon acts to increase it. This option incorrectly reverses their interaction.
D) It inhibits cellular respiration to conserve energy:
Insulin does not inhibit cellular respiration. In fact, it helps promote cellular metabolism by increasing glucose availability inside cells. Cells use glucose in respiration to produce ATP. Insulin ensures cells have access to this energy source. Inhibiting respiration would limit energy production, which is not insulin's function. Thus, this option inaccurately describes insulin’s role in metabolism.
Question 3:
A) Glycolysis
B) Citric acid cycle
C) Electron transport chain (ETC)
D) Fermentation
Correct Answer:
C) Electron transport chain (ETC)
Explanation:
The electron transport chain (ETC), located in the inner mitochondrial membrane, produces the majority of ATP during aerobic respiration. Electrons from NADH and FADH₂ are passed along the chain, releasing energy that pumps protons to create a gradient. ATP synthase then uses this gradient to generate ATP—approximately 28–34 ATP molecules—making it the most productive stage of aerobic respiration.
Why the Other Options Are Incorrect:
A) Glycolysis
Glycolysis occurs in the cytoplasm and breaks down glucose into pyruvate, producing only 2 ATP molecules per glucose. While essential to cellular respiration, it contributes only a small fraction of the total ATP yield. It is also anaerobic, meaning it doesn’t require oxygen, unlike the ETC. Therefore, it cannot be considered the main ATP-producing process in aerobic respiration.
B) Citric acid cycle
The citric acid cycle (Krebs cycle) generates 2 ATP per glucose molecule, along with high-energy electron carriers (NADH, FADH₂). These carriers feed electrons into the ETC, which is where most ATP is produced. While critical for harvesting electrons, the cycle itself does not produce the majority of ATP and thus is not the correct answer.
D) Fermentation
Fermentation is an anaerobic process that occurs when oxygen is unavailable. It allows glycolysis to continue by regenerating NAD⁺ but yields only 2 ATP per glucose. It’s not part of aerobic respiration and is vastly less efficient. Because it bypasses both the Krebs cycle and ETC, it produces far less ATP than aerobic pathways.
Question 4:
A) Osteoblast deposition of new bone.
B) Osteoclast resorption of bone.
C) Chondrocyte production of cartilage.
D) Fibroblast synthesis of collagen.
Correct Answer:
B) Osteoclast resorption of bone.
Explanation:
Osteoporosis is characterized by an imbalance in bone remodeling, where bone resorption by osteoclasts exceeds bone formation by osteoblasts. This excessive breakdown weakens bone structure, making bones porous and prone to fractures. Targeting osteoclast activity is a common therapeutic strategy in osteoporosis to slow down bone loss and maintain bone density.
Why the Other Options Are Incorrect:
A) Osteoblast deposition of new bone
Osteoblasts build bone by laying down new bone matrix. If their activity were excessive, bone density would increase, not decrease. In osteoporosis, it's the reduction in osteoblast activity or imbalance relative to osteoclast activity that contributes to bone fragility. Therefore, excessive osteoblast action is not the cause of osteoporosis.
C) Chondrocyte production of cartilage
Chondrocytes are responsible for cartilage production, particularly during bone growth and repair. They are not directly involved in adult bone remodeling. Osteoporosis is a disease of bone tissue, not cartilage. Thus, chondrocyte activity is not the primary concern in the development of osteoporotic bone loss.
D) Fibroblast synthesis of collagen
Fibroblasts produce collagen, which is important for connective tissues and wound healing. While collagen is a component of bone, fibroblasts are not the primary collagen producers in bone (that role belongs more to osteoblasts). Excess fibroblast activity does not explain the bone resorption and fragility seen in osteoporosis.