PHGY 215 - Midterm Exam Questions and Answers Already Passed Latest Update 2025-2026
Homeostasis - Answers The ability of a cell or organism to regulate and maintain its internal
environment
Set point - Answers The range or point at which a variable physiological state tends to stabilize.
3 components of homeostatic control - Answers Sensor, integrator, effector
Sensor - Answers Responsible for detecting an environmental variable
Integrator - Answers Compares the variable being detected to its set point
Effector - Answers Initiates the changes to restore the variable back to its set point
Intrinsic regulation - Answers Sensor, integrator, and effector are all located within a tissue so
that the tissue can regulate its own internal environment
Extrinsic regulation - Answers Regulatory mechanisms are outside of the tissue or organ (for
full-body processes)
Negative feedback - Answers Change in an environmental parameter causing the effector to
initiate a response in the opposite direction
Positive feedback - Answers Occurs when the effector causes changes that amplify the initial
signal.
Level & mechanism of control: blood clotting - Answers Intrinsic, positive
Level & mechanism of control: childbirth - Answers Extrinsic, positive
Level & mechanism of control: regulation of blood pressure - Answers Intrinsic, negative
Level & mechanism of control: regulation of blood glucose - Answers Extrinsic, negative
4 roles of the plasma membrane - Answers Regulating the internal fluid composition by
controlling what can move in/out of the cell.
Allows nutrients to enter cells and waste products to leave.
Permits chemical signals released from other cells in the body to influence a cell (cell-to-cell
communication).
,Participates in joining cells together, to form tissues & organs.
3 primary functions of the plasma membrane - Answers Ensure the cell's survival
Maintain homeostasis
Function cooperatively and in coordination with surrounding cells
Structures present in the plasma membrane - Answers Phospholipids, cholesterol, membrane
proteins, ion channels, carbohydrate chains
Phospholipids - Answers Lipid bilayer is comprised of phospholipids.
A phospholipid has a polar head (hydrophilic) with a negatively charged phosphate group and
two non-polar (hydrophobic) fatty acid tails.
Cholesterol - Answers Tucked in between phospholipids to prevent the fatty acid chains from
packing too tightly together, in order to keep the membrane fluid
Membrane proteins - Answers Can be associated with the inner side, outer side, or pass all the
way through the plasma membrane
These function to maintain cell structure, regulate cell function, allow transport across the
membrane, and facilitate signalling
Ion channels - Answers Permit the entry or exit of ions across the plasma membrane
Carbohydrate chains - Answers Short carbohydrate chains can be attached to proteins or the
bilayer itself to form glycoproteins and glycolipids, respectively
These are involved in stabilizing membrane structure, acting as cell surface receptors,
participating in transportation across the cell membrane, etc
Cystic fibrosis - Answers Caused by a defect in a particular chloride ion channel, which controls
the amount of fluid and mucous within the lungs - CF patients experience a buildup of fluid in
the lungs
Alzheimer's disease - Answers Results in oxidative stress: the generation of reactive oxygen
,species that may result in damage to cells
Oxidative stress leads to the alteration and degradation of phospholipids within neurons,
compromising the integrity of the membrane and impacting neural function (memory loss &
reduced cognition)
Three types of cell-to-cell adhesions - Answers Extracellular matrix, cell adhesion molecules, cell
junctions
Extracellular matrix - Answers Network of fibrous proteins embedded in a gel- like mixture of
complex carbohydrates that surrounds all cells & tissues to keep them in place
Watery gel allows for diffusion of nutrients & waste removal
Precise ECM composition is different in every tissue type to allow specialized function
The majority of the ECM is secreted by fibroblasts located within the interstitial space.
Three major protein fibres of ECM - Answers collagen, elastin, fibronectin
Collagen - Answers Forms the cable-like structures that give the ECM its tensile strength
Elastin - Answers Rubber-like protein that allows tissues to be stretched and then recoil after the
stretching force is removed
Fibronectin - Answers Promotes cell adhesion
Cell-adhesion molecules (CAMs) - Answers Transmembrane proteins: intracellular side interacts
with the cytoskeleton, and the extracellular side interacts with the ECM CAMs from other cells -
CAMs help cells stick to each other and to their surroundings
There are 4 families: cadherins, selectins, NCAMs, integrins
Types of cell junctions - Answers Desmosomes, tight junctions, gap junctions
Desmosomes - Answers Anchor together two adjacent cells: they are composed of dense
intracellular thickenings (plaques) that are connected by glycoprotein filaments containing
cadherins to attach the neighbouring plaques together.
, Within a cell, other cytoskeletal anchoring proteins can also attach to the plaque area to create a
network of strong fibres through the cell, giving the cell stretch
Tight junctions - Answers Found in epithelial tissues, and creates a very tight seal between cells
to regulate the passage of molecules - long strings of junctional proteins in the plasma
membrane between neighbouring cells align and adhere to form a tight junction.
Area where opposing junctional proteins from neighbour cells meet - Answers Kiss site
Gap junctions - Answers 6 connexon protein subunits form one half of a gap junction - when this
aligns with the connexon of an adjacent cell, it forms a tunnel that connects their intracellular
spaces and allows them to communicate directly by opening/closing; only small, water soluble
substances can pass through the junction
Found in cardiac and muscle cells to spread a wave of excitation
Factors determining membrane permeability - Answers Size, solubility
Channels for water - Answers Aquaporins
Two forces that underlie the movement of water - Answers Osmosis & hydrostatic pressure
Osmotic pressure - Answers The force moving water down its concentration gradient
Hydrostatic pressure - Answers The force created by a given volume of water
Mechanism of facilitated diffusion - Answers 1) Carrier protein takes a conformation in which
the solute binding site is exposed to the region of higher solute concentration
2) Solute molecule binds to the carrier protein
3) Carrier protein changes conformation so that the binding site is exposed to a region of lower
solute concentration
4) Transported solute is released and the carrier protein returns to conformation seen in Step 1
Methods of assisted membrane transport - Answers Facilitated diffusion, carrier mediated
transport, vesicular transport
Homeostasis - Answers The ability of a cell or organism to regulate and maintain its internal
environment
Set point - Answers The range or point at which a variable physiological state tends to stabilize.
3 components of homeostatic control - Answers Sensor, integrator, effector
Sensor - Answers Responsible for detecting an environmental variable
Integrator - Answers Compares the variable being detected to its set point
Effector - Answers Initiates the changes to restore the variable back to its set point
Intrinsic regulation - Answers Sensor, integrator, and effector are all located within a tissue so
that the tissue can regulate its own internal environment
Extrinsic regulation - Answers Regulatory mechanisms are outside of the tissue or organ (for
full-body processes)
Negative feedback - Answers Change in an environmental parameter causing the effector to
initiate a response in the opposite direction
Positive feedback - Answers Occurs when the effector causes changes that amplify the initial
signal.
Level & mechanism of control: blood clotting - Answers Intrinsic, positive
Level & mechanism of control: childbirth - Answers Extrinsic, positive
Level & mechanism of control: regulation of blood pressure - Answers Intrinsic, negative
Level & mechanism of control: regulation of blood glucose - Answers Extrinsic, negative
4 roles of the plasma membrane - Answers Regulating the internal fluid composition by
controlling what can move in/out of the cell.
Allows nutrients to enter cells and waste products to leave.
Permits chemical signals released from other cells in the body to influence a cell (cell-to-cell
communication).
,Participates in joining cells together, to form tissues & organs.
3 primary functions of the plasma membrane - Answers Ensure the cell's survival
Maintain homeostasis
Function cooperatively and in coordination with surrounding cells
Structures present in the plasma membrane - Answers Phospholipids, cholesterol, membrane
proteins, ion channels, carbohydrate chains
Phospholipids - Answers Lipid bilayer is comprised of phospholipids.
A phospholipid has a polar head (hydrophilic) with a negatively charged phosphate group and
two non-polar (hydrophobic) fatty acid tails.
Cholesterol - Answers Tucked in between phospholipids to prevent the fatty acid chains from
packing too tightly together, in order to keep the membrane fluid
Membrane proteins - Answers Can be associated with the inner side, outer side, or pass all the
way through the plasma membrane
These function to maintain cell structure, regulate cell function, allow transport across the
membrane, and facilitate signalling
Ion channels - Answers Permit the entry or exit of ions across the plasma membrane
Carbohydrate chains - Answers Short carbohydrate chains can be attached to proteins or the
bilayer itself to form glycoproteins and glycolipids, respectively
These are involved in stabilizing membrane structure, acting as cell surface receptors,
participating in transportation across the cell membrane, etc
Cystic fibrosis - Answers Caused by a defect in a particular chloride ion channel, which controls
the amount of fluid and mucous within the lungs - CF patients experience a buildup of fluid in
the lungs
Alzheimer's disease - Answers Results in oxidative stress: the generation of reactive oxygen
,species that may result in damage to cells
Oxidative stress leads to the alteration and degradation of phospholipids within neurons,
compromising the integrity of the membrane and impacting neural function (memory loss &
reduced cognition)
Three types of cell-to-cell adhesions - Answers Extracellular matrix, cell adhesion molecules, cell
junctions
Extracellular matrix - Answers Network of fibrous proteins embedded in a gel- like mixture of
complex carbohydrates that surrounds all cells & tissues to keep them in place
Watery gel allows for diffusion of nutrients & waste removal
Precise ECM composition is different in every tissue type to allow specialized function
The majority of the ECM is secreted by fibroblasts located within the interstitial space.
Three major protein fibres of ECM - Answers collagen, elastin, fibronectin
Collagen - Answers Forms the cable-like structures that give the ECM its tensile strength
Elastin - Answers Rubber-like protein that allows tissues to be stretched and then recoil after the
stretching force is removed
Fibronectin - Answers Promotes cell adhesion
Cell-adhesion molecules (CAMs) - Answers Transmembrane proteins: intracellular side interacts
with the cytoskeleton, and the extracellular side interacts with the ECM CAMs from other cells -
CAMs help cells stick to each other and to their surroundings
There are 4 families: cadherins, selectins, NCAMs, integrins
Types of cell junctions - Answers Desmosomes, tight junctions, gap junctions
Desmosomes - Answers Anchor together two adjacent cells: they are composed of dense
intracellular thickenings (plaques) that are connected by glycoprotein filaments containing
cadherins to attach the neighbouring plaques together.
, Within a cell, other cytoskeletal anchoring proteins can also attach to the plaque area to create a
network of strong fibres through the cell, giving the cell stretch
Tight junctions - Answers Found in epithelial tissues, and creates a very tight seal between cells
to regulate the passage of molecules - long strings of junctional proteins in the plasma
membrane between neighbouring cells align and adhere to form a tight junction.
Area where opposing junctional proteins from neighbour cells meet - Answers Kiss site
Gap junctions - Answers 6 connexon protein subunits form one half of a gap junction - when this
aligns with the connexon of an adjacent cell, it forms a tunnel that connects their intracellular
spaces and allows them to communicate directly by opening/closing; only small, water soluble
substances can pass through the junction
Found in cardiac and muscle cells to spread a wave of excitation
Factors determining membrane permeability - Answers Size, solubility
Channels for water - Answers Aquaporins
Two forces that underlie the movement of water - Answers Osmosis & hydrostatic pressure
Osmotic pressure - Answers The force moving water down its concentration gradient
Hydrostatic pressure - Answers The force created by a given volume of water
Mechanism of facilitated diffusion - Answers 1) Carrier protein takes a conformation in which
the solute binding site is exposed to the region of higher solute concentration
2) Solute molecule binds to the carrier protein
3) Carrier protein changes conformation so that the binding site is exposed to a region of lower
solute concentration
4) Transported solute is released and the carrier protein returns to conformation seen in Step 1
Methods of assisted membrane transport - Answers Facilitated diffusion, carrier mediated
transport, vesicular transport
