PHGY 215 – MIDTERM 2026 FINAL PAPER
COMPLETE QUESTIONS AND ANSWERS FULL
SOLUTION
◉ Cadherins.
Answer: Play important roles in cell adhesion by forming adherens
functions to bind cells within tissues together
◉ Tight Junctions.
Answer: - Creates a tight seal between cells, preventing movement of
molecules from cell to cell
- Long strings of junctional proteins in the plasma membrane
between the neighbouring cells align and adhere to form a tight
junction
- the area where opposing junctional proteins from neighbouring
cells meet is called a kiss site
- this type of junction is found primarily in epithelial tissues
◉ Epithelial Tissues.
Answer: Line the cavities and surfaces of blood vessels and organs
throughout the body
◉ Gap Junctions.
,Answer: - Within a plasma membrane, six connexin protein subunits
form one half of a gap junction (a connexon)
- When connexons of adjacent cells align a tunnel forms that
connects their intracellular spaces and allows them to communicate
directly
- One small water soluble substance can pass through the junction
and these tunnels can be opened and closed as needed to control cell
communication
- Common in cardiac and smooth muscle cells that rely on these
junctions to spread the wave of excitation
- Allow the spread of secondary messengers between connected
cells which provides a mechanism for cells to act in a cooperative
manner
◉ Permeable, Impermeable, Semi-permeable.
Answer: - If a substance can freely cross the membrane, the
membrane is said to be permeable
- If a substance cannot cross the membrane it is said to be
impermeable
- the plasma membrane is semi-permeable, which means that some
substances may pass freely while others cannot
◉ 2 Factors that determine membrane permeability.
Answer: Size and Solubility
,◉ Size - Membrane Permeability.
Answer: - Small substances like ions can enter through the
membrane spanning ion channels
- Larger substances require a transport protein to move it across the
membrane
◉ Solubility - Membrane Permeability.
Answer: - A principal factor which determines membrane
permeability is how lipophilic the substance is
- Uncharged or non-polar molecules are usually very lipophilic and
can readily cross the plasma membrane
Charged or polar substances are lipophobic and cannot pass through
he plasma membrane unaided
◉ Lipophilic.
Answer: Tending to combine with or dissolve in lipids or fats
◉ Lipophobic.
Answer: Compounds that are not soluble in lipids or other non-polar
solvents
◉ Passive transport.
Answer: - A mechanism used to transport impermeable molecules
across the membrane that does not require cellular energy
, - Includes Diffusion and Facilitated Diffusion
◉ Active transport.
Answer: - A mechanism used to transport impermeable molecules
across the membrane that requires cellular energy
- Includes carrier mediated transport and vesicular transport
◉ Diffusion Down a Concentration Gradient.
Answer: - when molecules in a solution have a high density they
frequently collide and bounce off each other which causes molecules
to spread from areas of high density to low density, or down a
concentration gradient
- this is known as diffusion and occurs until no concentration
gradient exists and the movement of substances are said to be in
dynamic equilibrium
◉ Dynamic Equilibrium.
Answer: Substance movement continues to occur in both directions
at the same rate, therefore there is no net movement
◉ Diffusion in the presence of a permeable membrane.
Answer: If the membrane is permeable to he substance then there
will be net diffusion of the substance passively down its
COMPLETE QUESTIONS AND ANSWERS FULL
SOLUTION
◉ Cadherins.
Answer: Play important roles in cell adhesion by forming adherens
functions to bind cells within tissues together
◉ Tight Junctions.
Answer: - Creates a tight seal between cells, preventing movement of
molecules from cell to cell
- Long strings of junctional proteins in the plasma membrane
between the neighbouring cells align and adhere to form a tight
junction
- the area where opposing junctional proteins from neighbouring
cells meet is called a kiss site
- this type of junction is found primarily in epithelial tissues
◉ Epithelial Tissues.
Answer: Line the cavities and surfaces of blood vessels and organs
throughout the body
◉ Gap Junctions.
,Answer: - Within a plasma membrane, six connexin protein subunits
form one half of a gap junction (a connexon)
- When connexons of adjacent cells align a tunnel forms that
connects their intracellular spaces and allows them to communicate
directly
- One small water soluble substance can pass through the junction
and these tunnels can be opened and closed as needed to control cell
communication
- Common in cardiac and smooth muscle cells that rely on these
junctions to spread the wave of excitation
- Allow the spread of secondary messengers between connected
cells which provides a mechanism for cells to act in a cooperative
manner
◉ Permeable, Impermeable, Semi-permeable.
Answer: - If a substance can freely cross the membrane, the
membrane is said to be permeable
- If a substance cannot cross the membrane it is said to be
impermeable
- the plasma membrane is semi-permeable, which means that some
substances may pass freely while others cannot
◉ 2 Factors that determine membrane permeability.
Answer: Size and Solubility
,◉ Size - Membrane Permeability.
Answer: - Small substances like ions can enter through the
membrane spanning ion channels
- Larger substances require a transport protein to move it across the
membrane
◉ Solubility - Membrane Permeability.
Answer: - A principal factor which determines membrane
permeability is how lipophilic the substance is
- Uncharged or non-polar molecules are usually very lipophilic and
can readily cross the plasma membrane
Charged or polar substances are lipophobic and cannot pass through
he plasma membrane unaided
◉ Lipophilic.
Answer: Tending to combine with or dissolve in lipids or fats
◉ Lipophobic.
Answer: Compounds that are not soluble in lipids or other non-polar
solvents
◉ Passive transport.
Answer: - A mechanism used to transport impermeable molecules
across the membrane that does not require cellular energy
, - Includes Diffusion and Facilitated Diffusion
◉ Active transport.
Answer: - A mechanism used to transport impermeable molecules
across the membrane that requires cellular energy
- Includes carrier mediated transport and vesicular transport
◉ Diffusion Down a Concentration Gradient.
Answer: - when molecules in a solution have a high density they
frequently collide and bounce off each other which causes molecules
to spread from areas of high density to low density, or down a
concentration gradient
- this is known as diffusion and occurs until no concentration
gradient exists and the movement of substances are said to be in
dynamic equilibrium
◉ Dynamic Equilibrium.
Answer: Substance movement continues to occur in both directions
at the same rate, therefore there is no net movement
◉ Diffusion in the presence of a permeable membrane.
Answer: If the membrane is permeable to he substance then there
will be net diffusion of the substance passively down its
