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Cell Membrane Transport and Homeostasis
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1
Question
What is homeostasis in cellular terms?
Answer
Maintenance of stable internal conditions by regulating exchange with the environment
2
Question
How does the plasma membrane contribute to homeostasis?
Answer
Regulates what enters and leaves the cell to keep conditions stable
3
Question
Why is the plasma membrane described as a phospholipid bilayer?
Answer
Two layers of phospholipids with polar heads and nonpolar tails
4
Question
Define passive transport.
Answer
Energy-free movement down the concentration gradient
5
Question
What type of molecules diffuse through channel proteins?
Answer
Ions and small polar molecules that need channels to cross the membrane
6
Question
What is the basic difference between simple diffusion and facilitated diffusion?
Answer
Simple: no transport proteins; Facilitated: uses transport proteins
7
Question
What is a similarity between simple and facilitated diffusion?
Answer
Both are passive and move with the concentration gradient
8
Question
What does ATP stand for?
Answer
Adenosine triphosphate
9
Question
What happens to ATP when it is hydrolyzed?
Answer
Releases energy used by the cell to perform work
10
Question
Give one example of active transport.
Answer
Sodium-potassium pump (Na+/K+ pump)
11
Question
What is the primary function of the Na+/K+ pump?
Answer
Creates concentration and electrical gradients by moving Na+ and K+ against their gradients
12
Question
Name three types of endocytosis.
Answer
Phagocytosis, pinocytosis, receptor-mediated endocytosis
13
Question
What is the main difference between endocytosis and exocytosis?
Answer
Endocytosis brings substances into the cell; exocytosis expels them
14
Question
What is an example of exocytosis?
Answer
Secretion of enzymes or neurotransmitters from vesicles to the extracellular space
15
Question
What is osmosis?
Answer
Diffusion of water across a semipermeable membrane toward higher solute concentration
16
Question
What drives passive transport?
Answer
Concentration gradient (differences in concentration)
17
Question
What molecule primarily drives cellular energy use in active transport?
Answer
ATP (via pumps like Na+/K+ ATPase)
18
Question
What role do membrane proteins play in facilitated diffusion?
Answer
Provide a passageway or a channel/carrier for specific molecules
19
Question
What types of molecules typically diffuse directly through the lipid bilayer?
Answer
Small, nonpolar molecules (e.g., O2, CO2) and some small lipophilic molecules
20
Question
Why must endocytosis occur for certain large particles?
Answer
They are too large to cross the membrane via channels or transporters
21
Question
What maintains the resting membrane potential in many cells?
Answer
Selective permeability and ion gradients created by pumps and channels
22
Question
Name a cell process that requires membrane vesicle transport.
Answer
Endocytosis or exocytosis (vesicle-mediated transport)
23
Question
What is a characteristic feature of phospholipids in the bilayer?
Answer
Amphipathic with a hydrophilic head and hydrophobic tail
24
Question
How does the plasma membrane protect the cell from viruses?
Answer
Regulates entry and can exclude or regulate entry of pathogens
25
Question
What happens to molecules that are too large to cross the membrane via diffusion?
Answer
They require transport proteins or vesicular transport (endocytosis/exocytosis)
26
Question
What is the function of channel proteins?
Answer
Facilitate passive movement of specific ions or water molecules
27
Question
What is the concept of diffusion?
Answer
Movement of particles from high to low concentration until equilibrium
28
Question
What is receptor-mediated endocytosis?
Answer
Endocytosis initiated by receptor-liberated binding of ligands to receptors
29
Question
Describe pinocytosis.
Answer
Cellular drinking; uptake of extracellular fluid and dissolved solutes via vesicles
30
Question
Why are endocytosis and exocytosis considered active?
Answer
Involve vesicle movement and energy-dependent processes in many cases