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Cell Membrane Structure and Transport
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1
Question
What is the cell theory?
Answer
The cell is the smallest unit of life; organisms are made of cells; cells arise only from other cells.
2
Question
What are the three main parts of a generalized human cell?
Answer
Plasma membrane, cytoplasm (with organelles), and nucleus.
3
Question
What is the extracellular fluid (ECF) in relation to a cell?
Answer
Fluid outside the cell that surrounds it.
4
Question
What is the plasma membrane’s primary structural composition?
Answer
A phospholipid bilayer with embedded proteins.
5
Question
Name two primary functions of the plasma membrane.
Answer
Physical barrier and selective permeability.
6
Question
What is the role of membrane lipids in the plasma membrane?
Answer
Form the bilayer; hydrophobic tails and hydrophilic heads; cholesterol stabilizes membrane.
7
Question
What is the glycocalyx?
Answer
A carbohydrate-rich coating formed by glycoproteins and glycolipids on the cell surface.
8
Question
What initiates cell–cell recognition and identity tagging in membranes?
Answer
Glycoproteins forming part of the glycocalyx.
9
Question
What are integral and peripheral proteins?
Answer
Integral proteins span the membrane; peripheral proteins are attached to one side or to other proteins.
10
Question
What are the six tasks commonly performed by membrane proteins?
Answer
Transport, communication as receptors, enzymatic activity, attachment to cytoskeleton/ECM, cell-to-cell joining, and determining membrane functions.
11
Question
How does a membrane protein participate in signal transduction?
Answer
It binds a chemical messenger and changes shape to trigger cellular reactions.
12
Question
What is the function of cholesterol in the membrane?
Answer
Stiffens the membrane and reduces water solubility.
13
Question
What does the plasma membrane’s selective permeability mean?
Answer
It allows certain substances to cross more easily than others.
14
Question
What are the main types of passive membrane transport?
Answer
Simple diffusion and facilitated diffusion (carrier- and channel-mediated) and osmosis.
15
Question
What drives diffusion across membranes?
Answer
Movement down a concentration gradient from high to low concentration.
16
Question
What is osmosis?
Answer
Movement of water across a membrane through aquaporins.
17
Question
What are aquaporins?
Answer
Channel proteins that facilitate water movement across membranes.
18
Question
What distinguishes simple diffusion from facilitated diffusion?
Answer
Simple diffusion moves solutes directly through the membrane; facilitated uses carrier or channel proteins.
19
Question
What is meant by membrane transport being energy-dependent in some cases?
Answer
Active transport uses energy (often ATP) to move substances against their gradient.
20
Question
What is the glycocalyx on the exterior of a cell composed of?
Answer
Carbohydrates forming a coating on the cell surface.
21
Question
What is the plasma membrane composed of?
Answer
A double layer of phospholipids with embedded proteins.
22
Question
Name three types of cell junctions mentioned?
Answer
Tight junctions, desmosomes, gap junctions.
23
Question
What is diffusion in passive membrane transport?
Answer
Movement of molecules down their concentration gradient.
24
Question
Differentiate simple diffusion from facilitated diffusion?
Answer
Simple diffusion bypasses proteins; facilitated diffusion uses carrier or channel proteins.
25
Question
What is osmosis?
Answer
Water movement across a membrane down its concentration gradient.
26
Question
What is tonicity?
Answer
Solute concentration effects on cell volume: isotonic, hypertonic, hypotonic.
27
Question
What are the two main types of active membrane transport?
Answer
Primary and secondary active transport.
28
Question
What characterizes primary active transport?
Answer
Direct ATP hydrolysis to move substances against their gradient.
29
Question
Which pump is a classic example of primary active transport?
Answer
Sodium-potassium (Na+-K+) pump.
30
Question
What is secondary active transport also called?
Answer
Cotransport.