Medical Biology Lecture 7: Cell Membrane Structure and Function

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Questions and Answers

What is the widely accepted model of plasma membrane structure?

Solid mosaic model

Fluid mosaic model (correct)

Stable phospholipid model

Rigid bilayer model

What is the main function of the cell membrane?

To allow only certain substances to pass through (correct)

To store genetic information

To provide energy for the cell

To maintain the rigid structure of the cell

What is the role of cholesterol in the plasma membrane?

To transport substances in and out of the cell

To facilitate energy production

To provide structural support to the membrane (correct)

To store genetic information

Which components form a bilayer in the plasma membrane?

Phosphate heads and fatty acid tails Signup and view all the answers

According to the fluid mosaic model, what forms a shifting pattern within the fluid phospholipid bilayer?

Protein molecules Signup and view all the answers

What type of membrane is the cell membrane?

Semi-permeable Signup and view all the answers

What does the fluid mosaic model state about the consistency of the cell membrane?

It is flexible and similar to vegetable oil Signup and view all the answers

Which type of transport involves the movement of substances across the cell membrane against their concentration gradient?

Active transport Signup and view all the answers

What does the term 'selectively permeable' mean in relation to the cell membrane?

It allows only certain substances to pass through while restricting others Signup and view all the answers

What is the function of vesicle transport in cells?

To transport substances within the cell or to/from the cell membrane Signup and view all the answers

Which model provides a working description of membrane structure by indicating that protein molecules form a shifting pattern within the fluid phospholipid bilayer?

Fluid mosaic model Signup and view all the answers

What does osmosis refer to in relation to cell membranes?

The movement of water across a semi-permeable membrane from an area of high concentration to low concentration Signup and view all the answers

Which of the following is NOT a function of the cell membrane?

Anchoring the cytoskeleton to provide shape to the cell Signup and view all the answers

In which type of junction are proteins that hold adjacent cells together very tightly so nothing can penetrate between them?

Tight junctions Signup and view all the answers

Which process describes the movement of substances across the membrane without the input of cellular energy?

Vesicle transport Signup and view all the answers

Which process involves vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell?

Active transport Signup and view all the answers

What are fingers like extensions of plasma membrane involved in absorption, particularly abundant on the surface of epithelial cells lining the intestine called?

Tight junctions Signup and view all the answers

What are carbohydrates attached to proteins forming glycoproteins or to lipids forming glycolipids, present only on the outer surface of the plasma membrane?

Carbohydrate Signup and view all the answers

What type of proteins serve as receptors that bind specific molecules such as hormones?

Receptor proteins Signup and view all the answers

Study Notes

College of Medicine Lecture by Zahraa Ch. Hameed on Medical Biology, topic: 3 Cell structures and function, specifically the Cell Membrane
Learning Objectives: define, describe structure, functions, and specializations of the Cell Membrane; understand processes of diffusion, osmosis, facilitated diffusion, active transport, and vesicle transport
Cell Membrane: thin, semi-permeable membrane surrounding cytoplasm; fluid mosaic model structure comprises phospholipids, cholesterol, proteins, and carbohydrates
Phospholipids: form bilayer with polar heads outward and nonpolar tails inward
Cholesterol: improves stability and reduces fluidity in animal cell membranes
Proteins: integral (transmembrane) or peripheral; serve various roles such as channel, carrier, cell recognition, receptor, and enzymatic functions
Carbohydrates: attached to proteins or lipids, forming glycoproteins or glycolipids, present only on outer surface
Function of Cell Membrane: protects, identifies, regulates substance passage, communicates, and anchors cytoskeleton
Cell Membrane Specialization: microvilli (fingers-like extensions), intercellular junctions (tight, gap, desmosomes)
Movement across Cell Membranes: passive (simple diffusion, facilitated diffusion, osmosis) and active (active transport, vesicle transport) processes
Passive ways: diffusion (net movement of particles from higher to lower concentration), facilitated diffusion (assisted by carrier protein), osmosis (diffusion of water)
Active ways: active transport (energy-demanding transfer from lower to higher concentration), vesicle transport (movement of macromolecules through vesicles)
Endocytosis: vesicles engulfing particles from outside; pinocytosis (small particles) and phagocytosis (solid particles)
Exocytosis: vesicles releasing contents to outside; occurs when cell produces substances for export or eliminates waste/toxins.

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