19 Questions
What is the widely accepted model of plasma membrane structure?
Fluid mosaic model
What is the main function of the cell membrane?
To allow only certain substances to pass through
What is the role of cholesterol in the plasma membrane?
To provide structural support to the membrane
Which components form a bilayer in the plasma membrane?
Phosphate heads and fatty acid tails
According to the fluid mosaic model, what forms a shifting pattern within the fluid phospholipid bilayer?
Protein molecules
What type of membrane is the cell membrane?
Semi-permeable
What does the fluid mosaic model state about the consistency of the cell membrane?
It is flexible and similar to vegetable oil
Which type of transport involves the movement of substances across the cell membrane against their concentration gradient?
Active transport
What does the term 'selectively permeable' mean in relation to the cell membrane?
It allows only certain substances to pass through while restricting others
What is the function of vesicle transport in cells?
To transport substances within the cell or to/from the cell membrane
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
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
Which of the following is NOT a function of the cell membrane?
Anchoring the cytoskeleton to provide shape to the cell
In which type of junction are proteins that hold adjacent cells together very tightly so nothing can penetrate between them?
Tight junctions
Which process describes the movement of substances across the membrane without the input of cellular energy?
Vesicle transport
Which process involves vesicles fusing with the plasma membrane and releasing their contents to the outside of the cell?
Active transport
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
What are carbohydrates attached to proteins forming glycoproteins or to lipids forming glycolipids, present only on the outer surface of the plasma membrane?
Carbohydrate
What type of proteins serve as receptors that bind specific molecules such as hormones?
Receptor proteins
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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