Lecture 4 - Plasma membrane and organelles Flashcards
What is a plasma membrane?
A semi-permeable barrier that allows the passage of nutrients, oxygen and waste.
What is a plasma membrane made out of?
Double layer of phospholipids with
various embedded or attached proteins
What are the requirements for a cell?
- Manufacture cellular materials
- Obtain raw materials
- Remove waste
- Generate the required energy
- Control all of the above functions
What are the three factors that effect the static status of the plasma membrane?
Saturation, temperature, cholesterol
How does saturation effect the static status of the plasma membrane?
- Saturated – packed
tightly together, less
fluidity - Unsaturated – tails
prevent tight packing,
more fluidity
How does temperature effect the static status of the plasma membrane?
- High temps more
fluidity - Low temps less fluidity
How does cholestoral effect the static status of the plasma membrane?
Stabilises membrane
fluidity
Which one of the following statements BEST describes the function of organelles.
They:
(A) provide separate compartments with discrete functions.
(B) increase the amount of membrane in a cell.
(C) allow cells to specialise for a specific function.
(D) allow the cell to manufacture cellular materials.
(A) provide separate compartments with discrete functions.
What is signal transduction?
Signal transduction uses membrane
proteins to relay messages from outside the cell to inside the cell
What are membrane proteins involved in? (5)
Signal transduction, cell recognition, intercellular joining, linking cytoskeleton & Extracellular Matrix (ECM), and membrane transport
Hydrophobic molecules normally move across cell membranes by:
(A) Facilitated diffusion.
(B) Active transport.
(C) Simple diffusion.
(D) Endocytosis.
(C) Simple diffusion.
Which two mechanisms are forms of passive transport?
Simple diffusion, facilitated diffusion
What is osmosis?
Movement from a high water
(low solute) concentration to a
low water (high solute)
concentration through facilitated diffusion
What is the main organelle that animal cells have that plant cells don’t?
Lysosome
What are the two main organelles that plant cells have that animal cells don’t?
Central vacuole and chloroplasts
What molecule stabilises membrane fluidity?
Cholesterol in the lipid bilayer
What is the difference between passive and active transport?
Passive - Molecules move down concentration gradient
Active - Molecules move against concentration gradient
What sort of molecules can passively diffuse across the plasma membrane?
Hydrophobic molecules - steroid hormones and gasses
Relaying messages
from the external
environment into the
cell can best be
described as:
A. Cell recognition
B. Intercellular joining
C. Signal transduction
D. Adhesion to ECM
C. Signal transduction
Plasma membranes restrict the movement of…
Water, soluble and charged molecules
