Cell membrane Flashcards
What is the general structure of a plasma membrane?
Fluid-Mosaic structure - contains a bilayer arrangement of phospholipids.
Which types of molecules can pass through a semi-permeable membrane, and by which method?
Small, non-polar molecules can pass through diffusion
Describe the structure of a phospholipid found in the cell membrane.
One polar end (head), which contains the phosphate group and glycerol, and one non-polar end (tail), which is the fatty acid.
Which types of molecules cannot pass through a semi-permeable membrane (and why)?
Large, polar , and/or charged molecules cannot pass through (due to protein blocking).
A phospholipid has a head and a tail. State the differences between the two (2)
Head: Hydrophylic and polar
Tail: Hydrophobic and non-polar
State 5 functions of proteins relating to cell membranes
> Cell recognition
> Intercellular joining
> Transport
> Enzymes
> Signalling
State the properties of channel proteins along with their function
Creates a passage so small, charged molecules can pass through. Does not require energy (Passive transport)
State the properties of carrier proteins along with their function
Binds to larger, polar molecules and changes shapes to help them go into the cell. (Active transport)
State the properties of passive diffusion
Small, non-polar molecules can diffuse through by passive transport
State the roles of cholesterol (4)
> Stability in structure
> Buffer (mainting pH)
> Temperature decrease -> increase fluidity
> Temperature increase -> decrease fluidity
Explain the process of signalling receptors
When a signalling molecule binds to its receptor, it changes the receptor’s shape, which in turn sends a message to the cell.
Explain the process of endocytosis receptors
Once a receptor binds to its molecule, it triggers the cell membrane to fold inwards, forming a pocket. This pocket pinches off to form a vesicle that brings the substance into the cell.
Explain the process of cell signalling
When there is a stimulus, a ligand is released to its target cell. Once there, it binds to the cell membrane’s receptor and activates it, which causes a signalling cascade, resulting in a response specific to the stimulus.
Explain the term ‘Signalling cascade’
When a ligand binds to a receptor on the cell membrane, it activates a G-protein inside the cell. The G-protein then triggers a series of reactions, passing the signal along in a chain. This chain, or signaling cascade, continues until it produces a specific response in the cell.
Differentiate between ‘Transduction’ and ‘Transmission’
> Transduction: Converting external signals into a usable form/internal response
> Transmission: Passing that now processed signal to other cells
Differentiate between Isotonic, Hypotonic and Hypertonic
Isotonic: Equal solute and taste
Hypotonic: Less solute, more solvent
Hypertonic: More solute, less solvent
(Note:
Solvent: Liquid
Solute: Substance/Material)
What are the factors affecting diffusion? (3)
> Surface area
> Steepness of the gradient (Concentration)
> The nature of the molecules (Polarity/Size)
State which of these are passive transport and which are active transport and which go against the concentration gradient:
Diffusion
Osmosis
Facilitated diffusion
Active transport
> Diffusion: passive
> Osmosis: passive
> Facilitated diffusion: passive
> Active transport: active, against concentration gradient
What is water potential?
The tendency pf water to move from one place to another
What is plasmolysis?
Plasmolysis is when a plant cell shrinks away from its cell wall due to water loss in a hypertonic solution.
What is incipient plasmolysis?
The moment just before the cell undergoes plasmolysis.
What are the requirements for active transport? (2)
> Needs a carrier protein
> Needs ATP
What is bulk transport?
Transport of large quantities of materials into (Endocytosis) the cell and out of it (Exocytosis)
What is the purpose of endocytosis? (2)
> Phagocytosis (Cell eating)
> Pinocytosis (Cell drinking)
