Chapter 5 - Biological Membranes Flashcards
Roles of membranes within cells
- selective permeability
- surface for enzyme attachment
- form vesicles
- compartmentalisation
- create concentration gradients
Roles of membranes at cell surfaces
- Plasma membranes are partially permeable
- Create barriers to substances
- cell recognition and signalling
Three. Intrinsic proteins.
Carrier channel, Glyco
Channel proteins
Diffusion of polar molecules or ions through membranes
Carrier proteins
Active transport of molecules into cells
Glycoproteins
Cell adhesion and receptors for cell signalling
Glycolipids
Cell markers, or antigen is to be recognised by the immune system
Cholesterol
Regulates membrane, fluidity and stability by preventing phospholipids, grouping and crystallising
What factors affect membrane permeability
Solvent and temperature
How to solvents affect membrane permeability
Organic solvents, dissolve membranes and disrupt cells creating gaps in membranes, which increases fluidity and permeability
How does temperature affect membrane permeability
Increasing temperature increases, kinetic energy of phospholipids increases fluidity, so the membrane loses structure
The effect of extreme temperatures on membrane permeability
Membrane breaks down completely channel, proteins, denature, so transport is limited
Define diffusion
The net movement of particles down a concentration gradient
What factors affect the rate of diffusion?
Temperature
concentration difference,
surface area
membrane thickness
Simple diffusion
Diffusion across a membrane without using channel proteins
Facilitated diffusion
Diffusion across a membrane through channel proteins
Active transport
Movement of molecules or ions against a concentration gradient, requiring energy from ATP and carrier proteins
Types of active transport
Endocytosis and exocytosis (bulk transport)
What is bulk transport?
Vesicle movement requiring ATP
Endocytosis
Into cells
Cell surface membrane, bends in forming a vesicle that pinches into the cytoplasm
Exocytosis
Out of cell
Versicles fuse with the cell surface membrane and the contents is released out of the cell
Osmosis
Diffusion of water across a partially permeable membrane down a water potential gradient
What is the highest water potential (pure water)
0 kPa (gets more negative)
Terms for animal cell, bursting, and shrivelling
Bursting – cytolysis
Shrivelling – crenation
Terms for plant cell, bursting and shrivelling
Bursting – plant cells don’t burst due to the cell wall, they become turgid
Shrivelling – plasmolysis the cell surface membrane, shrinks away from the cell wall
Hypertonic
More solute than water, lower water potential
Hypotonic
Less solute than water, high water potential
Isotonic
Solute and water equal
