2.5 Biological membranes Flashcards
Are phospholipid heads hydrophobic or hydrophilic?
Hydrophilic
Are phospholipid tails hydrophobic or hydrophilic?
Hydrophobic
Are phospholipid heads water soluble?
Yes
Are phospholipid tails water soluble?
No
What is an affinity?
An attraction
What part of the phospholipid forms an affinity with water?
Heads
What do phospholipids form when submerged in water?
Micelles
What are plasma membranes made up off?
Phospholipids (which form a bilayer)
What can diffuse straight through the bilayer?
Fat soluble organic molecules (polar molecules require proteins)
What does the plasma membrane do in terms of acting as a barrier?
Allows cellular compartments to have different conditions.
Are plasma membranes flexible?
Yes and they are able to break and fuse easily
What is the fluid-mosaic model?
Fluid - the proteins can move freely through the bilayer.
Mosaic - The arrangement of the proteins in the bilayer.
Model - Representation of the structure of the bilayer
What are the different types of carrier and channel proteins?
Passive and active
Gated-channel and channel
What is diffusion?
Diffusion is the movement of particles (if they are lipid soluble) or gases from an area of higher concentration to an area of lower concentration.
Down the concentration gradient.
Diffusion is a passive process. (means no ATP is required)
It is directly across a partially permeable membrane.
What is facilitated diffusion?
Facilitated diffusion is the movement of charged molecules from an area of higher concentration to an area of lower concentration.
Down the concentration gradient.
Facilitated diffusion is a passive process. (means no ATP is required)
A protein channel is needed to move across a partially permeable membrane.
What is osmosis?
Osmosis is the movement of water from a higher water potential to a lower water potential.
The water potential is affected by the solute.
It goes down a water potential gradient.
Osmosis is a passive process. (means no ATP is required)
It is directly across a partially permeable membrane.
What is active transport?
Active transport is the movement of lipid insoluble molecules or charged particles from a lower concentration gradient to a higher concentration gradient.
It goes up or against the concentration gradient.
It is an active process which means ATP is required.
A protein carrier is required to move across a partially permeable membrane.
What does a higher temperature do to membrane permeability?
Increases it
How does temperature affect membrane permeability?
As the temperature increases proteins denature (the bonds are disrupted which breaks down the tertiary structure). This leaves gaps in the membrane.
It also increases the kinetic energy, meaning the membrane will move around leaving the gaps bigger.
What as an example of membrane permeability increasing?
The tonoplast (membrane of the vacuole) then has gaps. The pigment of the beetroot is kept in the vacuole. As the membrane has gaps in it, the pigment can leak through.
How does ethanol affect membrane permeability?
Dissolves lipids which causes gaps in the membrane, increasing permeability.
Changing the solute will change the permeability.
What is a glycoprotein?
A carbohydrate chain attatched to a protein molecule (in the bilayer)
What is a glycolipid?
A carbohydrate chain attached to a lipid (in the bilayer)
What do glycoproteins and glycolipids do?
Stabilise membranes by forming hydrogen bonds with surrounding water molecules.
Receptor sites.
Cell signalling.
Antigens.
