Lesson 7: Membranes Flashcards
What is the permeability of a membrane dependent on?
size of molecules, hydrophobic nature
what is the function of a contractile vacuole?
Removes excess water to maintain a constant osmotic pressure in unicellular organisms.
which organisms have a contractile vacuole?
freshwater organisms - the freshwater is hypotonic compared to them.
What happens when a molecule is more hydrophobic when crossing the membrane layer?
Passes through more easily than hydrophilic molecules.
What is the structure of integral proteins
transmembrane, amphipathic
What are the two types of integral proteins?
channel and carrier proteins
What is the structure of a phospholipids?
glycerol + 2 fatty acids + phosphate group
What property does the phospholipid head have?
hydrophilic
What property do the phospholipid tails have?
hydrophobic
What does amphipathic mean?
having both hydrophilic and hydrophobic regions
what is the function of channel proteins?
facilitated diffusion - large + polar molecules
What is the function of carrier proteins
Active + passive transport: changes shape and binds to specific molecules to transfer them across the membrane
What is active transport?
transport that uses energy to move molecules against the concentration gradient.
What is passive transport?
transport that does not require energy.
What is facilitated diffusion?
a form of passive transport that involves integral proteins.
Where are peripheral proteins located?
bound to the surface of the membrane
What is one property of peripheral proteins?
hydrophilic
What is the role of aquaporins?
transport of water across cell membranes
What can impact the number of auqaporins in the membrane?
Anti-diuretic hormone
What cells do aquaporins act on?
kidney
red blood
lung
What does membrane fluidity depend on?
fatty acid composition
What happens to the membrane fluidity when the fatty acid is unsaturated ?
increases membrane fluidity as it has kinks that prevent the fatty acids from packing too closely together.
Why do cold blooded animals have unsaturated fatty acids?
To prevent fatty acids to pack too closely together in low temperatures.
Why is membrane fluidity important?
carry out processes such as endocytosis and exocytosis.
What is the function of cholesterol in low temperatures?
prevents fatty acids from fitting too close together.
What is the function of cholesterol in high temperatures?
reduces fluidity
What are aquaporins?
water channels
What is the structure of aquaporins
four monomeric subunits, transmembrane
what proteins does facilitated diffusion involve?
integral proteins - both carrier and channel
Which protein does active transport involve?
carrier proteins
What is the role of glycolipids and glycoproteins in cell recognition?
act as “markers” on the cell surface so cells can recognise each other.
What is the role of glycolipids and glycoproteins in cell adhesion?
helps cells to stick to other cells.
What is the role of glycolipids and glycoproteins in cell signalling?
function as receptors on the cell surface, binding to enzymes and other signaling molecules so they can respond to environment.
