Membranes Flashcards
What is the role is cholesterol ?
adds strength
What is the fluid - mosaic model?
the structure of membrane
what is an intrinsic protein ?
spans the whole membrane
What is the arrangement of phospholipids
phospholipid bilayer
What is the hydrophobic region?
fatty acid tails
What is the hydrophilic region?
the phosphate head
what is the majority lipid in a membrane
phospholipid
what is an extrinsic protein?
loosely bound to outside of a membrane
What is a passive process
does not require ATP
What is osmosis?
movement of water down water potential gradient
what is a glycoprotein?
a protein with a carbohydrate attached
what is a glycolipid?
a lipid with a carbohydrate attached
What is a carrier protein?
changes shape to transport substances across membrane
What is the role of proteins in membranes
enzymes
receptors
transport
recognition
what is a channel protein?
molecules travel through them in facillitated diffusion
what is diffusion?
random movement of molecules from high to low concentration
What is active transport?
move against concentration gradient
what is endocytosis?
moving large molecules into cells
What is exocytosis?
Moving large molecules out of cells
Why are membranes fluid?
hydrophobic and hydrophilic interactions
phospholipids and proteins can move horizontally
no bonds
What is the importance of a membrane being fluid?
can repair itself
flexible
for endocytosis and exocytosis
How does a protein stay in the membrane?
Has no charge in the middle, and charge in the outside
Charged amino acids are either highly hydrophobic or hydrophilic, uncharged amino acids go in the middle
What travels through channel proteins?
ions, water solvable substances
What is the structure and properties of a membrane?
phosphate head - hydrophilic
Fatty acid tails - hydrophobic
selectively permeable
What is diffusion
high concentration to low concentration
down a concentration gradient
passive
How to calculate rate of diffusion
amount diffused / time taken
What factors effect rate of diffusion?
temperature, surface area, different in concentration and thin exchange surface
What is facilitated diffusion?
larger water soluable molecules
carrier proteins with binding sites
specific
passive
What is osmosis?
cytoplasm contains soluable molecules and ions which attract water
net movement of solvent molecules from an area lower loconcentration to higher concentration of solute
depends of water potential
osmosis
what happens if an animal cell in solution with a lower water potential?
net movement out of cell
osmosis
what happens to a plant cell in solution with lower water potential
contents shrink away from cell wall
Osmosis
what happens to an animal cell in solution with higher water potential
bursts
osmosis
what happens to a plant cell in solution with higher water potential
becomes firm and rigid
what is active transport?
against a concentration gradient
uses carrier proteins and requires ATP
What is an example of active transport?
epithelial cells lining the intestine, lots of mitochondria which produces ATP for active transport
How does active transport occur?
molecules bind to receptor site
atp binds to protein , hydrolysed into ADP and Pi
Protein changes shape
Molecule is released
Pi is released, protein reverts to original shape
what is water potential
the tendency of water to move from one area to another by osmosis
measured in kPa
what is the water potential of pure water
0
what is hypertonic
higher concentration of solutes when compared to another solution
what is hypotonic
lower concentration of solute when compared to another solution
what is isotonic
same solute concentration in two or more solutions
