Organisms and Exchange no Flashcards
E. coli has no cholesterol in its cell-surface membrane. Despite this, the cell maintains a constant shape. Explain why
Cell unable to change shape;
2. (Because) cell has a cell wall;
3. (Wall is) rigid / made of peptidoglycan / murein.
Explain why the structure of a membrane is described as fluid-mosaic.
Fluid - the individual phospholipid molecules can move relative to one another - gives the membrane a flexible structure that is constantly changing shape
Mosaic - proteins that are embedded in the phospholipid bilayer vary in shape and size and pattern like a mosaic
2 Active transport and facilitated diffusion are two ways by which substances cross cell surface membranes.
State one difference and one similarity between active transport and facilitated diffusion. (2)
difference - FD occurs along a concentration gradient from high concentration to low concentration and does not require energy rather than AT from low concentration to high concentration occurs against the concentration gradient and requires energy
Similarity- both use proteins to assist them :???
Cholesterol function
regulates membrane fluidity/ stability
less fluid at higher temps
regulates lateral movement of phospholipids
Channel/carrier Protein function
transport of substances across the membrane by facilitated diffusion or Active transport
Glycoproteins function
cell signalling, binding cell together
cell recognition for hormones and neurotransmitters
Glycolipids function
receptor, antigens, stacking cells together
helps maintain stability of membrane
Describe how you would test a piece of food for the presence of lipid.
Dissolve in alcohol, then add water; emulsion test goes cloudy white
protein channel explained
protein with specific shape that complements shape of substrate to be transported across membrane
- passing of ion through
What is a glucolipid?
Carbohydrate attached to lipid phospholipid
protein channel
tertiary structure specific
passing of ions
facilitated diffusion
protein carrier def
protein with specific shape that complements shapes of substance to be transported across membrane
AT and facil diffusion
other word for protein carrier
integral protein
Intrinsic protein
in membrane
Extrinsic protein
outside membrane
Glycoprotein def
act as antigens allowing cells to recognise one another
Phospholipid bilayer structure
Phosphate -> head- hydrophilic - polar
Lipid -> tail -> hydrophobic - form semi- permentant bilayer
phospholipid bilayer def
allows lipid soluble substances to enter and leave and prevent water soluble entering and leaving
gives membrane fluidity
hydrophobic region
spinning - energy (kinetic)
Facilitated diffusion
passive - relays on input of kinetic energy
charged ions and polar molecules - by carrier and channel proteins - dont diffuse easily - hydrophobic fatty acids in phospholipid bilayer
Simple diffusion
non polar molecules
across phospholipid bilayer
passive transport - no ATP
down conc
down concentration
Diffuson
against concentration
Active transport
active tranport defintion
net movement of molecules form low to high conc against conc gradient
Endocytosis
a process by which cells absorb external material by engulfing it with the cell membrane.
Excocytosis
involves secretion from the cell
a vesicle containing molecules of substances fuses with the inside of the cell membrane and the molecules are secreted from the cell.
Diffusion and osmosis compare similarities
high to Low conc
both passive transport
How does glucose move through membrane
co transport?
contrasport
1- cotransport protein
2- carrier protein used
2- NA + conc kept low
3- Sodium potassium pump
Atp energy
Active transport of NA + into blood
glucose facilitated diffusion into blood
