Bio Chapter 7 Flashcards
How does Lipid bilayer forms in water
Spontaneously
Hugh Dawson& James Danielly they agreed that the phospholipid bilayer lies between 2 layers of globular proteins
Sandwich Model
What was the problem of sandwich model?
The placement of membrane proteins, which have hydrophilic and hydrophobic regions
What J.Singer& G. Nicolson proposed about the membrane
Membrane is a fluid structure with a mosaic of proteins embedded and attached within the bilayer, with only the hydrophilic regions exposed to water
what is most abundant ins mosaic model
phospholipids
two types of proteins in mosaic model
integral- inside the layer
peripheral - on top of layer
What are embedded proteins in the membrane
amphipathic
Membranes are what?
fluid
unsaturated
mosaics
glycoprotein
sugar covalently bonded to protein
differentiate different species
glycolipid
sugar covalently bonded to lipid
peripheral proteins
not embedded but loosely bound to membrane surface
bottom and top of the membrane
integral proteins
transmembrane proteins
amphipathic- penetrate the hydrophobic core if the lipid bilayer
functions of integral proteins
transport coded from the DNA, structure is specific, very specific things can come out and come in
enzyme activity
cell-cell recognitions
Why is membrane selectively permeable
conservative
homeostasis
What molecules can go through the membrane?
Not much regulation
small, non-polar molecules
What molecules can not?
Ions and polar molecules
What about water
Can cross over the membrane but slow
- aquaporins
Passive Transport
No energy required
AKA diffusion
Naturally move through the membrane
spontaneously move from high concentrations to low concentration
Facilitated diffusion
uses transport proteins to move things through the membrane
still move from area of high to low concentration
transport proteins
enable specific ions and polar molecules to cross membrane
very specific
Channel proteins
have a hydrophilic channel that certain molecules use as a tunnel
carrier proteins
hold on to passengers and change shape in a way that shuttles them across
osmosis
passive transport of water
water moves until when
until solution concentrations on both sides are equal
water moves
from area of lower solute concentrations to area of higher solute concentration
tonicity
ability of a solution to cause a cell to gain or lose H2O
isotonic
no net movement because same concentrations outside/inside
hypertonic
outside cell has higher solute concentration
hypotonic
outside cell has lower solute concentration
what is osmoregulation
control of water balance
osmoregulation example
Paramecium
Paramecium
lives in pond water (hypotonic)
plasma membrane permeability lower
contractile vacuole
contractile vacuole
fills with fluid that enters from a system of canals radiating throughout the cytoplasm
active transport
requires energy to move some molecules across the cell membrane
what are carrier proteins?
active transport pumps
membrane potential
voltage difference across a membrane
how does voltage created
by difference in the distribution of positive and negative ions
electrochemical gradient
two combined forces, drive the diffusion of ions across a membrane
chemical force
the ion’s concentration gradient
electrical force
the effect of the membrane potential on the ion’s movement
electrogenic pump
a transport protein that generates voltage across a membrane
sodium-potassium pump
the major electrogenic pump of animal cells
proton pump
main electrogenic pump of plants, fungi, and bacteria
contransport
active transport of 1 substance drives the transport of another substance
exocytosis
large molecules leaving the cell
secretion
cells secrete by fusion of vesicles with the plasma membrane
endocytosis
cell takes in molecules by forming new membrane vesicles from the plasma membrane
ligand
any molecule that binds specifically to a receptor site of another molecule
