1.3 Cell Membranes and Transport Flashcards
what is the fluid mosaic model?
mosaic - the proteins are varied in shape and size and scattered throughout the lipid bilayer like a mosaic
fluid - the components are free to move along the membrane as in fluid
What are the principle components of
the plasma membrane?
● Intracellular and extracellular proteins
● Glycoproteins
● Phospholipids
● Cholesterol
what is the role of the cell surface membrane?
- boundary between living cell content and non-living surroundings
- controls the exchange of nutrients, respiratory gases and toxins
role of extrinsic proteins?
● Receptors for hormones
● Act as antigens, enabling cell recognition
● Help cells adhere to each othe
role of intrinsic proteins?
● Structural support
● Carry water-soluble molecules across the
phospholipid bilayer
● Form ion channels to enable active transport
where are extrinsic proteins found?
embedded on the surface
where are intrinsic proteins found?
they span the full width of the membrane
describe the charges on the proteins
charged groups associates with polar hydrophilic heads
uncharged regions associate with inner hydrophobic tails
what is the role of carrier proteins?
- receptors for hormones
cell recognition and signalling - antigens
- stabilize cell shape
what is the role of cholesterol? (form of lipid)
gives stability and regulates the fluidity of the membrane
what factors affect the permeability of the plasma membrane?
- temperature
- pH
- Ethanol
how does high temperature affect permeability?
high temp denatures proteins and melts the bilayer, which becomes more fluid so it increases the permeability
Freezing temps cause ice crystals which disrupt the membrane and increase permeability
how does pH affect permeability?
extremes denature proteins so movement of molecules is affected
how does ethanol affect permeability?
lipid soluble, so it can diffuse through the bilayer and dissolve it. denatures proteins
makes membranes porous= increases permeability
who proposed the fluid mosaic model?
singer and nicholson
what is the function of the phospholipid bilayer
to allow small (co2+o2) and non-polar vitamins to pass through
what does the term lipid bilayer mean?
two layers of phospholipids
name the hydrophobic parts
fatty acid tails
state two roles of the plasma membrane
obtain oxygen and glucose
removes co2
what is passive transport?
transport that does not need energy
what is active transport?
transport that needs energy (ATP)
what is diffusion?
passive movement of molecules from a region of relative high conc to one of relative low conc
how does being small help molecules move?
higher kinetic energy molecules can pass between the phospholipid layer
what is facilitated diffusion?
type of passive transport that allows substances to cross membranes with the assistance of special transport proteins
what is the role of ion channels?
allows specific ions to pass through the protein channel
what cannot pass through the membrane?
glucose, sodium ions, chloride ions
what is the width of the plasma membrane?
7-8nm
what is the role of cholesterol
regulates the fluidity of the membrane
what is the role of carrier proteins?
bind to specific molecules - must be complementary
what is a glycocalyx ?
A glycoprotein and glycolipid coating
surrounding the cell membrane of some
cells.
State the factors that affect the rate of
diffusion.
● Temperature
● Steepness of concentration gradient
● Size of molecule
● Diffusion distance
● Surface area
State the factors that affect the rate of
diffusion.
● Temperature
● Steepness of concentration gradient
● Size of molecule
● Diffusion distance
● Surface area
define water potential?
A measure of the tendency of water
molecules to move from one area to
another.
example of facilitated diffusion?
co-transport
define active transport?
The movement of substances from a low
concentration to a higher concentration
(against the concentration gradient) through
carrier proteins with the use of energy in
the form of ATP
How does cyanide affect active transport?
Cyanide inhibits cytochrome oxidase,
stopping the production of ATP. This
prevents active transport.
What are the two mechanisms of bulk
transport?
endocytosis
exocytosis
define endocytosis?
The bulk uptake of substances into a cell
by invagination of the membrane to form a
vesicle. Uses energy in the form of ATP
State the two types of endocytosis
phagocytosis
pinocytosis
What is pinocytosis?
The bulk uptake of liquids into the cell
using energy in the form of ATP
What is phagocytosis?
The bulk uptake of solids into the cell
using energy in the form of ATP.
Define exocytosis
The bulk transport of substances out of a
cell via a vesicle that fuses with the
plasma membrane. Uses energy in the
form of ATP.
