Core Concepts (Cell Membranes and Transport) Flashcards
(26 cards)
What are the principle components of
the plasma membrane?
● Intracellular and extracellular proteins
● Glycoproteins
● Phospholipids
● Cholesterol
What is the fluid-mosaic model?
A model that describes membrane structure
as a ‘sea’ of mobile phospholipids studded
with various proteins.
What are intrinsic proteins?
Proteins found within the phospholipid
bilayer. Includes channel and carrier
proteins.
Outline the functions of intrinsic proteins
● Structural support
● Carry water-soluble molecules across the
phospholipid bilayer
● Form ion channels to enable active transport
What are extrinsic proteins?
Proteins found at the edges of the
phospholipid bilayer
Outline the functions of extrinsic
proteins.
● Receptors
● Act as antigens, enabling cell recognition
● Help cells adhere to each other
What is the glycocalyx?
A glycoprotein and glycolipid coating
surrounding the cell membrane of some
cells.
Name the factors affecting the
permeability of the plasma membrane.
● Temperature
● Organic solvents
● pH
How does temperature affect the
permeability of the plasma membrane?
As temperature increases, the phospholipids
have more kinetic energy and move more,
increasing the fluidity and permeability of the
plasma membrane.
What happens to the plasma membrane
if the temperature becomes too high?
● Channel and carrier proteins will become
denatured, affecting membrane permeability
● The cell will eventually break down completely
How do organic solvents affect the
permeability of plasma membranes?
Organic solvents dissolve membranes,
disrupting cells. This increases the fluidity
and permeability of the plasma membrane.
Define diffusion
The passive movement of small non-polar,
lipid-soluble molecules from an area of high
concentration to an area of low
concentration.
State the factors that affect the rate of
diffusion.
● Temperature
● Steepness of concentration gradient
● Size of molecule
● Diffusion distance
● Surface area
Define osmosis
The passive diffusion of water molecules from a
region of high water potential to a region of lower
water potential (down a water potential gradient)
through a selectively permeable membrane
What is water potential (Ψ)?
A measure of the tendency of water
molecules to move from one area to
another.
What is incipient plasmolysis?
● The effect produced by placing plant cells in an
isotonic solution
● Causes the cell membrane to pull away from the cell
wall in some areas
● The cell is neither plasmolysed nor turgid
Define facilitated diffusion
The net movement of substances from a high
concentration to a lower concentration (down
their concentration gradient) through transport
proteins without the use of energy.
Give an 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.
