Unit 1 (1.3) Flashcards
Cell membranes and transport
What are the principle components of the plasma membrane?
Intracellular and extracellular proteins
Glycoproteins
Phospholipids
Cholesterol
What is the fluid-mosaic model 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.
Functions of intrinsic proteins
Structural support
Carry water-soluble molecules across phospholipid bilayer
Form ion channels to enable active transport
What are extrinsic proteins?
Proteins found at the edges of the phospholipid bilayer
Functions of extrinsic proteins
Receptors
Act as antigens, enabling cell recognition
Help adhere cells to each other
Factors affecting permeability of the plasma membrane
Temperature
Organic solvents
pH
How does temperature affect the permeability of the plasma membrane?
As the temperature increases, the phospholipids have more kinetic energy and move more, increasing the fluidity and permeability of the plasma membrane
So what happens when the temperature becomes too high?
The cell will break down completely
Channel and carrier proteins will become denatured, affecting membrane permeability
How do organic solvents affect the permeability of the plasma membrane?
Organic solvents dissolve membranes, disrupting cells. This increases the fluidity and permeability of the plasma membrane
What is diffusion?
The passive movement of small non-polar molecules from an area of high concentration to an area of low concentration.
Factors affecting rate of diffusion
Temperature
Size of a molecule
Surface area
Steepness of concentration gradient
Diffusion distance
What is osmosis?
The passive diffusion of water molecules from a region of high water potential to a region of lower water potential (down water potential gradient) through a selectively permeable membrane
What is water potential
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
What is facilitated diffusion?
The net movement of substances from a high concentration to a lower concentration (down gradient) through transport proteins without the use of energy. An example is Co-transport
What is active transport?
The movement of substances from a low concentration to a high concentration (against 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 production of ATP. This prevents active transport.
What are the two mechanism of bulk transport?
Endocytosis and Exocytosis
What is endocytosis?
The bulk uptake of substances into a cell by invagination of the membrane to form a vesicle. Using energy in the form of ATP
What are the two types of endocytosis
Phagocytosis
Pinocytosis
What is phagocytosis?
The bulk uptake of solids into the cell using energy in the form of ATP
What is pinocytosis?
The bulk uptake of liquids 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
