Cell Membranes & Transport Flashcards
(31 cards)
What are the components of the plasma membrane?
•Intracellular Proteins
•Extracellular Proteins
•Cholesterol
•Glycoproteins
•Phospholipids
Describe the fluid mosaic model.
All cells and organelles are surrounded by a partially permeable cell membrane composed of phospholipids and protein molecules. The phospholipids are fluid as each molecule can move in relation to the others within the membrane. The proteins form a mosaic pattern within the phospholipid bilayer
Who created the fluid mosaic model?
Singer and Nicholson in 1972
What are intrinsic proteins?
Proteins found within the phospholipid bilayer: channel and carrier proteins that take part in faciliated diffusion. They have polar and non-polar regions; which correspond with hydrophilic and hydrophobic regions of the bilayer.
what are the functions of Intrinsic proteins?
•Structural support
•Form ion channels to enable active transport.
•Carry water soluble molecules across the membrane.
What are extrinsic proteins?
Proteins found at the edges of the phospholipid membrane. They are charged (polar) and associate with the hydrophilic heads of the phospholipids. Many are receptor sites and bind with proteins such as hormones or neurotransmitters.
what are the functions of extrinsic proteins?
•Receptors
•Acts as antigens, enabling cell recognition
•Helps cells adhere to each other.
What is the glycocalyx?
A glycoprotein and glycolipid coating surrounding some cell membranes.
What factors affect the permeability of the plasma membrane.
•Temperature
•Organic Solvents
•pH
Describe and explain how temperature affect the plasma membrane.
As the temperature increases, the phospholipids gain kinetic energy causing them to vibrate creating gaps in the cell membrane. Thus increasing the fluidity and permeability of the membrane. After optimum temperature is reached the proteins within the cell membrane denature allowing betalain pigments to diffuse out of the cells more readily.
Describe and explain how sodium chloride concentration affects the plasma membrane.
Sodium (Na+) ions attach to the oxygen atoms on the phosphate heads of the phospholipid bilayer, reducing the fluidity of the phospholipid molecules and so less betalain is released as membrane permeability decreases.
Describe and explain how organic solvents affect the plasma membrane.
Organic solvents such as ethanol dissolve phospholipids, disrupting the cell. Thus the higher the concentration of organic solvents, the more permeable the cell membrane becomes.
Define diffusion
Diffusion is a passive process involving the movement of molecules or ions from a region where they are in high concentration to a region of lower concentration, down a concentration gradient.
What factors affect the rate of diffusion
•Temperature
•Size of molecule
•length of diffusion path
•surface area
•concentration
Define osmosis
Osmosis is a passive process involving, the passage of water from a region of higher water potential to a region of
lower water potential, through a partially permeable membrane.
What is water potential?
The tendency of water molecules to move from one area to another area.
What is incipient plasmolysis?
In isotonic solutions plant cells become flaccid as the water potential is the same as the solute potential. The cell membrane partially pulls away from the cell wall making it neither plasmolysed nor turgid.
Define facilitated diffusion
The diffusion of polar molecules (ions + water soluble molecules) across a phospholipid bilayer requiring intrinsic proteins.
Define active transport
Active transport is an ATP requiring process in which ions and molecules are moved from an area of low concentration to an area of high concentration, against a concentration gradient.
How does cyanide affect active transport?
Cyanide is an respiratory inhibitor meaning it stops the production of ATP and thus prevents active transport.
Define endocytosis
The bulk uptake of large molecules into a cell by being engulfed into a vesicle.
Define exocytosis
The process in which molecules leave the cell via secretory vesicles that merge with the cell membrane releasing its contents outside the cell.
What is phagocytosis?
The bulk uptake of solids into the cell requiring ATP.
What is pinocytosis?
The bulk uptake of liquid into the cell requiring ATP.
