B2 Cell transport systems Flashcards
Define diffusion?
The movement of a substance from a high concentration to a lower concentration
Give two differences between active transport and facilitated diffusion.
Active transport requires energy/ATP whereas facilitated diffusion is passive. Active transport moves substances against the concentration gradient whereas facilitated diffusion moves substances down the concentration gradient.
Give a similarity between active transport and facilitated diffusion.
Both use carrier proteins.
Which type of molecule can diffuse across the phospholipid bilayer?
Non-polar or lipid soluble molecules.
Through what structure do water soluble molecules cross the membrane?
Through channel proteins/aquaporins
Which part of the phospholipid is hydrophobic?
Fatty acid tail.
Protein molecules found on the surface of the membrane are called …
Extrinsic proteins
Give 2 differences between a triglyceride and a phospholipid.
Phospholipids contain a phosphate group whereas triglycerides do not.
Phospholipids have 2 fatty acids whereas triglycerides have 3 fatty acids.
What is the function of the carbohydrates found on the outer surface of the membrane?
Antigens
Each carrier protein can transport …. type of molecule.
One
Name the two carbohydrate containing chemicals found in cell membranes.
Glycoproteins and glycolipid.
What effect does cholesterol have on the fluidity of the membrane?
Reduces the fluidity/movement of phospholipids in the membrane.
How can the structure of the membrane be changed to make the diffusion of water soluble molecules more rapid?
Increase number of channel proteins Increase surface area.
Give three ways in which the rate of gas exchange can be increased.
Increase the surface area.
Increase the concentration gradient.
Decrease the diffusion pathway/distance Increase the temperature
Why is the term fluid mosaic used to describe the model for membrane structure?
Fluid - phospholipid move within the membrane.
Mosaic - proteins form blocks on the surface of the membrane.
Define osmosis
Net movement of water from a high water potential to a lower water potential through a selectively/partially permeable membrane.
Name a chemical that moves by osmosis into cells.
Water
Name 2 molecules that move into cells and are used in respiration.
Oxygen and glucose
What happens to ATP during active transport?
It is hydrolysed.
A phosphate group is removed. Allowing the release of a small amount of energy.
Name the components of a cell surface membrane
Phospholipids
Proteins (extrinsic and intrinsic)
Glycoproteins
Glycolipids
Cholesterol
What are the functions of the phospholipids in the cell membrane
Allow non-polar molecules cross the membrane
Prevent polar molecules crossing the membrane
Makes membrane flexible and self healing
What are the functions of proteins in the cell membrane?
Provide structural support
Act as channels to transport polar molecules/facilitated diffusion
What is the function of cholesterol in the cell surface membrane?
Reduces lateral movement of molecules in the membrane
Acts as a buffer against temperature changes
Prevent leakage of water and dissolved ions from the cell
What are the functions of glycoproteins in the cell surface membrane?
Act as recognition sites for hormones and neurotransmitters
Help cells attach and form tissues
