Cell Membrane (Chapter 4)

Question 1

THE ROLE OF TRANSPORT PROTEINS/CARRIER PROTEINS

Answer 1

• This allows movement of ion and small water soluble molecules (Polar substances/hydrophilic molecules) to pass through the membrane, by the process of facilitated diffusion or active transport

Question 2

THE FUNCTION OF CARBOHYDRATE/PROTEIN RECEPTORS

Answer 2

• Help with cell recognition
• forms hydrogen bonds with water to stabilize the membrane structure
• The receptor is the recognition site, where is recognizes signals and other cells
• It also acts as a binding site. E.g. for signals to attach to and pass through to the membrane

Question 3

THE FUNCTION OF PHOSPHOLIPID BILAYER

Answer 3

• It acts as a barrier for water soluble/polar/hydrophilic molecules/ions
• It allows the passage of lipid soluble/hydrophobic/non-polar molecules.
• The structure of the fatty acid tails help to maintain the fluidity of the cell membrane

Question 4

FUNCTION OF CHOLESTEROL

Answer 4

• Helps to maintain/regulate the fluidity of the cell membrane
• Restricts movement of phospholipids
• Acts as a storage
• Influences permeability of membrane

Question 5

MEMBRANES SUCH AS THE CELL SURFACE MEMBRANE, ARE DESCRIBED AS HAVING A FLUID MOSAIC STRUCTURE.
EXPLAIN WHAT IS MEANT BY RHE TERM FLUID MOSIC.

Answer 5

• Fluid: indicating that phospholipid and protein molecules move about
• Mosaic: Indicating that different protein molecules are interspersed/ scattered/ not in a complete layer.

Question 6

IMPORTANCE OF CELL SURFACE MEMBRANE TO CELLS

Answer 6

• It acts as a barrier from the external environment
• It controls the substances that enter and exit the cell
• It enables recognition of self (antigens)/ cell recognition.
• Allows binding of signal molecules
• cell to cell adhesion

Question 7

THE STRUCTURE OF A CELL MEMBRANE

Answer 7

There is a phospholipid bilayer
The phospholipids have a hydrophilic Glycerol head and hydrophobic tails of fatty acids
They have different types of proteins scattered. Proteins such as glycoproteins (which are proteins with protein receptors on it). And most proteins are not in a fixed position.
They also have glycolipids (which are lipids with protein receptors on it)
They have cholesterol.
They also have carrier protein/transport proteins

Question 8

THE FUNCTION OF GLYCOPROTEINS

Answer 8

• Glycoproteins have receptors for hormones and neurotransmitters (e.g. insulin)
• They help to stabilize membrane structure and form hydrogen bonds with water molecules
• cell recognition/ adhesion, cell surface markers

Question 9

THE FUNCTION OF CARRIER PROTEINS

Answer 9

Allow hydrophilic molecules pass through the membrane by either active transport by using Atp energy to move the molecules against the concentration gradient or by using facilitated diffusion.

Question 10

WHAT A LYSOSOMES

Answer 10

Lysosomes contain digestives enzymes which digest bacteria/pathogen