Booklet 1 - Plasma Membrane

Question 1

Phospholipid bilayer

Answer 1

Consists of a hydrophilic head and a hydrophobic tail consisting of two fatty acid chains

Question 2

Transport proteins (passive transport)

Answer 2

Allows some substances, such as ions, to move through the membrane by facilitated diffusion
There are 2 types of transport proteins for this purpose: channel proteins and carrier proteins
Can become saturated

Question 3

Transport proteins

Answer 3

A gated protein channel that opens to transport a specific molecule in response to contact with another molecule, such as a hormone

Question 4

Plasma membrane

Answer 4

Binds all living cells, acts as a barrier between the internal and external environment, controls what substances enter and leave the cell

Question 5

Transport proteins (active transport)

Answer 5

Protein pump is involved in active transport and requires the input of ATP.
These proteins sometimes are referred as carrier proteins.

Question 6

Catalytic proteins

Answer 6

Enzymes speed up the rate of chemical reactions occurring across the membrane

Question 7

Receptor proteins

Answer 7

Hormones & other substances bind to them affecting the cell’s activities. Different types of cells have different receptor proteins.
e.g. glycoproteins

Question 8

Recognition proteins

Answer 8

Act as markers called ‘antigens’, which enable the immune system to recognize ‘self’ cells from ‘non-self’ cells, e.g. glycoproteins.

Question 9

Adhesion proteins

Answer 9

Join cells together in multi-cellular organisms. Includes; occluding, communicating and anchoring junctions.

Question 10

Cytoskeleton proteins

Answer 10

Anchor the cytoskeleton to the membrane

Question 11

Cholesterol

Answer 11

Steroid lipid, amphipathic, embedded within the phospholipid bilayer, regulates membrane consistency, maintains firmness stability and fluidity, reduces permeability to some solutes

Question 12

Glycolipids

Answer 12

Found on the plasma membrane, play a role in tissue recognition

Question 13

Glycoproteins

Answer 13

Found on outer plasma membrane, function as cell surface markers, also known as antigens

Question 14

Simple diffusion

Answer 14

Simple diffusion is the net movement of a substance (molecule or ions) across the phospholipid bilayer from a region of high concentration to a region of low concentration of that substance.

Question 15

Osmosis

Answer 15

Osmosis is the net movement of water from a low solute concentration (hypotonic) to a high solute concentration (hypertonic) across a selectively permeable membrane

Question 16

Hypotonic

Answer 16

Hypotonic refers to a solution with a low concentration of solutes compared to the solute concentration inside a cell.
There will be a net movement of water into the cell from surrounding solution.

Question 17

Hypertonic

Answer 17

Hypertonic refers to a solution with a high concentration of solutes compared to the solute concentration inside a cell.
There will be a net movement of water out of the cell into surrounding solution.

Question 18

Isotonic

Answer 18

When the surrounding fluid is of equal concentration to the solution inside the cell, it is said to be isotonic.
There will be no net movement of water (water will diffuse equally in both directions).

Question 19

Osmotic pressure

Answer 19

Pressure caused within turgid cells

Question 20

Turgid

Answer 20

Swollen

Question 21

Crenated

Answer 21

Shrunken

Question 22

Haemolysis

Answer 22

Swelling and bursting within animal cells

Question 23

Facilitated diffusion

Answer 23

Use channel proteins and carrier proteins to transport charged particles and larger molecules passively across the plasma membrane

Question 24

Carrier proteins

Answer 24

Carrier proteins combine with the molecule or ion and carry it across the membrane.
Once the molecule has bound to the protein, the protein changes shape and releases its content to the inside of the membrane. (or to the outside)

Question 25

Channel proteins

Answer 25

Channel proteins are channels, which open and close to allow specific water-soluble molecules and ions through

Question 26

Active transport

Answer 26

Active transport is the movement of molecules or ions from a region of low concentration to a region of high concentration.

Question 27

Exocytosis (bulk transport)

Answer 27

Substances are actively transported out of the cell by moving them in small vacuoles called vesicles.
The membrane of vesicles are filled with secretions that are not permeable in the membrane. E.g. digestive enzymes, hormones, wastes and carbohydrates.
The vesicle membrane fuses with the plasma membrane, releasing the content to the outside of the cell.
Requires energy (ATP)

Question 28

Endocytosis

Answer 28

Substances are actively transported into the cell.
Requires energy (ATP).

Question 29

Factors affecting diffusion

Answer 29

Size of the particle (molecular weight)
Temperature
Concentration difference
Diffusion distance
Surface area
Permeability

Question 30

Factors affecting active transport

Answer 30

Number and type of carrier proteins and protein pumps per unit area
Surface area
ATP availability
Temperature
pH

Question 31

Other factors affecting the membrane

Answer 31

pH
Molecules that disrupt the lipid layer
Electrical gradient
Temperature

Question 32

Ribosomes

Answer 32

• Smallest organelle composed of rRNA and protein
• It is not surrounded by a membrane therefore can be seen in both prokaryotic and eukaryotic cells
• Site of protein synthesis
• Each cell contains thousands
• Composes 25% of cell’s mass
• Stationary type: embedded in rough endoplasmic reticulum
• Mobile type: injects proteins directly into cytoplasm

Question 33

Golgi apparatus

Answer 33

• Proteins are modified
• Packaging of molecules, e.g. proteins
• A membrane structure found near nucleus
• Composed of numerous layers forming a sac
• Molecules are packaged in vesicles
• Abundant in cells that export cell products

Question 34

Excretory vesicles

Answer 34

• Proteins are packaged into excretory vesicles.
• Vesicles break free from the golgi apparatus.
• Vesicles move to and merge with the plasma membrane
• Proteins are removed from cell by exocytosis