Cell membranes and transport

Question 1

What makes up the phospholipid bilayer (base of plasma membrane)?

Answer 1

Phospholipids, with hydrophilic phosphate heads and hydrophobic fatty acid tails, that are facing each other with the fatty acid tails

Question 2

How thick is the plasma membrane?

Answer 2

7-8nm thick

Question 3

Functions of cell membrane?

Answer 3

-Separates cell membrane from outside environment
-Regulates transport of nutrients into and out of cell
-They are receptor sites
-Recognition of pathogens

Question 4

Functions of internal membranes?

Answer 4

-Separation of cell components
-Holding components for metabolic processes in place
-Chemical reactions e.g. ATP synthase in mitochondria

Question 5

Why is the cell membrane considered a “fluid mosaic” model

Answer 5

The components are free to move with respect to each other

Question 6

What does a cell membrane look like underneath an electron microscope?

Answer 6

Double line

Question 7

Draw out a diagram of a plasma/ cell membrane (same thing)

Question 8

Position in membrane and role for intrinsic proteins?

Answer 8

Across the membrane, provide structural support, used for facilitated diffusion

Question 9

Two types of intrinsic proteins and roles?

Answer 9

Carrier proteins- Active transport (ATP required) or diffusion of
large polar molecules by molecule attaching to its a binding site and changing the shape, returning back to og after (similar to enzyme)
Channel proteins- Molecule with pores lined with polar groups that a specific to let one type of molecule through, smaller water-soluble molecules. They open and close

Question 10

What is the role of glycoproteins and glycolipids in the cell membrane?

Answer 10

Cell-to-cell communication and recognition, hormone receptor

Question 11

What is a glycocalyx?

Answer 11

Carbohydrate layer around membrane

Question 12

What is the role of cholesterol in membrane?

Answer 12

Provides fluidity to membrane by fitting in between the fatty acid tails

Question 13

Is the cell membrane permeable or not?

Answer 13

It is selectively permeable

Question 14

What does heat do to membrane and rate of diffusion?

Answer 14

More kinetic energy, more fluidity, more permeable for e.g. pigments, more diffusion

Question 15

What does a larger SA and concentration gradient (difference in concentrations) do to rate of diffusion?

Answer 15

High rate of diffusion

Question 16

Thicker membrane means what to rate of diffusion?

Answer 16

Slower rate as greater diffusion distance

Question 17

Rate of diffusion equation

Answer 17

SA times difference n concentration divided by length in diffusion path

Question 18

What does the size and lipid solublitiy do to the rate of diffusion

Answer 18

Smaller= faster rate
More lipid soluble = faster rate

Question 19

High no. of protein channels does what to rate of diffusion?

Answer 19

High rate

Question 20

Definition of diffusion?

Answer 20

Movement of molecules from an area of high to low concentration down a concentration gradient

Question 21

Definition of water potential and its symbol?

Answer 21

Tendency for water to move out of a solution via osmosis
psi

Question 22

What has the highest water potential?

Answer 22

Pure water, which has 0

Question 23

Does -523 kPa solution or -83kPa have a bigger water potential?

Answer 23

-83kPa as

Question 24

Definition of osmosis?

Answer 24

Form of diffusion in which the water molecules move down the water potential gradient through a selectively permeable membrane

Question 25

Definition of facilitated diffusion

Answer 25

Diffusion of molecules or ions across membrane by protein carriers (passive process)

Question 26

How does active transport happen across a membrane?

Answer 26

-Molecule binds to specific carrier protein (think enzymes), on the outside of membrane -ATP transfers phosphate group to carrier protein inside of membrane (energy supplied) -Carrier changes shape and molecule is carried through -Molecule and phosphate group released, ADP into ATP -Protein back to og shape

Question 27

Definition of active transport

Answer 27

Movement of molecules from an area of low conc. to high conc. against the conc. gradient

Question 28

If a respiratory inhibitor is present, e.g. cyanide, what would happen to active transport and why?

Answer 28

Respiratory inhibitors prevent aerobic respiration and production of ATP, no ATP = no active transport **this also means that more oxygen in cells = more ATP and more active transport

Question 29

What is cotransport and describe process?

Answer 29

Facilitated diffusion which brings two substance across the cell membrane together into a cell e.g. glucose and sodium ions -Both bind outside to carrier protein -Carrier changes shape, glucose and sodium separately diffuse (glucose asses by facilitated diffusion, sodium is carried out of cell by active transport while potassium ions move into the cell)

Question 30

In what type of channel proteins does water move through?

Answer 30

Aquaporin (think aqua cause water, pore cause channel proteins have polar pores)

Question 31

If there is a higher concentration of solute (therefore a low concentration of water molecules) on one side of membrane then the other, would water molecules go into or out of the cell?

Answer 31

Into the cell as water goes to areas of higher solute concentration through osmosis down a concentration gradient (think that the water is trying to equalise the concentrations)

Question 32

What is a hypertonic solution?

Answer 32

A solution what has a lower water potential compared to the cell cytoplasm. It has more solutes

Question 33

What is a hypotonic solution?

Answer 33

A solution what has a higher water potential compared to the cell cytoplasm. It has less solutes

Question 34

What is an isotonic solution

Answer 34

A solution what has a equal water potential compared to the cell cytoplasm. It has same concentration of solutes

Question 35

Equation for water potential

Answer 35

Pressure potential (always positive) + solute potential (always negative)

Question 36

More solutes = what to water potential?

Answer 36

Lower water potential

Question 37

What happens to an animal cell in hypertonic, hypotonic and isotonic solution?

Answer 37

Hyper- Animal cell is **crenate** (water moves out of cell) Hypo- Cell bursts (lysis) Iso- Normal as water leaves and enters at same rate

Question 38

What happens to a plant cell in hypertonic, hypotonic and isotonic solution?

Answer 38

Hyper- Cell expands and becomes **turgid** (water goes into cell, pressure is pushed outwards on cell wall) Iso- Cell shows **incipient plasmolysis** (cell membrane moves away from cell wall) Hyper- Cell is plasmolysed and becomes willed

Question 39

What is the pressure potential of cell when its 50% plasmolysis

Answer 39

0 (as cell membrane is pulled away from wall), meaning water potential = solute potential

Question 40

What is endocytosis and the two types?

Answer 40

Active process (ATP) of bulk movement of substances into cell Phagocytosis- solids Pinocytosis- liquids

Question 41

Describe the process of phagocytosis and draw it out

Answer 41

-Receptor bind to antigen on bacterium -Membrane engulfs it and forms a phagosome (a spekil vesicle) and its absorbed by endocytosis -A lysosome fusses and secrets digestive enzymes into the phagosome forming a phagolysosome -Bacterium is digested and products are absorbed into cytoplasm