Chapter 4; Cell Membrane And Movement

Question 1

Describe six roles of cell membranes

Answer 1

Controls what enters and leaves a cell
Regulates fluidity
Cell adhesion
Cell recognition
Cell signaling
Enzymes to catalyse reactions

Question 2

Explain the roles of glycolipds and glyco protiens

Answer 2

-carb chain part can form h bonds with water and so stabilize membrane structure
-cell to cell adhesion
-cell recognition, so act as antigens to trigger immune response
-ONLY GLYCO PROTIENS, cell signalling molecules, so act as receptors for hormones eg like neurotransmitters to bind to them or for endocytosis
-some can act as enzymes to catalyse reactions
-for the cytoskeleton, attach to it to maintain the shape of the cell

Question 3

Why is it called a fluid mosaic model

Answer 3

Fluid
-phospholipids and protiens are able to move about their bi layers via diffusion
-phospholipids can move about its own onto layer, so eg polar heads can swap w polar heads
-protiens can move about in their bilayer

Mosaic, scattered pattern of proteins produced within bilayer looks like a mosaic

Question 4

Give examples of two types of transport proteins nd give general properties of these

Answer 4

Channel protein, facilitated diffusion, soluble eg glucose or water(aquaporim)
Carrier protein,facilitated diffusion and active transport, eg sodium potassium pump

-each protein is specific to a particular molecule or ion
-transport protiens control which substances enter or leave the cell

Question 5

What are carrier proteins, and give an example

Answer 5

Change shape to allow molecules to travel from one side to the other
And so protein constantly flips between both shapes.
Allows passive transport (vacillated diffusion) and active transport

Eg sodium potassium pump

Question 6

What are channel protiens and give an example

Answer 6

Channel is water filled and so lined with hydrophilic r groups on amino acids
To allow water soluble ions and molecules to pass through

Eg aquaporin allows water to pass through

Question 7

Where is cholesterol located and give three of its functions

Answer 7

Inbetween between phospholipid molecules, bc also has hydrophilic tails and hydrophobic heads

-regulates membrane guilty
-stabilizes membrane structure (by fitting between phospholipid molecules)
-blocks the passage of very small ions through the membrane

Question 8

Explain four factors affecting membrane fluidity

Answer 8

Ratio of saturated to unsaturated fatty acid tails.
-saturated pack tightly, more imf between them so less fluid
-unsaturated are bent and so form kinks, less tightly packed so more imf between them

Temperature,
Colder, less energy, move less freely, less fluid
Higher temper, more energy,more movement, more fluid

Phospholipid tail length
Longer, more surface area, so more integration between tails, less fluid
Shortedr, less surface area, less interaction between tails more fluid

Resence of a solvent,
More solvent more fluid

Question 9

Give an example of a non polar substances that can diffuse through membrane

Answer 9

Oxygen and carbon dioxide

Question 10

What two types of structures can phsoplipds form

Answer 10

Micelles, ball shaped
Bilayer, sheet

Question 11

Explain the process of cell signaling

Answer 11

-ligand is secreted from target cell into extracellular space
-tranported through extracellular space to target cell
-binds to receptors on target cell formed from glycoproteins and glycolipids, which are specific and complimentary to the ligand
-receptor changes shape when ligand binds to it
-stimulus carried through thr ligand is relayed through a chain of chemical messages inside the cell
-This triggers a response and this process is called transduction

Question 12

What is transduction

Answer 12

Process of converting a signal from one method of transmission to another

Question 13

What is a ligand and what are the types

Answer 13

A cell signalling molecule.
-water soluble ligand, can attach to receptors on the plasma membrane, eg adrenaline
-lipid soluble ligand, diffuse directly through the membrane and so bind to receptors eg in the nucleus, eg oestrogen

Question 14

What is the water potential of pure water, and what would it be for a olsution with lower water potential

Answer 14

0kpa,
For lower water potential, (so with more solutes dissolved in it it would be negative)

Question 15

Explain what is diffusion

Answer 15

The net movement of molecules as a result of the random motion of its molecules or ions.
form area of high concentration to low concentration
Down concentration gradient
Does not require atp

Question 16

State the 4 factors that affect rate of diffusion and explain one of these

Answer 16

Surface area
Temperature
Concentration gradient
-type of molecule.
(Smaller ones diffuse faster, bc reuire less energy to move them.
Non polar ones diffuse faster bc can diffuse directly through the membrane.

Question 17

What is simple diffusion, and which substances are transported in this way

Answer 17

Movement caused by natural kinetic energy of meocluels and continues to occur until equilibrium is reached.
Non polar and lipid soluble eg steroid.s

Question 18

What is facilaoted diffusion and what substances use faciliatted diffusion

Answer 18

Fissuion taht requires a transport protein so either channel or carrier protein.
Polar substances, eg glucose and amino acids.
Ions, eg sodium and chloride.

Question 19

What type of protiens des active transport use

Answer 19

Carrier proteins only. (No channel protiens).
And for carrier proteins in active transport they require energy produced from atp form respiration in order to change shape

Question 20

What is bulk transport and give three substances that can be transported this way

Answer 20

Movement of large quantities of materials.
-large molecules, parts of cells, whole cells like bacteria

Question 21

What are the two types of bulk transport

Answer 21

Exoxytosis, movement out of a cell
Enodutcois, movement into a cell

Question 22

Explain steps of exocytosis

Answer 22

1.substances to be released are packed into secretory vesicles by Golgi
-vesicles travel to cell surface membrane and fuse with it
-release its contents outside of the cell

Question 23

State the terms used for animal cells in osmosis. And terms used for plant cells

Answer 23

Animal cell water enters is called lysis
Animal cell water leaves is called shriveled

Plant cell water enters is called turgid, where protoplast pushes against cell wall
Leaves cell is called plasmolysed, where protiplast shrinks and p;ills away form cell wall