CELL MEMBRANES AND TRANSPORT

Question 1

Cell membranes

Answer 1

Controls what enters and leave the cell . Partially permeable . Made of proteins and phospholipids

Question 2

Phospholipids properties in a cell membrane

Answer 2

-can form bilayers with one sheet of phospholipids
- have hydrophilic heads and hydrophobic tails
-allows lipid soluble molecules across but not water soluble molecules

Question 3

Proteins are embedded through

Answer 3

The phospholipid bilayer they are embedded in two different ways . Extrinsic and intrinsic proteins.

Question 4

Extrinsic proteins

Answer 4

-on the surface of the bilayer
-provide structural support and form recognition sites by identifying cells and receptor sites

Question 5

Intrinsic proteins

Answer 5

-include transport proteins which use active or passive transport to move molecules and ions across cell membranes
-for example channel and carrier. Proteins

Question 6

Fluid mosaic model

Answer 6

Model of the structure of biological membranes in which proteins are studded through a phospholipid bilayer

Question 7

Cholesterol is

Answer 7

A mostly hydrophobic molecule that regulates membrane fluidity . And in animal cells sits between the phospholipid molecules making membrane stable at high temperatures

Question 8

Why is it called the fluid mosaic model of membrane structure

Answer 8

Fluid- individual phospholipid molecules can move within a layer with one another
-mosaic-the proteins embedded in the bilayer vary in shape and size and in their distribution (mosaic)

Question 9

Plant and animal cell membranes contain ………….

Answer 9

Glycoproteins ,glycolipids and sterols

Question 10

The permeability of a membrane differs due to

Answer 10

-ethanol
-heat
-Ph

Question 11

Water soluble substances cannot

Answer 11

Diffuse readily , they pas through intrinsic protein

Question 12

Diffusion

Answer 12

The passive movement of a molecule or ion down a concentration gradient from a region of higher concentration and lower concentration .

Question 13

Passive

Answer 13

Not requiring energy provided by the cell

Question 14

If ions and molecules are highly concentrated in

Answer 14

One area there will be a total movement away from that area

Question 15

Rate of diffusion is affected by

Answer 15

1.the concentration gradient -the greater the difference in concentration more molecules diffuse in a given time
2.the thickness of the exchange surface/distance of travel
3.the surface area o the membrane the larger the area the more molecules diffuse

Question 16

Rate of diffusion equation

Answer 16

Surface area x difference in concentration ➗length of the diffusion path

Question 17

Some other factors that can affect the rate of diffusion ;

Answer 17

1.the size of the diffusing molecule
2.the nature of the diffusing molecules
3. The temperature

Question 18

The rate of oxygen uptake increases the

Answer 18

Concentration gradient

Question 19

Facilitated diffusion

Answer 19

The passive transport of molecules or ions down a concentration gradient across a Chanel or a carrier protein

Question 20

Molecules such as glucose cannot pas though cell membrane because

Answer 20

They are insoluble in the phospholipid bilayer

Question 21

Water soluble molecules are

Answer 21

Repelled by the hydrophobic tails

Question 22

Channel proteins are proteins with

Answer 22

Pores lied with polar groups . The channels are hydrophobic water soluble ions can pass .

Question 23

channel proteins open and

Answer 23

Close acccording to the needs of the cells

Question 24

Carrier proteins allow

Answer 24

Diffusion of larger polar molecules .

Question 25

The carrier proteins attaches

Answer 25

To the binding site and the carrier protein changes shape and releases the molecule . It then changes back to its own shape

Question 26

Channel proteins contain ;

Answer 26

- a pore -allow diffusion and facilitated diffusion -allows for rapid transport

Question 27

Carrier proteins contain ; (3)

Answer 27

-contain no pores -allow diffusion. Facilitated diffusion and active transport -sower transport 10 to the power of 4 ions

Question 28

Active transport

Answer 28

The movement of molecules or ions across a membrane against a concentration gradient using the energy from the hydrolysis of ATP .

Question 29

Features of active transport

Answer 29

-ions and molecules moved from lower to a higher concentration -the process requires energy from ATP -anything affecting respiration will affect active transport -occurs through intrinsic carrier protein -rate of active transport determined by the availability of carrier proteins

Question 30

Examples of active transport in humans

Answer 30

- muscle contraction -nerve impulse transmission -mineral uptake in root hair cells

Question 31

Step to active transport

Answer 31

1. Molecule combines with carrier protein on the osteitis of cell 2. ATP transfers a phosphate group to he carrier protein 3. Carrier protein changes shape and carries the molecule 4. Molecule into cytoplasm 5. Phosphate ion releases back and recombines with ADP an ATP 6. Carrier protein returns to its original shape

Question 32

Cells performing Active transport

Answer 32

Are packed with mitochondria. As mitochondria provides energy from ATP

Question 33

The rate of uptake is reduced with

Answer 33

A respiratory inhibitor such as cyanide

Question 34

The higher the rate of

Answer 34

Respiration the higher the rate of active transport

Question 35

Co-transport

Answer 35

One type of facilitated diffusion that brings molecules and ions into cells together on the same transport protein

Question 36

Sodium glucose co-transport is significant in

Answer 36

Absorbing glucose and sodium ions across cell membranes into the blood in the ileum

Question 37

Osmosis

Answer 37

The net passive movement of water molecules across a partially permeable membrane from a region of higher water potential to a region of lower water potential . .

Question 38

Water potential

Answer 38

The tendency of water to move into a system .

Question 39

Water potential is decreased by

Answer 39

The addition of a solute

Question 40

Pure water has a water potential

Answer 40

Of zero 0 which is the highest value of water

Question 41

Solute potential

Answer 41

Is the magnitude for the solute to to decrease In water potential

Question 42

Solute potential measures

Answer 42

How easily for water molecules to move out of a solution

Question 43

Higher water potential =

Answer 43

Lower solute potential

Question 44

Water potential =

Answer 44

Pressure potential + solute potential

Question 45

Turgid

Answer 45

A plant cell that holds as much water as possible . Further entry of water is prevented s th cel wall cannot expand further

Question 46

Glycocalyx

Answer 46

A glycoproteins and glycolipid coating supporting the cell membrane of some cells

Question 47

How does temperature affect the permeability of the plasma membrane

Answer 47

As temperature increases the phospholipids make more kinetic energy and move more increasing the fluidity and permeability

Question 48

Isotonic

Answer 48

If the water potential is equal o that of the external and internal solution . “1m and 1m”. No net water movement

Question 49

Hypertonic

Answer 49

Is the water potential of the cell is lower than the water potential outside the cell. Cell starts to lose water TURGOR pressure decreases . Shrinks

Question 50

Hypotonic

Answer 50

If the water potential of the cell is higher than that of the external solution . Water will start to move into the cell . Exerts Turgor pressure and swells up .

Question 51

Plasmolysis

Answer 51

The drawing in of the cytoplasm and the cell membrane from the cell wall as it loses water by osmosis . TEARED UP

Question 52

Incipient plasmolysis

Answer 52

Cell membrane and cytoplasm are attached from the cell wall due to lack of water to make the cell turgid .

Question 53

Endocytosis

Answer 53

The bulk uptake of substances into a cell by invagination of the membrane to form a vesicle with the usage if energy from ATP

Question 54

Th two types of Endocytosis

Answer 54

1. Phagocytosis 2. Pinocytosis

Question 55

Phagocytosis

Answer 55

The engulfing of solid material such as pathogens via a vesicle

Question 56

Pinocytosis

Answer 56

The engulfing of fluids into the cell via a vesicle

Question 57

Exocytosis

Answer 57

The [process where substances may leave the cell via a vesicle using energy from AT P

Question 58

When bulk transport occurs

Answer 58

The cell membrane has to change shape requiring energy from ATP