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Biology Unit 1 ☁️ > 1.3 Cell membranes and transport > Flashcards

1.3 Cell membranes and transport Flashcards

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1
Q

what are the principle components of the plasma membrane?

A

Intracellular and extracellular proteins
glycoproteins
phospholipids
cholesterol

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2
Q

what is the fluid-mosaic model?

A

a model that describes membrane structure as a ‘sea’ of mobile phospholipids studded with various proteins

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3
Q

what are intrinsic proteins?

A

proteins found within phospholipid bilayer. includes channel and carrier proteins.

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4
Q

outline the functions of intrinsic proteins

A

structural support
carry water-soluble across phospholipid bilayer.
form ion channels to enable active transport.

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5
Q

what are extrinsic proteins?

A

proteins found at the edges of the phospholipid bilayer.

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6
Q

outline the functions of extrinsic proteins

A

receptors
act as antigens, enabling cell recognition
helps cells adhere to each other.

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7
Q

what is the glycocalyx?

A

a glycoprotein and glycolipid coating surrounding cell membrane of some cells.

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8
Q

name the factors affecting the permeability of the plasma membrane

A

temperature
organic solvents
pH

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9
Q

what happens to the plasma membrane if the temperature becomes too high?

A

channel and carrier proteins will become denatured, affecting membrane permeability
the cell will eventually break down completely.

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10
Q

how does temperature affect the permeability of the plasma membrane

A

as temperature increases, the phospholipids have more kinetic energy and move more, increasing the fluidity and permeability of the plasma membrane.

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11
Q

how do organic solvents affect the permeability of plasma membranes?

A

organic solvents dissolve membranes disrupting cells. This increases the fluidity and permeability of the plasma membrane.

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12
Q

define diffusion

A

the passive movement of non-polar lipid-soluble molecules from an area of high conc to an area of low conc

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13
Q

state the factors that affect the rate of diffusion

A

temperature
steepness of conc gradient
size of molecule
diffusion distance
surface area

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14
Q

define osmosis

A

the passive diffusion of water molecules from an area of high water concentration to an area of lower water concentration through a selectively permeable membrane

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15
Q

what is water potential?

A

a measure of the tendency of water molecules to move from one area to another

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16
Q

what is incipient plasmolysis?

A

the effect produced by placing plant cells in an isotonic solution

causes the cell membrane to pull away from the cell wall in some areas

the cell is neither plasmolysed nor turgid

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17
Q

define facilitated diffusion

A

the net movement of substance from a high concentration to a lower concentration through transport proteins without the use of energy

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18
Q

give an example of facilitated diffusion

A

co-transport

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19
Q

define active transport

A

the movement of substances from a low concentration to higher concentration through carrier proteins with the use of energy in the form of ATP.

20
Q

how does cyanide affect active transport?

A

cyanide inhibits cytochrome oxidase, stopping the production of ATP. this prevents active transport

21
Q

what are the two mechanisms of bulk transport?

A

endocytosis
exocytosis

22
Q

define endocytosis

A

the bulk uptake of substances into a cell by invagination of the membrane to form a vesicle. Uses energy in the form of ATP

23
Q

state the two types of endocytosis

A

phagocytosis
pinocytosis

24
Q

what is pinocytosis?

A

the bulk uptake of liquids into the cell using energy in the form of ATP

25
Q

what is phagocytosis?

A

the bulk uptake of solids into the cell using energy in the form of ATP

26
Q

define exocytosis (secretion)

A

the bulk transport of substances out of a cell via a vesicle that fuses with the plasma membrane. Uses energy in the form of ATP.

27
Q

name 3 factors that affect the permeability of a cell membrane

A

Heat
Ethanol
pH

28
Q

What is the function of calibration curves?

A

To determine an unknown concentration using a series of standard samples.

29
Q

State the definition of water potential.

A

The tendency of water to move from an area of high water potential to an area of low water potential.

30
Q

What is water potential determined by?

A

The concentration of solutes.

31
Q

Why is the percentage change in mass calculated instead of the actual change?

A

The potato discs may not have the same starting masses. Using percentage change allows comparison between different discs.

32
Q

What are the controlled variables of this practical?

A

Volume of sucrose solution
Size of potato chips
Length of time left in solution
Dab each potato disc with paper towels

33
Q

How is a calibration curve used to find the concentration of plant tissue?

A

Plot a calibration curve of percentage change in mass against concentration.
Find the x-intercept where the plant tissue is isotonic to the sucrose solution.

34
Q

What occurs when plant tissue is placed in a hypotonic solution?

A

Water moves into the plant tissue by osmosis, plant tissue increases in mass.

35
Q

What occurs when plant tissue is placed in a hypertonic solution?

A

Water moves out of the plant tissue by osmosis, plant tissue decreases in mass.

36
Q

Why are the potato discs left in the solution for 20 minutes?

A

To allow time for osmosis until the plant tissue reaches equilibrium with its surrounding solution.

37
Q

What is plasmolysis?

A

Where the protoplasm of the plant cell begins to shrink away from the cell wall.

38
Q

What is incipient plasmolysis?

A

Where the water potential of the cytoplasm is the same as the solution.
The point at which plasmolysis just begins to occur.
When 50% of cells in a tissue are plasmolysed.

39
Q

Why are the plant cells left in the mineral salt solution for 20 minutes before observation?

A

To allow time for osmosis to reach equilibrium.

40
Q

Outline the procedure to this practical.

A
  1. Transfer a small set volume of each mineral salt solution into a watch glass. Place one of the sections of plant tissue into the watch glass and leave for 20 minutes.
  2. Remove each section using forceps. Mount in a drop of the corresponding solution on a microscope slide and cover with a coverslip.
  3. Observe 25 cells and record how many are plasmolysed
41
Q

State 2 factors that affect the permeability of cell membranes.

A

Temperature
Concentration of solvents (ethanol)

42
Q

How is beetroot used to measure the permeability of cell membranes?

A

The higher the permeability, the more red pigment that leaks out into the surrounding solution within a given time. A colorimeter can be used to determine the absorbance, hence concentration of pigment.

43
Q

Outline the procedure to investigate the effect of temperature on the permeability of the cell membrane.

A
  1. Cut beetroot into 8 identical cubes with a scalpel.
  2. Place each cube in a different test tube with equal volumes of distilled water.
  3. Place each test tube into water baths ranging from 30-80°C.
    Leave for 20 minutes.
  4. Filter each solution out into a cuvette and measure the absorbance using a colorimeter.
44
Q

What are the safety hazards involved in testing the effect of ethanol concentration on membrane permeability?

A

Ethanol is an irritant and is flammable, keep away from naked flames, wear eye protection.
Keep sharp scalpel away from fingers.
Handle hot liquid and equipment with care.

45
Q

What is the effect of temperature on membrane permeability?

A

Increasing temperature results in increased membrane permeability, as high temperatures denatures the membrane proteins.

This creates gaps in the membrane for molecules to pass through.

Increasing temperature also increases the kinetic energy of phospholipids so they move more, increasing the permeability.

46
Q

What is the exception to the general trend of increasing temperature and membrane permeability?

A

At temperatures below 0°C, ice crystals form and pierce the membrane, forming holes for substances to leak out.

47
Q

What is the effect of ethanol concentration on membrane permeability?

A

Increasing ethanol concentration leads to increased membrane permeability, as ethanol ruptures the membrane to form gaps more molecules to pass through.

Biology Unit 1 ☁️ (7 decks)

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