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Y3 Biology > CH2: Movement of Substances > Flashcards

CH2: Movement of Substances Flashcards

1
Q

What are biological membranes made of?

A

Proteins, carbohydrates and phospholipids

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2
Q

What are biological membranes, plasma membranes and cell membranes?

A

Biological membrane: all membranes found in living cells.

Plasma membrane: membrane surrounding the cytoplasm of the cell

Cell membrane: membrane surrounding any membrane-bound organelle in the cell.

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3
Q

Describe the function of biological membranes (plasma membrane and cell membrane).

A

Plasma membrane separates the organelles in the cytoplasm from its external environment

Cell membrane forms COMPARTMENTS in the cell.

Both regulate the movement of substances n and out of the cell.

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4
Q

How does the fluid mosaic model describe the structure of a plasma membrane.

A

The plasma membrane is FLUID in that phospholipids and proteins are NOT STATIONARY but can MOVE across the surface of the membrane.

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5
Q

What are phospholipids?

A

Phospholipids are a group of compound lipids that contain
- 2 hydrocarbon tails
- 1 phosphate group

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6
Q

Define ‘hydrophobic’

A

insoluble in water

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7
Q

Define ‘hydrophilic’

A

soluble in water

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8
Q

Why do phospholipids have both hydrophobic and hydrophilic components?

A

The phosphate head is hydrophilic and attracted to the water molecules.

The hydrocarbon tails are hydrophobic and repelled by water molecules.

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9
Q

In a phospholipid bilayer, which way do the hydrophilic heads and hydrophobic tails face?

A

hydrophilic heads > aqueous environment

hydrophobic tails > inside the bilayer

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10
Q

Substances that have both hydrophobic and hydrophilic properties are described as?

A

Amphiphilic

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11
Q

What molecules CAN pass through the phospholipid bilayer?

A

Small, uncharged, hydrophobic molecules

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12
Q

What are the 2 major populations of membrane proteins?

A

Intergal proteins
Peripheral proteins

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13
Q

Where are intergal proteins found?

A
  • embedded in the phospholipid bilayer
  • held in place via strong hydrophobic and hydrophilic interactions with the phospholipids.
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14
Q

Where are peripheral proteins found?

A
  • attached to the surface of the membrane
  • easily dislodged from the membrane by gentle extraction procedures.
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15
Q

Function of channel proteins.

A
  • span across the membrane
  • provide hydrophilic channels for ions or hydrophilic molecules to enter or leave the cell
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16
Q

Function of carrier proteins.

A

Changes the shape of substances to transport them across the membrane by temporarily binding to them

Hydrolyses ATP as an energy source to actively pump substances across the membrane.

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17
Q

Types of cellular transport?

A
  1. Passive transport
  2. Active transport
  3. Bulk transport
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18
Q

Passive transport processes include?

A
  1. Simple diffusion
  2. Facilitated diffusion
  3. Osmosis
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19
Q

What is simple diffusion?

A

The NET MOVEMENT of a particles from a region of HIGHER to LOWER CONCENTRATION, DOWN its concentration gradient until equilibrium is reached.

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20
Q

Simple diffusion only allows what kind of particles through pass through the plasma membrane?

A

Small, uncharged and hydrophobic particles.

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21
Q

Diffusion is caused by?

A

The CONSTANT RANDOM MOTION of all atoms and molecules due to the K.E they posses.

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22
Q

Define ‘concentration’

A

The quantity of a substance in a fixed volume.

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23
Q

Define ‘concentration gradient’

A

The difference in concentration of the same particles in two regions.

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24
Q

Steeper the concentration gradient
> (faster/slower) the rate of diffusion is.

A

Steeper > faster

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25
What factors affect the rate of diffusion?
1. concentration gradient 2. distance at which diffusion occurs 3. surface area to volume ratio 4. temperature 5. size of particle/particle mass
26
The shorter distance over which diffusion occurs, the ________ the rate of diffusion.
The SHORTER distance over which diffusion occurs, the GREATER the rate of diffusion.
27
The larger the surface area to vol. ratio, the _____ the rate of diffusion.
The LARGER the surface area to vol. ratio, the GREATER the rate of diffusion.
28
Explain the importance of the surface area to volume ratio in limiting cell size.
cell increases in size volume increases more than SA SA to volume ratio decreases rate of diffusion of substances across the membrane decrease + Cell size increases, metabolic wastes accumulate, overheating might occur
29
Smaller size of particles = ________ rate of diffusion
Smaller size of particles = GREATER rate of diffusion
30
Lower temperature = ______ rate of diffusion
lower temperature = LOWER rate of diffusion
31
Rate of diffusion is _____ in gas and _____ in solid.
Fastest in gas. Slowest in solid
32
How is simple diffusion important to living things?
Allows GAS EXCHANGE of oxygen and carbon dioxide to take place in the lungs. Allows NUTRIENTS (amino acids and glucose) to be ABSORBED into blood capillaries in the small intestine.
33
How do epithelial cells increase the SA-to-volume ratio of the cell membrane?
They have LONG NARROW FOLDS that increase the SA-to-volume ratio and increases the rate of absorption.
34
What is facilitated diffusion?
- diffusion of ions and hydrophilic molecules - across the cell membrane - using 2 types of transport proteins, channel and carrier proteins, - down a concentration gradient.
35
Why are ions unable to pass through the plasma membrane?
Ions are repelled by the hydrophobic hydrocarbon tails in the interior of the phospholipid bilayer.
36
Differences between facilitated and simple diffusion.
Simple diffusion: 1. small, uncharged, hydrophobic particles can pass through membrane. 2. Particles move freely Facilitated diffusion: 1. ions and hydrophilic particles can pass through membrane 2. involves channel and carrier proteins
37
What is osmosis?
The NET movement of WATER molecules from a region of HIGHER water potential to LOWER water potential, DOWN a water potential gradient, through a PARTIALLY PERMEABLE MEMBRANE
38
What is water potential?
The measure of the tendency of free water molecules to move from one region to another.
39
Factors that affect rate of osmosis.
1. water potential gradient 2. distance over which osmosis occurs 3. temperature 4. surface area to volume ratio
40
What happens to an animal cell when it is placed in a hypotonic solution?
WP is higher outside the cell. Water moves into the cell through the selectively-permeable plasma membrane through osmosis. The cell expands and undergoes lysis.
41
What happens to an animal cell when it is placed in a hypertonic solution?
WP is higher in the cell. Water moves out of the cell through the selectively-permeable plasma membrane through osmosis. The cell crenates/shrivelles.
42
What happens to a plant cell when it is placed in a hypotonic solution?
WP is higher in the solution outside the cell than the cell sap. Water moves into the cell through the selectively-permeable plasma membrane through osmosis. The vacuole swells and pushes the cytoplasm and plasma membrane against the cell wall. The inelastic cell wall prevents the cell from bursting. Instead the cell becomes turgid.
43
What happens to a plant cell when it is placed in a hypertonic solution?
WP is higher in the cell sap than the solution outside the cell. Water moves out of the cell through its selectively-permeable plasma membrane through osmosis. The vacuole decreases in volume and size and the cytoplasm pulls away from the cell wall. Cell becomes plasmolysed and flaccid.
44
What happens to a plant and animal cell when they are placed in an isotonic solution?
WP is equal both inside and outside the cell. No NET movement of water. Water moves both directions. Cell remains normal size.
45
Passive transport does not require...
Additional energy input through the hydrolysis of ATP.
46
What is turgor pressure?
The pressure exerted by the water in the large central vacuole.
47
How is turgor important in plants?
1. Turgor in cell wall prevents cell from undergoing lysis 2. Keeps plants firm and upright by maintaining the shape of soft tissues in plants 3. Changes in turgor of guard cells cause the opening and closing of stomata 4. allows leaves to spread out more 2-4: increases rate of photosynthesis.
48
How does the cell wall prevent the cell from bursting?
- made from CELLULOSE - makes the cell INELASTIC - which prevents over-expansion - by EXERTING AN EXTERNAL PRESSURE to resist water entering the cell.
49
When a plant cell is fully plasmolysed, it is described as...
flaccid
50
similarities between diffusion and osmosis
- both are passive transport processes and do not require hydrolysis of ATP as an energy source - both involve the net movement of particles down a concentration gradient
51
differences between diffusion and osmosis.
diffusion: net movement of air and solid particles osmosis: net movement of water molecules. diffusion does not req. a semi-permeable membrane, but osmosis req. one.
52
Describe how the properties of phospholipids help to maintain the structure of cell membranes.
- Made of 1 phosphate group head which is hydrophilic, in which it is attracted to water, and 2 hydrocarbon tails that are hydrophobic, in which they are repelled by water. - In a plasma membrane, the environment surrounding the cell and the cytoplasm in the cell are aqueous mediums. Hence, the phospholipid forms a bilayer. - The hydrophilic phosphate group head faces towards the external aqueous environment, whereas the hydrophobic hydrocarbon tails face inside the bilayer.
53
What is active transport?
The process in which ATP is used to move particles across a membrane AGAINST its concentration gradient, from a region of lower concentration to high concentration.
54
How does ATP release energy?
Through hydrolysis of ATP into ADP (adenosine diphosphate) and free phosphate to release the stored energy.
55
Active transport only occurs in?
Living cells because living cells respire aerobically to produce ATP.
56
Where does active transport occur in living organisms.
1. Human body uptake of glucose by epithelial cells in the small intestine and kidney tubes into the blood capillaries 2. Plants root hair cells take in mineral salts
57
What is bulk transportation?
Active transportation of materials into or out of a cell by enclosing it within a vesicle, with the hydrolysis of ATP to provide energy.
58
2 types of bulk transport:
1. Endocytosis 2. Exocytosis
59
Describe the process of endocytosis
- When substances are taken into the cells by the inward folding of the cell membrane - to form vesicles - with the hydrolysis of ATP as an energy source
60
Example of endocytosis:
phagocytosis (process of engulfing or ingesting foreign particles) - bacteria by white blood cells - food by amoeba
61
key feature of phagocytosis:
formation of temporary protrusions > pseudopodia
62
What is exocytosis?
- When substances in secretory vesicles move towards and fuse with the cell membrane - releasing the contents of the vesicle into the aqueous environment surrounding the cell - with the hydrolysis of ATP as an energy source

Y3 Biology (5 decks)

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