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Cell biology 4 Flashcards

1
Q

How might substances move into and out of cells?

A

Across cell membranes via diffusion.

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2
Q

What is diffusion?

A

The random movement of particles in a substance from an area of higher concentration to an area of lower concentration across a partially permeable membrane.

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3
Q

Where does diffusion happen?

A

-Any substance in solution
-Particles of a gas

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4
Q

Give an example of some of the substances transported into and out of cells via diffusion:

A

-Oxygen and Carbon dioxide in gas exchange

-Urea (waste product) from cells into the blood plasma for excretion in the kidney.

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5
Q

What are the three factors that affect the rate of diffusion?

A
  • the difference in concentrations (concentration gradient)
  • temperature
  • the surface area of the membrane
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6
Q

What in a single-celled organism allows sufficient transport of molecules into and out of cells to meet the organisms needs?

A

A relatively large surface area to volume ratio.

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7
Q

How does temperature affect the rate of diffusion?

A

A higher temperature means a faster diffusion rate because the particles have more energy, so move around faster.

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8
Q

How does the concentration gradient affect the rate of diffusion?

A

The bigger the concentration gradient, the faster the rate of diffusion.

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9
Q

How does the surface area of the cell membrane affect the rate of diffusion?

A

The larger the surface are of the cell membrane, the faster the diffusion rate, as more particles can pass through at once.

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10
Q

Why does diffusion happen in both solutions and gases?

A

The particles in these substances are free to move about randomly.

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11
Q

What is the simplest type of diffusion?

A

The diffusion of gases through each other.

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12
Q

Name some small molecules which can diffuse through cell membranes.

A

-Oxygen
-Glucose
-Amino acids
-(water)

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13
Q

Name some large molecules which cannot diffuse through cell membranes.

A

-Starch
-Proteins

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14
Q

Explain what is meant by net movement.

A

Particles in a substance in a solution or a gas are moving about randomly, so go both ways.

However, if there are a lot more particles on one side of the membrane, then there’s a net (overall) movement from that side.

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15
Q

What determines how easy it is for an organism to exchange substances with its environment?

A

The organism’s surface are to volume ratio.

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16
Q

Do smaller organisms have a smaller or larger surface are to volume ration than larger organisms?

A

Larger because the surface area will be more times bigger than its volume than for a larger organism.

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17
Q

How do we calculate surface area to volume ratios?

A

Draw a block around the image

Find the total surface area of the object by doing length x width for each face

Find the volume of the object using length x width x height.

Write the two answers in a ratio (SA:V) and then simplify the ratio.

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18
Q

Is 6:1 or 3:1 a larger surface area to volume ratio?

A

6:1 as the SA is 6x the volume compared to 3x the volume.

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19
Q

Why can substances diffuse directly into and out of the cell across the cell membrane in single-celled organisms?

A

They have a large surface area to volume ratio and so enough substances can be exchanged across the membrane to supply the volume of the cell.

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20
Q

Why do multicellular organisms need some sort of exchange surface for efficient diffusion?

A

They have a smaller surface area to volume ratio than single celled organisms.

This means that not enough substances can diffuse from their outside surface to supply their entire volume.

Which means that they need exchange surface structures to allow enough of the necessary substances to pass through.

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21
Q

What adaptations/factors increase the effectiveness of an exchange surface?

A
  • having a large surface area so lots of substances can diffuse at once
  • a membrane that is thin, to provide a short diffusion path
  • (in animals) having an efficient blood supply (lots of blood vessels to so substances can diffuse in and out of the blood quickly)
  • (in animals, for gaseous exchange) being ventilated
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22
Q

In multicellular organisms, what are surfaces and organ systems are specialised for?

A

Exchanging materials.

This is to allow sufficient molecules to be transported into and out of cells for the organism’s needs.

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23
Q

How is the small intestine adapted for exchanging materials? (mammals)

A

-The inside is covered in millions and millions of tiny little projections called villi

-They increase the surface area of the intestine so that digested food is absorbed more quickly into the blood

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24
Q

How are the lungs adapted for exchanging materials? (mammals)

A

-They contain millions of little air sacs called alveoli where gas exchange happens.

25
If asked about surface exchange...
most likely you'll have to talk about surface area.
26
What are gills?
The gas exchange surface in fish.
27
How are gills adapted for exchanging materials?
-Each gill is made up of lots of thin plates called gill filaments which give a large surface area for the exchange of gases -These gill filaments are covered in lots of tiny structures called lamellae, which increases the surface area further -The concentration of oxygen in the water is always higher than in the blood, so as much oxygen as possible diffuses from the water to the blood (large concentration gradient)
28
How are lamellae on fish gills adapted for exchanging materials? (fish)
-Lots of blood capillaries to speed up diffusion -Thin surface layer of cells to provide a short diffusion path -Blood flows through the lamellae in one direction, and water in the opposite to maintain a large concentration gradient between the oxygen in the water and in the blood
29
How are leaves adapted for exchanging materials? (plants)
-Stomata -Flattened shape increases area of exchange surface -Cell walls and air spaces inside leaf
30
How is the underside of a leaf an adaptation for diffusion? (stomata)
-The underneath of the leaf is an exchange surface. -It's covered in stomata which CO₂ diffuses in through -O₂ and (most of the) water vapour diffuse out through the stomata -Guard cells control the size of the stomata, closing the stomata if the plant is losing water faster than it can be replaced by the roots. This prevents the plant from wilting.
31
How is the arrangement of palisade cells in leaves an adaptation?
-Air spaces inside the leaves (between palisade cells) increase the surface area on the walls of the cells so there's more chance for CO₂ to diffuse into them
32
What is osmosis?
The movement of water molecules from a dilute solution to a more concentrated solution through a partially permeable membrane.
33
What is a partially permeable membrane?
A membrane with very small holes in it, allowing only tiny molecules like water through them and not larger ones like sucrose.
34
Which way do water molecules pass through a partially-permeable membrane during osmosis?
Both ways as water molecules move about randomly. However, because there are more water molecules on one side than the other, there is a steady net flow of water into the region with fewer water molecules (i.e. the more concentrated solution).
35
Active transport
The movement of a substance from a more dilute solution to a more concentrated solution (against the concentration gradient). It occurs across semi-permeable membranes.
36
What does active transport require?
Energy from respiration.
37
Why do plants need to use active transport to absorb mineral ions?
The concentration of mineral ions is usually higher in the root hair cells than in the soil around them, so the root hair cells can't use diffusion to take up mineral ions from the soil.
38
Where does active transport occur in the human body?
-Taking in glucose from the gut (small intestine to blood) -Absorbing glucose from the kidney tubules
39
How is active transport used in the gut?
-It allows glucose molecules and amino acids to be absorbed from lower concentrations in the gut to higher concentrations in the blood. -So that the glucose molecules can be used in cellular respiration
40
How do we describe a plant cell in its normal state?
Turgid
41
Plasmolysis
Water leaves the cell by osmosis. The cytoplasm shrinks and pulls away from the cell wall. The cell becomes flaccid and the plant wilts. This means less support for the plant.
42
Suggest why potato is often used as a test plant tissue
-It has no chloroplasts -It's heavier than other plants so easier to weigh
43
How are villi adapted for fast absorption of nutrients into the blood?
-They have a single layer of surface cells -A good blood supply to assist quick absorption.
44
How are alveoli specialised to maximise the rate of diffusion of O₂ and CO₂?
-They have an enormous surface area -A moist lining to dissolve gases -Very thin walls -A good blood supply
45
Gas exchange in fish
-Water (containing oxygen) enters the fish through its mouth and passes out through the gills. -As this happens, oxygen diffuses from the water into the blood in the gills, and carbon dioxide diffuses from the blood into the water
46
What does active transport require?
Energy from aerobic respiration.
47
suggest why salt/sugar is used in the osmosis experiment.
either is used as a solute different concentrations of salt/sugar are used to determine whether water will move in/out of plant tissue by osmosis.
48
suggest why potato is often used as the experiment plant tissue (osmosis experiment)
-it has no chloroplasts -it is heavier than other plants as it's a root and therefore easier to weigh
49
Why is potato used rather than sweet potato/beetroot (other roots)
-They are more sugary
50
What is the point of having a distilled water condition in the osmosis experiment?
To compare the results with the salt or sugar solutions
51
Oxygen will diffuse into the cell in the diagram. Explain why.
There's a high to low oxygen concentration (more oxygen molecules outside the cell).
52
Describe two functional adaptations of a neuron/nerve cell
-Long -Have branches
53
Why is a large surface area on an exchange surface good?
Lots of molecules can diffuse across at the same time.
54
Why are walls only 1 cell thick on an exchange surface good?
Substances only have to diffuse across a short distance.
55
Why are permeable surfaces (for exchange) good?
Substances are able to pass through e.g. in the alveoli, oxygen and carbon dioxide are able to diffuse across.
56
Why is a good blood supply good? (exchange surfaces)
Maintains a strong concentration gradient as blood is constantly replaced.
57
Why is a good supply of the 'external medium' good? (exchange surfaces)
Maintains a strong concentration gradient e.g the air in the alveoli is constantly replaced with new oxygen rich air from the atmosphere.
58
What do both plant cells and red blood cells have?
Cytoplasm Cell membrane Pigments (although they are different)
59
Explain why the rate of water loss would be much lower at midnight than during the day. (2)
Stomata are almost completely closed Because there’s less light (or because it’s cooler)

Biology (19 decks)

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