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Biology > Cell biology 4 > Flashcards

Cell biology 4 Flashcards

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AP® Biology flashcards Biology 101 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.

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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 in 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
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.

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

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
Q

If asked about surface exchange…

A

most likely you’ll have to talk about surface area.

26
Q

What are gills?

A

The gas exchange surface in fish.

27
Q

How are gills adapted for exchanging materials?

A

-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
Q

How are lamellae on fish gills adapted for exchanging materials? (fish)

A

-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
Q

How are leaves adapted for exchanging materials? (plants)

A

-Stomata

-Flattened shape increases area of exchange surface

-Cell walls and air spaces inside leaf

30
Q

How is the underside of a leaf an adaptation for diffusion? (stomata)

A

-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
Q

How is the arrangement of palisade cells in leaves an adaptation?

A

-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
Q

What is osmosis?

A

The movement of water molecules from a dilute solution to a more concentrated solution through a partially permeable membrane.

33
Q

What is a partially permeable membrane?

A

A membrane with very small holes in it, allowing only tiny molecules like water through them and not larger ones like sucrose.

34
Q

Which way do water molecules pass through a partially-permeable membrane during osmosis?

A

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
Q

Active transport

A

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
Q

What does active transport require?

A

Energy from respiration.

37
Q

Why do plants need to use active transport to absorb mineral ions?

A

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
Q

Where does active transport occur in the human body?

A

-Taking in glucose from the gut
-Absorbing glucose from the kidney tubules

39
Q

How is active transport used in the gut?

A

-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 for cell respiration

40
Q

How do we describe a plant cell in its normal state?

A

Turgid

41
Q

Plasmolysis

A

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
Q

Suggest why potato is often used as a test plant tissue

A

-It has no chloroplasts
-It’s heavier than other plants so easier to weigh

43
Q

How are villi adapted for fast absorption of nutrients into the blood?

A

-They have a single layer of surface cells
-A good blood supply to assist quick absorption.

44
Q

How are alveoli specialised to maximise the rate of diffusion of O₂ and CO₂?

A

-They have an enormous surface area
-A moist lining to dissolve gases
-Very thin walls
-A good blood supply

45
Q

Gas exchange in fish

A

-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
Q

What does active transport require?

A

Energy from aerobic respiration.

47
Q

suggest why salt/sugar is used in the osmosis experiment.

A

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
Q

suggest why potato is often used as the experiment plant tissue (osmosis experiment)

A

-it has no chloroplasts

-it is heavier than other plants as it’s a root and therefore easier to weigh

49
Q

Why is potato used rather than sweet potato/beetroot (other roots)

A

-They are more sugary

50
Q

What is the purpose of using distilled water in the osmosis experiment?

A

to compare the results with the salt or sugar solutions

Biology (16 decks)

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