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Biology > B2 > Flashcards

B2 Flashcards

1
Q

Give four adaptations of a red blood cell.

A
  1. They are shaped like biconcave disks - meaning that they have a greater surface area to volume ratio, speeding up the diffusion of oxygen into the cell and carbon dioxide out.
  2. Contain lots of haemoglobin - this binds to oxygen.
  3. No nucleus - means there is more space to carry more haemoglobin molecules.
  4. Small and flexible - meaning they are able to fit through capillaries, meaning they are able to deliver oxygen to all parts of the body.
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2
Q

What is it called when cells become specialised to suit a certain function?

A

Differentiation.

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3
Q

WHAT IS PMAT

A

THE FOUR STAGES OF MITOSIS
PROPHASE
METAPHASE
ANAPHASE
TELEPHASE

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4
Q

What happens in Prophase?

A

Nuclear envelope breaks down. Chromosomes condense (supercoil).

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5
Q

Which type of stem cell is pluripotent?

A

Embryonic stem cells.

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6
Q

What happens in Metaphase?

A

Chromosomes line up in the middle of the cell.

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7
Q

What happens in Anaphase?

A

Chromatids are pulled apart to opposite sides of the cell by spindle fibres.

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8
Q

What happens in Telephase?

A

Nuclear envelope reforms and the cytoplasm starts to splitm A process called cytokinesis splits the cell into two genetically identical daughter cells.

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9
Q

Define osmosis.

A

The net movement (diffusion) of water molecules across a partially permeable membrane, from a region of high concentration to a region of low concentration, according to a concentration gradient.

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10
Q

Define diffusion.

A

The net movement of particles from a region of high concentration to a region of low concentration, according to the concentration gradient.

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11
Q

How does distance affect diffusion?

A

It takes less time to travel a shorter distance, so the rate of diffusion will increase as the distance decreases. E.g. blood capillaries are only 1 cell thick, meaning that the rate of diffusion of gases like oxygen into the bloodstream is increased.

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12
Q

What is the concentration of free water molecules known as?

A

Water potential.

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13
Q

What is the formula for calculating percentage change?

A

new result - original result ÷ original result x 100

positive value means a percentage gain, negative value means a percentage loss.

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14
Q

What is the function of pores on selectively permeable membranes?

A

They prevent larger molecules from passing through the membrane while allowing smaller ones, such as those for water, through.

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15
Q

Why don’t multicellular organisms solely rely on diffusion for their needs?

A

They have too many cells for diffusion to supply them all the time. It is not sustainable, and instead the organism requires a transport system and exchange surfaces.

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16
Q

What is the equation for respiration?

A

Oxygen + glucose -> carbon dioxide + water

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17
Q

What is the function of exchange surfaces?

A

They allow substances in and out of the transport system.

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18
Q

Give 4 adaptations of alveoli.

A
  1. Thin walls to decrease the diffusion distance, making the rate of diffusion much quicker.
  2. They are moist for the solution of gases. Gases have to be in a dissolved form to be taken in.
  3. Network of capillaries around each alveolus to maximise gas exchange - this allows for a steep concentration gradient and thus a fast rate of diffusion.
  4. There are lots of alveoli inside the lungs, meaning that altogether they have a high surface area.
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19
Q

How do you work out the surface area to volume ratio?

A

Surface area ÷ volume.

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20
Q

How does surface area affect the rate of diffusion?

A

As the surface area increases, the rate of diffusion also increases. This is because a higher surface area means that more particles can move into the space within a period of time, as more space is allowed for diffusion.

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21
Q

How does the concentration gradient affect the rate of diffusion?

A

The steeper the concentration gradient, the greater the net movement of particles and therefore the greater the rate of diffusion.

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22
Q

If an organism has a small SA:V ratio, does it require a transport system or diffusion to allow substances to enter and leave its cells?

A

It requires a transport system as a small SA:V ratio means that diffusion alone is not sufficient, as the rate of diffusion would be too slow to ensure cells got enough glucose and oxygen to sustain the organism. A transport system is needed to speed up this process.

23
Q

Explain how plant cells can become turgid.

A

Water moves from an area of high water potential outside the cell to an area of low water potential inside the cell through osmosis. This causes the cell to swell up and become turgid, as the cell wall prevents it from bursting.

24
Q

Explain how animal cells can shrivel.

A

Water molecules move from an area of high water potential inside the cell to an area of low water potential outside the cell through osmosis. This causes the cell to shrivel due to a lack of water.

25
Q

Explain how lysis occurs in animal cells.

A

Water molecules move from an area of high water potential outside the cell to an area of low water potential inside the cell through osmosis. This causes the cell to swell up and burst, referred to as lysis.

26
Q

If salts or sugars were dissolved in water, how would this affect its water potential?

A

It would decrease it. Water molecules are trapped by solutes as they are attracted to them, and are prevented from crossing the partially permeable membrane.

27
Q

Does diffusion require a membrane?

A

No

28
Q

Explain how plant cells become plasmolysed.

A

Water molecules move from an area of high water potential inside the cell to an area of low water potential outside the cell through osmosis. This causes the cell to shrivel, but as the cell wall retains its shape, it becomes plasmolysed.

29
Q

What does xylem transport?

A

Water and minerals.

30
Q

What does phloem transport?

A

Sugars.

31
Q

Which practical can be done to demonstrate how SA:V ratio affect diffusion rates?

A

Get 3 coloured jelly cubes of different surface areas and put them in separate beakers. Then, cover each cube in hydrochloric acid and start the stop clock. Measure how long it takes for each cube to decolourize, and compare the results. You should end up with the cube with the largest SA:V ratio taking the shortest time to decolourize.

32
Q

Define active transport.

A

The movement of molecules from an area of low concentration to an area of high concentration. This goes against the concentration gradient, and therefore requires energy in the form of ATP.

33
Q

What does ATP stand for?

A

Adenosine Triphosphate.

34
Q

Is diffusion a passive or active process?

A

Passive.

35
Q

Is osmosis a passive or active process?

A

Passive.

36
Q

Give 3 examples of active transport being used in living organisms.

A
  1. Minerals from the soil being taken up by plant roots.
  2. Uptake of glucose in the villi.
  3. Nerve impulse transmission.
37
Q

State where carrier proteins are found within cells.

A

They span across the cell membrane.

38
Q

Explain the difference between pluripotency and multipotency.

A

Pluripotent stem cells, such as embryonic stem cells, can differentiate into ALL different kinds of specialised cell.
Multipotent stem cells, such as adult stem cells, can differentiate into MANY different kinds of specialised cell.

39
Q

Give three different kinds of specialised cell and one of their adaptations.

A

Sperm cells - have a long flagellum that propels it forward to get to the ovum.
Fat cell - have a small layer of cytoplasm surrounding a fat reservoir. It can expand up to 1000 times its original size as it fills with fat.
Palisade cells - specialised for photosynthesis, so are found on the surface of the leaf and are packed full of chloroplasts.

40
Q

Define concentration gradient.

A

A measurement of how the concentration of a substance changes from one region to another.

41
Q

Give four purposes of mitosis.

A
  1. Tissue repair.
  2. Cell regrowth.
  3. Growth.
  4. Asexual reproduction.
42
Q

Where are plant stem cells found?

A

In the meristematic tissue.

43
Q

What are the meristems?

A

Plants to continue to grow throughout their life, but only certain areas referred to as meristems. These parts include shoot tips and roots. Stem cells are found in plant meristems.

44
Q

Give 3 differences between meristem plant cells and normal plant cells.

A

Meristem:
Small
Thin cell walls
Small vacuoles
No chloroplasts.

45
Q

Why can’t differentiated plant cells undergo mitosis?

A

They cannot divide as their cell walls are thick and rigid.

46
Q

Give two advantages of using embryonic stem cells and adult stem cells in the treatment of diabetes.

A

Embryonic stem cells are pluripotent, meaning they can differentiate into all different kinds of specialised cells. This would be useful in the treatment of diabetes as pancreatic cells can be formed.

47
Q

Where are embryonic stem cells found?

A

In embryos.

48
Q

Where are adult stem cells found?

A

In tissues such as the brain, bone marrow, skin and liver.

49
Q

Why may sperm cells contain more mitochondria than other body cells?

A

The Mitochondria is the site of aerobic respiration, which is responsible for providing energy to the cell (in the form of ATP). Sperm cells require more energy than most cells in order for their flagellum to move and propel it forward.

50
Q

Outline the process of active transport.

A
  1. A molecule that the cell requires binds to a specific carrier protein on the cell membrane. The carrier protein has a specific shape that corresponds to the shape of the desired molecule.
  2. The carrier protein uses energy in the form of ATP to rotate and release the molecules into the inside of the cell. ATP is required as carrier protein move the molecules against the concentration gradient - from an area of low concentration to an area of high concentration.
  3. The carrier protein rotates back to its original position facing outwards on the cell, also using ATP. this means it is ready to transport other molecules across the membrane.
51
Q

Explain why plants use active transport rather than diffusion to absorb minerals from the soil.

A

There is usually a lower concentration of minerals in the soil than in the plant’s roots. Therefore, plant roots hair cells must use active transport to move the molecules against the concentration gradient.

52
Q

State the complementary base pairs for the following DNA strand: ATTGCA

A

TAACGT

53
Q

State the steps to DNA replication.

A
  1. The DNA molecule ‘unzips’, forming two separate strands.
  2. The DNA bases on each strand are exposed.
  3. Free nucleotides in the nucleus line up against each of the strands following the rule of complementary base pairing.
  4. This forms DNA base pairs
  5. When the whole strand is complete, there are two identical molecules of DNA, ready tk be used in mitosis.

Biology (4 decks)

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