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GCSE Biology (AQA) > Topic 1: Cell Biology (Paper 1) > Flashcards

Topic 1: Cell Biology (Paper 1) Flashcards

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1
Q

What is an eukaryotic cell?

A

Plant and animal cells (eukaryotes) have a cell membrane, cytoplasm and genetic material enclosed in a nucleus.

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2
Q

What is a prokaryotic cell?

A

Prokaryotes don’t have their genetic material enclosed in a nucleus (e.g. bacteria)

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3
Q

Where is the genetic material stored in a prokaryotic cell?

A

It is a single DNA loop and there may be one or more small rings of DNA called plasmids, stored in the cytoplasm

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4
Q

What are some similarities and differences between prokaryotes and eukaryotes?

A

Differences
* Prokaryotes have no nucleus
* Prokaryotes have no chromosomes
* Prokaryotes are only unicellular (eukaryotic can be unicellular or muticellular)
Similarities
* Both have DNA
* Both have ribisomes
* Both have cell membranes

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5
Q

What is the function of the nucleus?

A

The nucleus controlls all the activities of the cell and contains the genetic information.

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6
Q

What is the cytoplasm?

A

The cytoplasm is a liquid gel where the organelles are suspended and where most of the chemical reactions take place.

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7
Q

What is the function of the cell membrane?

A

The cell membrane controls the passage of substances into and out of the cell.

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8
Q

What is the function of the mitochondria?

A

The mitochondria are structures in the cytoplasm where aerobic respiration takes place, relseaing energy.

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9
Q

What is the function of the ribosomes?

A

The ribosomes are where protein synthesis takes place.

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10
Q

What is the function of cholroplasts?
What does chlorophyll do?

A

Plant cells have chloroplasts which contain chlorophyll.
Chlorophyll absorbs light energy so the plant can make food by photosynthesis.

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11
Q

Why is the permanent vacuole important?

A

The large permenat vacuole is filled with cell sap and this is important becauseit keeps the cells rigid to support the plant.

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12
Q

What is the cell wall?
What is it made out of?

A

The cell wall is made out of cellulose and it strengthens the cell and gives it support.

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13
Q

What does being ‘specialised’ mean?
What is ‘differentaition’?

A

Specialised cells have different adaptations which help them carry out their particular function.
Differentitation is when a cell becomes specialised.

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14
Q

What is the job of a sperm cell?
What happens during fertilisation?

A

The sperm cell has to fuse with an ovum (egg cell) to fertilise it.
During fertilisation, the genetic material of both the sperm cell and ovum combine.

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15
Q

How are sperm cells specialised?

A
  • large nucleus containing genertic information
  • acrosome stores digestive enzymes for breaking down the outer layers of the ovum
  • long tail for swimming
  • middle section full of mitochondria to relsease energy for the tail
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16
Q

What do nerve cells do?

A

Nerve cells carry elecrical impulses around the body and provide a rapid communication system.

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17
Q

How are nerve cells specialised?

A
  • dendrites increase surface area so other nerve cells can connect more easily
  • long axon carries electrical impuleses
  • myelin insulates axon and speeds up transmission of nerve impulses
  • synapses allow impulse to pass from one nerve cell to another
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18
Q

What do muscle cells do?

A

Muscle cells contract and relac and work together to form muscle tissue.

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19
Q

How are muscle cells specialised?

A
  • protein fibres can change their length
  • lots of mitochondria to relsease energy for muscle contraction
  • can store glycogen that can be broken down into glucose to be used by mitochondria for respiration.
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20
Q

How are root hair cells specialised?

A
  • hairs increase surface area for efficient osmosis
  • no chloroplasts - as they are underground
  • many mitochondria for active transport
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21
Q

How are xylem cells specialised?

A
  • Cell walls made of lignin to withstand water pressure
  • dead cells from long hollow tubes so water and dissolved mineral ions can move easily through
  • no internal strucutres so water can flow easier
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22
Q

How are phloem cells specialised?

A
  • cell walls break down to from sieve plates
  • each phloem vessel call has a companion cell containing many mitochondria to transfer energy so phloem vessel sugars can move sugars up and down.
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23
Q

RP: Describe the method for viewing a prepared slide through an optical microscope.

A
  1. Place the slide on the stage and use the clips to secure it.
  2. Select the lowest power objective lens
  3. By slowly turning the course focus knob, make sure the objective lense almost touches the slide.
  4. Look through the eyepiece and slowly turn the coarse focus know to increase the distance between the objuective lense and the slide. Do this until the cells come into focus.
  5. Slowly turn the fine focus knob to bring cells into a clear focus.
  6. We can now select a higher power objective lens, but adjust the fine focuse knob to bring the cells back into focus.
    total magnification - eyepiece x objective lens
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24
Q

What are the disadvantages of a light mircoscope?

A
  • limited magnification
  • limited resolution
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25
Q

What are the key advantages of an electron microscope?

A
  • Greater magnification
  • Greater resolution
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26
Q

How do we calculate magnification?

A

magnification = image size ÷ actual size

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27
Q

How do bacteria divide?

A

They divide by binary fission

28
Q

RP: Describe the method for preparing an uncontaminated bacterial culture.

A
  1. Sterilise all petri dishes, bacterial nutrient broth and agar to kill any unwanted mircoorganisms and it prevents contamination
  2. Sterilise inoculating loop by passing it through a bunser burner flame
  3. Transfer bateria onto agar gel plate
  4. Attack the lid of the petri dish using adhesive tape top to stop the lid from falling off and prevent contamination with bacteria in the air.
  5. Place the agar plate upside down into an incubator to stop moisture dripping down and dristrupting the colonies.
    (at school, we normally incubate bacteria at 25°C to reduce the chances that harmful bacteria will grow)
29
Q

What 2 ways can bacteria be grown?

A
  • Nutrient broth solution
  • Agar gel plate
30
Q

Describe a method to investigate the effect of antibioticd on baterial gowth.

A
  1. Clean the bench with disinfectent solution to kill microorganisms that could contaminate our culture.
  2. Sterilise an incoculating loop by passing it through a bunsen burner flame.
  3. Open a sterile agar gel plate near a bunsen burner flame to kill bacteria in the air
  4. Use the inoculating loop to spread the chosen bacteria evenly over the plate.
  5. Place sterile filter paper discs containing antibiotic onto the place.
  6. Incubatee the plate at 25°C.
31
Q

What is the zone of inhibition?
How do we calculate the area where the bacteria haven’t grown?

A

The region where the bacteria haven’t grown = zone of inhibition
area = 𝝅 x radius squared (area of a circle)

32
Q

Where do we find DNA inside a cell?

A

The nucleus of a body cell contains chromosomes, which are made of the molecule DNA.

33
Q

How are chromosomes arranged in a body cell?

A

Chromosomes in the nucleus of a body cell are paired.

34
Q

What is the function of chromosomes?

A

Chromosomes carry a large number of genes which determine our features.

35
Q

What happens in the 1st stage of the cell cycle?

A

DNA replicates to form 2 copies of each chromosome, the cell grows ans copies its internal strucutres

36
Q

What is the 2nd stage of the cell cycle?

A

Mitosis - one set of chromosomes pulled to each end of the cell, nucleus also divides

37
Q

What happens in the final stage of the cell cycle?

A

cytoplasm and cell membrane divide –> 2 identical daughter cells

38
Q

What are the functions of mitosis?

A
  • growth and development
  • repair
  • asexual reproduction
39
Q

What is a stem cell?

A

A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentaition.

40
Q

Why are early-stage embryonic cells used as stem cells?

A

Cells in the early stage embryo haven’t differentaited yet but they are capable of differentiating into any type of body cell.

41
Q

What can stem cells in bone marrow differentiate to form?

A

Adult stem cells in the bone marrow can only differentiate to from cells found in blood, e.g. red blood cells, white blood cells and platelets

42
Q

What happens in a bone marrow transplant?

A

The patient recieves a bone marrow transplant from a donor. The stem cells in the bone marrow now divide ro doem new bone marrow, they also differentiate and form blood cells.

43
Q

What happens if the donor isn’t compatible for a bone marrow transplant?

A

The white blood cells produced by the bone marrow could attack the patient’s body.

44
Q

What is a risk of a bone marrow transplant.

A

There is a risk that viruses can be passed on from the donor.

45
Q

What happens in therapeutic cloning and what does it allow?
What medical conditions could therapeutic cloning be useful for?

A

An embryo is produced with the same genes as the patient. This means that the embryonic stem cells can be transplanted into the patient without being rejected by the patients immune sytem. Once inside the patient, the embryonic stem cells can differentiate to replace cells which have stopped working correctly.
This technique could be useful to treat diabetes or paralysis.

46
Q

Where are stem cells found in plants?
What is advantageous about these stem cells?
How could we use this type of stem cell?

A

Roots and buds contain maristem tissue.
These stem cells can differentiate into any type of plant tissue, at any point in the life of the plant.
We could clone a rare plant quickly and cheaply to stop it from extinction. Farmers could also produce cloned crop plants which are resistant to diseases.

47
Q

What is diffusion?

A

Diffusion is the spreading out of particles resulting in a net movement from an area of higher concentration to an area of lower concentration

48
Q

Why do cells need oxygen?
How can oxygen use diffusion to move into cells?

A

Cells need oxygen for respiration.
Cells are surrounded by a high concentration of oxygen as oxygen is transported in the bloodstream from the lungs. This means that oxygen molecules more into the cell from an area of higher concetration outside the cell, to an area of lower concentration inside the cell.

49
Q

Why do cells have a high concentration of carbon dioxide?
How does the carbon dioxide move out of the cell?

A

The oxygen is used to release energy in respiration and this produces the waste gas carbon dioxide.
As there is a higher concentration of carbon dioxide in the cell, molecules diffuse out.

50
Q

What is urea?
How can urea diffuse out of cells?

A

Urea is a waste product produced inside cells. It diffuses out of the cells into the blood plasma and is excreted by the kindeys.
Urea diffuses out of the cells as there is a lower concentration outside the cell.

51
Q

What are the factors affecting the rate of diffusion?

A
  • Concentration gradient
  • Temperature
  • Surface area of the membrane
52
Q

Why can single-celled organisms rely on diffusion?

A

Single-celled organisms have a huge surface area for their volume. This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.

53
Q

Why does SA:V present a huge problem for multicellular organisms?

A

The SA of a multicellular organism is not large enough for their volume.
Cells on the surface can get enough oxygen via diffusion but not enough oxygen can diffuse into the cells in the centre (they are too far away from the surface)

54
Q

How do animals solve the problem of a small SA:V ratio?

A
  • Animals have special structures for efficient gas exchange with a high SA
  • Animals have a transport system to carry gases around the body
55
Q

How does the blood in fish become oxygenated?

A

The oxygen-rich water passes into the fishes mouth. It then flows over gills where the oxygen is transported into the bloodstream.
Gills are covered in a very large number of fine gill filamnets. Deoxygenated blood passes into the filament. oxygen diffuses from the water into the blood. Oxygenated blood returns to the body.

56
Q

How are the gill filaments adapted for gas exchange?

A
  • filaments give gills a huge SA
  • filaments have a thin membrane to provide a short diffusion pathway
  • filaments have an efficient blood supply to take the oxygenated blood away –> always have a high concentration gradient
57
Q

What is osmosis?

A

Osmosis is the passive net movement of water from a dilute solution to a concentrated solution through a partially permable membrane.

58
Q

What happens to an animal cell if it is placed in a dilute solution?

A

Water mives in and it will cause the cell to expamd and the cell could even burst.

59
Q

What happens to an animal cell if it is placed in a very concentrated solution?

A

Water will move out of the cell by osmosis

60
Q

What does it mean if a plant cell is turgid?
Why would a plant cell not burst?

A

If we place a plant cell in water, the water will move into the cell and the cell will expand, becoming turgid.
The cell wall prevents the plant cell from bursting.

61
Q

What does it mean if a plant cell is flaccid?

A

If we place the plant cell into a concentrated solution, the water moves out of the plant cell by osmosis, and the plant cell shrinks, becoming flaccid.

62
Q

RP: Describe a method to investigate the effects of osmosis on plant tussie.

A
  1. Peel the potato as the skin can affect osmosis.
  2. Use a cork borer to produce three cylinders of potato (a cork borer makes all the cylinders the same diameter).
  3. Use a scalpel to trim the cylinders to the same length (3cm)
  4. Measure and record both the lengths and masses of the threee cylinders using a ruler and balance
  5. Place each potato cylinder into a test tube
  6. Add 10cm3 of a 0.5 molar sugar solution into one tube, 10cm3 of a 0.25 molar sugar solution to the second tube, and 10cm3 of distilled water to the last tube.
  7. Leave the cylinders overnight
  8. Remove the potato cylinders from the test tube and gently roll them on a paper towel to remove any surface moisture.
  9. Measure and record the length and mass of each cylinder again.
  10. Calculate the percentage change = (change ÷ original) x 100
63
Q

Why would a cell need to use active transport?

A

Active transport is ued when a cell needs to bring in substances that have a lower concentration outside the cell.

64
Q

What is active transport?

A

Active transport is the movement of substances from a more dilute solution to a more concentrated solution, against the concentration gradient, using energy from respiration.

65
Q

What is an example of active transport in the human body?

A

Active transport is used bu the cells in the small intestine to bring in dissolved sugars from the lumen of the small intestine.

66
Q

What is an example of active transport in a plant?

A

Root hair cells use active transport to move ions from the soil into them.

GCSE Biology (AQA) (4 decks)

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