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Biology - Cell biology > Cell structure > Flashcards

Cell structure Flashcards

Key: Anything referencing energy (such as mitochondria), don't write PRODUCES energy but rather PROVIDES/RELEASES energy.

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1
Q

What are the two types of cells?

A
  • Eukaryotic (plant and animal).

- Prokaryotic (bacteria).

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2
Q

What are the differences between eukaryotic and prokaryotic cells?

A

Prokaryotic cells are much smaller than eukaryotic cells.

Eukaryotic cells contain membrane bound-organelles and a nucleus containing genetic material, while prokaryotes do not.

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3
Q

What is the prokaryotic cell wall composed off?

A

Peptidoglycan.

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4
Q

How is genetic information stored in a prokaryotic cell?

A

Found free within the cytoplasm as:

  • Chromosomal DNA (single large loop of circular DNA).
  • Plasmid DNA.
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5
Q

What are plasmids?

A
  • Small, circular loops of DNA found free in the cytoplasm and separate from the main DNA.
  • Carry genes that provide genetic advantages such as antibiotic resistance.
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6
Q

What is the order of magnitude?

A

A power to the base 10 used to quantify and compare sizes.

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7
Q

What is a centimetre (cm)?

A

1 x 10^-2 metres.

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8
Q

What is a millimetre (mm)?

A

1 x 10^-3 metres.

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9
Q

What is a micrometre (μm)?

A

1 x 10^-6 metres.

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10
Q

What is nanometre (nm)?

A

1 x 10^-9 metres.

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11
Q

List the components of both plant and animal cells (5)

A
  • Nucleus.
  • Cytoplasm.
  • Cell membrane.
  • Mitochondria.
  • Ribosomes.
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12
Q

List the additional cell components found in plant cells (3)

A
  • Chloroplasts.
  • Permanent vacuole.
  • Cell wall.
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13
Q

Other than storing genetic information, what is the function of the nucleus?

A

Controls cellular activities.

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14
Q

Describe the structure of the cytoplasm

A
  • Fluid component of the cell.

- Contains organelles, enzymes and dissolved ions and nutrients.

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15
Q

What is the function of the cytoplasm?

A
  • Site of cellular reactions such as the first stage of respiration.
  • Transport medium.
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16
Q

What is the function of the cell membrane?

A

Controls the entry and exit of materials into and out of the cell.

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17
Q

What is the function of the mitochondria?

A

Site of later stages of aerobic respiration in which ATP is produced.

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18
Q

What is the function of the ribosomes?

A

Joins amino acids in a specific order during translation for the synthesis of proteins.

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19
Q

What is the plant cell wall made of?

A

Cellulose.

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20
Q

What is the function of the plant cell wall?

A
  • Provides strength.

- Prevents the cell bursting when water enters by osmosis.

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21
Q

What does the permanent vacuole contain?

A
  • Cell sap (a solution of salts, sugars and organic acids).
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22
Q

What is the function of the permanent vacuole?

A

Supports the cell, maintaining its turgidity.

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23
Q

What is the function of chloroplasts?

A

Site of photosynthesis.

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24
Q

Describe how sperm cells in animals are adapted to their function.

A
  • Haploid nucleus contains genetic information.
  • Tail enables movement.
  • Mitochondria provide energy for tail movement.
  • Acrosome contains enzymes that digest the egg cell membrane.
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25
Q

Describe how nerve cells in animals are adapted to their function.

A
  • Long axon allows electrical impulses to be transmitted all over the body from the CNS.
  • Dendrites from the cell body connect to and receive impulses from other nerve cells, muscles and glands.
  • Myelin sheath insulates the axon and speeds up the transmission of impulses along the nerve cell.
26
Q

Describe how muscle cells in animals are adapted to their function

A
  • Arrangement of protein filaments allows them to slide over each other to produce muscle contraction.
  • Mitochondria to provide energy for muscle contraction.
  • Merged cells in skeletal muscle allow muscle fibre contraction in unison.
27
Q

Describe how root hair cells in plants are adapted to their function

A
  • Large surface area to absorb nutrients and water from surrounding soil.
  • Thin walls that do not restrict water absorption.
28
Q

Describe how xylem cells in plants are adapted to their function

A
  • No upper or lower margins between cells to provide a continuous route for water to flow.
  • Thick, woody side walls (lignin) strengthen their structure and prevent collapse.
29
Q

Describe how phloem cells in plants are adapted to their function

A
  • Sieve plates let dissolved amino acids and sugars be transported up and down the stem.
  • Companion cells provide energy needed for active transport of substances along the phloem.
30
Q

What is cell diffferentiation?

A

The process by which cells become specialised.

31
Q

Why is cell differentiation important?

A

Allows production of different tissues and organs that perform various vital functions in the human body.

32
Q

At which point in their life cycle do most animal cells differentiate?

A

Early in their life cycle.

33
Q

For how long do plant cell retain the ability to differentiate?

A

Throughout their entire life cycle.

34
Q

What is the purpose of cell division in mature animals?

A

Repair and replacement of cells.

35
Q

What changes does a cell go through as it differentiates?

A

Becomes specialised through acquisition of different sub-cellular structure to enable a specific function to be performed by the cell.

36
Q

Define magnification

A

The number of times bigger an image appears compare to the size of the real image.

37
Q

Define resolution

A

The smallest distance between 2 objects that can be distinguished.

38
Q

How does a light microscope work?

A

1) Clip the slide carefully onto the stage.
2) Ensure the lowest-powered objective lens is over the slide.
3) Use the coarse adjustment knob to bring the stage up just below the lens.
4) Look down the eyepiece and gradually move the stage downwards using the coarse adjustment knob. Stop when the image is roughly in focus.
5) To bring the image into focus, adjust the fine-adjustment knob until a clear image is obtained.
6) To observe the image with a higher magnification, change the objective lens to a higher power and readjust the stage using coarse and fine adjustment knobs.

39
Q

What are the advantages of light microscopes? (4)

A
  • Inexpensive.
  • Easy to use.
  • Portable.
  • Observe both dead and living organisms.
40
Q

What is the disadvantage of light microscopes?

A

Limited resolution.

41
Q

How does an electron microscope work?

A

It uses a beam of electrons which are focused using magnets. The electrons hit fluorescent screen which emits visible light, producing an image.

42
Q

Name the two types of electron microscopes

A
  • Transmission electron microscope (TEM).

- Scanning electron microscope (SEM).

43
Q

What is the advantage of electron microscopes?

A

Greater magnification and resolution.

44
Q

Why do electron microscopes have a greater magnification and resolution?

A

They use a beam of electrons which has a shorter wavelength than photons of light.

45
Q

How have electron microscopes enabled scientists to develop their understanding of cells?

A
  • Allow small sub-cellular structure (such as mitochondria and ribosomes) to be observed in detail.
  • Enable scientists to develop more accurate explanations about how cell structure relates to function.
46
Q

What are the disadvantages of electron microscopes? (4)

A
  • Expensive.
  • Large so less portable.
  • Require training to use.
  • Only dead specimens can be observed.
47
Q

How can magnification be calculated?

A

Magnification = size of image / size of real object

48
Q

What is standard form?

A

A way of expressing numbers - written as a figure between 1 and 10 multiplied by a positive or negative power of 10.

49
Q

How do bacteria multiply?

A

Binary fission (simple cell division).

50
Q

How often do bacteria multiply?

A

Once every 20 minutes if enough nutrients are available and the temperature is suitable.

51
Q

State 2 ways in which bacteria can be grown

A
  • Nutrient broth solution.

- Colonies on an agar gel plate.

52
Q

What nutrients make up a nutrient broth solution?

A

All nutrients required for bacteria to grow including nitrogen for protein synthesis, carbohydrates for energy and other minerals.

53
Q

What are uncontaminated cultures of microorganisms needed for?

A

Investigating disinfectant and antibiotic action.

54
Q

Describe the preparation of an uncontaminated culture using aseptic technique

A

1) Whenever working aseptically, all work should be carried out in front of a lit bunsen burner with a yellow flame.
2) Hot agar jelly is poured into a sterilised petri dish. The agar is left to cool and set.
3) An inoculating loop is passed through a hot flame before it is used to transfer bacteria to the culture medium.
4) Petri dishes should only be opened as little as possible, at the side facing the bunsen burner.
5) The lid of the petri dish should be secured with tape at intervals around the dish and stored upside down.
6) The cultures should not be incubated above 25°C in a school laboratory.

55
Q

Why must Petri dishes and culture media be sterilised before use?

A

To kill any bacteria already present.

56
Q

Why must inoculating loops be sterilised by passing them though a Bunsen burner flame?

A

To kill any bacteria present on the inoculating loop.

57
Q

Why must the Petri dish lid be secured with tape and the whole dish stored upside down?

A
  • Stops bacteria in the air contaminating the culture.
  • The lid is not fully sealed to prevent growth of anaerobic bacteria in a lack of oxygen.
  • Upside down to prevent condensation dripping down onto the colonies.
58
Q

Why are cultures incubated at 25°C in school laboratories?

A

Harmful pathogens are less likely to grow at this temperature.

59
Q

What is the formula used to calculate cross-sectional area of a bacterial colony or clear area around a bacterial colony?

A

πr²

60
Q

How is number of bacteria in a population after a certain time calculated from the mean division time?

A

1) Calculate the number of times the bacteria will divide in the given time period from the mean division time.
2) Use the following equation:

Number of bacteria in population at end of time period = number of bacteria at the beginning of time period x 2^number of division in the time period

Express the answer in standard from if possible.

61
Q

Calculate the number of bacteria that will be present after 3 hours for a population that divides every 15 minutes and has 5 present bacterium present now

A

1) 15 minutes = 0.25 hours.
2) 3/0.25 hours = 12 divisions.
30 5 x 2^12 = 20480 or 2.048 x 10^4.

Biology - Cell biology (3 decks)

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