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Biology > 1.1 Cell Structure > Flashcards

1.1 Cell Structure Flashcards

Completed | T1 Cell Biology | physicsandmathstutor

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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? (3)

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 of?

A

Peptidoglycan

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4
Q

How is genetic information stored in a prokaryotic cell? (2)

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? (2)

A
  • Small rings of DNA found free in the cytoplasm and separate from the main DNA.
  • They carry genes that provide genetic advantages e.g. antibiotic resistance.
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6
Q

What is order of magnitude?

A

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

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7
Q

What is a centimetre (cm)?

A

1 × 10⁻² metres

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8
Q

What is a millimetre (mm)?

A

1 × 10⁻³ metres

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9
Q

What is a micrometre (μm)?

A

1 × 10⁻⁶ metres

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10
Q

What is a nanometre (nm)?

A

1 × 10⁻⁹ metres

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11
Q

What is the difference in order of magnitude between a human hair (100 μm) and the HIV virus (length = 100 nm)?

A

100 μm = 10⁻⁴ m
100 nm = 10⁻⁷ m
-4-(-7) = -4 + 7 = 3

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12
Q

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

A
  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Mitochondria
  • Ribosomes
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13
Q

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

A
  • Chloroplasts
  • Permanent vacuole
  • Cell wall
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14
Q

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

A

Controls cellular activities

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15
Q

Describe the structure of the cytoplasm. (2)

A
  • Fluid component of the cell.
  • Contains organelles, enzymes and dissolved ions and nutrients
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16
Q

What is the function of the cytoplasm? (2)

A
  • Site of cellular reactions e.g. first stage of respiration.
  • Transport medium.
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17
Q

What is the function of the cell membrane?

A

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

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18
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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19
Q

What is the function of the ribosomes?

A

Site of protein synthesis - joins amino acids in a specific order during translation for the synthesis of proteins.

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20
Q

What is the plant cell wall made of?

A

Cellulose

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21
Q

What is the function of the plant cell wall? (2)

A
  • Provides strength.
  • Prevents the cell bursting when water enters by osmosis.
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22
Q

What does the permanent vacuole contain?

A

Cell sap (a solution of salts, sugars and organic acids).

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23
Q

What is the function of the permanent vacuole?

A

Supports the cell, maintaining its turgidity.

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24
Q

What is the function of chloroplasts?

A

Site of photosynthesis - contains chlorophyll which is used to absorb sunlight energy / make food during photosynthesis.

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25
Q

Describe how sperm cells in animals are adapted to their function. (4)

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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26
Q

Describe how nerve cells in animals are adapted to their function. (3)

A
  • Long axon allows electrical impulses to be transmitted all over the body from the central nervous system.
  • 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.
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27
Q

Describe how muscle cells are adapted to their function. (3)

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.
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28
Q

Describe how root hair cells in plants are adapted to their function. (3)

A
  • Large surface area maximises rate of absorption of nutrients and water from surrounding soil.
  • Thin walls that do not restrict water absorption.
  • Contain lots of mitochondria which release energy for active transport of mineral ions.
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29
Q

How is the xylem adapted for its function? (3)

A
  • Lignin-thickened walls strengthen / support the structure and prevent collapse.
  • No end walls between cells allowing water and dissolved mineral ions to flow easily from the roots to the leaves by transpiration.
  • Made of dead cells with no internal structures providing a continuous route for water to flow.
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30
Q

How is the phloem adapted for its function? (3)

A
  • Vessel cells (no nucleus and limited cytoplasm) allow dissolved sugars to efficiently move through the cell interior.
  • Sieve plates (end walls of vessels) let dissolved amino acids and sugars translocate up and down the stem.
  • Companion cells (connected to vessel cells) have lots of mitochondria, providing energy to the vessel cell, which is needed for the active transport of substances.
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31
Q

What is cell differentiation?

A

The process by which cells become specialised.

32
Q

Why is cell differentiation important?

A

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

33
Q

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

A

Early in their life cycle

34
Q

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

A

Throughout their entire life cycle

35
Q

What is the purpose of cell division in mature animals?

A

Repair and replacement of cells.

36
Q

What changes does a cell go through as it differentiates?

A

As a cell become specialised, it goes through the acquisition of different sub-cellular structures to enable specific functions to be performed by the cell.

37
Q

Define magnification.

A

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

38
Q

Define resolution.

A

The smallest distance between two objects that can be distinguished.

39
Q

How does a light microscope work?

A

Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed.

40
Q

What are the advantages of light microscopes? (4)

A
  • Inexpensive
  • Easy to use
  • Portable
  • Observe both dead and living specimens
41
Q

What is the disadvantage of light microscopes? (2)

A

Limited resolution power and magnification

42
Q

How does an electron microscope work?

A

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

43
Q

Name the two types of electron microscope. (2)

A

Transmission electron microscope (TEM) Scanning electron microscope (SEM)

44
Q

What is the advantage of electron microscopes? (2)

A

Greater magnification and higher resolution power.

45
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.

46
Q

How have electron microscopes enabled scientists to develop their understanding of cells? (2)

A
  • Allow small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in finer detail.
  • Enable scientists to develop more accurate explanations about how cell structure relates to function.
47
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
48
Q

How can the magnification of an image be calculated?

A

Magnification = size of image / size of real object

49
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.

50
Q

Write 0.005 in standard form.

A

0.005 (3 jumps) = 5 × 10⁻³

51
Q

Write 10382 in standard form.

A

10382 (4 jumps) = 1.0382 × 10⁴

52
Q

What are the components of light microscopes? (7)

A
  • Stage
  • Clips
  • Objective lenses (3)
  • Eye piece (consists of an eye piece lens)
  • Fine focussing dial
  • Coarse focussing dial
  • Lamp / mirror
53
Q

What is the order of size (descending) of the following: chromosome, nucleus, cell, gene, DNA, and organism?

A
  1. Organism
  2. Cell
  3. Nucleus
  4. Chromosome
  5. Gene
  6. DNA
54
Q

List the components of bacterial cells. (8)

A
  • Capsule
  • Cell wall
  • Plasma membrane
  • Cytoplasm
  • Plasmid
  • Ribosome
  • Nucleoid (DNA)
  • Bacterial flagellum
55
Q

How do bacteria multiply?

Triple only

A

Binary fission (simple cell division)

56
Q

How often do bacteria multiply?

Triple only

A

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

57
Q

State 2 ways in which bacteria can be grown.

Triple only

A
  • Nutrient broth solution
  • Colonies on an agar gel plate
58
Q

What nutrients make up a nutrient broth solution? (5)

A

Nutrients required for bacteria growth; For example

  • Carbohydrates (for energy).
  • Nitrogen (for protein synthesis).
  • Glucose (for respiration).
  • Amino acids (for protein → growth).
  • Other mineral ions.
59
Q

What are uncontaminated cultures of microorganisms needed for?

Triple only

A

Investigating disinfectant and antibiotic action.

60
Q

Describe the preparation of an uncontaminated culture using aseptic technique. (6)

A
  1. Wipe workspace with disinfectant.
  2. Heat inoculating loop in the flame and allow to cool down.
  3. Open lid of the bottle slightly to insert the loop - quickly replace lid.
  4. Open lid of the Petri dish slightly and spread the loop on the surface.
  5. Quickly close lid of Petri dish then seal securely with tape.
  6. Incubate upside down in an oven at 25ºC to allow growth of bacteria.
61
Q

Why must Petri dishes and culture media be sterilised before use? (2)

A

To kill any present, and prevent growth of, unwanted bacteria.

62
Q

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

A

To kill unwanted microorganisms present on the loop.

63
Q

Why must the Petri dish lid be secured with adhesive tape? (2)

A
  • It prevents unwanted bacteria in the air entering the culture.
  • The lid is not fully sealed so that anaerobic bacteria won’t grow.
64
Q

Why are cultures incubated at 25ºC in school laboratories?

A

Harmful bacteria are more likely to grow at a higher temperature.

65
Q

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

A

πr²

[π = 3.14 | r = radius | r = diameter ÷ 2]

66
Q

How is the number of bacteria in a population after a certain time calculated from the mean division time? (3)

A
  1. Ensure both times (mean division time and the time dividing) are of the same units.
  2. Calculate the number of divisions by doing: time dividing / mean division time.
  3. Multiply the current population by 2 to the power of the number of divisions to find the number of bacterial cells produced.
67
Q

Why must the workspace be disinfected?

A

To sterilise/kill unwanted microorganisms.

68
Q

Why must we open the lid of the Petri dish slightly?

A

To reduce contamination of unwanted bacteria entering from surrounding air.

69
Q

Why must the Petri dish be stored upside down?

A

To prevent condensation from forming and dripping down onto the colonies.

70
Q

Question:

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

A
  1. Convert total division time.
    Total division time = 3 (hours) × 60 mins = 180 mins
  2. Calculate number of divisions.
    Number of divisions = 180 (mins) ÷ 15 (mins) = 12
  3. Calculate number of bacteria.
    Number of cells = 5 × 2¹² = 20480 bacteria or 2.048 × 10⁴ bacteria

Number of divisions = Total division time (mins) ÷ Mean division time (mins)
Number of bacteria = Current bacteria × 2number of divisions

71
Q

Question:

A bacterial cell has a mean division time of 40 minutes. How many cells will it have produced in 2 hours?

A
  1. Convert total division time.
    Total division time = 2 hours × 60 mins = 120 mins
  2. Calculate number of divisions.
    Number of divisions = 120 mins ÷ 40 mins = 3
  3. Calculate number of cells.
    Number of cells = 1 × 23 = 8 cells

Number of divisions = Total division time (mins) ÷ Mean division time (mins)
Number of bacteria = Current bacteria × 2number of divisions

72
Q

What are the two ways to calculate the number of bacteria cells produced in a given time?

A
  1. Number of divisions = Total division time (mins) ÷ Mean division time (mins)
  2. Number of bacteria = Current bacteria × 2number of divisions

OR

  1. Number of divisions = Total division time (hours) ÷ Mean division time (hours)
  2. Number of bacteria = Current bacteria × 2number of divisions
73
Q

How do you convert minutes into hours; how about hours to minutes?

A

Hours = number of minutes ÷ 60
Minutes = number of hours × 60

74
Q

Question:

A cell has a mean division time of 20 minutes. How many cells will it have produced after 3 hours?

A
  1. Convert total division time.
    Total division time = 3 hours x 60 mins = 180 mins
  2. Calculate number of divisions._
    Number of divisions = 180 / 20 = 9
  3. Calculate number of cells.
    Number of cells = 2⁹ = 512 cells

Number of divisions = Total division time (mins) ÷ Mean division time (mins)
Number of bacteria = Current bacteria × 2number of divisions

75
Q

Question:

Staphylococcus aureus replicates every 20 minutes. If there were 300 bacterial cells replicating in nutrient broth, how many cells would there be in the broth after 24 hours?

A
  1. Convert total division time.
    Total division time = 24 hours × 60 mins = 1440 mins
  2. Calculate number of divisions._
    Number of divisions = 1440 / 20 = 72
  3. Calculate number of cells.
    Number of cells = 300 × 272 = 1.45 × 1024 cells

Number of divisions = Total division time (mins) ÷ Mean division time (mins)
Number of bacteria = Current bacteria × 2number of divisions

Biology (19 decks)

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