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AS Level Biology > Chapter 1: Cell Structure > Flashcards

Chapter 1: Cell Structure Flashcards

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1
Q

What are the basics units to living organisms?

A

Cells

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2
Q

What piece of equipment is used to view cells?

A

Microscope

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3
Q

Describe how a light microscope works

A

Light rays pass through the specimen on a slide and are focused by an objective lens and an eyepiece lens. This produces a magnified image of the specimen on the retina of your eye

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4
Q

Name some alternative ways to view the images formed by a light microscope.

A
  1. Screen projection
  2. Camera Recordings
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5
Q

How does an electron microscope work?

A

It uses beams of electrons. The electrons are focused onto a screen, or onto photographic film, where they form a magnified image of the specimen.

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6
Q

What are the conditions required for an electron microscope to work well?

A

The specimen has to be very thin and must be placed in a vacuum, to allow electrons to pass through it

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7
Q

Define Magnification.

A

Magnification is the size of an image
divided by the size of the actual object

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8
Q

Define Resolution.

A

Resolution is the size of the smallest
objects that can be distinguished.

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9
Q

Describe Resolution.

A

It is the ability of the microscope to distinguish two objects as separate from one another. The smaller the objects that can be distinguished, the higher the
resolution.

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10
Q

What is the main determining factor for resolution?

A

the wavelength of the rays that are being
used to view the specimen.

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11
Q

Why do electron microscopes have a a higher resolution?

A

The wavelength of a beam of electrons is much
smaller than the wavelength of light.

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12
Q

Name the 3 units used to measure cells.

A

mm, µm, and nm

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13
Q

how many meters is 1 mm?

A

1 × 10−3 m

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14
Q

how many meters is 1 µm?

A

1 × 10−6 m

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15
Q

how many meters is 1 nm?

A

1 × 10−9 m

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16
Q

What is the formula for magnification?

A

Actual size

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17
Q

What is the eyepiece graticule?

A

It is a little scale bar that you can place
in the eyepiece of your light microscope.

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18
Q

How is an eye piece graticule and stage micrometer used to measure the length of a specimen?

A
  1. the length of the specimen is found in graticule units.
  2. Use the stage micrometer to calibrate the graticule, by replacing the specimen. then line the them up.
  3. Find the ratio between the values of graticule units and stage micrometer units.
  4. Then, find the real length of the specimen.
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19
Q

What is the stage micrometer?

A

A stage micrometer is the term typically referring to a slide that comes with a scale on its surface.

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20
Q

What is calibration?

A

It is the comparison of the grid or scale on the eyepiece graticule with the scale markings of a known dimension on a stage micrometre

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21
Q

What is the cell surface membrane?

A

is a double layer of lipids and proteins that surrounds a cell and separates the cytoplasm from its surrounding environment

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22
Q

why do cells have many other membranes?

A

To make different compartments so that different chemical reactions take place with out interfering with one another.

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23
Q

What is the main function of a cell surface membrane?

A

It controls what enters and leaves the cell.

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24
Q

what is the nuclear envelope?

A

It is a pair of membranes that surround the nucleus.

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25
Q

What is a chromosome?

A

A very long molecule of DNA contained inside the nucleus.

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26
Q

What is the role of DNA?

A

It determines the sequences in which amino acids are linked together in the cytoplasm to form protein molecules.

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27
Q

What does the nucleolus look like?

A

It is a darker area within the nucleus.

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28
Q

What is the role of the nucleolus?

A

It is where new ribosomes are made, following the code given by the DNA.

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29
Q

What are ribsomes?

A

They are small structures made of RNA and protein.

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30
Q

Where are ribosomes found?

A

They are found free in the cytoplasm and attached to the rough endoplasmic reticulum.

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31
Q

What is the ribosome in the RER and cytoplasm?

A

80S

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32
Q

what does an 80S ribosome mean?

A

They are larger than the ones found in mitochondria and chloroplasts.

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33
Q

What is the Rough endoplasmic reticulum?

A

It is an extensive network of membranes in the cytoplasm. The membranes enclose small spaces called cisternae.

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34
Q

Where and how are proteins made?

A

Proteins are made on the ribosomes, by linking together amino acids.

35
Q

What is the cisternae?

A

is small spaces in the RER enclosed by the membrane.

36
Q

Explain how proteins to be processed/exported are sent to the Golgi body.

A

The growing chains of amino acids move into the cisternae and then break off to form little vesicles that travel to the golgi body.

37
Q

What happens to the proteins that go to the golgi body?

A

They are modified, for example, adding carbohydrate groups to them.

38
Q

What is exocytosis?

A

Is when vesicles containing modified proteins break away from the Golgi body and are transported to the cell surface membrane to be released into the extracellular space.

39
Q

Describe the interrelationship between the RER and the Golgi body.

A
  1. Proteins made by the ribosomes on the rough endoplasmic reticulum and are pinched off into vesicles.
  2. Vesicles containing the proteins fuse to the Golgi body, where the proteins are modified.
  3. Vesicles containing modified proteins break away from the Golgi body.
  4. Vesicles fuse with the cell surface membrane,releasing the proteins outside the cell.
40
Q

What is the smooth endoplasmic reticulum

A

it is like the RER but less extensive. It does not have ribosomes and the cisternae are more flattened than those of the RER.

41
Q

What is the function of the SER?

A

It is involved in the synthesis of steroid hormones and the breakdown of toxins.

42
Q

What surrounds the mitochondria?

A

An envelope (two membranes)

43
Q

What is a Cristea?

A

is what is formed when the envelope of the mitochondria fold inwards.

44
Q

What is the matrix?

A

is a viscous gel-like material in the mitochondria.

45
Q

what is the function of the mitochondria?

A

It is where aerobic respiration takes place, producing ATP.

46
Q

name the two stages of aerobic respiration in mitochondria and where they take place.

A
  1. Krebs Cycle -> matrix
  2. Oxidative phosphorylation ->
    membranes of the cristea
47
Q

What does the mitochondria contain?

A
  1. Ribosomes (70S)
  2. Small, circular molecule of DNA
48
Q

What are lysosomes?

A

They are little membrane-bound packages of hydrolytic (digestive) enzymes.

49
Q

How are lysosomes formed?

A

They are formed by breaking off from the Golgi body.

50
Q

What is the main function of lysosomes?

A

They are used to digest bacteria or other cells taken into the cell by phagocytosis, or to break down unwanted or damaged organelles within the cell.

51
Q

What are centrioles

A

They are organelles found in animal cells, made of microtubules, arranged in a circular pattern.

52
Q

what are microtubules made of?

A

Actin.

53
Q

What is the main function of centrioles?

A

They are arranged in right angles to one another. From here, they microtubules are made and they form the spindle during cell division.

54
Q

Outside of cell division, what is the function of the microtubules?

A

they are found throughout the cell where they help form the cytoskeleton which helps the cell keep shape.

55
Q

what are chloroplasts surrounded by?

A

An envelope made from two membranes.

56
Q

What is stroma?

A

Is is the background material of the chloroplast.

57
Q

what are thylakoids?

A

They are paired membranes inside the stroma of the chloroplast.

58
Q

What are Grana?

A

they are structures formed when the thylakoids stack up.

59
Q

What is the function of the Grana?

A

They contain chlorophyll which allows energy to be absorbed from the sunlight.

60
Q

Name the two reactions of photosynthesis and name where they take place.

A
  1. The light dependent reaction/ photophosphorylation: membranes
  2. Calvin cycle: Stroma
61
Q

What are the starch grains of the chloroplast?

A

They are storage materials formed from the sugars that are produced in photosynthesis.

62
Q

What does chloroplasts contain?

A

70S ribosomes and a circular DNA molecule.

63
Q

What is the cell wall?

A

A structure surrounding plant cells made of cellulose, not found in animal cells.

64
Q

Name a few process that organisms use energy for.

A

active transport of substances across membranes, movement and the building up of large molecules

65
Q

What is the most immediate source of energy for organisms?

A

Adenine triphosphate (ATP)

66
Q

How does ATP release energy?

A

it is broken down to Adenine diphosphate and a phosphate ion, and releases a small packet of energy.

67
Q

how is ATP made?

A

Mitochondria make it by aerobic respiration while chloroplasts make with by the light dependent stage of photosynthesis.

68
Q

where are prokaryotic cells found?

A

In bacteria and archea.

69
Q

Where is eukaryotic cells found?

A

animals, plants, protoctista and fungi.

70
Q

what is the difference between a prokaryotic cell ad an eukaryotic cell?

A

they do not have a nucleus or any other organelles bound by a double membrane

71
Q

how many cells do prokaryotic and eukaryotic cells have?

A

Prokaryotic have 1 as they are unicellular. And Eukaryotic cells have variable amounts as the are multicellular.

72
Q

Describe the presence of cell surface membranes in prokaryotic and eukaryotic cells.

A

All cells have a cell surface membrane.

73
Q

Describe the presence of cell walls in prokaryotic and eukaryotic cells.

A

Prokaryotic cells always have cell walls which are made out of peptoglycans. Animal cells always never have a cell wall, while plant cells have cells walls made out of cellulose.

74
Q

Describe the presence of nucleus and nuclear envelopes in prokaryotic and eukaryotic cells.

A

Nuclei is not present in prokaryotic cells. They are always present in eukaryotic cells.

75
Q

Describe the presence of chromosomes in prokaryotic cells.

A

Prokaryotic cells contain a bacterial chromosome, which is a circular molecule of DNA not associated with histones (naked DNA) bacteria may contain DNA circles called plasmids.

76
Q

Describe the presence of chromosomes in Eukaryotic cells.

A

They contain several chromosomes,
each made up of a linear DNA
molecule associated with
histones.

77
Q

Describe the presence of in prokaryotic and eukaryotic cells.

A

They are never present in prokaryotic cells, but usually present in eukaryotic cells.

78
Q

Describe the presence of chloroplasts in prokaryotic and eukaryotic cells.

A

Prokaryotic cells never do, although they contain chlorophyll and other photosynthetic pigments. They are never present in animal cells, but usually present in plant cells.

79
Q

Describe the presence of ribosomes in prokaryotic and eukaryotic cells.

A

Prokaryotic cells have 70S ribosomes. Eukaryotic cells have 80S ribosomes while their mitochondria has 70S ribosomes.

80
Q

Describe the presence of centrioles in prokaryotic and eukaryotic cells.

A

Usually present in animal cells, but never present in prokaryotic or or plant cells.

81
Q

What are viruses?

A

Theyr are extremely small, non cellular particles of RNA or DNA surrounded by a protein
coat

82
Q

Why are viruses termed as parasitic?

A

Viruses are not able to carry out any of
the processes characteristic of living things unless they are inside a living cell,
where they ‘hijack’ the cell’s machinery to make copies of themselves.

83
Q

Why might viruses be dangerous?

A

They might cause disease.

AS Level Biology (7 decks)

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