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AQA BIOLOGY A LEVEL > 2.1 CELL STRUCTURE > Flashcards

2.1 CELL STRUCTURE Flashcards

1
Q

What is a eukaryotic cell?

A

The DNA has a nucleus, and it has membrane bound organelles.

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2
Q

What is a prokaryotic cell?

A

The DNA is free in the cytoplasm and it has no membrane bound organelles.

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3
Q

What is the structure of the nucleus?

A
  • Nuclear envelope membrane.
  • Nuclear pores, controls what come in and out of nucleus.
  • Nucleoplasm to make rRNA.
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4
Q

What is the function of the nucleus?

A
  • Site of protein synthesis.
  • Contains genetic information.
  • Makes ribosomes.
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5
Q

What is the structure of the mitochondria?

A
  • Double layer membrane controlling what enters and leaves.
  • Membranes folded over to form cristae that increase SA.
  • Matrix of biological molecules.
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6
Q

What is the function of mitochondria?

A
  • Site of aerobic respiration.

- Produces ATP for respiration.

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7
Q

What is the structure of the chloroplast?

A
  • Double membrane to control entry and exit.
  • Have discs of membrane called thylakoids.
  • Many thylakoids together form the grana to increase SA.
  • Stroma of biological molecules (matrix).
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8
Q

What is the function of chloroplasts?

A
  • Site of photosynthesis

- Stroma provides glucose for photosynthesis.

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9
Q

What is the structure of the Golgi apparatus?

A

Stacks of membranes with vesicles on them. (cisternae)

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10
Q

What is the function of the Golgi apparatus?

A
  • Modifies and packages proteins.
  • Forms lysosomes.
  • Makes glycoproteins.
  • Lipids come here to get modified, bind to vesicles, and the leave the apparatus.
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11
Q

What is the structure of a lysosome?

A
  • Single layer membrane

- Simple sac filled with lysozyme, digestive enzymes.

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12
Q

What is the function of a lysosome?

A
  • Breaks down cells after death.
  • Releases digestive enzymes by exocytosis.
  • Hydrolyses digested cell.
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13
Q

What is the structure of the endoplasmic reticulum?

A
  • 3d sheets of membrane, forming the cisternae.

Rough: has ribosomes on the surface

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14
Q

What is the function of rough endoplasmic reticulum?

A

Site of protein-synthesis.

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15
Q

What is the function of smooth endoplasmic reticulum?

A

Site of lipid-synthesis

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16
Q

What is the structure of ribosomes?

A

Has two subunits, and is formed by the combination of rRNA and proteins.

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17
Q

What is the function of ribosomes?

A

Site of translation where:
Large sub-unit: holds the amino acid binding site.
Small sub-unit: holts the mRNA binding site.

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18
Q

What is the structure of the cell wall?

A
  • Made up of polysaccharides

- Has a middle boundary lamallae to separate adjacent cell walls.

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19
Q

What is a plant cell wall made of?

A

Cellulose

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20
Q

What is a bacteria / fungi cell wall made of?

A

Murein

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21
Q

What is the function of the cell wall?

A
  • Provides support to cell.
  • Acts as a barrier to pathogens.
  • Provides the apoplast pathway for the diffusion of water in plants.
22
Q

What is the structure of the vacuole in plants?

A

Simple membrane containing cell sap.

23
Q

What is the function of the vacuole in plants?

A
  • Support the plant.

- Provides and stores sugars / amino acids / minerals / enzymes etc.

24
Q

What is the function of plasmids in prokaryotes?

A

Carries DNA.

25
Q

What is the function of the flagella in prokaryotes?

A

Allow some organisms to travel.

26
Q

What is the function of the capsule in prokaryotes?

A

Provides mechanical and structural support to prokaryotes.

27
Q

What are the similarities between eukaryotes & prokaryotes?

A
  • Cell membrane
  • Cytoplasm
  • Ribosomes
28
Q

How are prokaryotes different to eukaryotes?

A
  • No organelles
  • No nucleus
  • circular DNA
  • smaller ribosomes
  • DNA is not associated with histones
    (some have flagella, pilli, plasmids)
29
Q

What are the principles of optical microscopes?

A
  • Lenses focus light on specimen.

- Reflected light can be seen through the eyepiece.

30
Q

What are the advantages of an optical microscope?

A
  • Colour image
  • Can use lining specimen
  • Cheaper
31
Q

What are the limitations of an optical microscope?

A
  • Needs a long wavelength of light.
  • Has low/no resolution.
  • Specimen need to be dyed before they are observed.
32
Q

What are the principle of the transmission electron microscope?

A
  • Beam of electrons is absorbed by a thin specimen.
  • Darkest means more electrons absorbed.
  • Lighter means less electrons absorbed.
33
Q

What are the advantages of a TEM?

A
  • Very powerful magnification

- High resolution

34
Q

What are the limitations of a TEM?

A
  • 2D image.
  • Black and white image.
  • Electron beam kills specimen.
  • Very complex staining process for a thin specimen.
35
Q

What are the principles of the scanning electron microscope?

A
  • Beam of electrons is focused onto the specimen.

- Electrons are reflected off onto an observable plate. (where the image is produced)

36
Q

What are the advantages of a SEM?

A

3D image

37
Q

What are the limitations of a SEM?

A
  • Needs a vacuum for the specimen.
  • Lower resolution than TEM
  • Black and white image.
  • Very complex staining process for specimen.
38
Q

How do you prepare a slide for an optical microscope?

A
  1. Put a thin specimen onto a slide.
  2. Add a drop of stain on top.
  3. Add a coverslip, using a mounted needle at a 45 degree angle. (this prevents air bubbles)
39
Q

What is the definition of resolution?

A

The ability to distinguish between two objects.

40
Q

What is the definition of magnification?

A

How many times bigger images appear compared to the actual object.

41
Q

What is the formula that shows the relationship between magnification, image size and actual size?

A

Magnification = Image size / actual size

42
Q

How do you calibrate a microscope?

A

Using the eyepiece graticule and stage graticule.

43
Q

What does the stage graticule do?

A

Shown the true length (essentially a ruler)

44
Q

What does the eyepiece graticule do?

A
  • Has regular divisions, calibrated against the stage graticule at every magnification.
  • Stay the same at every magnification.
  • You need to find out the length of each division to calibrate to actual lengths of a structure.
45
Q

What is the process of cell fractionation?

A

When cells are broken up into their organelles.

46
Q

What are the conditions necessary for cell fractionation?

A

COLD, to stop enzyme action
BUFFERED, to keep a constant pH
ISOTONIC: to prevent osmotic changes in organelles

47
Q

What is the first stage of cell fractionation?

A

Homogenisation.

48
Q

Outline homogenisation.

A
  1. Cells are broken up in a homogeniser.
  2. This releases the organelles.
  3. The homogenate is then filtered to get rid of debris.
49
Q

What is the second stage of cell fractionation?

A

Ultracentrifugation

50
Q

Outline ultracentrifugation.

A
  • Homogenate us spun in a centrifuge at low speeds.
  • The heaviest organelle is forced to the bottoms and forms the sediment.
  • The sediment is removed, leaving the supernatant.
  • The supernatant is re-spun at a higher speed to obtain the next heaviest organelle as the sediment.
  • This process continues until all the organelles are separated.
51
Q

What is the order of sediment after ultracentrifugation?

A
  1. Nucleus
  2. Mitochondria
  3. Chloroplasts

AQA BIOLOGY A LEVEL (38 decks)

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