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A-level Biology Year 1 > Cell Structure and Magnification > Flashcards

Cell Structure and Magnification Flashcards

1
Q

What is a eukaryotic cell?

A

A cell that contains a membrane-bound nucleus and are found in multicellular organisms

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2
Q

What is a prokaryotic cell?

A

A cell that contains no membrane-bound nucleus and are found in unicellular organisms

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3
Q

What are the 4 types of eukaryotic cells?

A

Animal, plant, fungi and protists

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4
Q

What are the structure in an animal cell?

A
  • Nucleus (which contains the nuclear envelope, chromatin and nucleolus)
  • Rough endoplasmic reticulum (RER)
  • Smooth endoplasmic reticulum (SER)
  • Mitochondria
  • Free ribosomes
  • Lysosomes
  • Golgi apparatus
  • Vesicles
  • Cell surface membrane
  • Cytoplasm
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5
Q

What are the structure in a plant cell?

A
  • Nucleus (which contains the nuclear envelope, chromatin and nucleolus)
  • Rough endoplasmic reticulum (RER)
  • Smooth endoplasmic reticulum (SER)
  • Mitochondria
  • Free ribosomes
  • Lysosomes
  • Golgi apparatus
  • Vesicles
  • Cell surface membrane
  • Cytoplasm
  • Vacuole
  • Chloroplasts
  • Cellulose cell wall
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6
Q

What is the role of the 3 parts of the nucleus?

A
  • The nuclear envelope is a double membrane with pores for mRNA to exit
  • Chromatin is DNA and proteins
  • Nucleolus is where ribosomes are synthesised
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7
Q

What is the role of the rough endoplasmic reticulum?

A

It folds and processes proteins

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8
Q

What is the role of the smooth endoplasmic reticulum?

A

It synthesises and processes lipids

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9
Q

What is the role of the mitochondria?

A

It is the site of aerobic respiration in eukaryotes, which produces ATP

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10
Q

What is the role of the lysosomes?

A

They digest invading cells in phagocytosis and break down worn out parts of the cell with digestive enzymes (lysozymes)

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11
Q

What is the role of the Golgi apparatus?

A

They modify, identify, process and package new lipids and proteins (MIPP).

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12
Q

What is the role of the vesicles?

A

They store lipids and proteins made by the Golgi apparatus and transport them to where they need to go.

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13
Q

What is the role of the cell surface membrane?

A

It controls what enters and leaves the cell

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14
Q

What is the role of the vacuole?

A

It maintains pressure inside the cell, keeping it rigid.

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15
Q

What is the role of the chloroplasts?

A

They are the site of photosynthesis

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16
Q

What is the role of the cell wall?

A

It supports the cell and keeps its shape (cellulose in plants, chitin in fungi and murein in bacteria)

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17
Q

What is the role of the flagella?

A

They allows cell to be mobile

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18
Q

Which features do algal cells not have?

A

They have no RER, SER or vacuole

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19
Q

What is the structure of a bacterial cell?

A
  • Pili
  • Free DNA
  • Plasmids
  • Mesosomes
  • Capsule
  • Smaller ribosomes
  • Flagellum (optional)
  • Cell membrane
  • Cytoplasm
  • Cell wall
20
Q

What is the role of the pili?

A

They aid in movement and attachment to surfaces.

21
Q

What is the role of the plasmids?

A

They are small circular DNA molecules.

22
Q

What is the role of the mesosome?

A

It is the site of aerobic respiration in prokaryotes.

23
Q

What is the role of the capsule?

A

It protects the cell and helps attach to surfaces.

24
Q

What is the structure of viruses?

A
  • Glycoproteins
  • Viral envelope
  • Capsid
  • Two RNA strands (identical)
  • Reverse transcriptase
25
Q

What is the role of the glycoproteins?

A

They attach to the host cell.

26
Q

What is the role of the viral envelope?

A

Similar to the cell membrane.

27
Q

What is the role of the capsid?

A

It protects the viral RNA.

28
Q

What is the role of viral RNA?

A

It is the viruses genetic information.

29
Q

What is the role of the reverse transcriptase?

A

It is used to convert viral RNA into viral DNA when inside a host cell.

30
Q

What is an optical microscope?

A

A microscope that use glass lenses to focus light to view both dead and alive specimens in colour

31
Q

What is an electron microscope?

A

A microscope that uses electrons passing through a thin specimen that is focussed with magnets to view dead specimens in B&W

32
Q

What are the two types of electron microscope?

A
  • Transmission electron microscope
  • Scanning electron microscope
33
Q

What is the difference between transmission and scanning electron microscopes?

A

Transmission - 2D images and can see inside cells (due to very thin specimen)
Scanning - 3D images and cannot see inside cells

34
Q

How would you prepare a microscope slide?

A
  1. Thin slice/section;
  2. Put on slide in water / solution / stain;
  3. Lower cover slip with a mounted needle to try to avoid air bubbles.
35
Q

What are the rules of producing a scientific drawing?

A
  1. No sketching
  2. No overhanging or crossed lines
  3. No shading
    4. Must look similar;
    5.   Correctly labelled;
    6.   Correct scale stated
36
Q

What is the magnification calculation?

A

Magnification = image size/actual size

37
Q

How to turn mm into µm?

A

x1000

38
Q

How to turn µm into nm?

A

x1000

39
Q

How to turn mm into nm?

A

x1,000,000

40
Q

What are the stages of cell fractionation and ultracentrifugation?

A
  1. Cell homogenisation to break open cells.- often with a blender
  2. Filter to remove (large) debris / whole cells.
    a. Use isotonic to maintain the water potential of the solution to prevent osmosis so the organelles do not shrivel or burst.
    b. Ice cold to reduce kinetic energy of enzymes which could damage the organelles.
    c. Use a buffer to keep the pH constant to prevent protein/enzyme denaturation.
  3. Centrifuge (at lower speed / 1000 g) to separate nuclei / cell fragments /heavy organelles.
  4. Re-spin (supernatant / after nuclei / pellet removed) at higher speed to get mitochondria in pellet / at bottom.
41
Q

Describe how you could make a temporary mount of a piece of plant tissue to observe the position of starch grains in the cells when using an optical (light) microscope. (4)

A
  1. Add a drop of water to a glass slide;
  2. Obtain thin section of plant tissue and place on slide;
  3. Stain with potassium iodide;
  4. Lower cover slip using mounted needle
42
Q

Describe the principles and the limitations of using a transmission electron microscope to investigate cell structure (5)

A

Principles:
1. Electrons pass through thin specimen
2. Denser parts absorb more electrons
3. So denser parts appear darker
4. Electrons have short wavelength so give high resolution
Limitations:
5. Cannot look at living material - must be in vacuum
6. Specimen must be very thin
7. Artefacts present
8. Complex staining method/long preparation time
9. Image not 3D

43
Q

Skin cells may be studied with a transmission electron microscope or an optical microscope. Explain the advantages and limitations of using a transmission electron microscope to study cells. (6)

A
  1. TEM uses (beam of) electrons;
  2. These have short wavelength;
  3. Allow high resolution/greater resolution/Allow more detail to be seen/greater useful magnification;
  4. Electrons scattered (by molecules in air);
  5. Vacuum established;
  6. Cannot examine living cells;
  7. Lots of preparation/procedures used in preparing specimens/ fixing/staining/sectioning;
  8. May alter appearance/result in artefacts;
44
Q

Contrast the structure of a bacterial cell and the structure of a human cell. (5)

A
  1. Bacterial cell is much smaller than a human cell;
  2. Bacterial cell has a cell wall but human cell does not;
  3. Bacterial cell lacks a nucleus but human cell has a nucleus;
  4. Bacterial cell lacks membrane-bound organelles but human cell has membrane-bound organelles;
    Accept any named membrane-bound organelle
  5. Bacterial ribosomes smaller than human ribosomes / bacteria have 70S ribosomes whereas humans have 80S ribosomes;
  6. Bacterial DNA is circular but human DNA is linear;
  7. Bacterial DNA is ‘naked’ whereas human DNA is bound to histones / proteins
45
Q

Contrast how an optical microscope and a transmission electron microscope work and contrast the limitations of their use when studying cells. (6)

A

-TEM use electrons and optical use light.
-TEM allows a greater resolution
-TEM doesn’t show colour and optical can.
-TEM requires thinner specimens.
-TEM focuses using magnets and optical uses lenses.
-TEM requires a more complex preparation.

A-level Biology Year 1 (19 decks)

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