B Cells

Question 1

What is the cytoskeleton composed of?

Answer 1

1. Microfilaments - made of actin, help the cell move and contract during cytokinesis.
2. Microtubules - made of globular tubulin proteins that form tubes. Determine cellular shape and act as tracks for organelle movement.
3. Intermediate fibres - give cells strength.

Question 2

What are the functions of the cytoskeleton?

Answer 2

• Supports cell.
• Holds organelles in place.
• Allows cells to change shape during endocytosis and exocytosis.
• Facilitates movement of organelles.
• Makes up centrioles.

Question 3

What is the structure and function of centrioles?

Answer 3

• Made of microtubules.
• Assemble and organise spindle fibres during cell division.

Question 4

Structure and function of the flagella

Answer 4

• Tail-like extensions that detect changes in the cell’s environment and help the cell move.
• In eukaryotes they have a 9 + 2 arrangement of microtubules, and are thicker than flagella in prokaryotes .

Question 5

Structure and function of cilia

Answer 5

Hair-like extensions that move particles that surround the cell by beating rhythmically.

Question 6

Structure and function of the rough endoplasmic reticulum

Answer 6

• Made of folded membranes, with ribosomes attached to the membrane.
• Some proteins produced by ribosomes are converted to glycoproteins.
• Packages proteins and glycoproteins made by ribosomes into vesicles.

Question 7

Structure and function of smooth endoplasmic reticulum

Answer 7

• Made of a folded membrane.
• Secretes lipids and carbohydrates, which are packaged into vesicles.

Question 8

Structure and function of Golgi apparatus

Answer 8

• Made of a folded membrane.
• Vesicles from the rough and smooth ER bind to the Golgi apparatus. It modifies these molecules and then packages them into vesicles.
• When the Golgi apparatus fills vesicles with enzymes, it forms lysosomes (that contain digestive enzymes - lysozymes - which break down cell walls of bacteria that invade cells).

Question 9

Structure of mitochondria

Answer 9

• Contains an outermsmbrane, and an inner membrane that forms cristae.
• Matrix contains ribosomes and mitochondrial DNA.

Question 10

What is the cell wall composed of?

Answer 10

In plants and algae: cellulose
In fungi: chitin
In bacteria: peptidoglycan

Question 11

Function of the vacuole

Answer 11

• Keeps cells turgid.
• Stores sugars and amino acids as an energy source.

Question 12

Structure of chloroplasts

Answer 12

• Contain a double-membraned envelope.
• Filled with thylakoids, which are stacked to form grana.
• Thylakoids contain the pigment chlorophyll (essential for photosynthesis).
• Grana sit in a fluid called storm, which contains ribosomes, DNA and starch grains.

Question 13

What are prokaryotic cells?

Answer 13

Single-celled organisms that don’t contain membrane bound organelles (don’t contain a nucleus).

Question 14

Compare a eukaryotic cell and a prokaryotic cell (eg. bacteria)

Answer 14

• Similarities: contain a cytoplasm, cell-surface membrane, and non membrane-bound organelles, such as ribosomes.
• Differences: 80S ribosomes vs 70S ribosomes, prokaryotes contain a peptidoglycan cell wall and circular DNA in the cytoplasm, bacteria have an outer capsule to prevent excessive water loss.

Question 15

What are viruses?

Answer 15

• Non, living acellular parasitic particles.
• Made of DNA or RNA wrapped in a protein coat (capsid).

Question 16

How to use light microscopes?

Answer 16

• Start with the low powered objective lens to locate cells, then increase objective lens (increasing magnification).
• Shows 2D images of cells and tissues in a sample.

Question 17

Describe lascar scanning confocal microscopes

Answer 17

• Specimen is stained with a dye, a laser is put through the specimen, specimen becomes fluorescent and gives off light which is detected.
• High resolution image, can be 2D or 3D.

Question 18

How to calculate length of a cell?

Answer 18

Calibrate the eyepiece graticule

Question 19

Describe scanning electron microscopes:

Answer 19

• Detects electrons that bounce off the sample.
• Produces a 3D image of the outer surface.
• Resolution = 3-10 nm

Question 20

Describe transmission electron microscopes:

Answer 20

• Detects electrons that are transmitted through the sample surface.
• 2D black and white images of the internal structure.
• High resolution (0.5 nm).

Question 21

Compare optical and electron microscopes:

Answer 21

Optical (light) microscopes:
- 200nm resolution
- Can view living specimens
- Colour images

Electron microscopes:
- Greater magnification and resolution
- Black and white images

• Optical microscopes and SEMs allow for thick sample sections, so it is easier to prepare the sample, reducing the risk of artefacts.