2.1 Cell Structure

Question 1

Describe staining

Answer 1

Coloured stains bind to chemicals within the specimen which allows the specimen to be visualised and allows organelles to be viewed by improving contrast.

Question 2

Describe differential staining

Answer 2

More than one dye is used to differentiate between different components of the specimen.

Question 3

Which stains bind to specific cell structures?

Answer 3

Acetic Orcein stains DNA dark red
Eosin stains cytoplasm pink
Sudan black stains membranes and other lipids black

Question 4

Describe how the specimen should be prepared.

Answer 4

• Thin sections to allow light to pass through.
• Artefacts (damage to the specimen) could occur.

Question 5

What are light microscopes used for?

Answer 5

To view whole cells or tissues.

Question 6

Describe transmission electron microscope TEM

Answer 6

• Pass beam of electrons through thin (to prevent deflection of electrons) specimen
• Following treatment with heavy metal solutions, some areas appear darker as electrons cannot pass through.
• Allow you to look at organelles in detail.
  (TEM images may appear different to eachother if cut along different planes)

Question 7

Scanning electron microscopes

Answer 7

Look at cell surface
Beam of electrons scans the surface of the specimen
Reflected beam detected
Reflected beam and source on same side of specimen

Question 8

Describe laser scanning confocal

Answer 8

Look at object within certain depth of a cell
Specimen is treated with fluorescent dye
Laser focuses on this causing the dye to be seen
Very thin specimen, very high resolution, detect eye problems

Question 9

Define magnification and resolution

Answer 9

The number of times larger an image appears compared to the actual object

The ability to distinguish between two points

Question 10

Magnification of light, SEM and TEM

Answer 10

Light: x1500 (some ×2000)
SEM: ×100,000
TEM:×500,000

Question 11

Resolution of light, SEM and TEM

Answer 11

Light: 50-200nm
SEM: 0.20 nm
TEM: 0.05-1 nm

Question 12

Describe eye piece graticule and stage micrometer

Answer 12

Eyepiece: ruler
Stage micrometer: calibrate eyepiece graticule

Question 13

What equation is associated with microscopy images?

Answer 13

Image = actual × magnification

Question 14

Nucleolus

Answer 14

Region inside the nucleus where tRNA and rRNA are formed, makes ribosomes

Question 15

Nucleus

Answer 15

Contains linear chromosomes, regulates gene expression and protein synthesis, governs characteristics of a cell

Question 16

Nuclear envelope

Answer 16

Double membrane, separates nucleus contents from cytoplasm, nuclear pores allow substances to pass between the nucleus and cytoplasm

Question 17

Rough endoplasmic reticulum

Answer 17

Fluid filled cavities (cisternae) coates with ribosomes, involved in intracellular transport

Question 18

Smooth endoplasmic reticulum

Answer 18

Involved in transport, synthesis and absorption of lipids from the gut, contain enzymes which catalyse lipid metabolism reactions

Question 19

Golgi apparatus

Answer 19

Stack of membrane bound flattened sacs, site of protein modification, proteins packaged in secretory versicles

Question 20

Mitochondria

Answer 20

Spherical, rod shaped, branched, double membrane with fluid filled space between, cristae, fluid filled matrix, site of ATP production during aerobic respiration

Question 21

Lysosomes

Answer 21

Vesicles, single membrane, hydrolytic enzymes

Question 22

Ribosomes

Answer 22

Small (20nm), spherical, ribosomal RNA in nucleolus as two subunits which combine in cytoplasm, site of protein synthesis

Question 23

Cell wall

Answer 23

Cellulose fibres, strength and support, permeable

Question 24

Vacuole

Answer 24

Surrounded by a membrane (tonoplast), contains water and solutes, maintain cell stability and turgidity

Question 25

Cilia

Answer 25

Protrusions from cell membranes, contain microtubules (form centrioles)

Question 26

Cytoskeleton

Answer 26

Network of protein structures in the cytoplasm

Question 27

Centrioles

Answer 27

Two bundles of microtubules perpendicular to each other. Involved in cell division (spindles), involved in forming cilia

Question 28

Chloroplasts

Answer 28

Double membrane, membrane bound flattened sacs (thylakoid) in stacks (granum), fluid filled matrix (stroma), thylakoid contain chlorophyll. Loops of DNA and starch grains. Site of photosynthesis

Question 29

Describe the cytoskeleton

Answer 29

Microfilaments: actin, contract in cytokinesis, changes cell shape
Microtubules: tubulin, move chromosomes, move organelles
Intermediate filaments: actin and microtubules, whole cell support, mechanical strength

Question 30

Importance of cytoskeleton

Answer 30

Whole cell support
Movement of cilia and flagella (using ATP)
Changing cell shape
Moving organelles e.g. vesicles
Movement of chromosomes