How to examine cells and tissues

Question 1

State the relationship between milli, micro and nanometres

Answer 1

milli : 10^-3
micro : 10^-6
nano ; 10^-9

Question 2

State meaning of tissue

Answer 2

Tissue = latin for woven

Group of cells with similar structure, act together to form specific function

Question 3

Describe common biopsy techniques giving examples of tissues which can be sampled by each method

Answer 3

1. Needle biopsy (pipelle, trephine, punch biopsy) - for endometrial tissue
2. Bone marrow biopsy - for bone marrow
3. Liver biopsy - for liver tissue
4. Kidney biopsy - for kidney tissue
5. Skin biopsy - for skin tissue

Question 4

Explain why tissue needs to be fixed and state which fixatives are commonly used

Answer 4

• to preserve the biopsy and prevent digestion by microbes or destroyed by decay
• Formalin solution (10% buffered) : 37% formaldehyde + Distilled water 900ml + NaH2PO4 4g + Na2HPO4 (anhydrous) 6.5g

Question 5

State the components of tissue stained by routine stains (H&E) and specialist methods (immunohistochemistry and immunofluorescence)

Answer 5

Haematoxylin (basic dye) - binds to acidic structure (DNA,RNA)
Eosin (acidic dye) - binds to basic structure (Intrac and extrac protein)

• Utilise labelled antibodies to localise specific cell and tissue targets (antigen)
• antibodies directed labelled with fluorescent dyes allows structure to be visualised directly with incident light from UV light

Question 6

Define “limit of resolution”

Answer 6

The smallest distance by which two objects can be separated and still be distinguishable as two seperate objects

Question 7

Explain why electron microscopes are capable of finer resolution than light microscope

Answer 7

• Wavelength of electron is thousands of times shorter than visible light
• limit of resolution is smaller
• has magnification of x500,000 while LM is x600
• has resolution of 0.23nm while LM is 0.25um

Question 8

Describe structure and function of organelles

Answer 8

1. Plasma membrane
   - outermost bounding membrane of cell
   - glycoprotein and glycolipids projected outwards from pm
   - transport materials along and across membrane
   - signal transduction
2. RER
   - ribosomes attach to outer surface
   - generates protein for cell exterior, lysosomes, cell membrane incorporation
3. SER
   - not associated with r
   - Cisternae not as flattened as RER, less extensive, scattered around cytoplasm
   - lipid biosynthesis and intracellular transport
4. Golgi apparatus
   - Have polarity - proteins migrate from convex to concave end of stack
   - sort, concentrate, package and modify proteins synthesised by RER
5. Lysosomes
   - contain acid hydrolases
   - dense, spherical or oval
   - digestion and waste removal
6. Peroxisomes
   - bound by single membrane, contain granular matrix, spherical
   - parenchymal cell - modify toxic molecules before they re-enter bloodstream
   - neutrophils - peroxide use to kill bacteria
   - sites of oxygen utilisation and peroxide production
   - enzyme catalase use H2O2 to oxidise phenols, alcohols, formic acid, formaldehyde
7. Mitochondrion
   - elongated oval, double membrane, inner membrane highly folded - cristae
   - generate ATP by oxidative phosphorylation

Question 9

Describe structure and function of organelles

Answer 9

1. Plasma membrane
   - outermost bounding membrane of cell
   - glycoprotein and glycolipids projected outwards from pm
   - transport materials along and across membrane
   - signal transduction
2. RER
   - ribosomes attach to outer surface
   - generates protein for cell exterior, lysosomes, cell membrane incorporation
3. SER
   - not associated with r
   - Cisternae not as flattened as RER, less extensive, scattered around cytoplasm
   - lipid biosynthesis and intracellular transport
4. Golgi apparatus
   - Have polarity - proteins migrate from convex to concave end of stack
   - sort, concentrate, package and modify proteins synthesised by RER
5. Lysosomes
   - contain acid hydrolases
   - dense, spherical or oval
   - cellular digestion
6. Peroxisomes
   - bound by single membrane, contain granular matrix, spherical
   - parenchymal cell - modify toxic molecules before they re-enter bloodstream
   - neutrophils - peroxide use to kill bacteria
   - sites of oxygen utilisation and peroxide production
   - enzyme catalase use H2O2 to oxidise phenols, alcohols, formic acid, formaldehyde
7. Mitochondrion
   - elongated oval, double membrane, inner membrane highly folded - cristae
   - generate ATP by oxidative phosphorylation
8. Cytoskeleton
   - consist of microfilaments, intermediate filament and microtubules
   - maintaining cell shape
   - provides structural support and movement for plasma membrane and cell organelles
   - provides locomotor mechanism
   - provides contractility in cells - muscle
9. Nucleus
   - contains DNA, nucleoproteins and RNA
   - not present in terminally differentiated cells - erythrocyte, stratum corneum, lens fibre cell
10. Nucleolus
    - electron dense structure within nucleus
    - site of rRNA synthesis
11. Nuclear Envelope
    - double layer membrane
    - type of specialised ER
    - contain nuclear pore - macromolecules can be transported, micro molecules can diffuse without hindrance