Unit 1 - Cellular function

Question 1

what is the role of the peroxisome?

Answer 1

break down of lipids by beta oxidation producing hydrogen peroxide which is neutralised by catalase to water and oxygen

Question 2

what is the role of the golgi body?

Answer 2

• modifies/ packages proteins for secretion

- transport vesicles from endoplasmic reticulum to golgi to fuse with the cis face

Question 3

what chemical changes occur to proteins by the golgi body?

Answer 3

post-translational modification:

• glycosylation (addition of oligosaccharides)
• phosphorylation
• sulphation (addition of sulphates)

Question 4

where and how are vesicles budded off from the cisternae of golgi?

Answer 4

from trans face

- exocytosis

Question 5

what model describes the cell membrane?

Answer 5

• fluid mosaic model
• fluid - phospholipids can move relative to one another
• mosaic: embedding of proteins different size/shapes

Question 6

what type of proteins are found in the membrane?

Answer 6

• intrinsic/ integral: carrier proteins/ channels

- extrinsic/ peripheral: surface - receptors, recognition sites

Question 7

what else is found on extracellular surface in cell membranes?

Answer 7

carbohydrates - form glycocalyx (cell coat) and also involved in cell recognition

Question 8

what is the role of the cholesterol in the cell membrane?

Answer 8

interfere with hydrophobic interactions between tails so decreases the fluidity - sometimes causing crystallisation

Question 9

what is the cytoskeleton?

- name four functions

Answer 9

flexible lattice of fibrous proteins - filaments

functions: mechanical structure/ support, intracellular transport, suspension of organelles, adhesion

Question 10

what are the types of filament found in the cytoskeleton?

Answer 10

• microfilaments: actin - dynamic structure
• intermediate filaments - stronger/ more stable - keratin
• microtubules - formed of alpha/beta tubulin provide strength, form spindle fibres, components of cilia and flagella, moves vesicles around cell by motor proteins that walk them along the tubules (dynein= towards centrosome/ kinesins=away)

Question 11

what is another term for centrosome?

Answer 11

MTOC - microtubule organzing centre

Question 12

What is the outer surface of cilia called and what is it composed of?

Answer 12

• axoneme
• nine doublet microtubules arranged around a pair of microtubules with protein links at regular intervals which provide attachment to the cytoskeleton by basal body

Question 13

how does the rapid motion of cilia/flagella occur?

Answer 13

motor protein = ciliary dynein linked by polypeptide chain to one side of doublet microtubule and other free head interacts with neighbouring microtubule

• ATP hydrolysis occurs so able to bind to next protein subunit
• in this way it bends the cilium so bent region progresses along producing a rhythmic wave-like motion so material is swept across

Question 14

what defect causes cystic fibrosis?

Answer 14

defect in chloride channel (CFTR) in apical membrane of epithelial cells so no chlorine transport

• no osmotic gradient is formed - no water
• mucus undiluted - difficulty breathing - leads to pneumonia - fertile environment for bacteria

Question 15

what is lysosomal disease?

Answer 15

lack of lyzozymes so there is an accumulation of fats/sugars in lysosome which disrupts normal cell function leading to lsd

Question 16

What is kartagener’s syndrome?

Answer 16

defective dynein gene so cannot sweep mucus from airways leads to respiratory infection

Question 17

what type of cell is an enterocyte?

Answer 17

absorptive cell

• simple columnar epithelial cell
• microvilli on surface to increase SA for absorption

Question 18

what is the difference between the secretory cells of exocrine and endocrine?

Answer 18

• exo: mucus

- endo: hormones

Question 19

how does cell motility occur?

Answer 19

• extends projection called lamellopodium in direction of movement and attaches to substrate that provides traction to allow cell to be pulled along by polymerisation and depolymerisation of actin