L2 Cells and their organelles

Question 1

Cell polarity

Answer 1

Cells can have apical and basal polarity

Question 2

Single celled organisms can be infectious to humans

Answer 2

Salmonella typhimurium.

Escherichia coli

Question 3

Biomembranes [3]

Answer 3

plasma membrane defines cell limits

regulate solute transport

mediate cell to cell communication

Question 4

Membrane lipid example

Answer 4

phosphatidylcholine

Question 5

Fluidity of membrane affected by

Answer 5

percentage of cholesterol

Question 6

Anchors

Answer 6

Integrins

Link intracellular actin filament to extracellular matrix proteins

Question 7

Receptors

Answer 7

platelet-derived growth factor receptor

Bind extracellular PDGF and generate intracellular signals that cause cell to grow and divide

Question 8

Enzymes

Answer 8

Adenylyl cyclase

Catalyse production of intracellular signalling molecule cAMP due to extracellular signals

Question 9

Mitochondria [3]

Answer 9

Outer membrane is permeable
Inner membrane is far less permeable -> folded heavily to cristae
Inner membrane is matrix

Question 10

Golgi apparatus

Answer 10

Required for modification, packaging and sorting of proteins and lipids for secretion or for another organelle

Question 11

Lysosomes [3]

Answer 11

Small, irregular cytoplasmic vesicles

Packed with degradative enzymes

Principal sites of intracellular digestion

Question 12

Peroxisomes [4]

Answer 12

Small cytoplasmic vesicles

Contained environment for reactive H2O2 generation

Main function of oxidation - breakdown of fatty acids

Detoxify toxic substances ie ethanol (via catalyse)

Question 13

Cytoskeleton

Answer 13

Pull chromosomes apart in mitosis

Drives and guides intracellular traffic of organelles, proteins and RNA

Support plasma membrane

Enable some cells to move

Control cell shape

Question 14

Major components of cytoskeleton [3]

Answer 14

Intermediate filament
Microtubules
Actin filaments

Question 15

Actin filament

Answer 15

7 nm diameter

Polymers of actin monomers

Necessary for movement

Can form contractile bundles and microvilli

May associate with myosin to form powerful contractile structures

Carry cargo-bearing motor proteins (e.g. myosin)

Question 16

Intermediate filaments

Answer 16

10 nm diameter filaments
Made of a family of fibrous proteins;

Twisted into ropes and provide tensile strength
Needed to maintain cell shape

Question 17

Intermediate filaments fibrous proteins

Answer 17

keratin filaments in epithelial cells,
vimentin in many other cells,
neurofilament proteins in neurones,
lamins within the nucleus.

Question 18

Microtubules

Answer 18

20 nm diameter 
Polymers of tubulin dimers 
Organised from structures such as the centrosome 
Form the spindle in mitosis 
Important in cell shape and movement
Carry cargo-bearing motor proteins

Question 19

Adult stem cells

Answer 19

multipotent

Adult stem cells can divide to replace certain cell types. e.g. intestinal stem cells divide to replace gut tissue.

Question 20

Induced pluripotent stem cells advantage

Answer 20

Cells taken from patient should not elicit immune response
Fewer ethical issues
Theoretically, any cell type could be replaced

Question 21

Induced pluripotent stem cells disadvantage

Answer 21

More basic research needs to be done on developmental pathways
Transplanted stem cells could develop into cancer cells

Question 22

Apoptosis

Answer 22

Degrade intracellular structures and organelles
Collapse the cytoskeleton
Fragment the cell into mini-cells, which are engulfed by phagocytes for degradation.

Signalling processes within the cell activate intracellular suicide proteases

Question 23

Necrosis

Answer 23

The cell membrane’s integrity is destroyed.

The cell’s soluble contents are released into the tissue fluids.

Cell components are degraded by the actions of extracellular enzymes and phagocytic cells engulf the fragmentary remains.