Chapter 1 to finish.

Question 1

Microfilaments info?

Answer 1

Made from specialised protein - actin.
Thinnest.
2 intertwined strands

Question 2

Functions of microfilaments?

Answer 2

Maintain cell shape
Enable motility
Enable muscle contraction
Enable cytokinesis of cell division

Question 3

Intermediate filaments?

Answer 3

More stable than microfilaments
Made from specialised protein called keratin.
fibres wound together.

Question 4

Function of intermediate filaments?

Answer 4

Maintain cell shape

Anchor nucleus and organelles in cytosol

Question 5

Microtubules info?

Answer 5

Largest
Made of tubulin
Arranged in hollow cylinders

Question 6

Functions of microtubules?

Answer 6

Maintain cell shape
Enable motility
Enable movement of chromosomes
Enable movement of organelles.

Question 7

Function of cytoskeleton

Answer 7

Help to maintain cell’s shape and structure
Enable movement of organelles within cytosol.
Enable intracellular transport of molecules and materials.
Enable movement of chromosomes to occur during mitosis and meiosis.

Question 8

Why fluid mosaic model?

Answer 8

Fluid - phospholipids and protein molecules can move about laterally within their monolayer.

Mosaic - Protein molecules are interspersed and scattered within each monolayer.

Question 9

Functions of cell membranes?

Answer 9

Control entry and exit of molecules within organelles.
Provide internal transport system.
Provide surfaces for chemical reactions
Isolate enzymes to prevent cellular damage

Question 10

Properties of phospholipid bilayer?

Answer 10

Hydrophobic core allows lipid soluble molecules to cross bilayer.
Hydrophilic phosphate head prevents water soluble molecules from crossing bilayer.
Allows membrane to be flexible and stable.

Question 11

Function of intrinsic and peripheral proteins

Answer 11

Span both monolayers.
Channel proteins for water-soluble molecules and ions.
Structural role.

Question 12

Info on cholesterol?

Answer 12

Interspersed between PPL molecules.
Mostly hydrophobic but part is hydrophilic.
At low temps it increases membrane fluidity and prevents close packing of fatty acid tails.
At high temps it decreases membrane fluidity and prevents excessive movement of PPL molecules.

Question 13

Function of cholesterol?

Answer 13

Regulate fluidity of membrane
Prevent water and water-soluble ions crossing membrane.
Reduce lateral movement of PPL within monolayer.

Question 14

Function of glycocalyx (and glycoprotein and glycolipid)

Answer 14

Acts as recognition sites

Glycocalyx - act as antigens, and is a carbohydrate chain which can be added to a protein or a PPL.

Question 15

Phospholipids info?

Answer 15

Polar hydrophilic head - choline, glyerol and phosphate group.
Non polar hydrophobic fatty acid tails

Question 15

Phospholipids info?

Answer 15

Polar hydrophilic head - choline, glyerol and phosphate group.
2 Non polar hydrophobic fatty acid tails

Arranged as a bilayer
Acts as a barrier to water soluble molecules.

Question 16

Bulk transport info?

Answer 16

Active movement across cell membranes.
Endocytosis (where csm folds in and extends to form a small vesicle or vacuole)

• Phagocytosis and pinocytosis

Exocytosis.

Question 17

What is phagocytosis?

Answer 17

When cells take in solid material in large quantities

They produce phagocytic vesicles.

Question 18

What is pinocytosis?

Answer 18

When cells take in liquid material in large quantities.

Very small vesicles formed in micropinocytosis.

Question 19

Definition of exocytosis?

Answer 19

Reverse of endocytosis.

Removal of waste products or secretion of useful products.

Question 20

Testing for presence of lipids info.

Answer 20

For liquid samples:
Add ethanol and distilled water, observe sample.

For solid samples:
Add ethanol and allow solid to settle on bottom. Pipette ethanol from each sample into another tube
Add distilled water, observe sample.

Qualitative test - Presence/absence of substance.
Positive = milky emulsion.

Semi-quantitative = height of emulsion- quantity of lipid.

Quantitative - Density of emulsion using colorimeter.

Question 21

Colorimeter practical info?

Answer 21

Beetroot cells contain purple pigment, betanin.
Investigates effect of temperature on membrane structure by considering leakage of betanin from beetroot cells.

Procedure:

• Add distilled water to test tubes and acclimatise in thermostatically controlled water baths.
• Collect beetroot cylinders and cut them all the same size. Dry them.
• Add to each tube and leave
• Remove cylinders from tubes and put in cuvettes.
• Record absorption for each ( graph with temperature)

Question 22

Explanation for the beetroot practical?

Answer 22

High temps - Kinetic energy of phospholipid molecules increases. causing ppl to move within monolayer and gaps form so Csm and tonoplast become disrupted, so betanin molecules move out.

Question 23

What does ethanol do in the beetroot practical?

Answer 23

Will cause membrane disintegration as it forms temporary bonds with phospolipid heads in membrane causing phospholipids to move and huge gaps in membrane to pigment leaks out.