biology

Question 1

Describe ribosomes and what they do?

Answer 1

Function: Synthesis lipids and proteins, Ribsomes:
small and spherical, can be attached to Rough ER or be free floating

Question 2

describe vacuole, and what they are like in plant and animal cells?

Answer 2

Vacuole: Fluid filled space enclosed by membrane, containing food and water
Animal: vacuoles are small, numerous and temporary
Plants: One large central vacuole, containing cell sap

Question 3

what is the golgi body and what does it do?

Answer 3

Golgi body: stacks of flattened membrane sacs
Function: modifies, sorts and repackages content to be released out of cell/ used by cell

Question 4

what is smooth and rough ER and what do they do?

Answer 4

Smooth ER and Rough ER: layers of membrane folded through cytoplasm
Smooth ER: no ribosomes, detoxifies drugs and poison
Rough ER: has ribosome, modifies proteins by ribosomes

Question 5

what is the difference between animal and plant cells?

Question 6

what are the adaptations of RBCs?

Answer 6

1. Bi-concave shape: allow for higher surface area to volume ratio, to allow for maximum rate of oxygen diffusion
2. Elastic: to squeeze through capillaries
   3: No nucleus: to contain more hemoglobin (binds reversibly to oxygen, to carry oxygen)

Question 7

what are the adaptations of root hair cells?

Answer 7

RHC: root hair cells have long and narrow root hair extensions
1. Long and narrow extension: increase Surface area to volume ratio to increase rate of absorption
2. More mitochondria: to release more energy for active transport of mineral salts
Main concept: when concentration of mineral salts increase, water potential goes down and water enters from soil through osmosis

Question 8

what are the adaptations of xylem cells?

Answer 8

1. Dead cells with no cross walls, cytoplasm and nucleus: so allow for uninterrupted water flow
2. Lignified walls: strengthens xylem walls, preventing collapse

Question 9

Define diffusion and it’s role in nutrient uptake and gaseous exchange

Answer 9

Diffusion: net movement of substances from an area of higher to lower concentration down a concentration gradient
Factors affecting diffusion: Temperature, SA:V ratio, mass of molecule, concentration gradient

Question 10

Define osmosis and describe the effects of osmosis in plant and animal cells

Answer 10

Osmosis: Net movement of water from an area region of higher water potential to lower potential through a partially permeable membrane
Water loss in animal cell: Crenation (shrinking)
Water gain in animal cell: expand and burst
Water loss in plant cells: Flaccid (cell wall is fully permeable)
Water gain in plant cell: Turgid (cell wall prevents bursting)

Question 11

Define active transport, and ion uptake by RHCs and villi

Answer 11

active transport is when energy is used to transport substances from an area of lower concentration to higher concentration against a concentration gradient (only in respiring cells)

Question 12

What is the role of water in living organisms? (remember 3)

Answer 12

1. universal solvent for chemical reaction
2. keeps plant cells turgid
3. regulates body temperature

Question 13

Carbohydrates, Fats and Proteins

Answer 13

Carbohydrate(C, H and 0): Monosaccharides, Disaccharides, Polysaccharides (single sugars, double sugars, complex carbohydrates)
Monosaccharides:
- can pass through cell membrane
- can no longer be digested
eg: glucose and fructose
Disaccharides:
-can be digested into smaller molecules
eg: sucrose and lactose
Polysaccharides: starch, cellulose, glycogen
Proteins (C, H and O)
-building blocks: amino acids
- AAS linked by peptide bonds
- many AAS known as polypeptides
- 1 or more polypeptide chains are protein molecules
Lipids (C, H and O):
- fats oils and steroids
- insoluble in water
- structure: 3 fatty acid and 1 glycerol backbone

Question 14

Describe the starch test

Answer 14

Starch: Iodine test
1. Cut into fine pieces/2cm^3 of solution
2. Add 5 drops of iodine solution
3. Shake the mixture
Results:
Yellow brown: starch absent
Blue black: starch present

Question 15

Describe the test for reducing sugars

Answer 15

Reducing sugars: Benedict’s Test
1. Cut into fine pieces/2cm^3 of test solution
2. Add 2cm^3 and crush with glass rod (solid)
3. Add 2cm^3 of benedict’s solution and shake well
4. Heat in boiling water bath for 3 mins
5. Remove and observe the color
Results:
Light blue: Reducing sugar absent
Tinge of orange ppt: small amt of reducing sugar
Yellow-green ppt: small amt of reducing sugar
Orange-red ppt:
Lots of reducing sugars present

Question 16

describe the test for proteins

Answer 16

Proteins: Biuret test
1. For solid (cut into fine pieces, add 2cm^3 of water and crush with glass rod)/ take 2cm^3 of test solution
2. Add 2cm^3 of biuret solution
3. Shake well and let stand for 5 minutes
Results:
Pale blue: Proteins absent
Purple: Proteins present

Question 17

describe the tests of fats

Answer 17

Fats: Ethanol Emulsion test
1. Cut into fine pieces and crush and put into dry test tube/ Add 2cm^3 of test solution
2. Add 4cm^3 of alcohol and crush/ Add 4cm^3 of alcohol
3. Shake well filter and add 5 drops of water to filtrate drop by drop shaking/ Add water drop by drop shaking
Results:
Clear solution: Absent
Cloudy/ white emulsion formed: Fats present

Question 18

State what glycogen, polypeptides proteins, and lipds are synthesised from

Question 19

explain enzyme reaction in terms of lock and key hypothesis

Answer 19

Enzymes: Biological catalyst that speed up reactions and remain chemically unchanged after.
Lock and Key:
1. Each enzyme has specific 3D shaped active site
2. Only substrates with 3D shape complemetary to the active site can fit to the enzyme
3. Enzyme substrate complex is formed
4. Chemical reaction occurs
5. Substrate is converted into products
6. Products detach from active site
7. Enzyme remains chemically unchanged
Catabolic reaction:
split into two
Anabolic reaction: two substrates into one

Question 20

explain the effects of temperature and pH on rate of enzyme reactions