Biology Grade 12

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Lesson 1
Key Questions

1. Mg2+ has 10 electrons

2. Given that the half life of the radioisotope carbon -14 is 5730 years, it would not be useful in dating bones that are over a million years old. After 40 000 years of age less than 1% of the 14C is left in the bone and thus it is not useful for determining the exact age beyond that.

3. Hydrolysis - A chemical reaction where a chemical is broken down by a reaction with water. Hydrolysis is important for the digestion of food, making it biologically important.

1. Condensation - The opposite of hydrolysis, when two molecules form one. In most biochemical reactions water is produced when the molecules join. Condensation reactions are used to build muscle tissue making them biologically important.

2. Oxidation and Reduction (Redox) - An electron transfer between two substances where they both lose and gain electrons. It is used for cellular respiration making it biologically important.

3. Neutralization - The reaction of an acid and a base to produce water and a salt. It is used to maintain an optimal pH of around 7.4 in the human body making it biologically important.

4. a) Oxygen, Hydrogen, Carbon
b) 6

Lesson 2
Key Questions

5. Muscle cells require more mitochondria than fat cells because muscle cells are constantly using energy, where as fat cells store energy until it is needed. Mitochondria organelles produce energy.

6. a) Active transport requires energy to operate. Diffusion is passive transport and does not require energy. b) Active transport moves molecules up the concentration gradient, low to high concentration. Diffusion goes down the concentration gradient, high to low concentration.

7. Receptor-mediated endocytosis unlike Phagocytosis can aquire bulk quantities of specific substances, It can also recognize and bind molecules before they are engulfed. Phagocytosis only engulfs large, solid particles.

8. The phospholipid bilayer has a hydrophylic exterior and a hydrophobic interior, it does not allow polar charged molecules to pass through but it does allow small uncharged molecules to pass through. There are proteins and cholesterol in the membrane. Since it is semi-fluid at low temperatures cholesterol can keep the phospholipids apart, where at higher temperatures it brings the phospholipids together, stabilizing the membrane.

9. a) The problem being investigated is whether a carrot is hypertonic or hypotonic when put in pure distilled water and/or in a salt solution. b) Beaker A contained the distilled water, because the osmometer rose in level, where as in beaker B the osmometer decreased in level. In beaker A the carrot was hypotonic to the water and water moved by osmosis into the carrot causing it to swell up. In beaker B the carrot was hypertonic to the water and the water left the carrot causing it to shrivel up.

10. Salt water is hypertonic to the cells, because of the lower concentrations of solute outside compared to the inside of the cell, through osmosis, water is "pulled" out of the gum tissue to make fluid in mouth isotonic. This reduces the intracellular fluid and thus reduces the swelling of the gums.

Lesson 3
Key Questions

a) Carbohydrates
i) Monomer(s)
Monosaccharides, Oligosaccharides, Polysaccharides
ii) Functional groups
Aldoses and ketoses
iii) Linkage type
iv) Primary function
Building material for energy, cell identification and communication b) Proteins
i) Monomer(s)
Amino acids
ii) Functional groups
An amino group (NH2), carboxylic acids (COOH) and a radical group (R)
iii) Linkage type
Peptide bond
iv) Primary function
Almost everything cells do
c) Lipids
i) monomer(s)
ii) Functional groups
fatty acids and glycerol
iii) Linkage type
iv) Primary function
Energy storage, physical and thermal insulation, key components in cell membranes, raw...
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