A concise and clear overview of the key concepts covered in chapter 3. These notes make biology easy to understand and are a good place to start your revision and boost your grades.
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Biology A
Modules 1,2,3,4
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BIOLOGICAL MOLECULES
BIOLOGICAL ELEMENTS BONDING
•4 key elements: Hydrogen, Covalent Bond: 2 atoms share electrons
Carbon, Oxygen and Ionic Bond: one atom donates an electron and the other receives it,
they become ions
Nitrogen (+ Phosphorus and
Hydrogen Bond: unequal sharing of electrons between O and H, O is
Sulfur)
electronegative and H is electropositive, making it a polar molecule, so
bonds form between the OH molecules
FOOD GROUPS
•Water
•Carbs
•Fats
•Protein
•Minerals
•Fibre
•Vitamins CHEMICAL GROUPS USES
•Protein: structure, transport, antibodies, most hormones
•Nucleic Acid: information molecule
METABOLISM
•Water: contributor to reactions, transport, support for plants,
“every chemical reaction that solvent for metabolic reactions
happens in your body”
•Carbs: energy supply, energy storage, structure
- either: ANABOLIC or CATABOLIC
•Lipids: some hormones (sex), electrical insulator in neurones,
thermal insulation, energy storage, membranes, energy supply,
structure
•Vitamins and minerals: parts of larger molecules, enzyme
activators or coenzymes (iron in Hb)
WATER (H bonds)
VACANCY •Less dense as a solid than a liquid: less KE, more H bonds form
but molecules get pushed apart as H bonds can only form at specific
Carbon = 4 Nitrogen = 3 distances, therefore ice floats (stops water underneath freezing)
Oxygen = 2 Hydrogen = 1 •High specific heat capacity: energy needed to raise the temp of
1gram of a substance by 1°C. - energy needed to break H bonds
•High latent heat of evaporation: doesn’t fluctuate temp or
CARBOHYDRATES (SUGAR) evaporate easy - good for aquatic life, important for ectotherms (cold blooded
•Dissolves solvents: H is attracted to negative ions and O is attracted to
positive ions so water surrounds them (transport + chemical reactions)
•Cohesive: moves as one, H bonds hold together, goes up roots
•Adhesive: attracted to other materials - surface tension (pond skaters)
•Coolant: maintains temps at chemical reactions so enzymes don’t denature
•Important in all metabolic reactions
- glucose is a hexose sugar CARBS
- Pentose sugars - ribose / Cn(H2O)n, where n is no. of Carbons
deoxyribose, RuBP, Galactose • Monosaccharide: 1 sugar unit (glucose)
- Glucose is polar and dissolves in • Disaccharide: 2 sugar units. (lactose, sucrose, maltose)
water • Oligosaccharide: 3-9 sugars
• Polysaccharide: many units (cellulose, glycogen)
, ROLE OF MONOSACCHARIDES 3 main carbohydrates:
•Source of energy in respiration - high yield of energy due to
number of carbon-hydrogen bonds, energy released when they
- storage = starch (p)+
break making ATP glycogen (h) (alpha glucose)
•Building blocks for larger molecules (starch, glycogen, cellulose) - Structure = cellulose (beta
•Ribose used to make ATP and RNA, Deoxyribose = DNA
glucose)
Always stored as
CONDENSATION REACTIONS (alpha 1-4 glycosidic
polymers because…
bond)
- insoluble so doesn’t interfere
with water potentials in
osmosis
- Easier to stare and transport
CONDENSATION REACTIONS (beta 1-4 glycosidic bond)
- every other glucose flips so OH and H groups are
next to each other
HYDROLYSIS REACTIONS
- breaks glycosidic bonds, splits up to form OH on
glucose 1 and H on glucose 2
STARCH
•Either AMYLOSE or AMYLOPECTIN
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