All Notes Needed For OCR As Biology (F212 exam)

Biological Molecules

Water

• High Specific Heat Capacity – organisms survive in deeper warmer water; layer of ice prevents further heat loss.

• Hydrogen Bonds – creates surface tension; some small organisms can move across the surface of the water.

• Solvent – polar substances dissolve in water due to charges.

• Transport Medium – flows; blood plasma is mainly water.

• Involved in Metabolic Reactions – photosynthesis and respiration.

Proteins

Primary Structure – a sequence of amino acids.

Secondary Structure – twisting of the primary structure into alpha helix and beta pleated sheets.

Tertiary Structure – Hydrogen Bonds, Ionic Bonds, Disulfide Bridges, Hydrophobic Interactions.

Quaternary Structure – addition of prosthetic groups, carbohydrates, etc.

Haemoglobin

• Globular Protein
• Chain of amino acids
• Alpha helical secondary structure
• Hydrogen, ionic, disulfide, hydrophobic bonds in tertiary structure
• 4 polypeptide chains (2 alpha, 2 beta)
• 1 haem group per polypeptide
• Fe²⁺ ion in haem

Collagen

• Fibrous Protein
• High proportion of glycine
• 3 polypeptide chains
• Chains form a tight coil held by hydrogen bonds
• Ends of parallel molecules are staggered
• Covalent bonds form between adjacent molecules
• Prevents lines of weakness

Carbohydrates

Alpha Glucose – OH is below carbon 1

Beta Glucose – OH is above carbon 1

Amylose

• Energy Store (Plants)
• Polysaccharide
• Alpha Glucose
• 1,4 glycosidic links
• Non-branched
• Compact

Amylopectin

• Energy Store (Plants)
• Polysaccharide
• Alpha Glucose
• 1,6 glycosidic links
• Branched
• Insoluble to not affect water potential
• Easily hydrolysed

Cellulose

• Plant Cell Walls
• Beta Glucose
• 1,4 glycosidic links
• Each glucose molecule is rotated 180 to its neighbour
• Straight chains
• Adjacent chains held by hydrogen bonds

Glycogen

• Energy Store (Animals)
• Polysaccharide
• Alpha Glucose
• 1,4 glycosidic links and 1,6 glycosidic links
• Branched and Compact
• Insoluble to not affect water potential

Lipids

Triglyceride

• 1 Glycerol Molecule

• 3 Fatty Acids

• Ester Bonds

Phospholipid

• 1 Glycerol Molecule

• 2 Fatty Acids

• 1 Phosphate

Cholesterol

• 4 carbon rings

• Hydrophobic

• Hormones & Vitamin D

• Cause gallstones and atherosclerosis

Protein

• Biuret A and Biuret B
• Blue to Lilac

Reducing Sugar

• Benedicts
• Warm
• Blue to Brick Red

Non-Reducing Sugar

• Hcl
• NaOH
• Benedicts
• Warm
• Blue to Brick Red

Starch

• Iodine
• Brown to Black

Lipids

• Alcohol
• Water
• White Emulsion

Glucose Colorimetry

• Add Benedicts Solution

• Solution turns brick red

• Remove red precipitate

• Use colorimeter

• Calibrate using water

• use a red filter

• record readings of absorbance

• less absorbance = more glucose

• using known concentrations, set up calibration curve

• read concentrations off the graph

Enzymes

• Globular proteins.

• Soluble in water.

• Specific 3D shape.

• Catalyse chemical reactions inside and outside cells.

Enzymes are Specific to the Substrate they act on

• Tertiary structure form the active site.

Lock and Key Theory

• Active site has a specific shape that is complementary to the substrate.

Induced Fit Theory

• Enzyme changes shape slightly as the substrate binds with the active site.

• Makes active site fit more closely around the substrate.

• Change in shape put stress on bonds in substrate so reaction occurs more easily.

Factors Affecting Enzyme Controlled Reactions

Enzymes Concentration – Increases rate of reaction.

• More active sites available.

• More chance of substrate colliding with active site.

• More product produced.

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