OCR F212 Molecules, Biodiversity, Food and Health

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Molecules, Biodiversity, Food and Health
Biological Molecules
Amino Acids
Monomer of proteins
Join to form backbone of polypeptide
20 types naturally occurring
Differences caused by R-groups
Plants: Convert nitrates into amino group and bond to organic part made from photosynthesis products
Animals: Proteins broken down, 8 essential amino acids - can't be made from materials inside body
- Can only store certain amount, amino group toxic if too many
- Liver breaks amino acids down ­ deamination urea
Building proteins
Reaction between carboxyl group and amino group
Condensation reaction, bond broken by hydrolysis
Forms peptide bond to make dipeptide
Amino acid dissolves in water
Carboxyl group disassociates and releases H+
Amino group receives H+
No net charge
Protein Structure
Primary structure
Unique amino acid sequence of a polypeptide
Secondary structure
H-bonds form between amino acids
Non-specific, polypeptides can take up same shape
H-bonds 4 along the chain
Small parts of whole polypeptide can take up configuration
Beta-pleated sheet
Anti-parallel zigzagging chain
Stronger and less elastic than Alpha-helix
Tertiary structure
3D structure made in Golgi apparatus
H-bonds, Ionic bonds, Disulphide bridges
Globular proteins
Irregular, compact shape
Soluble ­ hydrophilic outside, hydrophobic inside
Fibrous proteins
Long chains rich with hydrophobic amino acids
Insoluble, unfolded, non-specific
Quaternary structure
How polypeptides link together (prosthetic group)
Haemoglobin: 4 polypeptide chains and haem group

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Molecules, Biodiversity, Food and Health
3 polypeptide chains wound around each other
H-bonds between chains = strength
Each collagen - strength
Collagen fibril collagen fibre
Arteries - collagen layer prevents bursting walls at high
Tendons mostly made of collagen
Bones formed from collagen
Cartilage and connective tissue made of collagen
4 polypeptide chains
- 2 a-chains, 2 b-chains, 1 haem group
Carries oxygen around the body
Bonds to oxygen in lungs, releases in tissues
Haem group contains Fe2+…read more

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Molecules, Biodiversity, Food and Health
Polysaccharide Structure Function
Starch Made of 2 polymers: Storage in plants
Amylose: polymer of glucoses joined by a-1,4-glycosidic bonds. Forms
helix with 6 molecules per turn & about 300 per helix
Amylopectin: polymer of glucoses jonied by a-1, 4-glycosidic bonds but
with branches of a-1,6-glycosidic bonds.…read more

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Molecules, Biodiversity, Food and Health
Cell membranes
All biological membranes are made of a phospholipid bilayer
Phospholipids have a hydrophobic head and hydrophilic tail
Partial permeability - substances don't move across the barrier
Most naturally occurring fats and oils are the fatty acid esters of
Esters with a low molecular weight are used as fragrances and found
in essential oils
3 fatty acids attached to a glycerol molecule
- Acids as they contain the carboxyl group -COOH
General formula C3H8O3…read more

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Molecules, Biodiversity, Food and Health
Add solution of potassium iodide to sample
If starch is present, the solution changes from yellow-
brown blue-black
Reducing sugars
Monosaccharide and disaccharide (molecule can react
with other molecule by giving electrons to them
When reducing sugar is heated to 80° with Benedict's
solution, solution changes from blue orange-red
Non-reducing sugars
Sucrose would have no colour change
Make sure there are no reducing sugars in sample ­
boil with hydrochloric acid
Hydrolyses any sucrose to glucose and…read more

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Molecules, Biodiversity, Food and Health
Nucleic Acids
Deoxyribonucleic acid
- Phosphate group
- Deoxyribose
- Organic base
Base can be a purine ­ two rings
- Adenine
- Guanine
Base can be a pyrimidine ­ one ring
- Cytosine
- Thymine
These components link together to form long
chains called polynucleotides
Two chains of nucleotide lie side by side in anti-
- Link by hydrogen bonds
- Forms a double-helix
Role of DNA
A gene is a sequence of DNA that…read more

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Molecules, Biodiversity, Food and Health
Ribonucleic acid
- Phosphate group
- Ribose sugar
- Organic base
Single stranded
Contains uracil instead of thymine
RNA uses information from the DNA to make
- Determines the primary structure of a
DNA replication
Semi-conservative replication
DNA replication takes place during Interphase
Each of the new DNA molecules are made of one old strand and one new strand of DNA
1. Hydrogen bonds between bases are broken by DNA helicase
2.…read more

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Molecules, Biodiversity, Food and Health
Enzyme action
Globular proteins
- Specific tertiary structure
Biological catalysts
- Catalyse reaction in the cell
- E.g. hydrolases inside lysosomes
- Released from cells onto food
- Break down organisms into nutrients
- E.g.…read more

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Molecules, Biodiversity, Food and Health
Changing conditions
Effect of changing concentration
Enzyme concentration
As enzyme concentration increases, more active sites become
- A maximum reaction rate will be reached when all the substrate molecules
occupy active sites
The substrate concentration becomes the limiting factor
Substrate concentration
As substrate concentration increases, collisions increase
- A maximum reaction rate is reached when all the active sites
are occupied
- Called Vmax
Effect of changing temperature
Higher temp More kinetic energy more collisions
higher rate of reaction…read more

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Molecules, Biodiversity, Food and Health
Enzyme inhibitors
A substance that slows down or stops an enzyme-controlled reaction
It is possible for other molecules to bind with the active site is it is similar to the substrate
Creates competition for it and the substrate for the site
Inhibitors that seriously disrupt controlled reactions act as metabolic poisons
- Death cap mushroom toxin called alpha-amanitin inhibits enzymes that catalyse production of RNA,
cells are no longer able to synthesise proteins
Competitive inhibitors
When the concentration of…read more


Brumack Ocaka

Thanks for this, it's a A LOT of help!:)<3

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