AS Unit 1 OCR Biology Revision

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Biology Revision
Biological Molecules
Risk factor - A factor that increases your chance of developing a disease
Metabolism - The sum total of all biochemical reactions taking place in the cells of an organism
Carbohydrates - Make up a group of molecules with C, H and O in the ration Cn(H2O)
Polysaccharides - Polymers of monosaccharide's
Chemical group and role
o Energy storage and supply - structure
o Structure, transport, enzymes, antibodies, most hormones
o Membranes, energy supply, thermal insulation, electrical insulation in neurones
Vitamins and Minerals
o Parts of larger molecules
o Take part in some metabolic reactions
o Act as coenzymes or enzyme activators
Nucleic Acids
o Information molecules, carry instructions for life
o Takes part in most reactions
o Support in plants
o Solvent - medium for most metabolic reactions
o Transport
Catabolic reaction
Breaking larger molecules into smaller ones - digestion
Anabolic reaction
Building smaller molecules into larger ones - muscle growth
Monomers and polymers
o Monomer = Monosaccharides
o Polymer = Polysaccharides
o Monomer = Amino Acids
o Polymer = Polypeptides and Proteins
Nucleic Acid
o Monomer = Nucleotides
o Polymer = DNA and RNA
Condensation and Hydrolysis reaction
o Water molecule released
o New covalent bond is formed
o Larger molecule is produced by bonding of two smaller molecules
o Water molecule is used
o Covalent bond is broken
o Smaller molecules are formed by the splitting of a larger molecule
Energy source - Glycogen
Energy store - Starch
Structure - Cellulose
o Soluble in water
o Sweet tasting
o Form crystals
3 carbons - triose sugars
5 carbons - pentose sugars
6 carbons - hexose sugars
Alpha glucose

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Beta glucose
o Formed by many condensations of alpha glucose
Glycosidic bond between glucose subunits occurs between Carbon 1 and Carbon 4
Thus 1,4 glycosidic bond
Coil into a spring makes it compact
Iodine turns from yellow to black as it becomes trapped in these coil
o Energy storage in plants
Mixture of long straight chain amylase and branched amylopectin
Stored in chloroplasts
o Can be broken down to glucose
o Energy storage in animals
Made up of alpha subunits like starch…read more

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Proteins are important for growth, repair and metabolic activity
Amino Acid structure
Amino acids in plants
Nitrates in soil converted to amino groups
These are then bonded to organic groups from the products of photosynthesis
Amino acids in animals
Taken in through the diet
o Proteins digested to amino acids more proteins built from these
o Amino acids 8 - 10 of the 20 are essential as they can't be constructed from in taken material
Found in meat and soya
o Animals can't store…read more

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Heating a protein increases the kinetic energy in the molecule
o Causes it vibrate
o Break the weak bonds
These are the Hydrogen and Ionic bonds
Tertiary structure unravels as more heat is applied
o This is denaturation
Shape of the protein
Globular protein
o Compact ball-shaped structure
Hydrophobic R group inside
Hydrophilic R group outside
o Usually soluble
o Metabolic role - Enzymes, Plasma Proteins, Antibodies
Fibrous proteins
o Form fibres
Regular, repetitive sequence of amino acids
o Usually insoluble
o Structural - Collagen,…read more

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Condensation reactions between acid groups of two more fatty acids with the two remaining OH groups on the glycerol form a triglyceride molecule
In phospholipids instead of a third fatty acid a phosphate group is covalently bonded to the 3rd OH group
o The phosphate head is hydrophilic
o Hydrocarbon chains are hydrophobic
Hydrolysis of lipids provides twice as much energy as carbohydrate respiration
o Release more water
Don't affect water potential when stored in cell
Made of 4 carbon rings
o Small narrow…read more

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Place solution in a sample chamber between light and photoelectric cell in a small container called a cuvette
The more Benedict's test used up in the reaction the more light will be transmitted
Zero or calibrated device with a `blank' sample to reset 100% transmission and use a red colour filter
Condensation reaction to form a nucleotide
The phosphate group in all nucleic acids is always the same
The sugar is a pentose sugar
o Ribose in RNA and Deoxyribose in DNA
In DNA there…read more

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Sugar molecule that makes up the nucleotides is ribose
o Nitrogenous base uracil instead of thymine
o Polynucleotide chain is usually single-stranded
o There are 3 forms of RNA
Messenger RNA
Strand complementary to one strand of a DNA molecule
o Template strand
Copy of the coding strand of the double helix
Ribosomal RNA
Found in ribosomes
Transfer RNA
Carries amino acids the ribosome where they bond to form polypeptides
Base Pairing Rules
RNA can be made which is complementary to DNA molecule
o This…read more

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Building up of glycogen by catalysing the joining together of glucose molecules
Endothermic animals maintain internal body temperature
o By doing so enzymes function at near optimum temperature
Requires lots of energy - food
But can survive well on land and in water
Organisms that obtain their nutrients by consuming other organisms are heterotrophs
o Break down the organisms they consume in order to get nutrient molecules for growth and energy
Some enzymes secreted outside onto the food source - Extracellular
Maltose molecules can collide…read more

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The hydrogen and ionic bonds are due to the attraction between oppositely charged R groups on the amino acids
o Hydrogen ions interfere by attracting the negatively charged groups breaking that ionic bond
Increasing or decreasing pH changes the shape of the active site
Changes the rate of an enzyme controlled reaction
o Induced fit requires charged groups in the active site
Changing pH breaks these bonds and changes the shape of the active site
Increasing the substrate concentration in a fixed concentration of enzyme…read more

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The outer layer called the epidermis layers of cells called keratinocytes, cytoplasm is replaced by a protein called keratin =
keratinisation. This keratinised layer effective barrier against pathogens.
o Another is mucous membranes, goblet cells and ciliated cells. Because we need to take in oxygen and nutrients from our food and these must
enter the blood.…read more


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