Biochemistry Flashcards
Water structure
Polar molecule
Form hydrogen bonds
Solid less dense than liquid
Tetrahedral arrangement
Water properties
Cohesive moves as a mass due to h bonding
Adhesive water molecules attracted to other materials
Water uses
Acts as a solvent due to its polarity helping transport in and out cells
Efficient transport medium cohesion and adhesion in capillary action
Coolant
Stable doesn’t change temp easily ice floats forming insulating layer for organisms under to survive
High surface tension for pond skaters
Carbohydrate structure
Contain carbon hydrogen and oxygen
Also known as saccharides or sugars
Glucose
Hexose monosaccharide
Polar
Highly soluble in water due to hydrogen bonds forming
2 forms beta and alpha
Alpha glucose
Carbon 1 OH is below
Beta glucose
OH is above carbon 1
Condensation reactions
2 alpha glucose molecules react
Hydroxyl groups interact forming water
Glycosidic bond is formed
Disaccharide forms - maltose
Sucrose
Fructose and glucose
Lactose
Galactose and glucose
Starch
Glucose is stored as starch after photosynthesis
Polysaccharide
Amylose
joined together by 1/4 glycosidic bonds
Forms a helix which is stabilised by h bonds less soluble and good for storage
Amylopectin
1/4 glycosidic bonds and 1/6 glycosidic bonds branches structure every 25 glucose subunits
Glycogen
Energy storage in animals and fungi
More branches mor compact many free ends to quickly remove or add glucose
Cellulose
Beta glucose 1 upside dow forms 1-4 glycosidic bond
Straight chain molecule
H bonds with other strands forming microfibrils which form macrofibrils makes cell walls
Important in diet forms fibre difficult to break down
Lipids
Know as fast and oils
Contain carbon hydrogen and oxygen
Fats solid at rtp oils liquid at rtp
Non polar molecules
Macromolecules
Large complex molecules that aren’t built from repeating monomers
Triglycerides
One glycerol (alcohol) and 3 fatty acids (carb acid)
Interact forming ester bonds
Esterification = condensation polymerisation
Store energy / insulation
Saturated fats
No double bonds present
Solid at rtp
Unsaturated fats
Fatty acid w double bonds
Causes molecule to kink and bend so can’t pack closely therefore liquid at rtp
Plants contain these
Healthier?
Phospholipids
Contain phosphate ions which are soluble in water
2 fatty acid hydrophobic tails
Surfactant - form thin layer on surface fatty tails sticking up
Key in cell membranes
Sterols
Complex alcohol molecules based on 4 carbon ring with oh one end which is polar hydrophilic
Cholesterol - keep fluidity of membrane and used in manufacturing steroid hormones and vitamin d etc
Roles of lipids
Formation of hydrophobic barriers
Hormone production
Electrical insulation
Waterproofing
Long term energy storage providing thermal insulation buoyancy and cushioning of organs
Amino acids
All have same basic structure
Varying R groups
20 AA commonly found
Require 9 essential
Synthesis of peptides
Carboxylic acid and amine form a peptide bond and water
Catalysed by enzyme peptidyl transferase in ribosomes
Different R groups interact forming different bonds which form different shapes
Primary structure
Only involves peptide bonds
Secondary structure
Atoms of aa structure interact forming H bonds
Pulls into coil shape - alpha helix
Can form sheet like structures forming beta pleated sheet
Result of H bonding
Tertiary
Folding or coiling of protein brings R groups closer so interact
Hydrophobic/Philic attractions
H bonds
Ionic bonds
Disulphide bonds between sulphur atoms
Quaternary structure
Two or more subunits (polypeptide chains)
Same as tertiary interactions
Eg Hb
Types of proteins
Globular
Conjugated
Fibrous
Globular proteins
Compact, water soluble, roughly spherical hydrophobic on inside
Insulin - hormone transported in blood stream so need to be soluble
Conjugated proteins
Globular proteins that contain a prosthetic group
Eg haemoglobin is a conjugated globular protein because it is soluble and contains Fe2+
Catalase enzyme which contains 4 haem groups to interact w H2O2
Fibrous proteins
Long insoluble molecules due to high proportion of hydrophobic r groups
Repetitive AA
Eg Keratin large No of sulphur r groups form disulphide bridges
Elastin quaternary protein stretchy fibrous molecules
Collagen -3 polypeptide chains wound together like rope
Reducing sugar test
Grind sample and put in test tube
Add equal vol of Benedict’s
Heat mixture in water bath
If sugar present reduces Cu2+ to Cu3+ turns to brick red
Non reducing test
First boil with HCl and then same test as reducing sugars
Test for starch
Add iodine if turn blue/black starch is present in the sample
Test for lipids
Emulsion test
Mix with ethanol and shake if white emulsion present lipid present
Nucleotides
Contain Penrose monosaccharide phosphate group and a nitrogenous base
Phosphate group bonds w oh group of Pentose sugar carbon 3- phosphodiester bond
Dna
Pentose sugar is deoxyribose one fewer oxygen than ribose
Each nucleotide has 1/4 different bases
Pyrimidines
Single carbon ring
Cytosine Thymine
CaT Egyptian pyrimidines
Purines
Double carbon ring
Adenine and guanine
Pure-ine Ag- pure silver
Dna helix
Double strand held together by hydrogen bonding
Run in opposite directions
Allows dna to be copied and transcribed
Base pairing rules
Adenine and Thymine form 2 hydrogen bonds
Cytosine and guanine form 3 hydrogen bonds
RNA
Transfer genetic info from dna
mRNA is shorter so can leave nucleus
Ribose sugar
Thymine replaced by uracil
Semi conservative replication
DNA helix unwound and separate into 2 strands
Free DnA nucleotide pair w comp base join up w phosphodiester bonds
DNA helicase
Unwinds and separates strands
Catalyses breaking of hydrogen bonds
Dna polymerase
Catalyses formation of phosphodiester bonds between free nucleotides
Can only bind to C3 3->5 replication
Continuous/discontinuous replication
Strand is unzipped from 3 end and continuously replicated as unzipping occurs
Other strand is unzipped from the 5 end so dna polymerase has to fully wait until finished- dna produced in fragments (Okazaki fragments) - discontinuous replication
Start and stop codons
Triplet base sequence which starts coding of a specific protein so sequence isn’t read from base 2 for example
Non overlapping code
Degenerate code
Lot more codons than AA
AA can be coded for by many different codons
Transcription
DNA is unzipped DNA helicase
Sense strand (coding strand) codes for protein from 5’ to 3’
Antisense strand acts as template rna comp base sequence as sense strand
Phosphodiester bonds / RNA polymerase forming mRNA
Leaves via nuclear pore to ribosome
Translation
mRNA binds to specific site on ribosome holds mRNA in position while decoded
tRNA carries anticodon which comp pairs with mRNA also carries a specific amino acid which is joined together in correct sequence peptide bond forms
Repeat until reach a stop codon
Test for proteins
Biuret test
Purple positive result
