bio molecules Flashcards
Carbohydrates
- Polysaccharides of monosaccharides
- contain C, H, O
- monosaccharides joined by condensation reactions
= disaccharides, then poly - form glycosidic bonds
- broken by hydrolysis
Disaccharides
Glucose + fructose = sucrose
Glucose + glucose = maltose
Glucose + galactose = lactose
Reducing sugars test
Monosaccharides and some disaccharides
- add Benedict’s reagent to sample (in excess)
- heat in water bath
+ coloured precipitate
(Blue to brick red)
- blue
Non-reducing sugars test
Eg sucrose
If reducing sugars test negative
Break into monosaccharides:
- add dilute HCl
- heat in water bath
- neutralise with sodium hydrogencarbonate
Do reducing sugars test
+ coloured precipitate
(Blue to brick red)
- blue
Starch
Plants store excess glucose as starch
2 polysaccharides of alpha glucose
Amylose
- long, unbranded chain of alpha glucose
- angle of glycosidic bonds = coiled
- compact for storage
- 1,4 glycosidic bonds
Amylopectin
- long, branched chain of alpha glucose
- branches allow enzymes to hydrolyse glycosidic bonds easier, released quick
- 1,4 and 1,6 glycosidic bonds
Insoluble in water
- doesn’t affect water potential or osmotic activity
- good for storage
How to test for starch
- Add iodine dissolved in potassium iodide solution
+ blue-black - brown/orange
Glycogen
Animals store glucose as glycogen
Polysaccharides of alpha glucose
Long, branched chain
Enzymes can hydrolyse glycosidic bonds easier, broken down and released quick
Compact for storage
(Angle of glycosidic = coiled)
- 1,4 and 1,6 bonds
Cellulose
In plant cell walls
Long, unbranched chains of beta glucose
= straight cellulose chains
1,4 glycosidic bonds
Linked by hydrogen bonds = microfibrils
Strong fibres to provide structural support
Due to positive of OH and H in beta, to form glycosidic bonds:
- every other molecule of b inverts
- allows hydrogen bonds between chains
Triglycerides
Glycerol + 3 fatty acids
- lipid
- joined by condensation reactions
- hydrophobic tails - insoluble in water
Fatty acid tails - contain chemical energy
- lots of energy released when hydrolysed
Insoluble - don’t affect water potential
- no osmotic activity
- arrange in droplets with hydrophobic tails facing in
function of triglycerides
energy storage
- long hydrocarbon tails store lots of energy in bonds, released when broken down
insoluble as hydrophobic - doesn’t affect water potential
act as insulator eg myelin sheath
Saturated fatty acids
Saturated
- no double binds between carbon
Unsaturated
- at least one double bind between carbons
Phospholipids
Glycerol + 2 fatty acids + phosphate
- phosphate group hydrophilic
- fatty acids hydrophobic
= arrange in belayer
Centre hydrophobic
- water soluble substances can’t pass through, barrier
Test for lipids
Emulsion test
- shake substance with ethanol (until dissolves)
- poor solution in water
+ milky solution
Proteins
Polymers of amino acids
- formed by condensation reactions = dipeptides, then poly
- form peptide bonds
Have same general structure
- carboxylate group, amine group
And variable group
- 4 structural levels
Quaternary, tertiary, secondary and primary
Structural levels of proteins
Primary
- sequence of amino acids in a polypeptide
Secondary
- folding of primary using hydrogen bonds
- alpha helix or beta pleated sheet
Tertiary
- folded and coiled further
- hydrogen, ionic and disulphide bridges
- for 1 chain = final 3D structure
Quaternary
- multiple polypeptide chains joined by bonds
- final 3D structure
4 functions of proteins
Enzymes
Antibodies
Transport proteins
Structural proteins
Test for proteins
Biuret test
- add sodium hydroxide (=alkaline)
- add copper II sulphate solution
+ purple
- blue
What are enzymes?
Catalyse metabolic reactions
- lower activation energy for a reaction
- less energy (heat) needed for reaction to start, speeds up rate
Can hold molecules together to join them
- bonds form more easily
Or binds to active site and puts pressure on bonds (bends them)
- substrate breaks up more easily
Proteins with specific tertiary structure = specific shape active site
If denatured, tertiary structure (shape) changes
= doesn’t fit so can’t catalyse
Lock and key model
Substrate is a complementary shape to enzymes active site so fits together
= enzyme substrate complex
Induced fit model
Active site and substrate not originally complementary
Substrate binds and change shape of active site slightly (tertiary structure)
= enzyme substrate complex
Factors affecting enzyme activity
Temperature
pH
Enzyme concentration
Substrate concentration
Temperature
More heat = molecules have more kinetic energy, more faster
= enzymes more likely to collide with substrates
- collisions also have more energy, so reaction more likely
At too high temperatures = enzyme denatures
- hydrogen bonds broken
- tertiary structure changes
= active site no specific shape - not complementary
(No longer catalyses)
pH
All have optimum pH
Too many H+ or OH- ions break ionic and hydrogen bonds
- change tertiary structure
= active site changes shape, denatured
Enzyme concentration
More enzyme molecules = more likely substrate will collide
= enzyme substrate complex
So rate increased
But substrate is limited
- adding more enzyme has no further effect on rate
Substrate concentration
Higher substrate concentration = collisions between enzyme and substrate more likely
- more active sites used
Up to saturation point
- active sites all full, adding substrate has no effect
Rate decreases overtime as substrates used (unless replaced)
Inhibition of enzyme activity
Competitive
- similar shape to substrate
- bind to active site, block it
- no substrate can fit = no reaction
Inhibition depends on concentration of either, more of one will increase its chance of colliding
Non-competitive
- not same shape as substrate
- bind to site away from active site
- causes active site to change shape, substrate can’t bind
Increasing concentration of substrate has no effect, still inhibited
Importance of water
Metabolite in metabolic reactions
- condensation and hydrolysis
Solvent
- can dissolve substances, eg cytoplasm
Temperature control
Structure of water
1 oxygen and 2 hydrogen
- joined by shared electrons
Polar molecule
- partial + and - charge on each side
- oxygen attracts + hydrogen
Creates hydrogen bonds
Useful properties of water
Metabolite
High latent heat
High specific heat capacity
Good solvent
Cohesion
Metabolite
Used in metabolic reactions
- condensation produce water
- hydrolysis use water
High latent heat of vaporisation
Takes a lot of energy to break hydrogen bonds between water molecules
So a lot of energy used when evaporated
Cools organisms down through evaporation, takes heat energy (eg sweating)
High specific heat capacity
Hydrogen bonds between molecule absorb a lot of energy
= high SHC, takes allot of energy to heat it
Means water doesn’t change temperature easily
- buffer to temperature change
Good habitat
Maintain stable internal temperature
Solvent
Water is polar
+ end attracted to - ion and - end attracted to + ion
= ions surrounded by water molecules, dissolve
Important solvent
Cohesion
Attraction between water molecules
Due to polarity, hydrogen binding between molecules
Useful for transporting substances eg in xylem
Creates high surface tension, creates droplet and some insects can walk on it
ATP
Adenine, ribose, 3 phosphates
Energy released from glucose in respiration used to make ATP
- energy stored between phosphate groups
When used:
- energy released
- ATP hydrolysed into ADP and Pi
- catalysed by ATP hydrolyse
When made:
- energy used
- ADP and Pi synthesised into ATP (condensation reaction)
- catalysed by ATP synthase
Iron ions
Used in haemoglobin
To transport oxygen
- 4 polypeptide chains and an iron ion
Iron ion that binds to oxygen = oxyhaemoglobin
Hydrogen ions
Determines pH
- high concentration of H+ = acidic
Affects enzyme reactions
Sodium ions
Transport of glucose and amino acids in co-transport
- absorption in digestion
sodium ions active transported from ileum epithelial cells into blood
by sodium potassium pump
makes concentration of sodium ions
higher in lumen then epithelial cells
sodium ions diffuse down concentration gradient into epithelial cells
through co-transporter proteins
takes glucose with it
Phosphate ions
Added as phosphate groups
DNA, RNA, ATP
Important:
bonds between phosphate group that store energy in ATP
allow nucleotides to join into polynucleotides
How is glucose stored? (In animals)
Alpha glucose join by condensation reactions
Produces water
1,4 glycosidic bonds = chains of alpha glucose
1,6 glycosidic bonds = branches
= glycogen
DNA
Nucleotide - deoxyribose, phosphate group and a base
- adenine, guanine, cytosine, thymine
Holds genetic information
Double helix
2 polynucleotide chains
Hydrogen bonds between specific complementary bases
Phosphodiester bonds between nucleotides (sugar and base)
RNA
Nucleotide - ribose, phosphate group, base
- adenine, cytosine, guanine, uracil
Transfers genetic matieral from DNA to ribosomes
Short polynucleotide chain
Single stranded
Semi conservative replication
In each new DNA molecule, one DNA strands if from the original DNA molecule
Importance:
- ensures genetic continuity
Meselson and Stahl
Confirmed semi conservative replication
Sample of DNA containing heavy nitrogen
Sample of DNA containing light nitrogen
If conservative, would contain only heavy or light
- sink in centrifuge
Eventually contained both heavy and light
- had conserved
- settled in middle of centrifuge
How do enzymes increase rate of reaction?
binds to active site and puts pressure on bonds (bends them)
- substrate breaks up more easily
Or? Can hold molecules together to join them
- bonds form more easily
Structure of amino acid
R
H2N - C - COOH
H
