Biological Molecules Flashcards
What’s a polymer?
Long molecule made from smaller molecules(monomers)
What’s a monomer?
Small molecules which are the building blocks of polymers
Bonds in a carbohydrate?
fats/lipids?
protein?
nucleic acids?
Glycosidic
Ester
Peptide
Phosphodiester
Monomer/polymer of a carbohydrate?
Monosaccharide
Polysaccharide
Monomer/polymer of a protein
Amino Acid
Polypeptide/protein
Monomer/polymer of fats/lipids?
Monomer: Triglyceride
Monomer/polymer of nucleic acids?
Nucleotide
DNA/RNA
Examples of monosaccharides
Glucose
Fructose
Galactose
Formula for monosaccharides?
C6H12O6
Example of disaccharides?
glucose + glucose = maltose
glucose + galactose = lactose
glucose + fructose = sucrose
Formula for disaccharides?
C12H22O11
What’s condensation?
A chemical bond forms between 2
molecules & a molecule of water is
produced.
What’s hydrolysis?
A water molecule is used to break a
chemical bond between 2 molecules.
What’s an organic molecule?
Contains carbon
Difference between alpha and beta glucose?
Hydroxyl group is flipped
on alpha glucose OH is on the bottom
on beta glucose the OH is on the top
How is glucose used as energy storage?
Glucose units contain a lot of bonds that can be broken down to release energy during respiration to create ATP.
Functions of carbohydrates?
–respiratory substrates
- provides energy
- stores energy
- Glycoproteins/ receptors
- builds macromolecules
What’s cellulose?
polymer of 𝛽-glucose gives rigidity to plant cell walls
prevents bursting under turgid pressure, holds stem up
What’s glycogen?
main storage polymer of 𝛼-glucose in animal cells
but also found in plant cells
What’s starch?
storage polymer of 𝛼-glucose in plant cells
Structure and functions of
cellulose
-1,4 glycosidic bonds-straight-chain, unbranched molecule
-alternate glucose molecules are rotated 180°
-H-bonds between parallel strands form
microfibrils -provides strength and structure for cell wall
Structure and functions of
glycogen
-1,4 & 1,6 glycosidic bonds
-branched = many terminal ends for faster hydrolysis,increases SA
-insoluble = no osmotic effect & does not diffuse
out of cells
-compact
Structure and functions of
starch
-insoluble = no osmotic effect on cells
-large = does not diffuse out of cells
Amylopectin:
-1,4 & 1,6 glycosidic bonds
-branched = many terminal
-ends for hydrolysis into glucose
Amylose:
-1,4 glycosidic bonds
-helical = compact
Where is glucose stored in the body?
As glycogen in the muscles/liver
Similarities between starch and glycogen
- both made of α-glucose monomers -both contain branched chains -insoluble, do not affect osmotic potential -Compact – maximum storage
Compare Cellulose and Amylose
-Glycosidic Bonds
-Insoluble in water
However, Cellulose is composed of β Glucose whereas Amylose is composed of α Glucose
Cellulose forms long straight chains, Amylose forms a coiled chain and tends to be found in granules.
Amylose is used as an energy storage in starch, whereas Cellulose plays a structural role.
Describe the test for reducing
sugars
-Add an equal volume of Benedict’s reagent
to a sample.
-Heat the mixture in an electric water bath at
100℃ for 5 mins.
-Positive result: colour change from blue to
orange & brick-red precipitate forms.
Describe the test for
non-reducing sugars
- Negative result: Benedict’s reagent remains blue
- Hydrolyse non-reducing sugars e.g. sucrose into their monomers by adding 1cm3 of HCl. Heat in a boiling water bath for 5 mins.
- Neutralise the mixture using sodium carbonate solution.
- Proceed with the Benedict’s test as usual
Describe the test for starch
Add iodine, turns blue/black
Describe the test for lipids
Add ethanol, then add water;
White (emulsion shows lipid)
Describe the test for proteins
- Sample is mixed with an equal volume of sodium hydroxide at room temperature
- Add a few drops of dilute copper sulphate solution then mix
- Purple colour change if not then stays blue
Uses of lipids in animals
- Storage as fat
- Hormones – steroids
- Cell membranes
- Thermal Insulation
- Electrical insulation (myelin)
- Waterproofing
Describe the structure of a triglyceride
- One glycerol molecule
- Attached to three fatty acid chains
- Glycerol head is hydrophilic –interacts with water
- Fatty acid tails are hydrophobic –repel water
Contrast saturated and unsaturated fatty
acids
Saturated-Contain only single bonds-straight-chain
Higher melting point = solid at room temperature
Unsaturated -Contain C=C double bonds -‘Kinked’ molecules ,Lower melting point = liquid
at room temperature
structure and functions of triglycerides
-Energy storage molecule
-Insoluble hydrocarbon chain = no effect on water
potential of cells & used for waterproofing.
-Slow conductor of heat = thermal insulation
structure and function of
phospholipids
Glycerol backbone attached to 2 hydrophobic fatty acid tails & 1 hydrophilic polar phosphate head
Forms phospholipid bilayer in water = membranes.
Tails = waterproofing.
Compare phospholipids and triglycerides
Similarities
Both have :
- glycerol backbone.
- elements C, H, O.
- been formed by condensation reactions.
Contrast phospholipids and triglycerides
differences
phospholipids: -2 fatty acids & 1 phosphate group attached -Hydrophilic head &hydrophobic tail -Use:in membrane formation triglycerides: -3 fatty acids attached -Entire molecule is hydrophobic -Use:storage molecule (oxidation releases energy)
Are phospholipids and triglycerides polymers?
No.They are macromolecules.
How does the presence of a double bond in a lipid affect its boiling point?
Lowers the boiling point as double bonds in unsaturated fats cause kinks in fatty acid chain which prevent the molecules from packing closely together
How is the structure of a phospholipid different from the structure of a triglyceride?
One of the fatty acids tails is replaced with a phosphate molecule
What are the 3 types of Lipids?
- Triglycerides (fat for energy store, insulation, protection of organs)
- Phopholipids (to make membranes)
- Cholesterol (for membrane stability and make hormones)
What are globular proteins?
soluble proteins with a specific 3D shape e.g. enzymes, hormones,antibodies, haemoglobin
What are fibrous proteins?
strong/insoluble/inflexible material e.g. collagen and keratin
How do amino acids differ?
have different R groups,there are 20 different amino acids
Define primary, secondary, tertiary, quaternary structure?
-Primary = sequence of AA, polypeptide chain (held by peptide bonds)
-Secondary = the primary structure (polypeptide chain) coils to form a helix, held by hydrogen bonds
-Tertiary = secondary structure folds again to form final 3d shape, held together by
hydrogen/ionic/disulfide bonds
-Quaternary = made of more then one polypeptide chain
Outline how chromatography could be used to
identify the amino acids in a mixture
-Use capillary tube to spot mixture onto pencil origin line &
place chromatography paper in solvent.
-Allow solvent to run until it almost touches other end of paper. Amino acids move different distances based on relative attraction to paper & solubility in solvent.
-Use UV light to see spots.
-Calculate Rf values & match to database
What are enzymes?
-Biological catalysts for cellular reactions.
-Specific tertiary structure determines shape of active
site, complementary to a specific substrate.
-Formation of enzyme-substrate (ES) complexes
lowers activation energy of metabolic reactions.
Describe each type of bond in the tertiary structure
of proteins
-Disulfide bridges: strong covalent S-S bonds
between molecules of the amino acid cysteine
-Ionic bonds: relatively strong bonds between charged R groups (pH changes cause these bonds to break)
-Hydrogen bonds: numerous & easily broken
Explain the induced fit model of enzyme
action
-Shape of active site is not directly complementary
to substrate is flexible-enables ES complexes to
form.
What’s the lock and key model?
rigid shape of active site complementary to only 1 substrate.
Name 5 factors that affect the rate of
enzyme-controlled reactions
- enzyme concentration
- substrate concentration
- concentration of inhibitors
- pH
- temperature
How does substrate concentration affect rate of
reaction?
- increase substrate concentration, increases chance of successful collisions, increase chance of forming an
ES complex, increase rate of reaction - this continues until all the enzyme’s active sites are full/saturated = maximum rate of reaction-rate then levels off
Effect of enzyme concentration on enzyme activity?
- increase enzyme concentration, increases chance of successful collisions, increase chance of forming an ES complex, increase rate of reaction
- this continues until all the substrates are used up = maximum rate of reaction
Effect of temperature on enzyme activity?
- as temperature increases
- the KE increases as the molecules move faster
- increase chance of successful collisions
- increase chance of forming ES complex
- increase rate of reaction
- carries on till optimum
- after optimum-bonds in tertiary structure break(hydrogen and ionic bonds)
- lose active site shape ,substrate no longer complementary
- cant form ES complexes
- enzyme denatured
Effect of pH on enzyme activity?
- change pH away from optimum, bonds in tertiary structure break, lose active site shape, can no longer form ES complex,
- enzyme denatured
Competitive vs Non-Competitive Inhibitors?
-Competitive = a substance with a similar shape to the substrate and a complementary shape to the
enzyme’s active site, binds to the active site, blocking it, preventing ES complexes from forming
-Non-Competitive = a substance that binds to another site on the enzyme other then the active site, causes
the active site to change shape, so less ES complexes can form
How to calculate rate of reaction from raw
data/graph
Change in concentration of product or
reactant / time.
Graph:Draw a tangent
