Topic 1A: Biological Molecules Flashcards
What is a monomer?
A small, basic molecular unit that can join to form a polymer.
What is a polymer?
A large, complex molecule made up of long chains of monomers joined together.
What is condensation?
A reaction to join molecules releasing a molecule of water.
What is hydrolysis?
A reaction to split up molecules requiring a molecule of water.
What monomer to polymer reaction makes carbohydrates?
Monosaccharides –> di/polysaccharides
Name 4 monosaccharides
- Alpha glucose
- Beta glucose
- Galactose
- Fructose
What is the structure of alpha glucose?
H H
OH OH
What is the structure of beta glucose?
H OH
OH H
What is the structure of galactose?
OH OH
H H
What is the structure of fructose and how is that different to the other monosaccharides?
It is a pentose sugar.
What is a disaccharide?
2 monosaccharides joined together
Name the three disaccharides and what they are made up of.
- Glucose + glucose –> maltose
- Glucose + galactose –> lactose
- Glucose + fructose –> sucrose
Draw the bonding of maltose
What is the name of the bond made?
Lose H from one glucose and OH from the other, now connected by a central O.
Glycosidic bond.
What is a polysaccharide?
More than 2 monosaccharides joined together.
Starch
- What is it used for?
- Which monosaccharide is it made of?
- What 2 polymers is it made up of?
- Energy store in plants.
- Alpha glucose
- Amylose + amylopectin
Starch
- How does its structure make it good for storage?
Amylose - unbranched chains, helical –> compact for storage
Amylopectin - branched chains –> allow enzymes in easily to break down molecules
Large molecule –> can’t leave cells
Insoluble –> doesn’t affect water potential of the cell.
Glycogen
- What is it used for?
- Which monosaccharide is it made of?
- Energy storage in animals.
- Alpha glucose
Glycogen
- How does its structure make it good for storage?
- Extremely branched –>stored energy can be released easily
- Compact –> good for storage
- Large molecule –> can’t leave cells
- Insoluble –> doesn’t affect the water potential of cells
Cellulose
- What is it used for?
- Which monosaccharide is it made of?
- Structural support in plants
- Beta glucose
Cellulose
- How does its structure make it good for its function?
- Long unbranched, straight chains
- Cellulose chains linked by hydrogen bonds to form strong fibres called microfibrils
- Strong fibres provide the structural support for cells
What is the difference between saturated and unsaturated fatty acids?
- Saturated –> no C=C
- Unsaturated –> one or more C=C
What makes up a triglyceride?
3 fatty acids + 1 glycerol –> triglyceride + 3H2O
What is the general form of a fatty acid?
Central C with =O, an OH group and an R hydrocarbon tail.
Draw the bonding of a triglyceride
Name the bonds used
- Lose H off OH side of glycerol and an OH off each fatty acid.
- O left over on glycerol bonds directly to C from fatty acid.
- Joined by -COO ester bond.
What is the function of triglycerides and how are they structured for this?
- Energy store –> hydrocarbon tails have lots of chemical energy which is released when broken down.
- Hydrophobic hydrocarbon tails - insoluble in water –> clump as insoluble droplets as tails face in shielded by glycerol heads –> don’t affect water potential of cells.
What makes up a phospholipid?
1 glycerol + 2 fatty acids + 1 phosphate group
Draw the structure of a phospholipid and name the bonds used.
- Glycerol in the middle with fatty acids bonded to one side and phosphate group to the other.
- Fatty acids bonded from central C to an O to the central C of the glycerol.
- Phosphate bonded from central P to O to central C of the glycerol.
- Uses ester bonds -COO
What is the function of phospholipids and how are they structured for this?
- Make up the bilayer of cell membranes
- Hydrophilic heads and hydrophobic tails - form double layer with heads facing out to water
- Centre of bilayer = hydrophobic –> water soluble substances can’t pass through –> acts as a barrier
What is the monomer to polymer reaction to make proteins?
Amino acids –> polypeptides (proteins)
What is the structure of amino acids?
- Central C
- Amino group (NH2)
- Single H
- Carboxyl group (COOH)
- Variable group (R)
Draw the bonding of a dipeptide
What is the name of the bonds used?
- OH from COOH of amino acid 1 and H from NH2 of amino acid 2 remove to make water.
- C (with =O) bonds to N of second amino acid
- Peptide bonds
How does the primary structure of a protein form?
The sequence of amino acids in a polypeptide chain.
How does the secondary structure of a protein form?
Hydrogen bonds form between amino acids in the chain to make an alpha helix or a beta pleated sheet.
How does the tertiary structure of a protein form?
More bonds form (hydrogen + ionic) as well as disulfide bridges between sulphur atoms in cysteine bond together.
How does the quaternary structure of a protein form?
Only needed with multiple different polypeptide chains and is how they are assembled together.
Name 4 functions of proteins?
- Enzymes
- Antibodies
- Transport proteins
- Structural proteins
What are fibrous proteins?
They provide structure as long parallel polypeptide chains with cross links between them to form long rope-like fibres that are generally insoluble e.g. collagen, silk, keratin.
What are globular proteins?
Spherical, tightly folded chains that are folded with hydrophobic groups inside and hydrophilic outside so they are mostly insoluble in water e.g. transport proteins, enzymes, hormones.
What is the test for lipids?
- Shake the substance with ethanol
- Pour into water
- Forms a milky emulsion
What is the test for proteins?
- Biuret solution (sodium hydroxide solution + copper (II) sulphate)
- Blue –> purple
What is the test for starch?
- Add iodine in potassium iodide solution
- Amber –> blue / black
What is the test for reducing sugars?
What are reducing sugars?
- All monosaccharides and some disaccharides
- Add Benedict’s solution and heat
- Turns blue -> green -> yellow -> orange -> brick red (precipitate)
What is the test for non-reducing sugars?
- Need to be broken down to reducing sugars first
- Add HCl and heat
- Neutralise with sodium hydrogencarbonate
- Then do Benedict’s test
How does the Benedict’s test work?
- Contains copper sulphate (blue)
- Reducing sugars reduce it into copper oxide (red)
- This forms the red precipitate
What is a substrate?
The substance that binds to the active site of an enzyme to form an E-S-C –> it is converted to product while attached to the enzyme and is then released.
What can enzymes do?
- Build things up
- Break things down
What is activation energy?
The minimum amount of energy needed for a reaction to occur.
What do enzymes do to the activation energy?
Lower it –> provide alternate reaction pathway
What is the lock and key model of an enzyme?
- Enzyme = lock, substrate = key
- Must fit exactly - is specific - complimentary shape
- Active site = fixed shape
What is the induced fit model of an enzyme?
- Enzyme = glove, substrate = hand
- Not exactly complimentary
- Substrate forces the enzyme’s active site to change shape
- Enzyme moulds around it
What two ways is rate often measured?
- Formation of product / time
- Disappearance of substrate / time
How do enzymes denature?
- Bonds in enzyme are broken or interfered with
- Changes the tertiary structure of the enzyme
- Changes enzyme shape –> active site shape changes
- Substrate no longer fits so cannot bind to an E-S-C
- Reaction cannot be catalysed
How does temperature affect enzyme activity?
- High temp = higher kinetic energy = molecules move more quickly = higher frequency of successful collisions = more frequent E-S-C formation
- Collisions occur with more energy –> more collisions likely to cause a reaction –> more molecules have activation energy
- Too high temp = denatures –> molecules vibrate too much breaking bonds
How is enzyme activity affected by pH?
- Non optimal / extreme pHs can denature enzymes
- They disrupt the bonds as the H+ or OH- disrupt it
How can you prevent pH interfering in reactions?
Use a buffer solution
How is enzyme concentration a factor affecting enzyme activity?
- High enzyme conc = higher number of active sites = higher likelihood of E-S-C
- As long as substrate is available - an inc in enzyme conc makes rate inc linearly with enzyme conc
- If substrate conc limited –> at a certain point any further inc in enzyme has no affect
- Substrate becomes the limiting factor
How does substrate concentration affect enzyme activity?
- Inc substrate conc = higher rate due to inc liklihood of E-S-C
- If enzyme conc fixed and substrate continues to increase –> eventually all active sites are full and rate stops increasing
How do competitive inhibitors work?
- Inhibitor has a similar shape to substrate –> occupies the active site instead of substrate –> competes with it
- Concentration of enzyme and concentration of inhibitor determines the effect it has on enzyme activity
How do non-competitive inhibitors work?
- Binds to a site that is not the active site –> makes active site change shape so substrate cannot bind
What enzyme experiment measures the formation of product?
- Formation of H2O2 in measuring cylinder experiment
- Trough of water with measuring cylinder full of water upside down in it –> delivery tube leads from cylinder out of the water
- Boiling tubes with H2O2 and buffer solution –> each put in a water bath of different temperatures with a boiling tube of catalase
- Wait 5 mins then add catalase to H2O2 and quickly put in the bung with the delivery tube and start a stopwatch
- Record how much O2 produced in 1 minute using measuring cylinder
- Repeat at each temp and 3 times for a mean
- Always use the same volume and concentration of H2O2 and catalase
What enzyme experiment measures the breakdown of a substrate?
- Starch and iodine spotting tile one
- Put a drop of iodine in each well of a spotting tile
- Mix amylase and starch in a test tube (known volume and concentration of each)
- Pipette some over iodine in a well at regular intervals e.g. 10s
- Observe colour change (amber = no starch, blue/black = starch)
- Test how fast starch is broken down by how quickly the colour changes
- Repeat with different amylase concentrations and each 3 times for a mean
