3.1 Biological Molecules

Question 1

What are the 3 most common carbohydrates?

Answer 1

Glucose, galactose, fructose.

Question 2

Define isomers.

Answer 2

Same chemical formula but different chemical structures.

Question 3

What are the 2 isomers of glucose and what is the main difference between them?

Answer 3

2 Isomers: Alpha and beta glucose

They’re essentially the same, C6H12O6 However, on the beta glucose, on C1, the OH group is at the top.

Question 4

What’s a condensation reaction?

Answer 4

One which water is removed from

Question 5

What bond is formed after condensation reaction of glucose?

Answer 5

1,4 Glycosidic bond

Question 6

What are the monosaccharides of the disaccharide of maltose?

Answer 6

2 alpha glucose

Question 7

What are the monosaccharides of the disaccharide of lactose

Answer 7

Glucose and galactose

Question 8

The monosaccharides of sucrose

Answer 8

Glucose and fructose

Question 9

What’s hydrolysis?

Answer 9

Splitting with water molecule.

Question 10

Draw structure of amylose

Answer 10

Straight chain.

Question 11

Between what carbons are bonds formed, what type of bond formed and why does it have a helical structure?

Answer 11

Helical as it can have hydrogen bonds formed between the chain. Forms 1,4 glycosidic bonds.

Question 12

What’s the structure of amylopectin?

between what carbons are glycosidic bonds formed

Answer 12

Branched.

1,4 & 1,6.

Question 13

How is starch adapted to its function?

Answer 13

• Compact, store a lot of starch in plant and takes less space
• Insoluble - so it doesn’t affect water potential therefore not too much water can enter or leave the cell. No osmotic effect.
• Glucose storage doesn’t leave cell.

Question 14

Structure of glycogen, why it’s adapted to its function and between what carbons are bonds formed?

Answer 14

• HIGHLY branched
• energy store/glucose storage in animals, so high branched allows more energy
• MORE 1,6 Bonds and fewer 1,4 glycosidic bonds.
• More compact than starch
• insoluble

Question 15

What’s structure of cellulose? Why is structure useful for properties and function?

Answer 15

B glucose used. Alternative glucose flips 180 degrees. Long and single chains gives mechanical strength to cell walls. For structural support in plants. It’s full of glucose molecules but most animals can’t digest it as we don’t have the right enzymes. Hydrogen bonds can form between chains and can form MICROFIBRILS.

Question 16

What’s the monomer of protein? Draw structure of monomer. How many different monomers are there? What causes them to be different?

Answer 16

Amino acid. Structure of amino acid drawn - central carbon, amino group, carbonyl group, R group and H. Different as have different R groups.

Question 17

Draw structure of peptide bond. How are peptide bonds formed

Answer 17

–C(O)NH–

Peptide bonds formed through condensation reactions.

Question 18

What are the 4 levels of polypeptide structure? Describe the types of bonding in each and appearance.

Answer 18

Primary: Sequence of amino acids
Secondary: Hydrogen bonds between amino acids and carboxyl groups –> Forms alpha helix and or beta pleated sheets.
Tertiary: Interaction of R groups form new bonds. More H bonds, ionic bonds and disulfide birdges. The Alpha helic is folded and forms complex 3d structure.
Quarternary: 2 or more polypeptide chains joined together. 3D structure important to function which is deteremined by amino acids sequence.

Question 19

What’s the difference between globular and fibrous? What is a fibril? How do you test for proteins?

Answer 19

Globular: Soluble e.g. haemoglobin, hormone, antibodies and enzymes.
Fibrous: Structural like keratin and collagen. This is insoluble.
Fibril is 3 polypeptide chains linked by disulfide bridges.
Test for proteins: Add biurette’s reagent to sample. Lilac/purple/violet colour change. Blue is negative. Positive is blue to purple colour change of solution.

Question 20

What are enzymes? What is the structure of enzymes? How does this structure linked to active sites? Define activation energy.

Answer 20

Enzymes are globular proteins. Usually have tertiary structure, sometimes quarternary. Tertiary structure arises to different shaped active sites that can temporarily bond with complementary substrates. Tertiary structure gives speficially shaped active sites that are complementary to the substrate.
Activation energy: The minimum amount of energy required for a chemical reaction to begin.
Enzymes lower the activation energy.

Question 21

What are the effects on the rate of enzyme of the following factors: enzyme concentration, substrate
concentration, concentration of competitive and of noncompetitive inhibitors, pH and temperature

Answer 21

Enzyme concentration: Increase enzyme concentration proportionally increases the rate of reaction (given that substrate conc. is in excess.)

Substrate concentration: A quicker initial rate of reaction. This is because substrate concentration is limiting factor. Then starts to level off - now enzyme concentration is limiting factor.

Adding fixed conc. of competitive inhibitor and increasing substrate conc.: Slower rate of reaction - higher chance competitive binds. As sub conc increases, rate inc. and will eventually level off at same rate - more likely substrate will bind with a.s. than inhib.

Adding a fixed conc of non-competitive inihibitor: Slower rate of reaction and levels off lower as enzymes denatrued as AS no longer complementory to substrate. Noncompetitive inhibitor bind to enzyme away from A.S.

pH: Different enzymes have different optimum pH. As pH gets closer to optimum, rate of reaction increases. As further away, drops as OH- and H+ interfere with h bonds of amino acids.

Temperature: Increasing will increase rate of reaction. Substrate more k.e. more likely chance of successful collisions. More enzyme substrate complexes formed, faster rate of reaction. Too high, ezymes start to denature - not immediate.

Question 22

What are constitutes of triglycerides? What are constitutes of phospholipids? What type of bond is formed between the constitutes? Why are lipids hydrophobic?

Answer 22

Triglyceride = glycerol + 3x fatty acids.
Phospholipids = Glycerol, 2x fatty acids, phosphate
Ester -coo- bond forms between fatty acids and glycerol and 3x h2o removed.
Lipids are non-polar therefore hydrophobic.

Question 23

What’s the test for proteins, lipids and reducing sugars and non-reducing sugars?

Answer 23

Proteins: Biurettes, blue to purple solution for positive.
Lipids: Add ethanol, add water, white emulsion indicates lipid presence
Reducing Sugar: Add benedicts, boil it/heat, brick red precipitate if reducing sugar.
Non-reducing sugar: Hydrolysis by boiling with dilute HCl. Neutralise with NaOH. Then benedicts again.

Question 24

Structure of DNA? What are the 4 nitrogenous bases involved called? What’s the monomer and polymer? What type of bond forms between the phosphate group and deoxyribose?

Answer 24

• A DNA molecule is a double helix with two polynucleotide chains held together by hydrogen bonds between specific complementary base pairs.
• Guanine, cytosine, thymine, adenine.
• Monomer = nucleotide - polymer = polynucleotide
• Phosphodiester bond

Question 25

What does RNA stand for? What are the nucleotides involved? Differences between DNA and RNA

Answer 25

• Ribonucleic acid
• Uracil, adenine, cytosine, guanine

DNA: 
- Alpha helix
- 2 polynucleotide chains
- long chains
RNA: 
- Has uracil instead of thymine 
- Single-stranded
- shorter

Question 26

What is semi-conservative replication? What are the 5 steps to replication?

Answer 26

Semi-conservative as one strand acts as a template so more complementary nucleotides can join on.
The process of semi-conservative replication of DNA in terms of:
• unwinding of the double helix
• breakage of hydrogen bonds between complementary bases in
the polynucleotide strands
• the role of DNA helicase in unwinding DNA and breaking its
hydrogen bonds
• attraction of new DNA nucleotides to exposed bases on template
strands and base pairing
• the role of DNA polymerase in the condensation reaction that joins
adjacent nucleotides.

Question 27

What is the evidence of semi conservative replication?

Answer 27

N14 and N15 stuff. (Useful to know, not on spec.)

Question 28

What does ATP stand for? What is the structure of ATP? How is ATP formed and broken down - what are the names of the enzymes involved?
Why is ATP Good?

Answer 28

• Adenosine triphosphate
• Adenine group, ribose group and 3x phosphate molecules
• ATP –> ADP + Pi By ATP HYDROLASE
• ADP + Pi –> ATP by ATP SYNTHASE
• Immediate source of energy compared to glucose, as it’s only a one-step reaction. Gives a manageable amount of energy release and quickly formed.

Question 29

What are the 5 useful properties of water? Explain why their uses are important.

Answer 29

Properities:

• Metabolite: Many metabolic reactions involve a condensation or hydrolysis reaction.
• HIGH LATENT HEAT OF VAPORISATION: Takes lots of energy to separate hydrogen bonds between water molecules - when they evaporate, they take away lot of energy - useful for sweat to cool down
• STRONG COHESION between water molecules - Cohesion allows water to flow e.g. up xylem, can also serve high surface tension for insects
• SOLVENT allows to dissolve some substances like salt
• HIGH SPECIFIC HEAT CAPACITY, maintain constant temp environment for fish and a good habitat. Can help maintain internal body temp.

Question 30

What is the structure and bonds present between water molecules?

Answer 30

The o is slightly negative and H is slightly positive. Lone pair of electron on O are attracted to positive H which is hydrogen bonds between molecules.

Question 31

Why is water useful for living organisms?

Answer 31

• metabolite useful for metabolic reactions.
• solvent so dissolve substances e.g. salt and in solution - cytoplasm.
• maintain constant temp control due to high latent heat of vaporisation and high specific heat capacity.
• Cohesive molecules allow water to move in plants and other organisms

Question 32

Name some ions used in a majority of organisms.

Answer 32

Phosphate ions, sodium ions, hydrogen ions. Ions part of haemoglobin.