Biological Molecules

Question 1

What is a biological molecule?

Answer 1

The chemical compounds found in living organisms that are essential for the growth, maintenance and functioning of cells and tissues.

Question 2

What is a monomer?

Answer 2

small units that form larger molecules. ie monosaccharides, amino acids, nucleotides.

Question 3

What is a Polymer?

Answer 3

large, long, complex molecules which consist of monomers strung together in a chain.#

They can be homogenous- all monomers are the same, or heterogenous- different monomers.

All Biological Molecules are polymers

Question 4

Talk about the structure and function of Carbohydrates

Answer 4

Molecules made from carbon, hydrogen and oxygen. Made of monosaccharides of simple sugars which can form disaccharides (2 monosaccharides) or polymers called polysaccharides.
They are the primary source of energy for the body as they are broken down into glucose and have a structural function in cell walls.

Saccharide monomers join via a condensation reaction to create a glycosidic bond.

Question 5

Give examples of Disaccharides.

Answer 5

MALTOSE- Glucose + Glucose to form a 1-4 linkage, Carbs get broken down into maltose in the mouth during digestion.

SUCROSE- Glucose + Fructose, helps transport carbon around a plant.

LACTOSE- Galactose + Glucose, found in milk and sugar. is easy to digest and get sugar intake for babies.

Question 6

Talk about glucose.

Answer 6

Monosaccharide containing 6 carbon atoms in each molecule and is the main substrate for respiration. There are 2 isomers: Apha with the OH group at the bottom, and Beta with the OH at the top.

Question 7

Talk about Starch

Answer 7

Starch is a polysaccharide made of alpha glucose and is used as a store of glucose in plants.
There are 2 versions:
- AMYLOSE- unbranched, coiled so therefore compact for maximum storage
- AMYLOPECTIN- branches which can be acted upon to be broken down to release energy

Starch in insoluble in water so will not affect cell water potential.

Question 8

Talk about Glycogen

Answer 8

Polymer of alpha glucose used as a main store of glucose in animals
Many side branches mean glucose stores can be released quickly, compact, insoluble.

Question 9

Talk about cellulose.

Answer 9

Polysaccharide made of beta gluose arranged in rows connected by hydrogen bonds to form strong microfibrils for maximum support and keep cell walls rigid.

Question 10

Talk about how you test for starch.

Answer 10

Add Iodine which reacts with amylose, one of the polymers in starch, and changes colour from red/brown to blue/black if starch is present.

Method:
1. Place a small amount of food in the dimple tile.
2. Add 2 or 3 drops of iodine solution.
3. Note the colour change.

Question 11

Talk about how to test for Sugar

Answer 11

Add Benedict Solution and boil. If carbs are present, Benedicts is reduced and changes from Bright Blue to Brick Red.

Method for REDUCING SUGARS:
1. Place a small amount of food in a test tube and fill the tube 1/3 with benedict solution.
2. Put test tube in beaker of hot water for 5 minuets.

Method for NON-REDUCING SUGARS:
Non-reducing sugars like sucrose shows up as negative in the reducing sugar test.
1. Add Hydrochloric Acid to sample and boil.
2. Add Benedicts and boil again.

Question 12

Explain the roles of lipids:

Answer 12

• Source of Energy- when oxidized, lipids provide twice the energy as carbohydrates.
• Waterproofing- Lipids are insoluble in water. Both Plants and Insects have waxy, lipid cuticles that conserve water while mammals produce an oily secretion.
• Insulation- Fats are slow conductors of heat and when stored beneath the body surface, they retain body heat
• Protection- Stored around delicate organs like the kidney

Question 13

Talk about triglycerides.

Answer 13

Lipids with three fatty acids and a glycerol molecule. Each fatty acid forms an ester bond with glycerol in a condensation reaction.
The three fatty acids may all be the same thereby forming a simply Triglyceride, or different, which is a mixed triglyceride is produced
- high ratio of energy storing bonds so good energy storage
- Large, non-polar lipids are insoluble in water so therefore their storage isnt affected by water potential of cells

Question 14

What is the difference between a saturated and unsaturated lipid.

Answer 14

Saturated Lipid- such as those found in animals, dont contain a double carbon bond

Unsaturated Lipid- contain carbon double bonds so therefore are liquid at room temperature and mainly in plants

Question 15

What are phospholipids?

Answer 15

In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate ion. Their heads are hydrophilic (water loving) and tails are hydrophobic (water repelling). This molecule is therefore polar
- In aqueous environments, polar means a bilayer can be formed
- The hydrophylic heas can be used to hold at the surface of the cell surface membrane
- Their structure allows them to form glycolipids whoch are important on the cell surface membrames for cell recognition

Question 16

Talk about how you test for lipids

Answer 16

1. add ethanol to sample
2. shake the test tube thoroughly
3. and water and shake again
4. a cloudy-white emulsion indicates presence of lipid

Question 17

Talk about ATP?

Answer 17

Plant and animal cells release energy from glucose- RESPIRATION. A cell can’t get its energy directly from glucose so in respiration, the energy released makes ATP

ATP is made from nucleotide base adenine, ribose sugar and three phosphate groups. It’s known as a nucleotide derivative as it’s modified from a nucleotide.

Once made ATP diffuses to the part of the cell that needs energy. ATP is stored in high energy bonds between the phosphate groups and released via hydrolysis reactions

Question 18

Talk about the hydrolysis of ATP.

Answer 18

ATP + H20 = ADP + Pi

broken down into ADP and P. This is hydrolysis reaction. A phosphate bond is broken and energy is released. The reaction is catalyzed by the enzyme ATP HYDROLASE

ATP hydrolysis can be ‘coupled’ to other energy- requiring reactions in the cell. this means that the energy released can be used to directly to make the coupled reaction happen, rather than being lost as heat.

The released inorganic phosphate can also be put to use- it can be added to another compound- phosphorylation- which often makes the compound more reactive

Question 19

Talk about the resynthesis of ATP

Answer 19

ADP + Pi (+ energy) = ATP + H20

ATP can be resynthesized in a condensation reaction between ADP and P, This happens during both respiration and photosynthesis and is catalyzed by the enzyme ATP synthase.

Question 20

Why is water important?

Answer 20

Water is vital for living organisms as it makes up about 80% of the cells contents and has loads of functions:

• Metabolite- It helps with many important metabolic reactions like condensation and hydrolysis.
• Solvent- So some substances dissolve in it, like most metabolic reactions.
• Temperature Control- It has a high latent heat of vaporization and high specific heat capacity
• Cohesive- (stick together), which helps water transport in plants and organisms.

Question 21

Talk about the structure of water

Answer 21

A molecule of water H2O is one atom of oxygen joined in two atoms of hydrogen by shared electrons.

Because the shared negative hydrogen electrons are pulled toward the oxygen atom, the other side of each hydrogen atom is left with a slight positive charge. The unshared negative electrons on the oxygen atom give it a slight negative charge. This makes water a polar molecule- it has a slight negative charge on one side and a slight positive charge on the other.

Question 22

Talk about features of water

Answer 22

mportant Metabolite: Many metabolic reactions involve a hydrolysis (requires water), or a condensation (releases water) reaction.

Good solvent: Many important substances in biological reactions are ionic. This means they’re made of one positively charged atom and one negatively charged atom. Because water is polar, the p;ositive end will be attratcted to the negative ions and the negative end will be attracted to the positive atoms, so its completely surrounded by water, so it can dissolve substances. This allows organisms to take us substances and transport around the body.

High Latent Heat of Vapourisation (evaporation): Water evaporates when the hydrogen bonds break. It takes alot of energy to break the bonds meaning less energy is available to heat body so heat is evaporated away of the surface of the body which helps organisms keep cool.

High Specific Heat Capacity- Takes a lot of energy to break the bonds so less energy is available to heat the water so they maintain constant internal temperature..

Cohesion- Strong cohesion as they are polar. It enables effective transport of water in the xylem.

Question 22

Talk about the properties of water?

Answer 22

Important Metabolite: Many metabolic reactions involve a hydrolysis (requires water), or a condensation (releases water) reaction.

Good solvent: Many important substances in biological reactions are ionic. This means they’re made of one positively charged atom and one negatively charged atom. Because water is polar, the p;ositive end will be attratcted to the negative ions and the negative end will be attracted to the positive atoms, so its completely surrounded by water, so it can dissolve substances. This allows organisms to take us substances and transport around the body.

High Latent Heat of Vapourisation (evaporation): Water evaporates when the hydrogen bonds break. It takes alot of energy to break the bonds meaning less energy is available to heat body so heat is evaporated away of the surface of the body which helps organisms keep cool.

High Specific Heat Capacity- Takes a lot of energy to break the bonds so less energy is available to heat the water so they maintain constant internal temperature..

Cohesion- Strong cohesion as they are polar. It enables effective transport of water in the xylem.

Question 23

Talk about amino acids.

Answer 23

Amino acids are monomers which join together in a linear chain to form proteins. There are only 20 amino acids in nature which makes millions of proteins.
All amino acids have a common structure, however the R group is different in each amino acid that determins how it interacts with other amino acids and ultimatly how the amino acid chain folds up into a protein.

The NH2 is called an amino group whereas the C,O,OH represents the carboxyl group.

Question 24

Talk about protein formation.

Answer 24

Amino acids are linked by peptide bonds to form polypeptide chains of up to several thousand amino acids. The bonds form between the amine group of one acid and the carboxyl group of another. This is a condensation reaction and releases water. Hydrolysis reaction splits up the amino acids providing a water molecule, hydrogen atom and hydroxyl group.

Question 25

Talk about protein structure.

Answer 25

The sequence and type of amino acids determine the proteins 3D shape and function.

Primary Structure- Amino acids are linked by peptide bonds to make polypeptide chains. Initial sequence of amino acids and will therefore determine the proteins function in the end

Secondary Structure- Folded polypeptides into either alpha helix or beta pleated sheet. It is maintained by hydrogen bonds between neighboring CO and NH groups

Tertiary Structure- The 3D shape it forms when the secondary structure folds up. A number of bonds maintain the structure. Like disulfide bridges, Ionic bonds and hydrogen bonds. These can be destroyed by heavy metals or solvents and extremes PH and temperature

Quaterary Structure- Complex proteins of polypeptide chains into a functional protein. An example is hemoglobin comprising of 2 alpha and 2 beta chains each enclosing an iron group.

Question 26

What’s the difference between globular or fibrous proteins

Answer 26

Globular proteins like enzymes are compact whereas fibrous proteins like keratin are long thus can be used to form fibres

Question 27

Talk about how you test for the precense of proteins?

Answer 27

The Biuret test can be used to test for the presence of peptide bonds in a protein:

• Add 2cm3 of a test solution into the test tube
• Add 2cm3 of Biuret Reagent
• Dark blue/ purple indicates a positive reaction

Question 28

What are enzymes?

Answer 28

• Globular proteins that act as biological catalysts.
• Speed up the rate of reaactions by lowering activation energy and dont undergo permanent changes themselves.
• They can be reused repeatedly
  A specific region of the enzyme is functional known as the active site which is a depression made up of a small amount of amino acids.

Question 29

Talk about Enzyme action.

Answer 29

The molecule of which the enzyme acts is called the substrate. This fits neatly and specifically into the avtive site to form a enzyme-substrate complex. The substrate molecule is held within the active site by bonds that temorarily form between certain amino acids of the active site and grojps on the substrate molecule. The structure of the enzyme is altered so the active site of the enzyme fits around the substrates- Induced Fit Model.

Question 30

What are the factors affecting Enzyme Action?

Answer 30

Temperature- The rate of reaction increases up to the optimum temperature as the kinetic energy of the enzyme increases. Above the optimum temperature rate of reaction decreases as enzymes denature.

Ph-The optimum pH differs for different enzymes, for example hydrogens is pH 9. Anymore or less can disrupt the tertiary structure of the enzyme.

Enzyme Concentration-The rate of reaction increases as concentration increases as there is more active site to bind to, however beyond a certain point, the rate of reaction the increased concentration becomes a limiting factor.

Substrate Concentration- As concentration increases, rate of reaction increases as more enzyme-substrate complexes are formed. However, beyond a certain point the rate no longer increases and it becoms a limiting factor.

Question 31

Talk about enzyme inhibitation.

Answer 31

Substances that directly or indirectly interfere with the functioning of an active site on an enzyme therefore reducing its activity.

Competitive Inhibitors- These have molecular shape similar to that of the substrate therefore occupy the active site.
- substrate concentration increased, inhibitor effectiveness decreases
- Inhibitor isnt permanently bound to active site

Non-Competitive Inhibitors- Attach to the binding site not the active site which alters the shape of an enzyme and active site so molecules cant function anymore

Question 33

Talk about DNA structure.

Answer 33

• Double Helix structure meaning its made of two strands which wind together to form a spiral. The strands are polynucleotides.
• They are really long and coiled tightly so a lot of genetic information can fit into a small space
• Watson and Crick worked out the structure of DNA following work by Rosalind Franklin which opened a door for many major developments in biology.

Question 34

Talk about the nucleotide structure.

Answer 34

Nucleotides are formed by a condensation reaction.

DNA nucleotide is made from a phosphate group, the pentose sugar deoxyribose and a nitrogen containing base.

Each nucleotide has the same sugar and phosphate however the base can vary.

Two mononucleotides are joined by condensation reactions between the deoxyribose sugar of one nucleotide and the phosphate group of another via a phosphodiester bond.

Question 36

Talk about the structure of RNA.

Answer 36

Ribonucleic acid is a shorter, single stranded polynucleic acid chain in which the pentose sugar is ribose instead of deoxyribose. RNA transfers genetic information from DNA to the ribosomes in ordr to make proteins and another type if RNA- mRNA which is involved in protein synthesis

Question 37

Talk about the stability of DNA

Answer 37

• Phosphodiester backbone protects the more chemically reactive organic bases
• Hydrogen bonds that link the base pairs forming phosphodiester bridges- there are 3 hydrogen bonds between cytosine and guanine, the more C.G bridges, the more stable the DNA molecule.

Question 38

Talk about the function of DNA.

Answer 38

contains hereditary material which is responsible for passing genetic material from generation to generation. adaptions include:

• stabke, normally passes without any significant change
• Hydrogen bonds join the strands so easy replication
• Large- can hold alot of information

Question 39

Talk about the process of semi-conservative conservation.

Answer 39

1. The enzyme DNA helicase breaks the hydrogen bonds linking the base pairs of DNA
2. As a result the double helix separates into its two strands and unwinds
3. Each exposed polynucleotide strand then acts as a template which free, complementary nucleotides binf to by specific base pairings.
4. DNA nucleotides are joined together in a condensation reaction by the enzyme DNA polymerase in the 5’ → 3’ direction to form the missing polynucleotide chain on each of the two origional strands.
5. Each of the new DNA molecules contain one of the origional DNA strands and one new strand.
   in the 3’ → 5’ direction, the strand is synthasised discontinuosly in small sections in the 5’ → 3’ direction to form okasaki fragments which are eventually combined.

Question 40

Talk about the evidence for semi-conservative replication.

Answer 40

Conservative model- suggests the origional DNA molecule stays intact while a daughter DNA copy was built with new components

Semi- conservative model- one new strand one old strand.

The distrabution of the strands from the origional DNA molecule after replication is different in each model. Then look at how the DNA was distributed after replication.