Biological Molecules

Question 1

What is the structure of the two glucose isomers - alpha and beta glucose?

Answer 1

Both have an O. Alpha glucocorticoid has 2 H’s at the top (heavens above) whereas beta glucose has one H and an OH.

Question 2

What are monomers and polymers?

Answer 2

A monomer is a small single unit of a molecule. As polymer is a chain of monomer molecules bonded together in a chain. This i also called a polymerisation reaction.

Question 3

What is a biological molecule?

Answer 3

An organic molecule that contains carbon

Question 4

How do molecules bond and break apart ?

Answer 4

Condensation reactions form bonds between molecules by removing a H2O molecule to create a bond. To break the bonds the polymer is hydrolysed and water is added back in.

Question 5

What is hydrogen bonding?

Answer 5

H bonds are individually weak but many together are very strong. They are water molecules bonding covalently due to opposite charges.

Question 6

What are carbohydrates hydrolysed by?

Answer 6

Carbohydrase, amylase and Maltese enzymes to turn starch into glucose.

Question 7

What are monosaccharides and give examples?

Answer 7

3 carbons = triode (glyceraldehydre)
5 carbons = Pentose (ribose)
6 carbons = hexose (glucose and galactose)
General formula = (CH2O)n -> n is 3-7.
Sweet tasting due to simple sugars.
Same number of carbon atoms to oxygen atoms.
- glucose
- fructose
- galactose

Question 8

What are disaccharides and give the examples?

Answer 8

Monosaccharide + monosaccharide (chain oof monosaccharides) bonded by condensation reactions and and by glycosidic bonds.
Maltose = glucose + glucose
Sucrose = glucose + fructose
Lactose = glucose + galactose

Question 9

What are polysaccharides and give examples?

Answer 9

Many glucose units bonded together because of condensation reactions and glycosidic bonds. Starch, glycogen and cellulose.

Question 10

What is the structure and function of starch?

Answer 10

Starch is used for storage of energy/glucose in plants. It’s a mixture of two polysaccharides of alpha glucose - amylose and amylopectin.

Amylose - long, unbranched, coiled structure due to angle of glycosidic bonds. This makes it compact and good for storage.

Amylopectin - long, branched, with side branches so enzymes can break down molecule to be to glycosidic bonds easily. This means that energy can be released easily and glucose can be released.

Question 11

What is the structure and function of glycogen?

Answer 11

It is the molecule that stones energy in animals and is a polysaccharide of alpha - glucose.
Loads of side branches so glucose can be released quickly for energy.
Very compact so good for storage.

Question 12

What is the structure and function of cellulose?

Answer 12

Cellulose is the major component in plant cell walls.
Long, unbranched, chains of beta - glucose that are straight chains.
The chains then for layers which are linked by hydrogen bonds (stronger together).
Strong fibres formed = microfibrils that provide strength to plant cells.

Question 13

What is triglyceride - function and structure?
Basic structure of a fatty acid?

Answer 13

It is a lipid molecule with a glycerol and 3 fatty acid molecules.
The fatty acids are hydrocarbon tails that are hydrophobic.
The basic structure of a fatty acid is 1 carbon atom with a double bond to an oxygen atom and single bonds to an R group and an HO molecule. The carbon atom links the fatty acid to the glycerol.
They are formed by condensation reactions when an H2O moleule is released.
They form ESTER bonds = the glycerol bonded to each fatty acid by at oxygen atom.
All 3 fatty acids must be bonded to form a triglyceride.
Triglycerides are used as good storage molecules because they contain lots of chemical energy.
INSOLUBLE - don’t affect water potential because they clump together with the hydrophobic heads facing inwards.

Question 14

What is the difference between a saturated and an unsaturated fatty acid?

Answer 14

They difference is in the hydrocarbon tails.
Saturated fatty acids have NO double carbon bonds between carbon atoms. Saturated with hydrogen.
Unsaturated fatty acids have at least ONE DOUBLE BOND between carbon atoms to cause chain to kink.

Question 15

What is a phospholipid and how is it different from a triglyceride?

Answer 15

Phospholipids found in cell membranes. They have a glycerol, 2 fatty acids and a PHOSPHATE group which is hydrophilic.
They make up the belayer of the cell surface (plasma) membrane.
Heads face out towards water on the inside and outside of the cell whereas the tails have inwards as the repel water.

Question 16

What is the test for lipids?

Answer 16

Emulsion test!
- add ethanol to test substance
- shake well so it dissolves
- pour in water
- wait for milky white emulsion - more lipid = more milky.

Question 17

Test for reducing and non-reducing sugars?

Answer 17

BENEDICT’S TEST!
- add reagent to sample and HEAT in water baths to boil
- positive = coloured precipitate (brick red)
- more sugar the more colour change (filter out and weight solids to compare)
- negative = NRS present.

SO…..
- NRS must be broken down into monosaccharides.
-> add dilute HCL and GENTLY heat in water bath.
- NEUTRALISE with sodium hydrogencarbonate
NOW REPEAT BENEDICT’S TEST
- positive = coloured precipitate
- still negative = stays blue (NO SUGAR)

Question 18

Starch test?

Answer 18

IODINE TEST.
- add iodine in dissolved POTASSIUM IODINE SOLUTION to test sample.
- positive = blue/black
-negative = browny/orange

Question 19

Describe the test for proteins?

Answer 19

BIURETS TEST! (2 STAGES)
- start with alkaline solution so add SODIUM HYDROXIDE solution.
- then add COPPER (II) SULFATE solution.
Positive = purple
Negative = stays blue
- pale so look carefully

Question 20

Describe the basic structures of a protein and amino acid structures?

Answer 20

Long chain of amino acid monomers. Dipeptide is 2 AA’s.Polypeptide is 2 or more AA’s.
Proteins are many polypeptides together.
Amino acids structure is ….:
- carboxyl group (-COOH)
- amino group (-NH2)
- R group (variable between 20 types)
Polypeptides are linked by condensation reactions and form PEPTIDE bonds.

Question 21

What are the four types of protein structure?

Answer 21

Primary structure:
- sequence of amino acids in polypeptide chain
Secondary structure:
- H bonds form between AA’s in a chain and cause a coil. Beta pleats form and alpha helix’s form.
Tertiary structure:
- amino acid chains coil more
- more H bonds and ionic bonds
- disulphide bonds
- 3D structure
Quaternary structure:
- many polypeptide chains held together by bonds
- like haemoglobin

Question 22

Types of proteins and their functions?

Answer 22

Enzymes - usually spherical due to tight folding polypeptide chains. Soluble and has a role in metabolism and synthesise large molecules.
Antibodies - involved in immune response and are two light polypeptide chains and 2 heavy one. They have variable regions.
Transport proteins - channel proteins in cell membranes. Contain hydrophobic and hydrophilic amino acids which fold to form channels. Transport ions across membranes.
Structural proteins - very strong and are long polypeptide chains parallel with cross-links between them. Include keratin and collagen.

Question 23

What are enzymes and their structure?

Answer 23

• biological catalysts
• very specific
• proteins
• complimentary to to substrate due to active site
• tertiary structure determines active sight
• form enzyme - substrate complex

Question 24

Lock and key theory VS Induced fit model

Answer 24

Lock and key theory:
- substrate fits into enzymes active sight like a lock and key because they are complimentary
But….. the enzyme - substrate complex changes slightly fit completely fit which leads us to the induced fit model.
Substrate requires complimentary shape to specific enzyme but the active shape is also made to change shape to fit better.

Question 25

What affects enzymes activity?
X4

Answer 25

TEMPERATURE:
As temp increases so does rate of enzyme controlled reaction.
More kinetic energy and vibrations.
Increased collisions.
Optimum temp changes active sight and enzyme denatures.
PH:
Opt pH value (mostly pH 7)
Enzyme denatured at any ph above or below the opt due to H+ and OH- ions found in acids and alkalis because they mess up ionic and hydrogen bonds in the enzymes structure.
ENZYME CONCENTRATION:
More enzymes increases the rate of the reaction because there are more things for the substrates to collides with to for E-SC.
But when limited substrate, more enzymes will have no effect.
SUBSTRATE CONCENTRATION:
More substrate molecules increases rate of reaction.
More collisions.
Only until saturation point though.

Question 26

How is enzyme activity inhibited with competitive inhibition?

Answer 26

Bing to enzymes.
Inside active site.
Same shape as the substrate to competes with it to get to active site but no reaction takes place.
BLOCK.
If high concentration of inhibitor, rate of reaction will be much slower.
But high substrate concentration increases their chances of binding to enzyme, increasing rate of reaction.

Question 27

How is enzyme activity inhibited by non-competitive inhibition?

Answer 27

Inhibitor binds outside the enzymes structure. Away from active site.
Changes active site shape to substrate no longer binds.
Don’t complete with substrate because they are different shape.
Increasing substrate concentration won’t make a difference.

Question 28

What is a nucleic acid and its structure?

Answer 28

Made of nucleotides.
DNA and RNA are nucleic acids carrying information.
Structure = pentose + nitrogen containing organic base + phosphate group.
Ester bonds between phosphate group and pentode sugar.
Glycosidic Bon between pentose sugar and base.
Condensation reactions occur to join pentose sugar to phosphate group and base and water is removed.

Question 29

Structure and function of DNA and RNA?

Answer 29

DEOXYRIBOSE NUCLEIC ACID:
2 polynucleotide chains (anti parallel) in double helix.
HYDROGEN BONDS!!!
Complimentary bases = A-T, C-G.

Pentose sugar (5 C atoms) = deoxyribose.
Phosphate group.
4 types of bases : adenine, guanine, THYMINE, cytosine.

RNA = ribose
Short polynucleotide chain (only one)
Ribose sugar.
Phosphate group.
4 types of bases : adenine, URACIL, cytosine, guanine.

Adenine and guanine are purine due to double ringed structure.
Cytosine and thymine are pyrimidines due to single ring.

Question 30

What are polynucleotides and how so they form?

Answer 30

Polymers of nucleotides. (Formed by DNA or RNA)
Join by condensation reactions between phosphate group and sugar of different nucleotides.
PHOSPHODIESTER BONDS!! (Phosphate and 2 ester bonds)
Chain of sugars = sugar-phosphate backbone.

Question 31

What is semi-conservative replication and how does it work?

Answer 31

DNA copies before cell division.
Semi conservative is only half of strands of each new dna molecules or of ogininal dna.
Steps:
1. DNA helicase enzyme breaks H bond between bases on two polynucleotides dna strands. UNWINDS and form 2 single strands.
2. Each original strand is a template for a new strand. Complimentary base pairings means the free-floating dna nucleotides are attracted to the exposed bases and match up.
3. Condensation reactions join together the nucleotides catalysed by the enzyme DNA polymerise. H bonds form between bases.
4. Each new dna polymerase molecule contains a new strand and an organically strand (semi conservative).

Question 32

What is the meselson and stahl experiment?

Answer 32

Theory to test semi conservative replication (in conservative, original DNA strands would have stayed together and new DNA molecules would create new strands).
Uses ISOTOPES of NITROGEN!!! - Heavy = 15N Light = 14N

1. Bacteria grown (2x) one light and one heavy. Bacteria reproduces and take up nitrogen for DNA nucleotides.
2. DNA sample taken from each and SPUN in CENTRIFUGE. DNA from heavy nitrogen settles lower than lighter because its heavier.
3. Bacteria from heavy nitrogen taken out and put into light nitrogen. Becateria left for round of dna replication then new dna spun again in centrifuge.
4. If conservative, original heavy will settle at bottom and new, light at top.
5. If semi conservative, new bacterial dna would contain 1 strand of old dna (heavy) and one of new (light). So dna would settle would between them.
6. Dna settles in the middle showing that its a mixture of the heavy and light N. The bacteria dna had replicated semi-conservatively in light N.

Question 33

Water structure and functions?

Answer 33

Structure:
H2O
Shared electrons.
Due to negative h electrons pulled towards O2 atom then other side of each h atom is left with a positive charge.
O2 atom has slight negative charge.
Polar molecule - partially neg and partially pos.

Function:
Metabolite in metabolic reactions like condensation and hydrolysis.
It’s a solvent so things can dissolve in it.
Help temperature control due to high latent heat of vaporisation and high specific heat capacity.
Water molecules are cohesive so stick together and helps transport in plants.

Question 34

What are useful properties of water?

Answer 34

1. Important metabolite - condensation and hydrolysis
2. High latent heat of vapourisation - takes lots of energy to break H bonds and lots of energy to vaporise it. Useful because organisms wont lose water as easily.
3. Can buffer (resist) temp changes - h bonds absorb energy due to high specific heat capacity. Useful as water doesn’t react to large temperature changes.
4. Good solvent - due to polarity.
5. Strong cohesion between water molecules - due to polarity, helps water flow and transporting substances, also means high surface tension when in contact with air.

Question 35

ATP structure and function?

Answer 35

ADENINE + RIBOSE + PHOSPHATE X3!

Energy released from glucose used to make ATP. Nucleotide derivative due to modified form of nucleotide.
Once made, ATP diffuses to part of the cell that needs energy.
Energy of ATP stored in high energy bonds between phosphate group. Released via hydrolysis.
When energy is needed by the cell, ATP is HYDROLYSED into ADP > phsosphate bond broken > energy released (catalyst = ATP hydrolyse.
Can be re-synthesised in condensation reaction > hydrolysed by ATP synthesise.

Question 36

What are inorganic ions and importance in haemoglobin?

Answer 36

Inorganic ions have an electric charge and NO CARBON.
Positive - cation.
Negative - anion.
In cytoplasm and bodily fluids of organisms. Ions role depends on high or low concentrations.
Haemoglobin = protein that carries O2 in RBCs.
- made of 4 polypeptide chains with iron ion.
- it binds to the O2 which turns FE2+ into FE3+ temporarily until o2 is released.

Question 37

Name the inorganic ions and there uses?

Answer 37

HYDROGEN IONS:
- determines pH
- more H+ = lower pH (acidic)
- affects enzyme controlled reactions (denaturation)

IRON IONS:
- component in haemoglobin (in polypeptide chains)
- FE2+ + O2 = FE3+

SODIUM IONS:
- co-transport of glucose and amino acids
- helps them cross membranes

PHOSPHATE IONS:
- components of DNA and ATP.
- production of ATP and phospholipids and nuclei acids.
- especially in membranes
- when phosphate bonds broken in ATP lots of energy is released.

CALCIUM IONS:
- required for blood clotting
- forms matrix in cellulose in plant cells
- transmitting of impulses from neurone to neurone
- stimulates muscle contraction
- regulate protein channels
- enzymes activated by CA2+

POTASSIUM IONS:
- constantly pumped into the into cells by active transport in exchange for sodium ions.
- important in transport of nerve impulses.

MAGNESIUM IONS:
- forms chlorophyll
- important for light absorption

NITRATE IONS:
- production of amino acids and proteins from carbs in plants by photosynthesis.

CHLORIDE IONS:
- moved out of cells lining lungs and digestive system to provide low water potential outside cell causing water to follow so mucus less thick and stiff.
- lack of it causes cystic fibrosis.

Question 38

How is DNA different in prokaryotes and eukaryotes?

Answer 38

Eukaryotes:
DNA is linear and have HISTONES to form chromosomes.
HISTONES order DNA into nucleosomes which the DNA winds around.
Some organelles also have DNA like like mitochondria and chloroplasts.

Prokaryotes:
Small, circular and not associated with proteins.
NO CHROMOSOMES.
Additional DNA in plasmids.

Question 39

Types of RNA?

Answer 39

RRNA - ribosomal (80% of all rna)
- involved in formation of ribosomes and important for protein synthesis.
MRNA - messenger (3-5% of all rna)
- single stranded and forms in nucleus.
- uses sone strand of DNA as a template.
- communicates genetic code in allele to ribosome during protein synthesis.
TRNA - transfer (15% of all rna)
- single stranded, clover leaf molecule.
- H bonds
- carry amino acids through cytoplasm to correct places in growing polypeptide chain.