Lecture Notes

Question 1

What is meant by theory of use and disuse?

Answer 1

Parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate.

Question 2

Why is it said that evolution leads to both diversity and unity?

Answer 2

Whilst animals share a common ancestor (unity), different environmental conditions led to the individual evolutionary changes of each species (diversity species). As a result, they are considered homologous structures.

Question 3

What are homologous structures?

Answer 3

All organisms shared a common ancestor and different environmental conditions led to individual evolutionary changes.

Question 4

What are the two types of cells/organisms?

Answer 4

Prokaryotes and Eukaryotes

Question 5

Describe key features of ALL cells

Answer 5

• Have plasma membrane
• Have cytoplasm (semi-fluid)
• Have protein and carbohydrates

Question 6

How do eukaryotes differ from prokaryotes?

Answer 6

• They are larger (10-100um)
• Their DNA is encapsulated in the nucleus
• Have additional membrane-bound compartments.

Question 7

What are the three domains of life?

Answer 7

Bacteria, Archaea (PROKARYOTES) and Eukarya (EUKARYOTES)

Question 8

What are the four main macromolecules and where are they found in the cell?

Answer 8

1. Carbohydrates (Within and outside the cell)
2. Lipids (Membrane and membrane-bound compartments)
3. Protein (Cytoplasm)
4. Nucleic Acid (Nucleus)

Question 9

How are polymers synthesised and degraded?

Answer 9

They are synthesised from monomers via a dehydration reaction (SHOW DIAGRAM)
They are degraded into shorter polymers via a hydrolysis reaction (SHOW DIAGRAM).

Question 10

What are the three main types of carbohydrates?

Answer 10

Monosaccharides
Disaccharides
Polysaccharides

Question 11

List key features of monosaccharides

Answer 11

• Simple sugars (most common: glucose)
• Can be used for fuel, converted into other organic molecules, or combined into polymers
• May be LINEAR or form RINGS when dissolved in water.

Question 12

List key features and examples of disaccharides

Answer 12

-Consist of two mono-saccharides joined by glycosidic linkage.
E.g. Maltose, sucrose, lactose

Question 13

What is glycosidic linkage?

Answer 13

The covalent bond formed between two monomers via a dehydration reaction. The most common glycosidic linkages are the 1-4 and 1-6

Question 14

What are the five examples of polysaccharides?

Answer 14

1. Starch
2. Glycogen
3. Cellulose
4. Glycoproteins
5. Chitin

Question 15

What is the difference between 1-4 and 1-6 linkage, and what does this result in?

Answer 15

• DRAW DIAGRAM*
• 1–4 linkage is flat and results in tightly packed, dense layers (which are difficult for enzymes to enter and digest)
• 1–6 linkage causes branching, and therefore the polymers are less tightly packed and have space inbetween, allowing enzymes to access and digest.

Question 16

What is the difference between alpha and beta configuration and what does it result in?

Answer 16

Alpha configuration has both OHs on the bottom (results in bulky configuration, hence easier for enzyme to access and break down)
Beta configuration has an OH on the bottom and an OH on the top (results in tightly packed structure which slows down enzyme reaction speed)

Question 17

Describe key features of starch

Answer 17

• Storage form of glucose in PLANTS
• Has many 1-4 and few 1-6 linkages
• Humans can digest as its in alpha config.
• Plants store starch as granules known as plastids.

Question 18

Describe key features of glycogen

Answer 18

• Storage form of glucose in ANIMALS
• Has frequent 1-6 linkages and gew 1-4 linkage
• Alpha config

Question 19

Desccribe key features of cellulose

Answer 19

• Major component in cell walls (as it is rigid)

- Beta config (therefore, mammals are unable to digest)

Question 20

Key features of glycoproteins?

Answer 20

• Combination of proteins and carbohydrates
• Usually found on cell surfaces
• Used as unique identifiers of cell types (useful for immunity)

Question 21

What is chitin?

Answer 21

A carbohydrate found in the exoskeleton of arthropods, cell walls of fungi
It is resistant to enzymatic digestion and can be used as surgical thread.

Question 22

What are lipids generally made from?

Answer 22

A single glycerol and three fatty acids join to form triacyl glycerol (DRAW)

Question 23

Two main forms of lipids?

Answer 23

Fatty acids and phospholipids

Question 24

Key features of fatty acids

Answer 24

• Vary in length, number and locations of double bonds.
  1. Saturated fatty acids= max no. of hydrogen atoms possible (no double bonds, as flat as possible) SOLID
  2. Unsaturated fatty acids= one or more double bonds (LIQUID), cis-healthy, trans-bad (less bending)

Question 25

Key features of phospholipids

Answer 25

Have only two fatty acids and a phosphocholine head group (DRAW) Hydrophilic head and hydrophobic tail Results in bilayer arrangement in cell membranes.

Question 26

Main component of proteins?

Answer 26

Polypeptides = polymers of amino acids

Question 27

Draw an amino acid

Answer 27

Amino group, carboxyl group, R side chain group

Question 28

How are amino acids linked?

Answer 28

Peptide bonds (formed between C and N) - also involve the removal of a water molecule

Question 29

How is the function of a peptide determined?

Answer 29

By its structure

Question 30

What are the four levels of Protein Structure? Describe appearance

Answer 30

1. Primary (sequence of amino acids) 2. Secondary (alpha-helix or beta-pleated sheets) 3. Tertiary (globular unit-3D) 4. Quarternary (Multi-protein complex)

Question 31

Why was the lock-and-key theory abolished in favour of the induced-fit model of enzyme ?

Answer 31

The lock and key theory assumed the shape of the enzyme, the active site and the susbtrate were all fixed. I.e. one enzyme for one substrate. However, the induced-fit model states that an active site has a specific shape that may not fit, but an interaction causes the enzyme to change shape to induce a tight fit.

Question 32

Draw a nucleotide, labelling the three key parts.

Answer 32

DRAW | Nitrogenous base, sugar ring, phosphate group.

Question 33

What are the purines and pyrimidines?

Answer 33

``` Purines= guanine and adenine Pyrimidines= cytosine and thymine ```

Question 34

What is the difference between a free nucleotide and one that has been incorporated into DNA

Answer 34

``` Free= Nucleotide in tri-phosphate form DNA= Nucleotide has one phosphate group ```

Question 35

Name and describe the three possible models of DNA replication

Answer 35

DRAW 1. Conservative model: Original DNA used as 'master template'- it is never destroyed. All copies are exactly identical to original DNA. 2. Semi-conservative model: Two parental strangs separate and each functions as a template for synthesis of a new complementary strand. 3. Dispersive model: Ancestor DNA 'ripped apart' into little pieces and is littered evenly through all new/other DNA.

Question 36

How did the Meselson-Stahl experiment prove the correct model of DNA replication?

Answer 36

Materials: Cultures of E. Coli, Ultracentrifuge (to separate less dense material from more dense material), isotope of nitrogen. Process INCOMPLETE

Question 37

What are the enzymes involved in DNA replication and their functions?

Answer 37

Prepare Team 1. Helicase: Unwinds DNA 2. Topoisomerase: Reduces tension by making small frequent cuts 3. SSBP: Stabilises single strand-keeps it open Leading Team (5'-3'): 1. Primase: Synthesises RNA primer at 5' end. 2. DNA pol 3: Removes RNA primer and replaces with DNA nucleotides. Lagging Team (3'-5'): 1. Primase: Joins RNA nucleotides into a primer 2. DNA pol 3: adds DNA nucleotides to the primer (forming Okazaki fragments) 3. DNA pol 1: Replaces RNA with DNA (where DNA pol3 missed) 4. Ligase: Glues fragments together to create continuous DNA strand.

Question 38

Why is telomerase needed and what does it do?

Answer 38

Problem: DNA daughter molecule on lagging strand is shorter than original as there is not enough room to replace with DNA. Therefore, telomerase creates an extension to the unreplicated end of DNA to allow the full length to be replicated.

Question 39

What is the difference between a capsid and an envelope?

Answer 39

``` Capsid= general protein coat present in all viruses Envelope = covering for capsid (combo of protein and phospholipids) ```

Question 40

What are the steps involved in PCR?

Answer 40

The double strand DNA separates (using heat), the primer binds to the single strands and then polymerase incorporates nucleotides to build a new DNA strand.

Question 41

How do restriction enzymes recognise cutting sites? give an example of a site that would be recognised

Answer 41

Most restriction enzymes recognise perfect palindromes (i.e. reading 5'-3' on one strand should match sequence reading 5'-3' on complementary strand).

Question 42

How does crossing over increase genetic variation?

Answer 42

Non-sister chromatids from homologous chromosomes exchange genetic information, usually at two or more locations per chromosome

Question 43

What is the function of the sigma factor in bacterial transcription?

Answer 43

To enable specific binding of RNA polymerase to promoters.