Lecture Notes Flashcards
What is meant by theory of use and disuse?
Parts of the body that are used extensively become larger and stronger, while those that are not used deteriorate.
Why is it said that evolution leads to both diversity and unity?
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.
What are homologous structures?
All organisms shared a common ancestor and different environmental conditions led to individual evolutionary changes.
What are the two types of cells/organisms?
Prokaryotes and Eukaryotes
Describe key features of ALL cells
- Have plasma membrane
- Have cytoplasm (semi-fluid)
- Have protein and carbohydrates
How do eukaryotes differ from prokaryotes?
- They are larger (10-100um)
- Their DNA is encapsulated in the nucleus
- Have additional membrane-bound compartments.
What are the three domains of life?
Bacteria, Archaea (PROKARYOTES) and Eukarya (EUKARYOTES)
What are the four main macromolecules and where are they found in the cell?
- Carbohydrates (Within and outside the cell)
- Lipids (Membrane and membrane-bound compartments)
- Protein (Cytoplasm)
- Nucleic Acid (Nucleus)
How are polymers synthesised and degraded?
They are synthesised from monomers via a dehydration reaction (SHOW DIAGRAM)
They are degraded into shorter polymers via a hydrolysis reaction (SHOW DIAGRAM).
What are the three main types of carbohydrates?
Monosaccharides
Disaccharides
Polysaccharides
List key features of monosaccharides
- 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.
List key features and examples of disaccharides
-Consist of two mono-saccharides joined by glycosidic linkage.
E.g. Maltose, sucrose, lactose
What is glycosidic linkage?
The covalent bond formed between two monomers via a dehydration reaction. The most common glycosidic linkages are the 1-4 and 1-6
What are the five examples of polysaccharides?
- Starch
- Glycogen
- Cellulose
- Glycoproteins
- Chitin
What is the difference between 1-4 and 1-6 linkage, and what does this result in?
- 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.
What is the difference between alpha and beta configuration and what does it result in?
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)
Describe key features of starch
- 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.
Describe key features of glycogen
- Storage form of glucose in ANIMALS
- Has frequent 1-6 linkages and gew 1-4 linkage
- Alpha config
Desccribe key features of cellulose
- Major component in cell walls (as it is rigid)
- Beta config (therefore, mammals are unable to digest)
Key features of glycoproteins?
- Combination of proteins and carbohydrates
- Usually found on cell surfaces
- Used as unique identifiers of cell types (useful for immunity)
What is chitin?
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.
What are lipids generally made from?
A single glycerol and three fatty acids join to form triacyl glycerol (DRAW)
Two main forms of lipids?
Fatty acids and phospholipids
Key features of fatty acids
- 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)
Key features of phospholipids
Have only two fatty acids and a phosphocholine head group (DRAW)
Hydrophilic head and hydrophobic tail
Results in bilayer arrangement in cell membranes.
Main component of proteins?
Polypeptides = polymers of amino acids
Draw an amino acid
Amino group, carboxyl group, R side chain group
How are amino acids linked?
Peptide bonds (formed between C and N) - also involve the removal of a water molecule
How is the function of a peptide determined?
By its structure
What are the four levels of Protein Structure? Describe appearance
- Primary (sequence of amino acids)
- Secondary (alpha-helix or beta-pleated sheets)
- Tertiary (globular unit-3D)
- Quarternary (Multi-protein complex)
Why was the lock-and-key theory abolished in favour of the induced-fit model of enzyme ?
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.
Draw a nucleotide, labelling the three key parts.
DRAW
Nitrogenous base, sugar ring, phosphate group.
What are the purines and pyrimidines?
Purines= guanine and adenine Pyrimidines= cytosine and thymine
What is the difference between a free nucleotide and one that has been incorporated into DNA
Free= Nucleotide in tri-phosphate form DNA= Nucleotide has one phosphate group
Name and describe the three possible models of DNA replication
DRAW
- Conservative model: Original DNA used as ‘master template’- it is never destroyed. All copies are exactly identical to original DNA.
- Semi-conservative model: Two parental strangs separate and each functions as a template for synthesis of a new complementary strand.
- Dispersive model: Ancestor DNA ‘ripped apart’ into little pieces and is littered evenly through all new/other DNA.
How did the Meselson-Stahl experiment prove the correct model of DNA replication?
Materials: Cultures of E. Coli, Ultracentrifuge (to separate less dense material from more dense material), isotope of nitrogen.
Process
INCOMPLETE
What are the enzymes involved in DNA replication and their functions?
Prepare Team
- Helicase: Unwinds DNA
- Topoisomerase: Reduces tension by making small frequent cuts
- SSBP: Stabilises single strand-keeps it open
Leading Team (5’-3’):
- Primase: Synthesises RNA primer at 5’ end.
- DNA pol 3: Removes RNA primer and replaces with DNA nucleotides.
Lagging Team (3’-5’):
- Primase: Joins RNA nucleotides into a primer
- DNA pol 3: adds DNA nucleotides to the primer (forming Okazaki fragments)
- DNA pol 1: Replaces RNA with DNA (where DNA pol3 missed)
- Ligase: Glues fragments together to create continuous DNA strand.
Why is telomerase needed and what does it do?
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.
What is the difference between a capsid and an envelope?
Capsid= general protein coat present in all viruses Envelope = covering for capsid (combo of protein and phospholipids)
What are the steps involved in PCR?
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.
How do restriction enzymes recognise cutting sites? give an example of a site that would be recognised
Most restriction enzymes recognise perfect palindromes (i.e. reading 5’-3’ on one strand should match sequence reading 5’-3’ on complementary strand).
How does crossing over increase genetic variation?
Non-sister chromatids from homologous chromosomes exchange genetic information, usually at two or more locations per chromosome
What is the function of the sigma factor in bacterial transcription?
To enable specific binding of RNA polymerase to promoters.
