the 1st unicram (4)

Question 1

What are Amphoteric properties?

Answer 1

A substance which can act as an acid or a base

Proton donor or proton acceptor

Question 2

Do amino acids have amphoteric properties?

Answer 2

Yes

Question 3

How are peptide bonds formed/broken?

Answer 3

Formed by condensation, broken by hydrolysis

Needs ATP

Question 4

What is primary structure?

Answer 4

• Order or sequence of the polypeptide chain, joined by peptide bonds
• Determined by the codons on DNA
• Determins the tertiary structure of the polypeptide

Question 5

What is secondary structure?

Answer 5

• The primary structure folds back on itself
• Hydrogen bonds form between C=O and N-H of primary structure
• ALPHA HELIX OR BETA PLEATED SHEET
• R groups project out from the alpha helix
• Beta pleated folds backwards and forwards in pleats with the H bonds forming between C=O and N-H of adjacent folds
• R group project alternately above and below the plane of the sheet

Question 6

The Alpha Helix

Answer 6

Right - hand coil, R groups project out from helix

Polar residues face outwards toward liquid and hydrophobic residues face protein interior

Kinked

Question 7

The Beta Pleated sheet

Answer 7

3 Types:

parallel beta sheet - all bonded strands have the same N to C direction. Seperated by long sequence stretches

Antiparallel beta sheet - Beta strands run in alternating directions, can be formed between regions that are close on the primary sequence

Mixed beta sheet - A mixture of parallel and antiparallel hydrogen bonding

Question 8

When does a turn occur for beta pleated sheets?

Answer 8

When protein chain needs to change direction to connect two other elements of secondary structure

Question 9

What are random coils?

Answer 9

Regions of the protein chain that don’t form a regular secondary structure or have a regular hydrogen bonding pattern

Found in Terminal arms and loops

Question 10

Tertiary Structure?

Answer 10

Secondary structure folds back on itself to form a 3D globular structure

Determined by nature of R groups

Bonds between R groups are Hydrogen, Ionic, Disulphide
(Weakest to strongest) - Also weak molecular forces and hydrophobic,philic interactions

Question 11

What are chaperone proteins?

Answer 11

Chaperone proteins assist in ensuring the tertiary correctly folds to ensure the correct structure is formed

Prevents hydrophobic patches of amino acids from aggregating into non-functional aggregates

Question 12

Conjugated proteins

Answer 12

Proteins that contian a non-protein prosphetic group (attached by covalent bonds)

Protein is called the apoprotein

Question 13

Quaternary proteins ?

Answer 13

Consist of more than one polypeptide chain

Joined by bonds between R groups

Either fibrous or globular

Question 14

Collagen?

Answer 14

Organic phase of bones, teeth and most other connective tissues

Fibrous quaternary protein

Made of 3 amino acids repeated over and over, one of which is glycine

Glycine has H as the R group, makes it small and so pulls the helix in. Helices are joined by bonds between R groups

Question 15

Haemoglobin?

Answer 15

Global heteromeric quanternary protein

Conjugated chromoprotein with heme groups

Hydrophobic interactions hold 4 subunits together
Hydrophilic interactions allow it to dissolve in water

Question 16

Types of signal transduction?

Answer 16

Autocrine
Intracrine
Juxtracrine
Paracrine
Endocrine

Question 17

Autocrine and Intracrine transduction?

Answer 17

Autocrine:
A cell secrets a chemical messenger out of the cell which binds to receptors on the same cell membrane. Activates effector on the same cell

Intracrine:
Chemical messenger is released within the cell and is not secreted out of the cell. Instead, a nuclear and cytosolic receptor

Question 18

Juxtacrine and Paracrine transduction?

Answer 18

Juxtacrine:
Utilises gap-junction proteins to transport a chemical messenger across the cell membrane of an adjacent cell to cause an effect on that adjacent cell

Paracrine:
Chemical messenger is released from a cell and is allowed to diffuse into the local tissue.
Allows it to target a series of neighbouring cells for effect

Question 19

Endocrine transduction?

Answer 19

Release of cellular messengers (hormones) from a cell and is transported to the tissue/cell of activity via the bloodstream. This requires transportation into and out of the bloodstream

Question 20

Cell signalling: Dopamine?

Answer 20

Neuotransmitter molecule, promotes reward and pleasure responses to beneficial activities

Binds to several different types of dopamine receptors, each has a unique effect

Question 21

Release of dopamine?

Answer 21

Synthesised within the cytol of neurons from L-DOPA and packaged into synaptic vesicles

Dopamine vesicles are released from the first neuron by an action potential activated exocytosis

Question 22

Binding of dopamine?

Answer 22

Dopamine is released into the intrasynaptic gap

Dopamine can then bind to specific dopamine activated receptors on both sides of the synaptic gap

While binding to receptors on the opposite neuron, dopamine acts as a paracrine signalling molecule

While binding to receptors on the neuron which released it, dopamine acts as an autocrine signalling molecule

2 types of Dopamine binding receptors:
Type 1 and 2

1: Increase production of cAMP which acts as an intracellular secondary messenger, passing on the message to new effectors

2: Reduce or inhibit cAMP production, reducing the secondary messenger effects, halting the message to new effectors

Question 23

Process of Dopamine binding?

Answer 23

1) Dopamine is synthesised from L-DOPA
2) Dopamine is packaged into the vesicle awaiting an action potential
3) Action potential fires, releases the dopamine via exocytosis
4) Dopamine binding to type 1 receptor activates cAMP continuing the message
5) Dopamine binds to a type 2 receptor deactivates cAMP, halting the message
6) Dopamine binding to an autocrine type 2 receptor prevents dopamine production

Question 24

Motor proteins?

Answer 24

• Set of molecular motors which move molecules along the cytoskeleton of cells
• Utilises the hydrolysis of ATP, convert chemical potential energy into movement
• Kinesins and dynein are two motor proteins, transport molecules and structures along the structural microtubule structures to the periphery and interior of the cell respectively

Question 25

Kinesin structure?

Answer 25

Kinesin proteins are made up two pairs of protein chains bound together to make a quaternary-structure protein complex

Made of 2 chains (KHC) which are bound together to form a dimer pair. KHC dimer then bind a pair of light chains (KLC)

Question 26

Kinesin movement mechanism explanation?

Answer 26

Works in junction with microtubules

Microtubules act as the skeleton within cells allowing for both structural rigidity and allows for active and reicted transportation within the cell

Question 27

Movement mechanism of Kinesin?

Answer 27

One KHC motor head is bound, other isn’t. ADP molecule is bound to ATP binding site, other is free. Free ATP within the cytosol is free to bind with the ATP binding site of Beta tubulin KHC motor head

Binding of ATP to the KHC-tubulin complex (B) results in the half rotation of the whole kinesin, due to conformation shape-change. promotes uncouping of ADP from unbound motor head

With ADP decoupling from the unbound KHC motor (A), additional conformation shape change to occur. Motor A binds to tubulin. Both KHC motors bound to the tubulin puts additional pressure on the ATP binding site, forcing hydrolysis of the bound ATP and converts it to ADP.

With ADP bound to the ATP binding site, there is a final conformation shape change to the now-trailing KHC motor head. KHC head B decouples from beta tubulin molecule resetting movement mechanism

Question 28

What are the 3 stages of glycolysis?

Answer 28

Investing: Phosphorylation of glucose by 2 ATP molecules

Cleaving: Fructose I-6 bisphosphate is cleaved into 2x 3C molecules

Harvesting: 4 molecules of ATP are produced as Pi is removed from intermediates

Question 29

Why phosphorylate glucose?

Answer 29

Makes it more reactive (Turns it into Pyruvate) and keeps it in the cell

Glucose –> Glucose-6-phosphate (Hexokinase) –> Pyruvate