Control Systems

Question 1

What is positive feedback?

Answer 1

Positive feedback is when the stimulus creates a response that increases the stimulus and can only be stopped from external factor

Question 2

What is negative feedback?

Answer 2

Negative feedback is when the
stimulus causes a response in reducing the stimulus, allows the closer of the loop that could form

Question 3

Limitations of negative feedback?

Answer 3

The response to inhibit stimulus is initiated AFTER the stimulus has been present.
Correction could result in a over correction or not enough correction.

Question 4

Characteristics of membrane transporters

Answer 4

Channels:
- From aqueous pores
- Transport inorganic ions
- High capacity
- Highly selective
Carriers:
- Bind to specific substances, leading to conformational changes
- Lower transport capacity
- Highly selective

Question 5

Types of diffusion

Answer 5

Simple diffusion- Molecules move down gradient (high to low) - no energy
Facilitated diffusion - Molecules moved down there gradients by channels or carriers - no energy
Active transport - mores molecules against their gradient (low to high) - requires energy

Question 6

Types of Gated Channels

Answer 6

Mechanically-gated:
- requires an outside source (temp, pressure) to open
Voltage-gated:
- requires a change in membrane potential to open and close
Ligand-gated:
- requires the binding of a ligand to open or close

Question 7

Classifications of Carriers

Answer 7

Uniport:
- transports one type of substance
Symport:
- transport two or more substances in the same direction
Antiport:
- transports two or more substances in different directions

Question 8

How is Calcium regulated in the intracellular cell

Answer 8

The plasma membrane Ca ATPases pumps Ca out of the cell. Na/Ca exchanger transports Ca out. Ca ATPases pumps Ca into intercellular stores (ER mitochondria)

Question 9

Different Membrane Signalling - Messengers

Answer 9

Paracrine:
acts locally and is initiated from an indivdiual cell, there is minimal entry into the bloodstream.
Paracrine secretions can also be autocrine.
Endocrine:
Only cells with specific receptors for the specific hormone can respond.

Question 10

Cell membrane receptors

Answer 10

Receptor -channels
G-protein-coupled receptors (GPCR)
Receptor-enzyme
Integrin receptor

Question 11

Explain the various signal transduction pathways

Answer 11

Receptor-channels (ionictropic receptors) - Binding of agonist to receptor causes ion channels to open and thus a change in the membrane.
GPCR (metatotopic) - signalling molecules binds to GPCR, G-protein opens/closes ion channels, thus causing a confomational change.
Enzyme-receptor: Binding of signal molecule to the receptor causes a conformational change, this causes enzyme activation, leading to autophorylation, this phosphorylation (activates) of other proteins.
Intracellular receptor signalling - Steroid hormones and NO(nitric oxide)

Question 12

Types of GPCR linked ion channels

Answer 12

Adenylyl cyclase pathway:
G protein activates Adenylyl cyclase, this then converts ATP into cyclic AMP and pyrophospate, 2nd messenger cAMP activates protein Kinase A. Protein Kinase A then phosphoralates target proteins and changes their activity.
Phospholipase C Pathway (PLC):
PLC converts membrane PIP into 2nd messenger DAG or IP3, DAG activates protein Kinase C. IP3 releases Ca from stores into the ER, activating protein Kinase C. Protein Kinase C then phosphoralates target proteins and changes their activity.