Chapter 17 (Metabolism and Exercise 3)

Question 1

What is actin

Answer 1

Complex of several proteins
5nm in diameter
2 micrometres in length
G-actin molecules link together to form chains which together are called F actin. (fibrous)
2 chains of G-actin intertwine around each other.
Also consists of Tronponin complex and tropomyosin.

Question 2

What is troponin complex

Answer 2

Globular protein bound to G actin at regular intervals.

3 binding sites - one for myosin head, one for calcium ions, one for tropomyosin.

Question 3

What is tropomyosin

Answer 3

Long thin molecule that lies within the groove between 2 chains of G actin.

Question 4

What is myosin

Answer 4

10nm in diameter
2.5 micrometres in length.
Rod shaped
Has 2 bulbous heads - which contain an ATP binding site allowing the myosin head to have enzymatic function.

Question 5

What is a sarcomere

Answer 5

A contractile unit of proteins.
2.5 - 3 micrometres long.
Defined by 2 Z lines at each end.

Question 6

What is the sarcoplasmic reticulum function?

Answer 6

Stores and regulates release of Ca 2+ ions vital for muscle contraction.

Question 7

What is a triad?

Answer 7

T-tubule (transverse) with sarcoplamsic reticulum on either side.
site of excitation - contraction coupling.
(2 terminal cisternae and 1 T tubule)

Question 8

Haemoglobin information

Answer 8

Respiratory
Pigment

two different types
Adult haemoglobin
Fetal haemoglobin.
Globular proteins
Quaternary structure
produced from 2 different genes.
Have 4 prosthetic groups (haem groups)

Question 9

Erythrocytes information

Answer 9

Immature RBC produced in bone marrow of long bones.

Become specialised via differentiation.

Question 10

What is a haem group

Answer 10

Each haemoglobin (Fe2+) can bind to 4 oxygen molecules.

Question 11

What is a respiratory pigment.

Answer 11

a molecule that can bind reversibly to oxygen.

Question 12

Function of haemoglobin

Answer 12

transport oxygen to cells for aerobic respiration.

Question 13

Definition of association

Answer 13

Binding of an oxygen molecule to 1 haem group to form oxyhaemoglobin.

Question 14

Cooperative binding

Answer 14

1st oxygen binds to haemoglobin.
causes allosteric effect
causes second haem group to be exposed, so increases the binding ability.
second oxygen to bind to second haem group faster than first.
causes further allosteric effect….

Question 15

Fetal haemoglobin information? (compared to adult Hb)

Answer 15

Has higher affinity
Haem exposed more
o2 binds more readily
2 alpha and 2 gamma ppcs.

Question 16

What is myoglobin

Answer 16

only 1 ppc with 8 alpha helices.
1 haem group so 1 Fe 2+
can only bind 1 oxygen

Question 17

Function of myoglobin

Answer 17

Acts as an oxygen store within skeletal muscle

Only gives up oxygen at very low partial pressures of oxygen.

Question 18

How is carbon dioxide transported in the blood?

Answer 18

Aqueous solution in plasma
As bicarbonate ions dissolved in plasma.
Combined with amine group of 4 ppc. in each Hb molecule.

• forms carbaminohaemoglobin.

SHOW PERCENTAGES!!!

Question 19

Effect of carbon dioxide on curve?

Answer 19

• Binds irreversibly with Hb.
• Forms carboxyhaemoglobin.
• Less Hb can form oxyhaeoglobin.
• O2 carriage in blood decreases.

Question 20

Effect of temperature on curve?

Answer 20

• Hyperthethermia ( raised body temp)
• Shifts curve right
• Incr temp weakens association between O2 and Fe2+, so disrupts ionic and hydrogen bonds within Hb.
• Hb loses quaternary structure
• This promotes release of Oxygen from oxyhaemoglobin.
• Saturation falls.
  INCREEASE IN TEMPERATURE DECREASES AFFINITY OF HB FOR O2.

Question 21

Effect of pH on curves?

Answer 21

• Decrease in pH
• result of H2CO3 or lactic acid (dissociates to form H+)
• Shift dissociation curve to right as H.Hb is formed. (haemoglobinic acid)
• Which promotes release of o2, so percentage saturation falls.
• Decreases affinity of Hb for O2.
  DECREASE IN PH DECREASES AFFINITY FOR HB FOR O2.

Question 22

Myoglobin on graph

Answer 22

• Has higher affinity than adult haemoglobin
• Hyperbolic shape
• At any PO2, will have a higher saturation level than aHb.
• Binding is not cooperative (only one haem group)

Question 23

Fetal haemoglobin on graph.

Answer 23

• Shifted adult haemoglobin to left.
• At any given partial pressure of oxygen, more oxygen is offloaded from maternal adult haemoglobin and is taken up by fetal haemoglobin.