Topic 7 Muscles and respiration

Question 1

Describe the structure of a myofibril

Answer 1

Long chain of sarcomeres attached together

Question 2

Describe the structure of a sarcomere

Answer 2

Myosin and actin with tropomyosin and troponin bound to the actin.

Question 3

Explain the role of Calcium ions in muscle contraction

Answer 3

Released from sarcoplasmic reticulum, bind to troponin and causes it to move which pulls tropomyosin to move away from myosin binding sites on actin so myosin can bind to actin and begin contraction

Question 4

Describe the sequence of events from the arrival of a nerve impulse at the neuromuscular junction to the contraction of a muscle

Answer 4

Nerve impulse causes release of Ca2+ from sarcoplasmic reticulum, Ca2+ binds to troponin and causes troponin to move and tropomyosin to be pulled away from myosin binding sites on actin, Myosin binds to actin forming crosslink and releases ADP + P, Myosin head rotates towards the centre of the sarcomere, pulling actin to centre, ATP binds to myosin head which causes it to detach from actin, ATP hydrolysed to ADP + P, Myosin head rotates back to original position and forms another crosslink

Question 5

Explain what would need to happen in order to get a muscle to relax following contraction

Answer 5

Ca2+ not being released means troponin moves back to original position so tropomyosin covers myosin binding sites again so myosin can no longer form crosslinks so Actin is no longer pulled towards middle of sarcomere causing it to return to original position

Question 6

State where glycolysis takes place

Answer 6

Cytoplasm

Question 7

State the site of glycolysis

Answer 7

Cytoplasm

Question 8

Describe the process of glycolysis

Answer 8

Glucose, 2 ATP turn into ADP and glucose phosphorylated, causing it to turn into an unstable molecule and split into two 3 carbon sugars. Each 3 carbon sugars phosphorylates 2ADP into 2ATP and reduces an NAD to form NADH, 3 carbon sugar turns into pyruvate

Question 9

State the ratio of glucose to pyruvate formed in glycolysis

Answer 9

1 : 2

Question 10

State the net gain of ATP in glycolysis

Answer 10

2 ATP

Question 11

Give a definition of decarboxylation

Answer 11

Removal of a carbon.

Question 12

Give a definition of dehydrogenation

Answer 12

Removal of Hydrogen / Oxidation

Question 13

Locations of the link reaction and Krebs cycle

Answer 13

Matrix of mitochondria

Question 14

Describe the process of the link reaction

Answer 14

Pyruvate reduces NAD to form NADH, Pyruvate gets decarboxylated, releasing CO2 and Acetate is formed, which combines with Coenzyme A to form Acetyl coenzyme A.

Question 15

Describe the process of the Krebs cycle

Answer 15

Acetate delivered by Acetyl coenzyme A, Acetate and oxaloacetate (4C) combine to make Citrate (6C). Citrate Reduces NAD to form NADH and gets decarboxylated, releasing CO2 and forming a 5C compound. 5C compound reduces NADH to form NADH and gets decarboxylated, releasing CO2 and forming a 4C compound. 4C compound reduces NAD, forming NADH, reduces FAD, forming FADH and causes phosphorylation of ADP to form ATP, and forms Oxaloacetate (4C). Cycle repeats

Question 16

State the role of NADH and FADH

Answer 16

Coenzymes responsible for the transport of Hydrogen.

Question 17

Explain why the link reaction and Krebs cycle can only occur if sufficient oxygen is present

Answer 17

Oxygen is required for oxidation of NADH and FADH to allow them to be reduced once again during the Krebs cycle.

Question 18

Devise a valid and reliable method for investigating the rate of respiration at different temperatures

Answer 18

IV: Temperature 10, 20, 30, 40, 50 degrees
DV: distance respirometer moved in mm
CV: Time allowed for respiration (3 mins), Mung beans used.
- Mung bean with respirometer

Question 19

Describe bhow you would calculate the rate of respiration of an organism in a given time period

Answer 19

Respirometer for 3 mins, measure respirometer at start and end of 3 mins in mm and find the difference, divide difference by 180 to find mm/s

Question 20

Define stroke volume

Answer 20

Volume of blood released from left ventricle per beat

Question 21

Define cardiac output

Answer 21

Volume of blood released from heart per minute

Question 22

State what tidal volume is and how it is calculated using a spirometer graph

Answer 22

Volume breathed in/out in one breath cycle, dm^3, height of one regular spike on a spirometry graph from peak to trough.

Question 23

State what breathing rate is and how it is calculated using a spirometry graph.

Answer 23

Number of breaths performed per minute, it is calculated by counting the number of peaks within a given time period on a spirometry graph and multiplying it to get to 60s worth of peaks

Question 24

State what the minute volume is and how it is calculated using a spirometry graph

Answer 24

Volume of air breathed in one minute. Tidal volume x breathing rate

Question 25

State what oxygen consumption is and how it is calculated using a spirometry graph

Answer 25

Volume of oxygen consumed within one minute of regular breathing. Caluclated by finding the difference between the heights of the first and last peaks within a minute of regular breathing on a spirometry graph

Question 26

Explain how hormones bring about a response in a target cell.

Answer 26

Hormones bind to target cell, Transcription factors activated, Transcription factors and RNA polymerase bind to the promoter region of a specitic gene, Gene is transcribed into mRNA, mRNA translated into the protein, Protein produced determines the function of the cell.