7A Muscles and Respiration

Question 1

skeletal muscle

Answer 1

muscle you use to move

contractions are voluntary

Question 2

flexor

Answer 2

muscle bends at joint when contracting

Question 3

extensor

Answer 3

muscle that straightens at joint when contracting

Question 4

antagonistic pairs

Answer 4

muscle pulls in one direction at a joint and the other muscle pulls in the opposite direction

Question 5

sarcomere

Answer 5

each repeated pattern of proteins

Question 6

ligaments

Answer 6

join bone to bone

Question 7

tendons

Answer 7

join muscle to bone

used to repair ligaments in keyhole surgery

NOT ELASTIC

Question 8

A band

Answer 8

AMIABLE

has both myosin and actin
-> shows movement of actin fibres BETWEEN myosin fibres

Question 9

myofibrils

Answer 9

bundles of actin and myosin filaments
-> slide past each other during muscle contraction

Question 10

H zone

Answer 10

H ate
A ctin

only myosin present
-> shortens when contracts

Question 11

I band

Answer 11

only actin

Question 12

myosin

Answer 12

dark bands

Question 13

actin

Answer 13

light bands

Question 14

cartilage

Answer 14

protects bones within joints by
absorbing shock

Question 15

synovial fluid

Answer 15

fluid that acts as lubricant as enables bones to move freely

Question 16

why do muscle work in pairs?

Answer 16

they can only pull when they contract

Question 17

how do cells get their energy?

Answer 17

during respiration -> glucose broken down
-> releases energy which is used to
make ATP (phosphorylation)

Question 18

explain why glycolysis happens in the cytoplasm?

Answer 18

• cytoplasm has enzymes needed for glycolytic pathway
• only place where these enzymes are found!!!

Question 19

state the coenzymes used in respiration and their function

Answer 19

• NAD and FAD
  -> transfer H⁺ from one molecule to another - so they can red / ox molecule
  -> so NAD stops area where other** enzymes** are getting too acidic so enzymes don’t denature
• Coenzyme A
  -> transfers acetate between molecules (link reaction)

Question 20

substrate level phosphorylation

Answer 20

breaking of bonds in glucose gives energy needed to phosphorylate (add Pi group) ADP to ATP

Question 21

why does the link reaction happen in the mitochondrial matrix?

Answer 21

• enzymes and coenzymes needed located here
• NADH made is in right place to be used by oxidative phosphorylation (in inner mitochondrial membrane)

Question 22

why does the Kreb cycle happen in the mitochondrial matrix?

Answer 22

• each reaction in Krebs is controlled by specific intracellular enzyme
• which is found in mitochondrial matrix

Question 23

describe how acetate in made from pyruvate in the link reaction

Answer 23

• pyruvate is decarboxylated (carbon removed) - 1C removed in form of CO₂
• NAD is reduced (NADH) by collecting H from pyruvate -> making acetate!!

Question 24

for every 1 glucose molecule …

Answer 24

link reaction occurs x2

• 2 acetyl co. A go into Krebs
• 2 CO₂ molecules released as waste product of respiration
• 2 NADH made and are used in oxidative phosphorylation

Question 25

chemiosmosis

Answer 25

movement of H⁺ ions across selectively permeable membrane down grad to generate ATP

Question 26

e- lose energy down the E.T.C. what is this energy used for?

Answer 26

used by e- carriers to pump H⁺ ions into intermembranal space

Question 27

suggest why acetyl co. A cannot be made in anaerobic respiration

check

Answer 27

pyruvate cannot be ox as NADH not recycled

Question 28

describe how ATP is synthesised in oxidative phosphorylation

Answer 28

• H⁺ ions move down electrochemical gradient back into mitochondrial matrix via enzyme ATPsynthase
• this movement drives ADP + Pi -> ATP
• this is chemiosmosis

Question 29

suggest why a cell may have more cristae (folds) in mitochondria

Answer 29

if cell is metabolically active
= more ATP made = more cristae

Question 30

state why glycolysis is an anaerobic process itself

Answer 30

doesn’t need O₂ to take place

Question 31

what is the final e- acceptor in oxidative phosphorylation?

Answer 31

O₂ (from blood)

1/2 O₂ + 2H⁺ + 2e⁻ -> H₂O

Question 32

what happens to lactate (lactic acid) after a period of anaerobic respiration?

Answer 32

• ox. back into pyruvate
• pyruvate directly ox. into CO₂ and H₂O via Krebs
• some lactate converted to …
  -> glycogen (stored form of glucose)
  and stored in liver cells
  -> OR glucose and respired

Question 33

metabolic pathway

Answer 33

• many stepped process
• with each step controlled and catalysed by specific intracellular enzyme

Question 34

state the adv. and disadv. of using a simple respirometer in finding the rate of respiration

Answer 34

adv.

• easy to set up
• not many connections so makes ‘good seal’ easier to obtain

disadv.

• cannot be reset
• needs control tube alongside it
• scale not as accurate = measurements not as accurate

Question 35

state the adv. and disadv. of using a u-tube respirometer in finding the rate of respiration

Answer 35

adv.

• doesn’t need additional control
• syringe allows dye to be reset

disadv.

• tendency for connections to leak in old models
• more expensive

Question 36

what is the use of soda lime / KOH sol in rate of respiration practical?

Answer 36

absorbs CO₂

Question 37

why can’t filaments slide past each other when muscle is relaxed?

Answer 37

• actin-myosin sites blocked by tropomyosin held in place by troponin
• so myofilaments cannot slide past each other …
• as myosin heads cannot bind to actin-myosin binding sites on actin filaments

Question 38

what happens to troponin during muscle contraction and what is the effect of this?

Answer 38

• Ca²⁺ bind to troponin …
• changing its shape so tropomyosin is moved …
• and actin-myosin binding sites exposed

Question 39

describe what happens in the sarcomere when a muscle contracts

(6 marks)

Answer 39

1. action potential stimulates muscle cell and depolarises sarcolemma
2. depolarisation spreads down T-tubules to sarcoplasmic reticulum -> causes SR to release Ca²⁺ into sarcoplasm
3. Ca²⁺ bind to troponin -> causing it to change shape and make tropomyosin move…
4. … exposing actin-myosin binding site -> allows myosin heads to bind to them -> ACTIN-MYOSIN CROSSBRIDGE FORMED
5. Ca²⁺ activate ATPase -> breaks down ATP->ADP + Pi to provide energy needed for muscle contraction
6. energy moves myosin head -> pulls actin over myosin
7. energy also used to break actin-myosin crossbridge -> myosin head detaches from actin
8. myosin head reattaches to binding site further along actin -> new crossbridge formed and cycle repeats
9. many crossbridges form and break v rapido = shortens sarcomere = muscle contracts

Question 40

why is ATP required for muscle contraction?

Answer 40

• provides energy to move myosin head
• and break crossbridge to allow binding to next binding site