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A2 Biology > 12 .1 - ENERGY > Flashcards

12 .1 - ENERGY Flashcards

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1
Q

State processes that require energy in living organisms

A

> active transport

  • using Na+/K+ pump in cell membranes
  • exocytosis/ endocytosis

> movement

  • muscle contraction
  • cellular movement of chromosomes via spindle

> anabolic reactions

  • synthesis of DNA from nucleotides
  • synthesis of proteins from amino acids
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2
Q

Describe features of ATP that makes it suitable as the universal energy currency

A

> small and soluble
- easily transportable

> links energy-requiring and energy-yielding reactions

> hydrolysis of ATP releases 30.5kJmol^-1 of energy
- quick and easy to allow cells to respond to sudden increase of demand

> Breakdown of ATP is a reversible reaction

  • ATP can be reformed from ADP + Pi
  • ADP can be recycled

> short-term energy store

> stable molecules
- only breaks down when catalyst (ATP synthase) is present

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3
Q

Describe and draw structure of ATP

A

> phosphorylated nucleotide

> made up of

  • ribose sugar
  • adenine base
  • three phosphate groups
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4
Q

Name two ways ATP can be synthesised

A

> substrate - linked phosphorylation

> chemiosmosis
- in membranes of mitochondria and chloroplasts

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5
Q

State the reversible reaction of ATP

A 
ADP + Pi ------> ATP 
(condensation) 
 water released as by-product 
ATP ---------> ADP + Pi 
(hydrolysis)

*ATP synthase catalases reaction

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6
Q

Describe substrate-linked phosphorylation

A
  • ADP + Pi —-> ATP
  • ATP formed by transferring a phosphate molecule from a substrate molecule to ADP
  • energy-requiring reaction
  • occurs in cell cytoplasm and matrix of mitochondria
  • small amount of ATP released (4/6 ATP) (glycolysis)
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7
Q

Describe chemiosmosis

A
  • there is a proton gradient across the inner membrane of mitochondria/ thylakoid membrane of chloroplasts
  • E.T.P produce proton gradient
  • high energy electrons are passed down to a chain of electron carriers across the membrane
  • this provides the energy to pump proton to intermembrane space via active transport through a proton pump
  • Protons then move down the conc gradient across the membrane through ATP synthase
  • energy released used to synthesise ATP
  • O2 acts as final electron and proton acceptor
  • large amount of ATP is generated (32/34 ATP)
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8
Q

Name the main respiratory substrate for aerobic respiration

A
  • glucose

- glucose + oxygen –> water + carbon dioxide + energy

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9
Q

Name other substrates that are used when glucose is used up by cells to continue respiration

A
  • other carbohydrates
  • lipids
  • proteins
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10
Q

Why amino acids from proteins is the last to be respired

A
  • respired anaerobically after all other substrates used up
  • proteins have essential functions elsewhere
  • amino acids are required to synthesise proteins which have structural (cytoskeleton) and functional (enzyme) roles
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11
Q

State the different energy values released of different substrates when they break down

A
  • carbohydrate = 15.8
  • lipid = 39.4
  • protein = 17.0
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12
Q

Explain why carbohydrates, lipids and proteins have different energy values as substrates in respiration in aerobic conditions

A
  • lipids > proteins > carbohydrates
  • difference of energy values depends on the number of hydrogen atoms available when the substrate molecule breaks down
  • when hydrogen atoms are available, NAD and FAD carrier molecules are reduced and transfers the H+ to inner mitochondrial membrane
  • reduced carrier molecules will release protons and e-
  • these protons are pumped to the intermembrane space to form a proton gradient
  • via chemiosmosis, protons diffuse down the conc gradient and synthesise ATP
  • protons are oxidised to form water
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13
Q

Why lipids have the highest energy value

A
  • highest hydrogen content molecule
  • lipids consist of fatty acids which are made up of long hydrocarbon chains
  • many hydrogen atoms will be released when the substrate molecule is broken down
  • greater proton gradient form across the mitochondrial membrane
  • more ATP will be produced via chemiosmosis
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14
Q

State the definition of the respiratory (RQ)

A
  • the ratio of carbon dioxide molecules produced
  • to oxygen molecules taken in
  • during respiration
  • ratio (molecules/ mole/ volume)
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15
Q

Why different substrates have different RQ values

A
  • RQ= CO2/O2
  • different RQ values as number of C-H bonds differ
  • more hydrogen –> larger proton gradient –> more ATP formed –> more O2 required (to form water)
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16
Q

State the equation when glucose is respired aerobically

A
  • C6H12O6 + 6O2 —> 6CO2 + 6H2O
  • therefore, RQ = 6/6
  • RQ value when glucose (carbohydrate) is the substrate is 1.0
17
Q

State the RQ values of different substrates

A
  • carbohydrate = 1.0
  • protein = 0.9
  • lipid = 0.7
18
Q

To note: when calculating RQ for aerobic respiration

A
  • when balancing equation, remember to divide by 2 for O2 reactant
    steps:
    > form equation and balance
    > ratio and divide
19
Q

How to investigate RQ value?

A

> respirometers:

  • are used to measure and investigate the rate of oxygen consumption during respiration in organisms
  • can be used to calculate RQ values
20
Q

Draw the setup of respirometer

A

check google notes

21
Q

How to calculate oxygen consumed (cm3/min)

A
  • use equation: (pi)r2h
  • r = radius
  • h = distance moved by manometer fluid in a minute
22
Q

How to determine RQ (respiratory quotient) experimentally

A
  • measure oxygen consumption by set up respirometer and run experiment with soda-lime present in both tubes
  • Use manometer reading to calculate the change in gas volume within a give time (pi)r2h
  • reset apparatus: allow air to enter the tubes via screw cap and reset manometer fluid via syringe
  • run experiment again without soda-lime from both tubes, use manometer reading to calculate the change in gas volume in a given time (cm3/min)

CALCULATION:
- 1st experiment –> volume of O2 consumed
- 2nd experiment –> O2 consumed - CO2 produced
- can be positive or negative depending on the movement of fluid
RQ = CO2 / O2
= 1 + 2/ 1

23
Q

What does it mean when an RQ value is changing?

A
  • substrate being respired has changed
  • some may use mixture of substrates
  • usually carbohydrates –> lipids –> proteins
  • RQ > 1 means excess carbohydrate intake
  • RQ < 0.7 means underfeeding
24
Q

State ways to increase the reliability of the respirometer experiment

A

> keep temp constant
- use a controlled water bath

> pressure
- have control tube with equal volume of inert material to compensate changes in atmospheric pressure

> repeat
- use average

A2 Biology (3 decks)

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