12 .1 - ENERGY Flashcards
State processes that require energy in living organisms
> 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
Describe features of ATP that makes it suitable as the universal energy currency
> 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
Describe and draw structure of ATP
> phosphorylated nucleotide
> made up of
- ribose sugar
- adenine base
- three phosphate groups
Name two ways ATP can be synthesised
> substrate - linked phosphorylation
> chemiosmosis
- in membranes of mitochondria and chloroplasts
State the reversible reaction of ATP
ADP + Pi ------> ATP (condensation) water released as by-product ATP ---------> ADP + Pi (hydrolysis)
*ATP synthase catalases reaction
Describe substrate-linked phosphorylation
- 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)
Describe chemiosmosis
- 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)
Name the main respiratory substrate for aerobic respiration
- glucose
- glucose + oxygen –> water + carbon dioxide + energy
Name other substrates that are used when glucose is used up by cells to continue respiration
- other carbohydrates
- lipids
- proteins
Why amino acids from proteins is the last to be respired
- 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
State the different energy values released of different substrates when they break down
- carbohydrate = 15.8
- lipid = 39.4
- protein = 17.0
Explain why carbohydrates, lipids and proteins have different energy values as substrates in respiration in aerobic conditions
- 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
Why lipids have the highest energy value
- 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
State the definition of the respiratory (RQ)
- the ratio of carbon dioxide molecules produced
- to oxygen molecules taken in
- during respiration
- ratio (molecules/ mole/ volume)
Why different substrates have different RQ values
- 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)
State the equation when glucose is respired aerobically
- C6H12O6 + 6O2 —> 6CO2 + 6H2O
- therefore, RQ = 6/6
- RQ value when glucose (carbohydrate) is the substrate is 1.0
State the RQ values of different substrates
- carbohydrate = 1.0
- protein = 0.9
- lipid = 0.7
To note: when calculating RQ for aerobic respiration
- when balancing equation, remember to divide by 2 for O2 reactant
steps:
> form equation and balance
> ratio and divide
How to investigate RQ value?
> respirometers:
- are used to measure and investigate the rate of oxygen consumption during respiration in organisms
- can be used to calculate RQ values
Draw the setup of respirometer
check google notes
How to calculate oxygen consumed (cm3/min)
- use equation: (pi)r2h
- r = radius
- h = distance moved by manometer fluid in a minute
How to determine RQ (respiratory quotient) experimentally
- 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
What does it mean when an RQ value is changing?
- 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
State ways to increase the reliability of the respirometer experiment
> 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
