A Level CIE Biology: 12 Energy and Respiration

what does work in a living organism require?

energy and usable carbon compounds

four types of work

• transporting substances across membranes

• anabolic reactions

• movement

• maintaining body temperature

two examples of transporting substances across membranes

• active transport using the sodium-potassium pump in cell membranes

• exocytosis of digested bacteria from wbcs

two examples of anabolic reactions

• synthesis of DNA from nucleotides

• synthesis of proteins from aas

two examples of movement

• cellular movement of chromosomes via the spindle

• mechanical contraction of muscles

example of maintaining body temperature

• occurs only in mammals and birds

description of energy in active transport diagram

as the metal ions are both moving against their concentration gradient, they cannot move by simple diffusion. require carrier protein and ATP

what is the primary source of energy for nearly all organisms

the sun

the reactions of photosynthesis store energy in ______ ________

organic molecules

light energy from the sun is transformed into…

chemical potential energy in the synthesis of carbohydrates

what happens to the carbs formed

used in synthesis of ATP from their breakdown or are combined and modified to form al the usable organic molecules that are essential for all metabolic processes within the plant

photosynthesis is carried out by…

the first organism in a food chain, such as plants and other small organisms such as blue-green algae

what is respiration in all living cells…

releases energy from the breakdown of organic molecules

respiration involves…

transfer of chemical potential energy from nutrient molecules e.g. carbs, fats and proteins into a usable energy form through the synthesis of ATP that can be used for work within an organism1

glucose + oxygen →

carbon dioxide + water [+ energy]

C₆H₁₂0₆ + 6 O₂ →

6 CO₂ + 6 H₂0 (+ 2870kJ)

autotrophs:

organisms that are able to synthesize their own usable carbon compounds from carbon dioxide in the atmosphere through photosynthesis

heterotrophs:

require supply of pre-made usable carbon compounds which they get from their food

description of reactions of photosynthesis and respiration

transfer of energy and materials between autotrophs and heterotrophs through the processes of photosynthesis and respiration

laws of thermodynamics:

energy cannot be created or destroyed, it is transformed

adenosine triphosphate [atp]

the molecule that energy released during respiration is transferred

atp:

small, soluble molecule that provides a short-term store of chemical energy that cells can use to do work

atp is vital in…

linking energy-required and energy-yielding reactions

why is atp described as a universal energy currency

• universal: used in all organisms

• currency: can be used for diff purposes and reused countless times

three reasons atp as an energy currency is beneficial:

• hydrolysis of atp can be carried out quickly and easily when energy is required within cell by action of just atpase

• useful qt. of energy released from hydrolysis of one atp mol so reduces waste and gives cell control over processes

• atp relatively stable at cellular pH levels

atp is a _____ nucleotide

phosphorylated

atp is made up of what three things

• ribose sugar

• adenine base

• three phosphate groups

what is produced when atp is hydrolysed

adp and phosphate

as adp is formed what is released and what is that used for

free energy, can be used for processes within cells e.g. dna synthesis

removal of ___ phosphate group releases ____ kJmol-1 of energy, forming ___

• one phosphate group from ATP releases approximately 30.5 kJ mol ^-1 of energy, forming ADP

• second phosphate group from ADP also releases approximately 30.5 kJ mol^-1 of energy, forming AMP

• third and final phosphate group from AMP releases 14.2 kJ mol^-1 of energy, forming adenosine

six features of atp

• releases a small but sufficient amount of energy (75.2 kJ mol^-1 from the complete hydrolysis of ATP)

• exists as stable mol

• can be recycled

• quick and easy hydrolysis

• soluble and moves easily in cell

• forms phosphorylated intermediates

benefit of releasing small but sufficient energy (75.2 kJ mol^-1 from the complete hydrolysis of ATP)

enough energy to drive important met. reactions while keeping energy wastage low

benefit of atp’s stability

doesn’t breakdown unless atpase/catalyst is present so no energy waste

benefit of atp being recyclable

breakdown of atp is reversible and can be reformed from adp and pi meaning same mol can be used elsewhere in cell for diff reactions

benefit of atps quick and easy hydrolysis

cells can respond to sudden increase in energy demand

benefit of atps solubility and easy movement

can transport energy to diff areas of cell

benefit of atp forming phosphorylated intermediates

can make metabolites more reactive and lower activation energy needed for reaction

energy:

capacity/power to do work

why must cells make atp as and when they need it

organisms cannot build up large stores of atp and it rarely passes thru the csm. humans use 50 kg of ATP in a day but only have a maximum of ~ 200g of ATP in their body at any given time

atp is formed when adp is combined w/ inorganic phosphate [pi] group. what two things happen during this reaction

• energy requiring

• water released as waste product [atp synthesis = condensation reaction]

when is atp made

during respiration or photosynthesis

two ways atp can be made

• substrate-linked phosphorylation

• chemiosmosis

how does SLP work

atp is formed by transferring phosphate directly from substrate mol to ADP

SLP equation

ADP + Pi → ATP

where is energy required in SLP from

provided directly by another chemical reaction

when and where does SLP occur

in glycolysis. cell cytoplasm and mitochondria matrix

what amt of atp synth does slp account for during aerobic resp

small amt ~ 4 / 6 ATP per glucose molecule

what does chemiosmosis involve

a proton/hydrogen ion gradient across a membrane

where does chemiosmosis take place

across inner memb of mitoch and thylakoid memb of chloroplasts

how is proton concentration gradient established in chemiosmosis

electron transport chain where high energy e- move from carrier to carrier releasing energy that is used to pump protons up a conc grad across the inner memb into the intermembrane space

chemiosmosis: protons are pumped from___ conc in __________ to ___ conc in _______

low, inner mitoch matrix, high, intermembrane space

chemiosmosis: when is energy released

when protons move down conc grad into matrix

chemiosmosis: how is atp phosphorylated

protons move through atp synthase complex with released energy driving phosphorylation

chemiosmosis: why is water formed

oxygen acts as final e- and proton acceptor to form water

how much atp is synthesised via chemiosmosis during resp

most : ~ 32 / 34 ATP per glucose molecule

SLP proces

phosphate of a substrate mol is transferred directly from adp to atp and uses energy provided directly by another chem reaction.

chemiosmosis process

energy release by movement of h ions down conc grad is used to synthesize atp via enzyme atp synthase. oxygen acts as final hydrogen/electron acceptor

______ is the principal respiratory substrate for aerobic resp in most cells

glucose

how does the cell continue respiration when glucose supply is used up

by using other substrates such as carbs, lipids, proteins

when are amino acids respired aerobically and why

only when all other substrates have been exhausted because they often have essential functions elsewhere in the cell and are required to make proteins with structural e.g. cytoskeleton and functional e.g. enzymatic roles.

respiratory substrate [carb, lipid, protein] and energy value/kJg-one

• carb - 15.8

• lipid - 39.4

• protein - 17.0

why are the energy value of substratees different

because they have different molecular compositions and number of hydrogen atoms that become available when substrate mols are broken down

what happens to hydrogen during respiration

• sub mols broken down and H atoms become available

• H carrier mols called NAD and FAD pick them up/become reduced and transfer them to inner mitoch membrane

• reduced NAD and FAD release H atoms which split into protons and electrons

• protons are pumped across inner mitoch memb into intermembrane space forming proton/chemiosmotic gradient

• proton grad in chemiosmosis used to make atp

• after protons have flowed back into matrix of mitoch via atp synthase they are oxidised to form water

mols w/ higher hydrogen content will result in…

greater p+ gradient across mitoch memb which allows for formation of more ATP via chemiosmosis e.g. fatty acids release H when lipid broken down

respiratory content [rq]:

ratio of carbon dioxide mols produced to oxygen mols taken in during resp

rq:

 co2/o2

why do carbs, lipids and proteins have diff rq values

because no. C-H bonds differs in each type of bio molecule

higher no. C-H bonds means that…

more H atoms used to create p+ gradient meaning that more ATP mols can be produced by chemiosmosis so more oxygen is required to break down the mol [in last step of oxidative phosphorylation to form water]

when glucose is respired aerobically…

equal volumes of carbon dioxide are produced and oxygen take in meaning it has rq value of one

carb, protein, lipid typical rq value

carb - 1.0

protein -0.8 - 0.9

lipid - 0.7

mammalian muscle cells and plant tissue cells use what anaerobic resp

lactate fermentation, ethanol fermentation

can the rq for anaerobic respiration in animals and yeast be calculated

cannot be calculate because no oxygen used and no carbon dioxide produced during lactate fermentation and for yeast, the rq tends towards infinity as no oxygen is used but carbon dioxide is produced

respirometers use

measure and investigate the rate of oxygen consumption during respiration in organisms and calculate rq.

what are respirometers usually involved with

experiments with germinating seeds or invertebrates

equation for calculating change in gas volume =

volume of oxygen [cm3 min-1] can be worked out using the diameter of the capillary tube r (cm) and the distance moved by the manometer fluid h (cm) in a minute using the formula: πr2h

what is the method of using a respirometer to determine the rq

• measure oxygen consumption, set up respirometer and run experiment w/ soda-lime present in both tubes

• use 1manometer to calc change in gas volume in given time x cm3 min-1

• always read from side of the u-tube manometer closest to respiring organism [left]

• reset apparatus by allowing air to re-enter tubes via screw cap and reset manometer fluid w/ syringe

• run experiment again and remove soda-lime from both tubes and use manometer reading to calc change in gas volume in given time y cm3 min-1

what do x and y give in respirometer experiment and how to use them to calculate

x : volume of oxygen consumed by respiration within given time

y: volume of oxygen consumed by respiration within a give time - volume of carbon dioxide produced within given time

[x-y] = volume of carbon dioxide given off by organisms. rq=x-y/x

what three things could it mean when the rq value changes

• substrate being respired has changed

• or that cells are using a mixture of substrates in respiration

• overfeeding [more than one = excessive carb/calorie intake, less than .seven = underfeeding]

under normal cellular conditions what is the order that substrates are used in respiration

carb → lipid → protein

what is mitochondria [shape, size, function]

• rod-shaped organelles 0.5 - 1.0 µm in diameter

• site of aerobic resp in euk cells

• synthesises atp during last stage of resp = oxidative phosphorylation

what does oxidative phosphorylation rely on

proteins that make up electron transport chain and atp synthase enzyme

mitochondria structure [four parts]

• two phospholipid membranes

• outer membrane

• inner membrane

• intermembrane space

outer membrane is: [two]

• smooth

• permeable to several small molecules

inner membrane is [four]: [pic of crristae]

• folded cristae

• less permeable

• site of e- transport transport chain used in oxidative phosphorylation

• location of atp synthase used in oxidative phosphorylation

intermembrane space two features

• low pH due to high conc. of protons

• conc grad across inner memb is formed during oxidative phosphorylation and is essential for atp synthesis

matrix two features: [pic of mitoch]

• aqueous solution within inner membranes of mitochondrion

• contains ribosomes, enzymes and circular mitoch dna necessary for mitoch to function

the structure of mitoch makes them…

well adapted to their function

mitoch large sa reason + benefit

bc presence of cristae [inner folds] which enables membrane to hold many e- transport chain proteins and atp synthase enz

why can more active cells have a larger mitoch w/ longer and more tightly packed cristae

to enable synthesis of more atp bc larger sa

no. mitoch in each cell varies depending on…

cell activity e.g. muscle cells more active have more mitoch per cell than fat cells due to diff levels of metab. activity in those cell types = diff levels of demand for atp

four stages of aerobic respiration

• glycolysis - takes place in cell cytoplasm

• link reaction - takes place in matrix of mitoch

• krebs cycle - takes place in matrix of mitoch

• oxidative phosphorylation - occurs in inner membrane of mitoch

stages of respiration description + location

• glycolysis : phosphorylation and splitting of glucose in cell cytoplasm

• link reaction : decarboxylation and dehydrogenation of pyruvate in mitoch matrix

• krebs cycle : cyclical pathway w/ enz-controlled reaction in mitoch matrix

• oxidative phosphorylation : production of atp through oxidation of H atoms in inner memb of mitoch

when does glycolysis take place and involve:

cytoplasm of cell

• trapping glucose in cell by phosphorylating molecule

• splitting glucose mol into two

what does glycolysis result in

production of:

• 2 pyruvate (3C) molecules

• Net gain 2 ATP

• 2 reduced NAD

phosphorylation:

glucose (6C) is phosphorylated by 2 ATP to form fructose bisphosphate (6C)

Glucose + 2ATP → Fructose bisphosphate

lysis:

fructose bisphosphate (6C) splits into two molecules of triose phosphate (3C)

Fructose bisphosphate → 2 Triose phosphate

oxidation:

hydrogen is removed from each molecule of triose phosphate and transferred to coenzyme NAD to form 2 reduced NAD (sometimes called NADH)

4H + 2NAD → 2NADH + 2H+

dephosphorylation:

phosphates are transferred from the intermediate substrate molecules to form 4 ATP through substrate-linked phosphorylation

4Pi + 4ADP → 4ATP

pyruvate produced:

the end product of glycolysis which can be used in the next stage of respiration

2 triose phosphate → 2 pyruvate

glycolysis pathway diagram

process of glycolysis