C1.2 Cell respiration Flashcards
How is energy transferred in cells
by the breakdown of nutrients like carbohydrates
what is cell respiration
the process by which energy is made available (controlled release of energy from organic compounds)
why is ATP used as energy store
because glucose is relatively stable whereas ATP breaks down, releasing energy in reactions
structure of ATP
a nucleotide with three outer phosphate in a linear sequence
they can lose both outer phosphates
what does ATP act as a common intermediate between
energy yielding and energy requiring actions
features of ATP
a substance that moves easily within cells
a reactive molecule
an immediate source of energy, delivering it in small amoutns
what does ATP provide energy for
active transport
synthesis of macromolecules
movement of the whole cell
movement of cell components
examples of short term energy stores
glucose and fatty acids
examples of long term energy stores
glycogen, starch and triglycerides
how is ATP formed
from ADP and P using energy from respiration
how is energy released from ATp
hydrolysis of ATP to become ADP and phosphate
why is glucose the preferred respiratory substrate
even though energy yield is lower than lipids, oxidation is easier in glucose and molecules can directly enter glycolysis
why arent fats the preferred respiratory substrate
they would need to be converted to carbs first through gluconeogenesis
why arent proteins the preferred respiratory substrate
they would have to be hydrolysed and then deaminated which would require ATP
what respiration happens in the absence of oxygen
glucose is respired through anaerobic respiration which occurs in cytoplasm of cells
what happens as a result of anaerobic respiration
lactic acid fermentation occurs in muscle fibres when the demand for energy is very great and cant be met by aerobic respiration
waste produt of anaerobic respiration
lactate
metabolic rate affecting rate of cell respiration
some cells require more energy and have higher rates of respiration
size of organism affecting rate of cell respiration
smaller organisms have a large SA compared to size and thus have higher respiratory rates to allow for heat loss
supply of oxygen affecting rate of cell respiration
cells that arent supplied enough oxygen will start to respire anaerobically
supply of substrates for respiration affecting rate of cell respiration
rate of respiration and quantity of products produced will depend on the respiratory substrate being used
temperature affecting rate of cell respiration
respiration is controlled by enzyme and temperature affects enzymes
pH affecting rate of cell respiration
release of carbon dioxide during respiration decreases the pH of cell content and body tissues, which affects the function of enzymes
how can rate of cell respiration be determined
through a respirometer
uses U tubes and soda lime to remove carbon dioxide, allowing only absorption of oxygen from germinating seeds to be measured through the movement of a fluid
What are the 4 reactions that glucose undergoes in aerobic respiration
glycolysis
link reaction
krebs cycle
Electron transport chain
oxidation
the loss of electrons in a chemical reaction
done by adding oxygen or removing hydrogen atoms
OIL - Oxidation is loss of electrons
reduction
the gain of electrons in a reaction
done by removing oxygen atoms or by adding hydrogen atoms
RIG - Reduction is gain of electrons
In respiration what happens to the hydrogen atoms
they are gradually removed from glucose, causing the substrate to become oxidized
the hydrogen is added to hydrogen acceptors which are thus reduced
oxidizing agents
compounds with a strong tendency to take electrons
reducing agents
strong tendency to donate electrons to
endergonic reaction
when reduction occurs, energy is absorbed
exergonic reaction
when oxidation occurs, energy is released
coenzymes
they link oxidation and reduction
hydrogen acceptors are all coenzymes
electron carriers
NAD- main electron carrier
FAD- second electron carrier
What is NAD reduced to
NADH and H
reduced NAD can pass hydrogen ions and electrons on to other acceptor molecules and when it does so becomes oxidized back to NAD
glycolysis steps
glucose molecule is split into two 3-carbon molecules
products converted to pyruvic acid, exists as the pyruvate ion
a small amount of ATP is also formed, using energy from the glucose molecule
first stage of glycolysis is
phosphorylation by reaction with ATP activates glucose, forming glucose phosphate. makes it more unstable nad higher in energy, reactive
then converted to fructose 6-phosphate and further phosphate group is added through another ATP.
forms fructose biphosphate
means two molecules of ATP are consumered per molecule of glucose respired
second stage of glycolysis
lysis of the fructose forms two molecules of triose phosphate
third stage of glycolysis
oxidation of the triose phoshpate molecule done through removal of hydrogen. Enzyme for this reaction works with NAD
fourth stage of glycolysis
ATP formation occurs twice in the reaction by which each triose phoshpate molecule is converted to pyruvate
2 molecules of triose phosphate mean 4 molecuels of ATP synthesised
Thus in total there is a net gain of two ATP in glycolysis
what happens after pyruvate is formed in the cytoplasm
passes into mitochondria through facilitated diffusion where its completely oxidized to carbon dioxide, water and ATP
how is pyruvate oxidized
removal of hydrogen atoms by hydrogen acceptors and the addition of oxygen to carbon to form carbon dioxide
what happens to the hydrogen that is taken from the pyruvates in the mitochondria
hydrogen carried by the reduced acceptor molecule reacts with oxygen to form water
reduced hydrogen acceptor then reoxidized and is available for reuse in pyruvate production
majority of ATP is produced during these steps
what causes pyruvate to remain in the cytoplasm
lack of oxygen causes it to convert to lactate
what happens to pyruvate in yeast
even in the rpesence of oxygen, pyruvate is converted to ethanol
hydrogen acceptors in anaerobic cellular respiration
the reduced hydrogen acceptor molecules donate their hydrogen to form lactate or ethanol from pyruvate. This causes it to be reoxidised in the absence of oxygen and become available for further pyruvate synthesis
how much ATP does anaerobic respiration yield
two molecules of ATP per glucose respired
steps of the link reaction
pyruvate diffuses into the matrix of the mitochondria as if forms and is metabolized there
3 carbon pyruvate is decarboxylated by removal of carbon dioxide and also oxidised by removal of hydrogen
forms reduced NAD and the produces acetyl group which then combines with coenzyme A to form acetyl CoA
The krebs cycle steps
acetyl CoA reacts with a 4 carbon organic acid. product is 6 carbon and coenzyme A which is released and reused in link reaction.
citrated then converted back to the 4 carbon acid by the reaction of the krebs cycle
2 molecules of carbon dioxide released in separate reactions
molecule of ATP is formed
3 molecules of reduced NAD
one molecule of FAD
why does the krebs cycle “take place” twice
because glucose is converted into two molecules of pyruvate so it repeats
After the Krebs cycle what are the total products formed
6 carbon dioxide
4 ATP
10 reduced NAD
2 reduced FAD
what is the electron transport chain
series of protein in inner mitochondrial membrane
reduced coenzymes pass to it
how is energy transferred in electron carries and electron transport chain
pair of electron pass to the first carrier in the chain, turning reduced NAD back to NAD. removal of electrons from hydrogen creates proteins which play a role in the generation of ATP
where do the electrons go in the electron transport chain
the electrons recieved from the reduce coenzymes are transported along a series of carriers to be combined with oxygen to form water
what happens when electrons are passed between the carriers in the series
energy is released. energy is transferred to ADP and P to form ATP
what is the total yield of ATP from aerobic respiration
32 ATP molecules per molecule of glucose respired
generation of a proton gradient by flow of electrons along the electron transport chain
carrier proteins oxidize the reduced coenzymes. energy from the oxidation is used to pump protons from the matrix of the mitochondria to the space between the membranes.
hydrogen ions/protons accumulate here which builds up a gradient across the inner membrane
generates a potential difference across the membrane which represents a store of potential energy
The synthesis of ATP in the mitochondrion through protons
protons concentrated in the space between the inner and outer mitochondria membranes flow back into the matrix via ATP synthase, located on the inner membrane
as protons flow down their concentration gradient, through ATP synthase, energy is transferred as ATP synthesis occurs. ATP synthase therefore couples release of energy from proton with phosphorylation of ADP
how is energy generated by ATP synthase
has a rotational mechanism, generating energy through the rotation leading to production of ATP
oxygen as a terminal acceptor
electrons and protons need to be removed to create the proper gradients and low. this is done through oxygen which when combined, forms water
why are fats good for storing energy
transfer much more energy because they are more concentrated
also insoluble, do not cause water uptake
complete oxidation of fats and oils produces a large amount of water
