5.7 respiration Flashcards
what is respiration
a process that occurs in living cells and releases the energy stored in organic molecules such as glucose
what examples of biological processes does ATP drive
- Active transport
- Movement
- Endocytosis/ Exocytosis
- Synthesis of large molecules (e.g. proteins)
- DNA replication
- Cell division
- Activation of chemicals
what is metabolism
all the chemical reaction which take place in a living cell
what are anabolic reactions
metabolic reactions where large molecules are synthesised from smaller molecules
what are catabolic reactions
metabolic reactions involving the hydrolysis of large molecules to smaller ones
what type of energy is in ATP
chemical potential energy
what does a molecule of ATP consist of
- Adenine
- Ribose
- Three phosphate groups
What causes the hydrolysis of ATP?
readily hydrolysed by enzyme catalysis even though it is relatively stable
What is produced when ATP is hydrolysed?
ATP is hydrolysed into ADP and Pi.
- a small quantity of energy is released for use in cells.
-some energy is released as heat
what is ATP commonly referred to as
-referred to as the universal energy currency, as it occurs in all living cells and is a source of energy which can be used by cells in
Why is ATP called the Universal energy currency?
It is found in all living organisms/all types of cells.
It is concerned with transmitting energy and is readily available for hydrolysis, releasing small manageable amounts of energy to meet the cell’s needs, but not in quantities that could damage the cell.
why is releasing heat when ATP is hydrolysed not considered wasteful
heat can keep organisms warm
what is the numerical amount of energy that is released when a phosphate group is hydrolysed from ATP
30.5kJ
describe and explain the role of ATP in the cell (3)
-energy ‘currency’
-energy released in small packets
-it releases 30.5kJ of energy when a phosphate is removed by hydrolysis (3)
What is Glycolysis?
Glycolysis is the first stage of respiration. It is a 10-stage metabolic pathway that converts glucose to Pyvurate.
Where does Glycolysis occur?
Glycolysis occurs in the cytoplasm of all living organisms that respire
what enzyme can be seen to be helping glycolysis
the coenzyme, NAD
whats a coenzyme
-organic molecule
-can change shape
whats a cofactor
-inorganic molecule
-cant change shape
wha are the 3 main stages of glycolysis
- Phosphorylation of glucose to hexose bisphosphate
- Splitting each hexose bisphosphate molecule into two triose phosphate molecules
- Oxidation of triose phosphate to pyruvate
what do enzymes that catalyse oxidation and reduction reactions need help of
need help of coenzymes that accept hydrogen atoms during oxidation
What is NAD?
***NAD is a non-protein enzyme coenzyme that helps dehydrogenase enzymes catalyse oxidation and reduction reactions.
What is the structure of NAD?
NAD is synthesised in living cells from Nicotinamide, Ribose, Adenine, and phosphate groups.
The Nicotinamide group can accept two protons to become reduced.
How does NAD work?
NAD accepts the hydrogen atoms removed during oxidation.
Why do living organisms have low levels of NAD in their cells, despite using many molecules of NAD throughout the day?
It is continually being recycled - reduced and then reoxidised
whats the first step in glycolysis?
- glucose is phosphorylated to become hexose monophosphate and then phosphorylated again to hexose biphosphate (2 inorganic phosphate groups added)
-the energy produced prevents it from being transported out of the cell
-one ATP is hydrolysed to ADP and Pi for each time glucose is phosphorylated so 2 ATP is used in total
whats the second step in glycolysis?
- the 6 carbon hexose biphosphate is unstable and breaks into two 3 carbon molecules called TP (each with a phosphate group attached)
whats the third step in glycolysis (after TP is formed)?
process is anaerobic but oxidation is involved (cus it involves the removal of H atoms from substrate molecules)
-dehydrogenase enzymes, aided by the coenzyme NAD, remove hydrogens from triose phosphate
-the two molecules of NAD accept the hydrogen atoms (protons and electrons) and become reduced (2 molecules of reduced NAD formed, 1 H atom for each)
-two molecules of NAD are reduced for every molecule of glucose undergoing this process. Also, at this stage, four molecules of ATP are made for every two triose phosphate molecules undergoing oxidation.
whats the products of glycolysis
for each molecule of glucose:
-two molecules of (3C) Pyruvate
-two molecules of reduced NAD
-a net gain of two molecules of ATP
why is there only a net gain of 2 molecules of ATP for glycolysis
2 molecules of ATP are used in the Phosphorylation of Glucose to Hexose Biphosphate.
Then 4 molecules of ATP are regenerated in the Oxidisation of Triose phosphate
state two roles of reduced NAD
-carries protons and electrons to the cristae of mitochondria and delivers them to be used in oxidative phosphorylation for the generation of ATP from ADP and Pi
-can give up protons and electrons that is accepted during on of the first three stages of respiration, it becomes oxidised and can be re-used to oxidise more substrate in the process of becoming reduced again
what are the 4 stages of respiration of glucose
-glycolysis (anaerobic- cytoplasm)
-the link reaction (aerobic- mitochondria)
-the krebs cycle (aerobic- mitochondria)
-oxidative phosphorylation (aerobic- mitochondria)
(pyruvate molecules from glycolysis are actively transported to the mitochondria for the link recation)
what occurs to pyruvate in anaerobic conditions
its converted in the cytoplasm to lactate or ethanol. in the process reduced NAD molecules are re-oxidised so that glycolysis can continue to run producing 2 molecules of ATP for every glucose molecule metabolised
whats the envelope of the mitochondria
the envelope consists of the inner and outer phospholipid bilayer
What is the role of the outer membrane?
The outer phospholipid bilayer membrane contains some proteins which form channels or carriers that allow the passage of molecules, such as pyruvate, into the mitochondria.
what is the role of the intermembrane space (its between the inner and outer membranes)
The intermembrane space is involved in oxidative phosphorylation.
-the inner membrane is in close contact with the mitochondrial matric, so the molecules of reduced NAD and FAD can easily deliver hydrogens to the electron transport chain
what is the role of the inner membrane
The inner phospholipid bilayer membrane is less permeable to small ions such as hydrogen ions.
It folds into the cristae giving a large surface area for the electron carriers and ATP synthase enzymes embedded in them.
The inner membrane is in close contact with the mitochondrial matrix, so the molecules of reduced NAD and FAD can easily deliver protons to the electron transport chain.
there are proteins that transport electrons, protons and protein channels associated with ATP synthase enzymes that allow protons to diffuse through them.
what is the role of the mitochondrial matrix
the matrix is where the link reaction and Krebs cycle takes place
it contains:
-enzymes that catalyse the stages of these reactions
-molecules of the coenzymes NAD and FAD
-oxaloacetate- the four-carbon compound that accepts the acetyl group from the link reaction
-mitochondrial DNA- looped, some of which codes for mitochondrial enzymes and other proteins
-mitochondrial ribosomes- structurally simmilar to prokaryotic ribosomes, where these proteins are assembled
whats the function of cristae
highly folded to increase surface area
What is the role of ATP Synthase?
ATP synthase enzymes are large and protrude from the inner membrane into the matrix.
Protons can pass through them.
What is the structure of Electron carrier protein?
Each electron carrier protein contains a cofactor - a non-protein haem group that contains an Iron ion.
Each electron carrier also have a coenzyme.
How do Electron carriers work?
The Iron ion can accept and donate electrons because it can become reduced (Fe2+) by gaining an electron and then become oxidised when donating an electron (Fe3+) to the next electron carrier. Electron carrier proteins are oxido-reductase enzymes.
why is it important that electron carriers also have a coenzyme
the coenzyme uses energy released from the electrons to pump protons from the matrix to the intermembrane space
what occurs when the coenzyme in an electron transport chain pumps protons into the inter membrane space
protons accumulate in the intermembrane space and a proton gradient forms across the membrane. this gradient can produce a flow of protons through the channels associated with ATP synthase to make ATP
Where does the Link Reaction take place?
The Link Reaction takes place in the Mitochondria Matrix.
How is Pyvurate brought into the Mitochondrial Matrix?
Pyruvate produced during glycolysis is transported across the outer and inner membrane via specific Pyruvate-H+ symport.
Pyrvuate-H+ symport is a transport protein that transports two molecules into the matrix.
