OCR F214 Respiration

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F214 Module 4: Respiration
4.4.1 Respiration
(a) outline why plants, animals and microorganisms need to respire, with reference to active transport and
metabolic reactions
Respiration ­ the process whereby energy stored in complex organic molecules (carbohydrates, fats and proteins)
is used to make ATP, occurring in living cells.
All living organisms need energy to drive their biological processes in order to survive. Metabolic reactions that
need energy include:
Active Transport moving ions and molecules across a membrane against a concentration gradient.
Secretion large molecules made in some cells are exported by exocytosis.
Anabolism synthesis of large molecules from smaller ones, e.g. proteins from amino acids, steroids into
cholesterol and cellulose from glucose.
Replication of DNA and s ynthesis of organelles before a cell divides.
Endocytosis bulk movement of large molecules into cells.
Movement movement of bacterial flagella, eukaryotic cilia and undulipodia, muscle contraction and
microtubule motors that move organelles around inside cells.
Activation of chemicals glucose is phosphorylated at the beginning of respiration so that it is more
unstable and can be broken down to release energy.
(b) describe, with the aid of diagrams, the structure of ATP
ATP stands for adenosine triphosphate and is a phosphorylated nucleotide .
Each molecule consists of adenine , ribose and three phosphates .
(c) state that ATP provides the immediate source of energy for biological
ATP can be hydrolysed to ADP and Pi (inorganic phosphate), releasing
30.6 kJ
energy per mol . So, energy is immediately available to cells in small, manageable amounts that will not damage
the cell (enzymes and proteins can denature or membranes could become too fluid if too much energy is
released), so it's easier to harness the energy and it will not be wasted . The energy released from ATP hydrolysis
is an immediate source of energy for biological processes, such as DNA replication and protein synthesis.

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F214 Module 4: Respiration
the next electron carrier. They are oxidoreductase enzymes as they are involved in oxidation
and reduction reactions.
3. Some of the electron carriers also have a coenzyme that pumps (using the energy released
from the passage of electrons) protons from the matrix to the intermembrane space .
4. Protons flow down a proton gradient, through the ATP synthase enzymes , from the
intermembrane space into the matrix this is called chemiosmosis .…read more

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F214 Module 4: Respiration
1. The acetate is offloaded from coenzyme A and joins with oxaloacetate (4C), to form citrate (6C).
2. Citrate is decarboxylated and dehydrogenated forming a 5carbon compound . The pair of hydrogen atoms is
accepted by the coenzyme NAD (hydrogen acceptor), which becomes reduced NAD .
3. The 4carbon compound is decarboxylated and dehydrogenated forming a 4carbon compound and another
molecule of reduced NAD .
4. The 4carbon compound is changed into another 4carbon compound .…read more

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F214 Module 4: Respiration
1. NADH is reoxidised to form NAD+ and 2 hydrogen atoms, aided by the enzyme NADH dehydrogenase
which is attached to the first electron carrier. The hydrogen atoms split into protons and electrons.
2H 2H + 2e
2. The electrons are passed along electron carriers in the electron transport chain and lose energy by doing
3.…read more

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F214 Module 4: Respiration
The electron transfer enzymes are embedded in
the inner membrane.
The pH of the intermembrane space was lower than There's a higher concentration of H+ ions in the
that of the matrix . intermembrane space meaning the H ions move
from the matrix, across the membrane , to the
intermembrane space.
Electron transfer in mitoblasts (mitochondria The intermembrane space is involved in
stripped of their outer membrane) did not produce chemiosmosis .
any ATP .…read more

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F214 Module 4: Respiration
(v) define the term respiratory substrate
Respiratory Substrate ­ an organic substance that can be used for respiration.
The more protons , the more ATP produced as most ATP is formed from the flow of protons through channel
proteins during chemiosmosis . Therefore the more hydrogen atoms there are in a molecule of respiratory
substrate, the more ATP can be generated when that substrate is respired.…read more

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F214 Module 4: Respiration
How does a respirometer work?
1. In the boiling tube the volume of oxygen decreases due to respiration . The volume of carbon dioxide also
decreases as the soda lime absorbs it.
2. Overall, the volume of the boiling tube decrease , causing an air pressure decrease .…read more


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