topic 5 energy for biological processes Flashcards
what do organisms need energy for?
Metabolism – many chemical reactions require energy Movement – from a cellular to whole organism level Maintenance, Repair and Division – of cells and organelles Production of Substances – such as hormones, enzymes etc. Thermoregulation – endotherms (birds and mammals) require energy to maintain their body temperature
what is ATP
Adenosine triphosphate, or ATP, is the molecule used by cells to ‘power’ individual processes. The bonds between the inorganic phosphates are unstable and release an amount of energy when broken. Usually, only the terminal phosphate is removed to produce ADP (adenosine diphosphate)
how is ATP linked to ADP
•ATP is reformed from ADP by the addition of another inorganic phosphate and energy.
what are the three ways ADP forms ATP
- Photophosphorylation – this is where energy from sunlight is captured by chlorophyll molecules during photosynthesis and used to form ATP.
- Oxidative Phosphorylation – this is where energy from the breakdown of larger organic molecules is harnessed to produce ATP
Substrate-level Phosphorylation – where inorganic phosphates are directly transferred from donor molecules to ADP
what is the role of ATP
- ATP is not an effective long-term energy store as it is relatively unstable.
- Cells will therefore only maintain a few seconds supply of ATP which is constantly replenished by respiration/photosynthesis.
- At any one time there will be in the region of 0.2 moles of ATP in the body but over the course of a day the body will use approximately its own body weight in ATP.
why is ATP better than glucose
•ATP is able to be quickly hydrolysed in a single step releasing a ‘small’ amount of energy. This is better than using glucose directly which releases a much larger amount of energy (38 ATP) over a longer series of reactions.
explain what are and the difference of autotrophs and heterotrophs
Organisms such as mammals (including Man) needing need a ready made organic supply. These are heterotrophs
Autotrophs use an inorganic carbon source (CO2) to produce organic molecules
explain the oxidation of glucose
The oxidation of glucose takes place in small stages, allowing precise control and improving energy harnessing
Glucose is a stable compound and its oxidation does not happen spontaneously. Activation energy has to be overcome.
Activation energy is lowered by the use of enzymes and by phosphorylating the glucose to start with, to raise its energy levels
what is the formula for respiration
explain activation energy with respiration
explain ATP as an energy currency
- consists of adenine (organic base) and ribose (pentose sugar), together these form adenosine
- the addition of 3 phosphate groups makes ATP
- ATP is a small, water soluble molecule which makes it easily transported around the cell
- used by cells in all forms of work, universal intermediary between energy-yielding and energy-requiring molecule.
how is energy released by ATP
energy is released by the hydrolysis of ATP (add water)
- when a phosphate 1 is removed to make ADP and phosphate 2 to form AMP 30.5 Kj mol -1 is released
- however when the final phosphate is removed leaving adenosine only 14.2 kj mol -1 is released
explain how ATP is generated by using electrical potential energy
energy from transfer of electrons by electron carriers in mitrochondria and chloroplasts
stored as a difference in hydrogen ion concentration across some phosphilipid membranes in chloroplasts and mitrochondria which are impermeable to hydrogen ions
they then flow down their concentration gradient through a protein which spans the phospholipid bilayer
part of this protein is an enzyme which synthesises ATP called ATP synthase
The transfer of three hydrogen ions allows the production of 1 ATP molecule from the ADP and P
explain how atp is formed in chloroplasts
ATP synthase has 3 binding sites and a part that rotates as H+ ions pass through it
1) binding ADP and P
2) forming tightly bound ATP
3) releasing ATP
how is ATP synthesised in mitrochondria
ATP synthase has 3 binding sites and a part that rotates as H+ ions pass through it
1) binding ADP and P
2) forming tightly bound ATP
3) releasing ATP
explain the role of ATP in active transport
the energy can be used to move molecules/ions up a concentration gradient
most cell membranes contain sodium ion active transport pumps, usually associated with the ability to pump potassium in the opposite direction
about 50% of ATP in resting mammals is used for such pumps
explain the first stage in respiration
glycolysis
- multistage reaction that breaks down 6 carbon glucose into 2 molecules of 3C pyruvate
‘splitting or lysis of glucose’
2 ATP needed to start the reaction, however net gain of 2 ATP molecules for each glucose
- 2 NADH (6 ATP) also formed per glucose molecule
happens in the cytoplasm
explain the link reaction within respiration
pyruvate passes by active transport from the cytoplasm, through the double mitochondrial membrane, into the stroma of the mitochondrion
once in the stroma, pyruvate is decarboxylated (CO2 diffuse out) and dehydrogenated (hydrogen removed aka oxidised) and combines with coenzyme A (CoA) to form acetyl coenzyme A
The hydrogen removed from pyruvate is combined with NAD to form NADH
Acetyl CoA now enters krebs cycle (fatty acids, fat breakdown products can also enter via acetyl CoA for respiration)
remember this happens 2x as we get 2 molecules of pyruvate from glucose!
explain the krebs cycle
to start acetyle CoA (2c) combines with oxaloaceticacid (OAA, 4c) to form citric acid (6c)
citric acid is oxidised in a series of reactions which end with OAA again
OAA combines with new acetyle coA and cycle repeats
during each turn of the cycle 2 co2 molecules, 1 atp, 1 FADH and 3 NADH molecules are formed
overview of respiration cycle
yah
explain the electron transfer chain and oxidative phophorylation
most the energy for ATP production comes from the elecyron transport chain which also takes place in the mitochondrial membranes
reduced NAD and FAD diffuse into the electron transport chain where the H atoms they were carrying are split into H+ and an electron
The electron passes through a series of carriers releasing energy for ATP production
the electrons are finally transferred to oxygen and recombined with H+ ions to form water
3 ATP per NAD and 2 ATP per FAD
explain mitochondrial structure regarding the krebs cycle
the site of the krebs cuycle and electron transfer chain
Liver cell which have a high metabolic rate have up to 2000 mitochondria (20% of cell volume)
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