Cellular respiration Flashcards
what is glycolysis?
break down of glucose into 2 molecules of pyruvic acid
where does glycolysis take place?
cytoplasm
what does glycolysis require?
2 ATP
what is produced from glycolysis?
2 ATP (4 ATP minus 2 ATP) and 2 NADH
what are the two major phases of glycolysis?
Energy investment phase: 2 ATP is broken down into 2 ADP, energy is released, enabling 6 carbon molecule from glucose to be broken down into two 3 carbon molecule
Energy payoff phase: for each 3 carbon molecule, electrons are transferred to NAD+ to form NADH + H^+ and 2 ADP is converted to 2 ATP by forming bonds. ATP bond stores energy. in total, 2 NADH +2H^+ + 4ATP are formed
The NADH is transported to Electron Transport Chain
glycolysis: aerobic vs anaerobic
aerobic: pyruvate is further oxidised to form more ATP
anaerobic: pyruvate converted into lactic acid
Functions of NAD+
- carrier molecule
2. traps electrons (e-) and protons (H+) from pairs of hydrogen atoms (2H) and transfers them to where they are needed
When does link reaction occur?
After glycolysis, when oxygen is present
Purpose of link reaction
to prepare pyruvate molecules before Kreb’s Cycle
what happens during link reaction?
pyruvate enters the matrix of the mitochondria via active transport and is converted to acetyl coA
1. decarboxyation: each pyruvate molecule has co2 removed
2.Hydrogen(2H) is then removed and the 2e- and 2H+ are trapped by NAD+ to form NADH + H+
3. Coenzyme A (CoA) added, to form the final product of Acetyl-CoA.
one pyruvate –> co2, NADH + H+, acetyl coA (x2 for 2 pyruvates) since there are two pyruvate molecules, link reaction takes place twice
where does the Kreb’s Cycle take place?
matrix of mitochondria
when does the Kreb’s cycle take place?
When oxygen is present
what are the products of Kreb’s cycle?
one pyruvic acid undergoes Kreb’s cycle to release 2 co2, 3 NADH and 1FADH2 and 1ATP
since one glucose molecule produces 2 pyruvic acid, Kreb’s cycle occurs twice and 2 ATP is formed for one glucose molecule
Electron carriers in Kreb’s Cycle
NAD+ and FAD both accept electrons which is energy to form NADH and FADH2. energy is trapped in the form of electrons within them to be used later on
What is the electron transport chain?
a series of protein complexes embedded in the mitochondrial membrane
Where does ETC occur?
in the folds of the inner membrane of the mitochondria (cristae)
what happens during ETC/oxidative phosphorylation?
- electon carrier NADH and FADH2 harvested from glycolysis and Kreb’s cycle are carried to the electron transport chain
- electrons are passed down a chain of protein complexes until they reach the final electron acceptor which is oxygen
- the electrons provide energy to pump protons from the mitochondria matrix to the intermembrane space, creating a steep proton gradient across the inner mitochondrial membrane
- the potential energy of this proton gradient across the inner mitochondrial membrane is used to synthesise ATP when the protons diffuse back down their concentration gradient through the ATP synthase, driving the synthesis of ATP.
- oxygen joins with protons H+ and electrons and is reduced to form water
What is aerobic respiration?
energy in biological molecules is released and then trapped as energy in the form of ATP in the presence of oxygen
Can glycolysis still take place in absence of oxygen?
Glycolysis can still occur in the absence of oxygen. However, cells will run of NAD if it is not regenerated. in aerobic respiration, ETC turns NADH to NAD+ with the aid of oxygen, allowing glycolysis to continue to take place. For anaerobic respiration, NAD is regenerated through fermentation
Types of fermentation
Lactate fermentation in animals’ muscles and alcoholic fermentation in plants and yeasts
Purpose of fermentation
to regenerate NAD by oxidising reduced NAD (NADH) so that glycolysis can continue to produce 2 ATP to sustain muscular activity (low yield) it produces 2 lactate as well
how is lactic acid removed?
lactic is carried from muscle cells to liver through blood where it is oxidised and converted back to pyruvate to enter the Link reaction and Kreb’s cycle to release energy which converts the rest of lactic acid into glucose
what happens during exercise?
muscles contract vigorously to enable movement, increasing respiratory rate and heart rate so as to enable oxygen to reach the muscles. increased oxygen intake does not meet oxygen demand, resulting in oxygen debt and anaerobic respiration occurs to provide energy. This results in the accumulation of lactic acid in muscles cells causing fatigue, pains and cramps
what are in the inner walls of the trachea and bronchi and what are their functions?
Gland cells: secrete mucus to trap dust and bacteria from the air channelled into the lungs
Ciliated cells: sweeps the trapped particles up the bronchi and trachea, and into the pharynx
what is the purpose of the nasal passage?
there is a fringe of hair and layer of mucus lining the nasal passage which traps dust and foreign particles. The air that passes through the nasal passage becomes warmed and moistened
what are bronchioles?
bronchial tubes divide repeatedly to form bronchioles
what are alveoli?
bronchioles end in a cluster of air sacs called alveoli, it is the site of gaseous exchange. numerous alveoli increases surface area for gaseous exchange
where do the lungs lie in?
In the pleural cavity, within the pleural membrane which is the fluid that occupies the open space
what is the purpose of the c-shaped cartilage?
it supports the trachea by ensuring that it is always open
where does gaseous exchange take place?
between alveoli in the lungs and surrounding blood capillaries
what is gaseous exchange facilitated by?
- film of water on the inner walls of the alveoli, this allows for the oxygen to dissolve in the water before diffusing through the alveolar wall
- one cell thick walls of the alveolar and blood capillaries, this decreases the distance for diffusion and increases the rate of gaseous exchange across the alveolar wall
- alveoli is surrounded with a dense network of blood capillaries, the constant blood flow within these capillaries maintains a steep concentration gradient for diffusion, thereby allowing for constant gaseous exchange
what happens during gaseous exchange?
- oxygen molecules diffuse from the alveolar air across the alveolar wall into red blood cells where they combine reversibly with haemoglobin to form oxyhaemoglobin
- carbon dioxide produced by respiring cells enters the blood plasma and into the rbcs, where it combines with water to form carbonic acid. the reversible reaction is catalysed by carbonic anhydrase.
- the carbonic acid dissociates into hydrogen ions and hydrogen carbonate ions. the hydrogen carbonate ions are mainly carried in the blood plasma and into the alveolar capillaries in the lungs.
- the reverse reaction occurs for the conversion of hydrogen carbonate ions into carbon dioxide in the lungs. the carbon dioxide is removed via exhalation
what happens to the structures in the respiratory system during inspiration(breathing in)?
external intercostal muscles: contract
internal intercostal muscles: relax
ribcage and sternum: ribcage swings outwards and upwards, sternum is raised
diaphragm muscles: contracts, diaphragm flattens
thorax (chest cavity): volume increases, pressure decreases
lungs: expands, pressure in lungs decrease to lower than atmospheric pressure
so air rushes into the lungs
what is main chemical stimulus for breathing?
it is the increase in carbon dioxide concentration in the blood. when blood carbon dioxide levels increased, chemoreceptors in the blood system send nerve impulses to the breathing centre in the brain which would stimulate the contraction of the diaphragm muscles and external intercoastal muscles
what are main components of tobacco smoke?
nicotine, carbon monoxide and tar (irritant)
what is nicotine and what does it do?
it is highly addictive, stimulates secretion of adrenaline, suppresses insulin secretion and promotes blood clotting
it results in increase in heart rate, blood glucose levels and blood pressure. higher risk of thrombosis
what is carbon monoxide and what does it do?
it combines readily and irreversibly with haemoglobin to form carboxyhaemoglobin. it also increases the build up of fatty deposits along the inner arterial wall.
results in reduce oxygen-carrying capacity of rbcs, and increases risk of atherosclerosis
what is tar and what does it do?
it contains carinogenic chemicals, paralyses the cilia lining the air passage and reduces efficiency of gaseous exchange.
results in higher risk of lung cancer, dust or foreign particles are trapped in the mucus and are not expelled effectively. increases risk of chronic bronchitis and emphysema
what is lung cancer?
it is the uncontrolled abnormal division of cells in the lungs due to tar
what is chronic bronchitis?
it is the inflammation of cells lining the air passage, excessive mucus is secreted, cilia gets paralysed and narrowing of air passages –> bretahing difficulties
what is emphysema?
it is the break down of alveolar walls due to intense coughing which decreases rate of gaseous exchange. persistant inflammation cause lung tissues to lose elasticity. breathing difficulties
what are the traits of ATP
it is small and soluble and can be transported easily to where it is needed, it is an univeral energy carrier and can be recycled/rephosphorylated
inner membrane of mitochondria
cristae consists of infoldings, effectively increasing the surface area to volume ratio to provide more space for electron carrier complexes in the ETC. it is also impermeable to hydrogen ions, thus allowing hydrogen ions to accumulate in the intermemberane space.
