Cellular respiration

Question 1

what is glycolysis?

Answer 1

break down of glucose into 2 molecules of pyruvic acid

Question 2

where does glycolysis take place?

Answer 2

cytoplasm

Question 3

what does glycolysis require?

Answer 3

2 ATP

Question 4

what is produced from glycolysis?

Answer 4

2 ATP (4 ATP minus 2 ATP) and 2 NADH

Question 5

what are the two major phases of glycolysis?

Answer 5

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

Question 6

glycolysis: aerobic vs anaerobic

Answer 6

aerobic: pyruvate is further oxidised to form more ATP
anaerobic: pyruvate converted into lactic acid

Question 7

Functions of NAD+

Answer 7

1. carrier molecule

2. traps electrons (e-) and protons (H+) from pairs of hydrogen atoms (2H) and transfers them to where they are needed

Question 8

When does link reaction occur?

Answer 8

After glycolysis, when oxygen is present

Question 9

Purpose of link reaction

Answer 9

to prepare pyruvate molecules before Kreb’s Cycle

Question 10

what happens during link reaction?

Answer 10

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

Question 11

where does the Kreb’s Cycle take place?

Answer 11

matrix of mitochondria

Question 12

when does the Kreb’s cycle take place?

Answer 12

When oxygen is present

Question 13

what are the products of Kreb’s cycle?

Answer 13

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

Question 14

Electron carriers in Kreb’s Cycle

Answer 14

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

Question 15

What is the electron transport chain?

Answer 15

a series of protein complexes embedded in the mitochondrial membrane

Question 16

Where does ETC occur?

Answer 16

in the folds of the inner membrane of the mitochondria (cristae)

Question 17

what happens during ETC/oxidative phosphorylation?

Answer 17

1. electon carrier NADH and FADH2 harvested from glycolysis and Kreb’s cycle are carried to the electron transport chain
2. electrons are passed down a chain of protein complexes until they reach the final electron acceptor which is oxygen
3. 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
4. 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.
5. oxygen joins with protons H+ and electrons and is reduced to form water

Question 18

What is aerobic respiration?

Answer 18

energy in biological molecules is released and then trapped as energy in the form of ATP in the presence of oxygen

Question 19

Can glycolysis still take place in absence of oxygen?

Answer 19

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

Question 20

Types of fermentation

Answer 20

Lactate fermentation in animals’ muscles and alcoholic fermentation in plants and yeasts

Question 21

Purpose of fermentation

Answer 21

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

Question 22

how is lactic acid removed?

Answer 22

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

Question 23

what happens during exercise?

Answer 23

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

Question 24

what are in the inner walls of the trachea and bronchi and what are their functions?

Answer 24

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

Question 25

what is the purpose of the nasal passage?

Answer 25

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

Question 26

what are bronchioles?

Answer 26

bronchial tubes divide repeatedly to form bronchioles

Question 27

what are alveoli?

Answer 27

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

Question 28

where do the lungs lie in?

Answer 28

In the pleural cavity, within the pleural membrane which is the fluid that occupies the open space

Question 29

what is the purpose of the c-shaped cartilage?

Answer 29

it supports the trachea by ensuring that it is always open

Question 30

where does gaseous exchange take place?

Answer 30

between alveoli in the lungs and surrounding blood capillaries

Question 31

what is gaseous exchange facilitated by?

Answer 31

1. 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
2. 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
3. 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

Question 32

what happens during gaseous exchange?

Answer 32

1. oxygen molecules diffuse from the alveolar air across the alveolar wall into red blood cells where they combine reversibly with haemoglobin to form oxyhaemoglobin
2. 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.
3. 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.
4. the reverse reaction occurs for the conversion of hydrogen carbonate ions into carbon dioxide in the lungs. the carbon dioxide is removed via exhalation

Question 33

what happens to the structures in the respiratory system during inspiration(breathing in)?

Answer 33

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

Question 34

what is main chemical stimulus for breathing?

Answer 34

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

Question 35

what are main components of tobacco smoke?

Answer 35

nicotine, carbon monoxide and tar (irritant)

Question 36

what is nicotine and what does it do?

Answer 36

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

Question 37

what is carbon monoxide and what does it do?

Answer 37

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

Question 38

what is tar and what does it do?

Answer 38

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

Question 39

what is lung cancer?

Answer 39

it is the uncontrolled abnormal division of cells in the lungs due to tar

Question 40

what is chronic bronchitis?

Answer 40

it is the inflammation of cells lining the air passage, excessive mucus is secreted, cilia gets paralysed and narrowing of air passages –> bretahing difficulties

Question 41

what is emphysema?

Answer 41

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

Question 42

what are the traits of ATP

Answer 42

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

Question 43

inner membrane of mitochondria

Answer 43

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.