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What is cellular respiration?

Set of metabolic reactions in cells to convert biochemical energy from nutrients into adenosine triphosphate (ATP) for use in energy requiring activities of cells


What are Anabolic reactions?

Generate complex molecules from smaller substrates
Need energy
Suffix – genesis


What are catabolic reactions?

Break down complex molecules into smaller products
Release energy, which is transferred to ATP molecules
Suffix – lysis


What is catabolism used for?

40% energy released by catabolism is used for cellular functions
Rest is converted to heat which maintains body temp or is lost to environment


What are carbohydrates metabolised to?

Polysaccharide and disaccharide catabolised to monosaccharides: glucose, fructose and galactose
Shortly after absorption (small intestine) fructose and galactose converted to glucose


What is the preferred source of ATP?



What happens to glucose if ATP is needed immediately?

Glucose is Oxidised


What happens to glucose if ATP is not needed immediately?

Converted to glycogen for storage in liver cells & skeletal muscle fibers
If these full then liver converts glucose to triglycerides for storage in adipose tissue. Released when ATP required


What increases rate of facilitated diffusion of glucose?



Describe cellular respiration of glucose

1 glucose + 6O2 = 38 ATP + 6CO2 + 6H2O


What is the final electron acceptor in glucose respiration?



What are the key reactions in cellular respiration of glucose?

Formation of acetyl CoA
Krebs cycle
Electron transport chain


What are NAD+ and FAD?

Coenzymes: temporary carriers of atoms being removed or added to a substrate during the reaction
NAD+ accepts electrons and H+ ions, becomes reduced and forms NADH+H+, which can be oxidised to donate electrons and H+ ions to electron chain


What is glycolysis?

Glucose --> 2 x pyruvate + 2NADH + 2ATP


What are the 2 pathways of pyruvate?

Anaerobic: Lactate dehydrogenase --> lactate
Aerobic: Pyruvate dehydrogenase complex --> Acetyl coA + CO2


Describe the lactic acid pathway and why it happens

For glycolysis to continue, must be adequate amounts of NAD+ available, NADH has to be oxidised
If oxygen available this happens in the mitochondria and eventually donated to oxygen
If not enough oxygen NADH is oxidised in the cytosol donating
electrons to pyruvate and reduction of pyruvate by H+ forms lactic acid
Reaction is catalysed by lactic acid dehydrogenase


What respiration related factors are required for cells to survive?

As long as they make enough ATP
Lactic acid concentrations don’t rise too high


Which tissues cope best with lactic acid?

Skeletal muscle > cardiac muscle > brain


How do red blood cells undergo respiration?

No mitochondria
Only anaerobic respiration
Spares the oxygen they are carrying


Describe the Formation of Acetyl CoA

Pyruvate enters mitochondria and is converted into 2-carbon fragment acetic acid (+CO2 – removed via blood and respiration)
Acetic acid + coenzyme A --> acetyl coenzyme A
Pyruvate dehydrogenase


Describe the Krebs cycle

Acetyl CoA (2 carbons) combines with oxaloacetic acid (4 carbons) to form citric acid (6 carbons)
Series of reactions citric acid is converted to oxaloacetic acid, join with a new acetylCoA and start again
For each cycle:
1 GTP produced (donates P to ADP to form 1 ATP)
3 NAD+ reduced to NADH
1 FAD is reduced to FADH2


What things other than pyruvic acid can pass into the Krebs cycle?

Amino acids
Ketone bodies
Fatty acids


Describe the electron transport chain

NADH and FADH2 oxidised by transferring electrons to ETC
Free energy released during oxidation of NADH or FADH2 molecule by O2 sufficient to drive synthesis of ATP from ADP and Pi
Mitochondria maximise production of ATP by transferring electrons from NADH and FADH2 through series of electron carriers all but one of which are integral components of inner membrane
Step-by-step transfer of electrons allows free energy in NADH and FADH2 to be released in small increments
Oxidised forms (NAD+ and FAD) are regenerated and continue to shuttle electrons from Krebs cycle to electron chain


What is oxidation?

Loss of electrons from an atom or molecule as occurs when hydrogen is removed from the molecule or oxygen is added


Summarise cellular respiration

Glycolysis: Glucose --> 2ATP +2NADH
Krebs Cycle: 2 x acetyl CoA --> 2ATP + 6NADH + 2FADH2
Electron chain transport: 34ATP + 2NADH
Glucose = 38 ATP (anaerobic 2ATP, aerobic 36 ATP)


What is diabetes Mellitus?

Heterogeneous complex metabolic disorder characterised by elevated
blood glucose concentration secondary to resistance to action of insulin, insufficient insulin secretion, or both


Where can glucose supply come from?

Dietary sources
Breakdown of glycogen stores (glycogenolysis)
Formation of glucose (gluconeogenesis)


What is the significance of the hydrophilicity of glucose?

Require specific transport proteins to move into cells


Name some glucose transporters

GLUT family: Facilitated diffusion, not energy dependent
GLUT 1,3 &4 movement at low glucose levels, GLUT 4 insulin dependent response in fat & muscles, GLUT 2 present on β-islet cells
SGLT (sodium dependent glucose transporter): Use sodium to move glucose against concentration gradient, SGLT1 – responsible for dietary uptake in intestines, SGLT2 – glucose re-absorption in kidney


What is Gluconeogenesis? And where does it happen?

Production of glucose from molecules (not carbohydrates)
Substrates are: Lactate, Glycerol (from fats), Glutamine and alanine (from protein)
Occurs in both liver and kidneys