Week 1/2 - C - Biochemistry 1-4 - Glucose (Glycogenolysis, Glycolysis, gluconeogenesis), Fats/Ketones/Lipolysis/genesis, amino acids

Question 1

uDefine Glycogenesis Glycogenolysis Gluconeogenesis What is the main storage form of glucose in the liver and muscle cells?

Answer 1

Glycogenesis - synthesis of glycogen from glucose Glycogenolysis - breakdown of glycogen to form glucose Gluconeogenesis - de novo synthesis of glucose from metabolic precursors The main storage form of glucose in the liver and muscle cells is glycogen

Question 2

Is liver or muscle glycogen made available to be broken down to glucose between meal times and why? (glycogenolysis) Which type provides energy via glycolysis during bursts of physical activity?

Answer 2

Liver glycogen is broken down between meal times and released to maintain blood glucose levels for red blood cells and the brain Muscle glycogen provides energy via glycolysis and the TCA during bursts of physical activity (is borken down into glucose via glycogenolysis and then via glycolysis provides energy)

Question 3

What is the rate limiting step of glycogenolysis?

Answer 3

The rate limting step is the conversion of glycogen to glucose-1-phosphate by glycogen phosphorylase

Question 4

What is glycolysis? What is the function of glycolysis?

Answer 4

Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Glyclosis breaksdown glucose to release ATP and form pyruvate (which is involved in metabolism in the TCA cycle and oxidative phosphyrlation of Acetyl Coa to supply much more ATP)

Question 5

What is the netgain of ATP from glycolysis? What is the rate limting step in glycolysis?

Answer 5

The net gain of ATP from glycolysis is 2 ATP The rate limting step is the conversion of fructose 6-phosphate to fructose 1,6 biphopshate as it requires 1 ATP molecule it is controlled by phosphofructokinase

Question 6

When sufficient oxygen is not present in the muscle cells for further oxidation of pyruvate and NADH produced in glycolysis, what does this cause in order to keep producing ATP?

Answer 6

Causes continued glycolysis as glycolysis is anaerobic - When oxygen supply is insufficient, typically during intense muscular activity, energy must be released through anaerobic metabolism. In order to provide ATP, NAD+ is regenerated from NADH by reduction of pyruvate to lactate.

Question 7

What can continued anaerobic respiration (glycolysis) result in the build up of?

Answer 7

This can result in the build up of lactic acid can cause a burning sensation in the muscles

Question 8

During prolonged starvation, new glucose has to be synthesized What is the primary source of glucose in these periods eg overnight as hepatic glycogen is depleted?

Answer 8

This would be gluconeogenesis - de novo synthesis of glucose from metabolic precursors Gluconeogenesis is essentially the reverse of glycolysis

Question 9

What are the metabolic precursors used for gluconeogenesis in periods of prolonged starvation?

Answer 9

Lactate - synthesised by skeletal muscle under anaerobic conditions Amino acids - derived from muscle protein by proteolysis Glycerol - derived from triglycerides by lipolysis in adipose tissue

Question 10

Which two hormones are important in the regulation of blood glucose levels?

Answer 10

Insulin and glucagon are important in the regulation of blood glucose levels

Question 11

What do insulin and glucagon cause?

Answer 11

High blood glucose causes the pancreas to release insulin causing the uptake of glucose into different cells (inhibits glycogen phosphrylase - glycogenolysis) Low blood glucose causes the pancreases to releases glucagon which causes the liver to release glucose into the blood (promotes glycogen phosphrylase - glycogenolysis)

Question 12

How long do these provide energy ATP Phosphocreatinase Free circulating glucose Glycogen stores Fat stores

Answer 12

ATP - 4 seconds Phosphocreatinase - 15seconds Free circulating glucose - 4minutes Glycogen stores - 77 minutes Fat stores - 4+ days

Question 13

What does increased fat intake without appropriate energy expenditure lead to?

Answer 13

This leads to an increase in number of adipocytes and more fat in the adipocytes Overall, will eventually cause obesity

Question 14

Fat is required for many reasons eg as an energy source, for essential fatty acids, and for fat-soluble vitamins What are the fat -soluble vitamins? What are the other vitamins and how are they soluble?

Answer 14

Fat soluble vitamins Vitamin A, D, E, K Water soluble vitamins Vitamin B (all types) and vitamin C

Question 15

What is the main energy storage form of fats in adipose tissue? What do they consist of?

Answer 15

This would be triglycerides aka triacylglycerol Consist of glycerol (3 carbon structure) and 3 fatty acids

Question 16

What are the main products of fat digestion? (ie what are triglycerides broken down into)

Answer 16

Glycerol Fatty acids Monoglycerides Breaking down fats by digestive enzymes enables absorption of fats from the lumen of the large intestine

Question 17

What are the fatty acids further broken down into and what can this be used for? What is the breakdown of fatty acids known as?

Answer 17

Where does lipolysis usually occur and what is the function?

Question 18

Where does lipolysis usually occur and what is the function?

Answer 18

In periods of starvation or diabetes, what can be consumed from the Kreb’s cycle for gluconeogenesis as a result of fatty acid breakdown? (in conditions where there is not enough glucose) What will the increased in the blood due to the increased fatty acid breakdown which is also used as an energy source?

Question 19

In periods of starvation or diabetes, what can be consumed from the Kreb’s cycle for gluconeogenesis as a result of fatty acid breakdown? (in conditions where there is not enough glucose) What will the increased in the blood due to the increased fatty acid breakdown which is also used as an energy source?

Answer 19

In periods of starvation or diabetes, oxaloacetate can be provided for gluconeogenesis Due to the increased fatty acid breakdown, acetyl-CoA (the breakdown product of fatty acids) is converted to KETONE BODIES which can be used as an energy source

Question 20

What can an elevated level of ketones cause? ie what organs are affected, what type of breathing?

Answer 20

Ketone bodies are moderate acids and severe accumulation can lead to severe acidosis - where the blood cannot buffer the acid levels anymore This can lead to Kaussmaul breathing Impaired tissue functon especially in the CNS Smell of the acetone (sweet smell) can be detected in breath

Question 21

What is de novo synthesis of fatty acids known as? Where does it mainly occur?

Answer 21

De novo synthesis of fatty acids is known as lipogenesis It minly occurs in the liver, kidney, mammary gland, adipose tissue and brain

Question 22

When does lipogenesis take place? What is the substrate for this process?

Answer 22

Lipogenesis takes place mainly during excess energy intake, when excess carbohydrate is consumed Lipogenesis converts the carbohydrate to fats

Question 23

Amino acids are compounds that combine to make proteins When proteins are digested or broken down, amino acids are left Where are amino acids stored?

Answer 23

Thee is no storage site for amino acids Amino acids which are not used as building blocks are degraded mainly in the liver

Question 24

What does amino acid breakdown produce?

Answer 24

Amino acids breakdown produces ammonia (NH3) and ammonium ions (NH4+)

Question 25

Ammonium ions become toxic at high concentrations an therefore a safe way of ecreting excess nitrogen is needed Give examples of major nitrogen-containing excretory molecules?

Answer 25

Urea Uric acid Creatinine Ammonium ion (NH4+)