Energy conversions: storage and release

Question 1

Where is the energy in ATP?

Answer 1

Phosphoenhydride bonds

Question 2

What charge do phosphate ions have

Answer 2

Oxygen ions are negatively charged

Question 3

How are phosphate groups held together

Answer 3

Phosphoenhydride bonds

Question 4

Hydrolysis

Answer 4

• ATP and 2x water
• ATPase needed for hydrolysis
• Active site of enzyme encapsulated phosphate groups
• Amino acids in active site are positively charged - distract -vely charged oxygen to allow water in and take phosphate group
• Water molecule takes up first phosphate group
• One hydrogen ion from water molecule transferred to second water molecule
• Breakage of phosphate group from ATP releases free energy

Question 5

Phosphocreatine

Answer 5

• When ATP is low, phosphocreatine can lend a PO4(3-) to ADP to make ATP
• When ATP is replenished by catabolism. PO4 (3-) is paid back
• During rest, muscle cells make more ATP than they can use - phosphate groups from ATP are transferred to creatine to form phosphocreatine
• Phosphocreatine has high free energy levels compared to ATP
• Phosphocreatine passes on phosphate group to ADP during high intensity exercise - energy provided by hydrolysis of phosphocreatine

Question 6

Phosphoryl groups

Answer 6

• Measure of tendency of compound to transfer PO4(3-) to water
• ATP is intermediate - can donate or accept PO4(3-)

Question 7

How is ATP produced?

Answer 7

• Catabolic reaction - bigger molecules broken into smaller ones
• Synthesis of bigger molecules from smaller ones = anabolic pathway
• Catabolic + anabolic = metabolic

Question 8

Metabolic fuels

Answer 8

• Carbohydrates (glucose)
• Lipids (fats) - most ATP
• Proteins (amino acids)
• Fatty acids only broken down in mitochondria but not all human cells contain mitochondria - RBC and lens etc
• Glucose - pyruvate - lactate (lactic acid fermentation) in renal medulla cells
• Major ATP source of cardiac muscle is fat
• Cells of CNS rely solely on glucose

Question 9

Proteins and amino acids

Answer 9

• Body exhausted fat stores
• Proteins converted to amino acids which are converted to pyruvate, intermediates of glycolysis and citric acid cycle
• Stimulated by adrenaline
• Glycerol converted to glucose intermediate
• Lactate → glucose by gluconeogenesis
• Gluconeogenesis stimulated by cortisol

Question 10

Releasing glucose from storage

Answer 10

• Glycogen → glucose = glycogenolysis
• Glycogenolysis stimulated by glucagon
• Triglycerides turned into glycerol and fatty acid (lipolysis)
• Lipolysis is hydrolysis reaction
• Fatty acids → acetyl COA for citric acid cycle and oxidative phosphorylation
• Acetyl CoA during intense starvation is not tunnelled down citric acid cycle in hepatocytes, they convert acetyl coa to ketone bodies
• Ketone bodies are acidic - relying entirely on fats makes too many ketone bodies and body becomes acidic and you die
• Brain and heart switch from glucose use to ketone body use

Question 11

Converting glucose for storage

Answer 11

• Lactate is temporary energy store
• Glucose converted to glycogen after transport to liver
• Glycogenesis makes glycogen from glucose
• Glycogenesis stimulated by insulin
• Glycogen in liver and muscle
• When liver and muscle stores full, excess glucose converted to triglycerides (fat)
• Acetyl CoA converted to fatty acids - fatty acid synthesis
• Fatty acid + glycerol = triglycerides (lipogenesis)
• Glycerol from glycolysis and is temporary energy store for glucose
• Lipogenesis stimulated by insulin, happens in fat tissue
• Excess glucose can be converted to amino acids - intermediates of glycolysis and citric acid cycle + pyruvate = amino acids
• Amino acids either converted to glucose or muscle
• Amino acid to muscle = protein synthesis - stimulated by insulin

Question 12

Anaerobic respiration

Answer 12

• No oxygen means glucose broken into pyruvate (glycolysis)
• Glucose-6-phosphate can be converted to ribose which is used for DNA and RNA
• Glycolysis releases 2x ATP
• Lactate is temporary storage molecule for pyruvate - normally stored in liver
• Lactate to glucose takes up 6xATP (gluconeogenesis)
• Lactate to glucose = Cori cycle
• Gluconeogenesis stimulated by cortisol
• Glycolysis is insulin
• Acetyl CoA made into citrate
• Citric acid cycle produces 6x NADH and 2x FADH2
• Oxidative phosphorylation = oxygen accepting electrons
• Aerobic respiration = 34 ATP and carbon dioxide