Chapter 7 - Metabolism Flashcards
What are the 5 simplified steps of the energy-yielding pathways?
- The macronutrients get broken down into their basic elements, and then into pyruvate.
- All of the energy-yielding nutrients can be broken down to Acetyl CoA.
- Acetyl CoA can enter the TCA cycle
- Most of the reactions above release hydrogen atoms with their electrons, which are carried by coenzymes to the electron transport chain
- ATP is synthesized
What is metabolism?
sum total of all the chemical reactions that take place in living cells
What is energy metabolism?
All reactions by which the body obtains and uses the energy from food.
What is anabolism?
Reactions in which smaller molecules are put together to build larger ones
What is catabolism?
Reactions where larger molecules are broken down to smaller ones
What is ATP?
The body’s quick energy molecule
What is ATP is composed of?
Sugar, purine, and 3 phosphates
How is ATP energy-yielding?
The phosphates can be readily broken off, releasing energy from the phosphoanhydride bonds
How is energy released?
Energy is released when a high-energy phosphate bond in ATP is broken. With the loss of a phosphate group, high-energy ATP (charged battery) becomes low-energy ADP (used battery)
How does ADP become ATP?
Energy is required whan a phosphate is attached to ADP, making ATP. ADP needs eneergy from the breakdown of carbohydrate, fat, and protein to make ATP.
What is the difference between pyruvate and Acetyl CoA?
- Pyruvate can be used to make glucose while Acetyl CoA cannot
- Pyruvate is a 3 carbon structure, Acetyl CoA is a 2 carbon structure
How does glucose change to pyruvate?
Glycolysis
* 2 pyruvates are made (2 3C structures)
* Hydrogens are carried to ETC
* Pyruvate can be converted back (gluconeogenesis)
What is gluconeogenesis?
The process that converts pyruvate into glucose
In what conditions does glycolysis occur?
In anaerobic conditions
* If there is a shortage of oxygen, pyruvate is converted to lactic acid
* Lactic acid can be converted back to glucose through the Cori Cycle
When does the Cory cycle occur?
When the muscles need energy; it brings energy to the muscles during intense workouts and other times of low O2 levels
Quick vs. Slow energy needs
- Quick = anaerobic: pyruvate to lactic acid
- Slow = aerobic: pyruvate to Acetyl CoA
What are the amino acids called that are used to make glucose?
Glucogenic
What are the amino acids called that are converted to Acetyl CoA?
Ketogenic
Is pyruvate to Acetyl CoA reversible?
No; it is higher exergonic (energy is released)
How is Acetyl CoA broken down?
TCA cycle and electron transport chain
Glycerol to Pyruvate
Glycerol can be converted to glucose and pyruvate
Fatty acids to Acetyl CoA?
Fatty acid oxidation
* hydrogens and electrons go to the ETC
* Acetyl CoA go to TCA
What are the six steps for fats entering the energy pathway?
- Glycerol enters the glycolysis pathway about midway between glucose and pyruvate
- Pyruvate becomes Acetyl CoA
- Acetyl CoA goes to the TCA
- Fatty acids are broken down into fragments combine with CoA to form Acetyl CoA
- Coenzymes take hydrogens and electrons to ETC
- Acetyl CoA goes to the TCA cycle
Where do amino acids enter the energy pathway?
- They are converted to pyruvate, which is used to make glucose
- Converted to acetyl CoA
- Enter TCA cycle directly
When do amino acids enter the energy pathway?
They only come into the pathway when there is not enough glucose/calories
How many triglycerides are needed to make one glucose?
2 triglycerides, and 120 fatty acids
Describe the electron transport chain (3)
- Electrons bind hydrogen to Vitamin B coenzymes
- In a series of reactions, electrons lose energy in small amount until the end where water is produced
- The energy the electrons lose is captured in ATP
Do amino acids yield energy?
yes
Does glycerol yield energy?
Yes
Do fatty acids yield energy?
Yes
Do carbohydrates yield glucose?
Yes
Do fatty acids yield glucose?
No
Does glycerol yield glucose?
Yes - when carbohydrates are unavailable
Do amino acids yield glucose?
Yes - when carbohydrates are unavailable
Do carbohydrates yield amino acids and body proteins?
Yes - when nitrogen is available, can yield nonessential amino acids
Do fatty acids yield amino acids and body proteins?
No
Do glycerol yield amino acids and body proteins?
Yes - when nitroen is available, can yield nonessential amino acids
Do carbohydrates yield fat stores?
Yes
Do amino acids yield fat stores?
Yes
What is glycolysis?
Metabolic breakdown of glucose to 2 units of pyruvate
What happens to excesses in glucose metabolism?
It is converted to fat for storage
What are the two things protein and fat can be converted into?
- Pyruvate, which can then provide glucose
- Acetyl CoA (which cannot be converted to glucose)
What occurs during fat metabolism?
- Glycerol turns to pyruvate, which can yield either glucose or Acetyl CoA
- Fatty acids turn to Acetyl CoA
What happens if there is excess in fat metabolism?
It readily goes into storage
What is deamination?
The first step in amino acid catabolism
When is urea produced?
During amino acid catabolism
Where does TCA cycle occur in the cell?
In the matrix of the mitochondria; like the conversion of pyruvate to Acetyl CoA
Where does the ETC occur?
In the inner membrane mitochondria
What occurs in the ETC?
- Transfer of electrons, where oxygen accepts electrons
- Water and ATP is formed
What is the issue of oxygen production in the ETC?
Oxygen is fundamental to life but it also produces oxygen metabolites which result in cellular damage
How do reactive oxygen species cause cellular damage?
It contributes to lipid peroxide formation
What does overeating result in?
Lipid deposition
Why does lipid deposition occur?
It is energy efficient; it takes 5% of ingested energy to take dietary lipids to adipose
Why do carbohydrates favour glycogen production over lipid deposition?
It uses 25% of ingested energy intake to convert carbs to TG
Where is excess fat stored?
In adipocytes
What occurs in the 0-4 hours following a meal?
You are in the postprandial state (digestion and absorption of nutrients
What occurs in a initial fast (3-4 hours)?
The body uses glycogen and triglycerides for ATP production
What occurs in an prolonged fast (>24 hours)?
Use triglycerides and protein for ATP production
In a >24 hour fast, where is glucose sourced?
90% from protein, 10% from glycogen
Why is most glucose not sourced from glycogen in an extended fast?
After 24 hours, glycogen sources are depleted causing the body to utilized energy stores from adipose tissue and protein stores
What occurs in an extended fast after protein and glycogen is used for glucose?
The body switches to ketosis where ketones are syntehsized and protein is conserved
How does ketosis work?
Ketones are an alternative energy source for neurons
What are the symptoms of ketosis?
The blood pH decreases, ketonuria, acetone breath
What are the energy sources used in fasting?
- First triglycerides stores are used as well as glycogen
- Protein is used to make glucose, while fat converts to ketones
- Death if all stores are depleted
What occurs with the suppression of appetite?
Ketosis is induced when fasting
What occurs when metabolism is slowed?
Basal metabolic rate is decreased
What are the symptoms of starvation?
- Wasting msucle/fat
- Low body temperature
- Prone to illness
- Organ failure
- Depression
- Anxiety
- Food dreams
What are tthe goals of intermittant fasting and time restricted eating?
Reduced kcal intake, which results in body wieght loss, and improvements in metabolic markers (blood sugar, HDL cholesterol, BP, waist circumference?
What is a risk of intermittant fasting and time restricted eating?
‘Catch up consumption’ of kcal, cravings
What is the alcohol used to make triglycerides?
Glycerol
How does alcohol disrupt metabolism?
- Fatty liver
- Build up of NADH and Acetyl CoA
- Fatty acid synthesis
- Ketone bodies synthesis
- Lowered blood pH
What is the result of decreased blood pH?
Suppression of nervous system
What is the difference between fibrosis and cirrhosis liver disease?
- Fibrosis is reversible; loss of function
- Cirrhosis is irreversible; death of hepatic cells with permanent loss of function
What is MEOS?
Microsomal ethanol-oxidizing system; cytochrome enzymes in liver/intestines
What does MEOS do?
A part of alcohol and drug metabolism
* Reduced deoxification and/or metabolism-catabolism of other drugs
* Delayed or amplified effects of drugs
What issues can be caused by alcohol consumption? (3)
- Nutrient displacement
- Malabsorption
- Vitamin B deficiencies (folate, B12, thiamin, pyridoxine)
- Interference with nutrient metabolism
What are the dietary alcohol recommendations?
Low risk is 2 or less standard drinks/week
