L13 Introduction to Metabolism Flashcards
What is Anabolism?
Anabolism refers to reactions that synthesis new (larger) molecules from smaller precursors. These need energy.
What is Catabolism?
Catabolism refers to reactions that break down larger molecules into smaller ones, usually to release energy.
What are the different stages if energy metabolism?
- Absorptive state - the products of digestion are transported to the liver, adipose tissue or muscles for them to be processed for energy. Any excess is stored for later fasting stages.
- Post-absorptive - occurs after digestion, when food is no longer the source of energy for the body. The body relies on glycogen for energy. Maintaining homeostasis between meals.
- Fasting
- Intense exercise
Where is phosphocreatine stored? What is its role?
Ketones - it acts as a short term energy store. It produces creatine as PCr is converted to creatine through creatine kinase releasing ATP.
What do most cells use as an energy source?
Fatty acids
Which amino acids are exported for gluconeogenesis?
Alanine and Glutamine
What is special about the energy requirements of erythrocytes?
Lack mitochondria and so cannot undergo aerobic respiration - as they need to carry oxygen. They get all their energy from anaerobic glycolysis.
What is special about the energy requirements of the brain?
- Brain tissue does have mitochondria and a very high metabolic demand
- BBB limits foodstuff that gets across. Glucose acts as the main energy store.
- Under normal conditions, the brain depends on a fairly steady plasma glucose concentration.
* Glucose from the blood enters the brain via specialised protein transport GLUT1. This is rich in the brain epithelial cells. Transport glucose molecules from the BBB in to the brain.
What blood glucose concentration must be maintained?
5 mM
What is the role of adipocytes when the insulin level is high?
When insulin concentration is high, adipocytes are stimulated to take up glucose and convert it to triacylglycerides.
What does the liver synthesis ketone bodies from?
Acetyl CoA
Ketone bodies are created from fats (and amino acids) and served as a preferential food store for the heart and other organs so the brain can still use glucose.
What is the source of energy for cardiac muscle?
Fatty acids but can use lactate or ketone bodies. Glucose uptake is insulin sensitive.
Give characteristics of type 1 skeletal muscle.
- Contains slow-twitch muscle fibres. These are the muscles that are found in a marathon runner. They are bright red, high levels of myoglobin, a good vascular supply and a good oxygen supply. They are adapted for long, relatively moderate activity and their main source of energy is fatty acids.
- Rather like cardiac muscle: highly aerobic
- Adapted to prolonged, relatively modest, activity: for example, postural muscles
- Main energy source is fatty acids.
Give characteristics of type 2a skeletal muscle.
• Intermediate between Type 1 and Type 2b. Contain some mitochondria, and myoglobin. Will maintain aerobic metabolism as much as possible.
• Phosphocreatine and glycogen provide a good store of energy.
• Adrenalin (or insulin) allow glucose uptake.
• At lower exercise levels, fatty acids are the main energy source.
During fasting, release amino acids for gluconeogenesis
Give characteristics of type 2b skeletal muscle.
• “Fast-Twitch” muscle: explosive performance, but quickly fatigue. Usually only recruited for severe efforts.
• Few mitochondria, and little or no myoglobin (hence white)
• Phosphocreatine provides rapid replenishment of ATP, but only for a few seconds.
• Rely mainly on anaerobic glycolysis, with glucose coming from their glycogen store.
Adrenalin (or insulin) allow glucose uptake.
