4.3 Whole Body Metabolism Flashcards
Why don’t our bodies take fat that we can do without and make it into sugar?
We cannot turn fatty acids into sugar, we do not have the enzymes
What is the primary, readily mobilized source of energy?
Glycogen in the liver and muscle
Other sources of glucose-like carbohydrates
Recycled lactic acid
Glycerol from triglycerides
Amino acid “skeletons”
Gluconeogenesis
Making glucose from any ‘carbon skeletons’ available (amino acids, glycerol, lactic acid, etc) to primarily feed the brain
Do fatty acids go through gluconeogenesis?
NO they go to ketone bodies
When are proteins catabolized for energy?
Only when carb supply is limited (starvation or very long term physical exertion)
Amino acids must undergo_________ to remove the amino group
Deamination
What is the amino group excreted as?
Urea in the kidneys
After deamination, what happens to the remaining C-skeleton?
Converted to a molecule that enters gluconeogenesis, glycolysis, pyruvate oxidation or Kreb’s cycle
What are triglycerides catabolized into? Where?
Fatty acids and glycerol in adipocytes
What happens to glycerol after it is separated from the fatty acids?
It is a carb so it enters glycolysis
Beta Oxidation
Fatty acids are converted to acetyl-CoA (can enter Krebs) to generate ATP in various tissues (heart, muscle, etc)
Does beta oxidation require oxygen?
Yes
Why is beta oxidation important?
It preserves carbohydrate reserves for the brain
What happens to fatty acids during starvation?
They go to the liver and become ketone bodies
Downside to ketone bodies being produced
Ketoacidosis
- Drops blood pH
- Ketones can be toxic
What are the three factors that go into your body deciding which fuel your tissues burn?
Intensity of activity
Duration
Starvation
What type of activity are carbs favored for? (intensity)
High intensity (because they sustain inefficient cellular respiration)
What type of activity are lipids favored for? (intensity)
Lower intensity
Duration
Glycogen depletion leads to the use of alternate fuel sources (fatty acids and even amino acids if very long duration)
Starvation
Prolonged energy deprivation, by 4 days without eating 75% of fuel for the brain is ketone bodies
What do tissue proteins do during starvation?
Mobilize to save the brain and heart which are preserved to the last
What types of food molecules can you make ATP from?
Virtually any
Essential nutrients
Specific term used to describe molecules that must be food derived, your body cannot synthesize them itself
Nutrients for survival
Minerals Vitamins Proteins Lipids Water
Are carbohydrates essential nutrients?
Technically they are not
Main carbohydrate function
Provide energy and carbon skeletons to build other molecules (like amino acids)
Starch
When eaten as a part of whole grains, fruits and vegetables…takes time and energy to break down into absorbable glucose
Fiber
Carbs that can’t be digested down to glucose
Insoluble fiber
Bulk that hastens movement through digestive tract
Activates stretch receptors in GI (makes you feel full)
Soluble fiber
Binds dietary fat and cholesterol, reduces their absorption in small intestine
Simple sugars like table sugar have a _____ glycemic index
High
Why do table sugars have a high glycemic index?
They are so quickly absorbed in the small intestine
Cycle initiated by high glycemic index foods
Blood sugar elevates
Insulin over-secreted
Too much sigh removed from blood
You feel hungry again
Proteins are made of ____ amino acids: ____ are essential and must be supplied in the diet
20
10
When consuming sufficient energy from multiple foods, it is virtually impossible to develop an ________ deficiency
Amino Acid
Two essential fatty acids
1) Alpha linolenic (canola, soy, flax)
2) Linoleic (Not an issue, lots of sources)
Can plants make cholesterol?
NO
Most vitamins are ________
Enzyme cofactors
How many vitamins are there?
13
What matters in terms of osteoporosis?
- Bone stress (exercise)
- Menopause
- Low protein diets
- Vitamin D plus calcium
What do acidic foods do to iron absorption?
Promote absorption in intestine
