Carbohydrates and lipids
The big molecules of energy and structure: monosaccharides, disaccharides and polysaccharides (starch, glycogen, cellulose), saturated and unsaturated fatty acids, triglycerides, phospholipids, cholesterol and lipoproteins, and what nutrition makes of them.
- 36 cards
- 3 topics
- Free
The outline, topic by topic
Each topic is weighted the way the exam weighs it.
- Concepts
- Scenarios
- Understand
A few cards from the deck
Glucose: what is it?
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A six-carbon sugar (C₆H₁₂O₆), the cells' main fuel and the only fuel red cells normally use.
The brain uses about 120 g a day.
After an overnight fast, what first keeps blood sugar up?
- Breakdown of liver glycogen
- Breakdown of muscle glycogen into blood
- Cellulose in the gut
- Cholesterol
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Breakdown of liver glycogen
The liver releases glucose into blood; its stores last about a day.
Sucrose: what is it?
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A disaccharide of one glucose and one fructose: table sugar.
It is split in the gut by sucrase.
Why can we not digest cellulose although it is made of glucose?
- It is made of fatty acids
- Acid destroys it
- It is absorbed as is
- No human enzyme can cut its beta bonds
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No human enzyme can cut its beta bonds
Ruminants manage it thanks to the bacteria in their rumen.
Lactose: what is it?
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Milk's disaccharide, made of glucose and galactose, split by lactase.
Without lactase, it ferments in the colon.
Why does muscle glycogen not raise blood sugar?
- Muscle has no enzyme able to break its glycogen down
- Muscle lacks the enzyme that releases glucose into blood
- Its stores are too small to affect blood sugar
- Insulin permanently blocks muscle glycogen breakdown
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Muscle lacks the enzyme that releases glucose into blood
Only the liver and kidney have glucose-6-phosphatase: muscle keeps its 400 g or so of glycogen for itself, far more than the liver's 100 g.