26. Digestion Flashcards
What are heterotrophs?
A heterotroph is an organism that cannot manufacture its own food by carbon fixation and therefore derives its intake of nutrition from other sources of organic carbon, mainly plant or animal matter
What are autotrophs?
Plants can make organic compounds - they can make their carbon skeletons and are autotrophs
What are the essential major nutrients?
- Carbohydrates
- Proteins
- Fats
What are the major uses of carbohydrates?
Provides energy via ATP, stored as glycogen
What are the major uses for fats?
Provide more energy via ATP
What are the major uses for amino acids?
Building blocks for proteins
What are the other essential nutrients?
- Mineral elements in different amounts (macro and micronutrients)
- Vitamins
What is the function of B1, thiamin vitamin?
It is a coenzyme in cellular respiration
What are the deficiency symptoms of B1 thiamin vitamins?
Beriberi, loss of appetite, fatigue
What is the function of vitamin C, ascorbic acid?
Aids formation of connective tissues, prevents oxidation of cellular constituents
Who does beriberi usually affect?
- Occurs in people whose staple diet consists mainly of polished white rice (which contains minimal thiamine)
- Disease seen in people of Asian countries and in chronic alcoholics with impaired liver function
What are the symptoms of scurvy?
- Exhaustion and weakness
- Swelling of the limbs
- Softening of the gums
What is the function of vitamin D, calciferol?
Absorption of calcium and phosphorus
What are the symptoms of vitamin D deficiency?
Rickets
What is the difference between water soluble and fat soluble vitamins?
Unlike water soluble vitamins, fat soluble vitamins (stored in the liver) can become toxic at high concentration
What does rickets cause?
Affects calcium absorption
What is the main essential fatty acid?
Linoleic acid which is needed to synthesise other fatty acids and prostaglandins
What are saprobes?
They obtain carbon and energy directly from dead organic matter (eg bacteria or fungi)
What are detritovores?
Obtain energy from the waste products of other organisms
What are filter feeders?
Trap tiny particles of organism or organisms suspended in water (e.g primitive fish, molluscs, baleen whales)
What are predators?
Catch and kill another organism for food (carnivores, omnivores, herbivores)
How is a calorie defined?
1 Cal is the amount of energy required to raise the temperature of 1gm of water by 1 degrees
Why is there a rapid initial weight loss after fasting?
Carbohydrates are stored as glycogen, which has a very high water content, and is very heavy
What is the order of things that are metabolised in the body for weight loss?
- Carbohydrate metabolised first, then fat and protein
What does leptin do?
Involved in the long term regulation of body weight
What cells produce leptin?
Fat cells
What does leptin act on?
It circulates in the blood and acts on different tissues, including the hypothalamus, skeletal muscle and liver
What happens when you cannot produce leptin?
You are unaware of when you have sufficient amounts of fats stored so you overeat and then become obese
Where are receptors for leptin found?
In the regions of the hypothalamus that are involved in the control of hunger
- Ventromedial hypothalamus
Could leptin be used to treat obesity?
- A few obese people do not produce leptin and injections of leptin can reduce their appetites and enable them to lose weight
- Most obese people have higher than normal leptin levels though
What is the effect of leptin on its own receptors?
Leptin receptors have reduced sensitivity to leptin and therefore leptin cannot have its normal appetite suppressing effects
- Long term leptin treatment will not be effective in controlling obesity
