Digestion

Question 1

Why do we need to eat?

Answer 1

• we are heterotrophs

* animals cannot synthesise organic compounds and so must eat plants and other animals to obtain them

Question 2

What are autotrophs?

Answer 2

• can make their own organic compounds

- ie plants

Question 3

What are the major nutrients to be used as building blocks to make more complex molecules?

Answer 3

• carbohydrates
• protein
• fat

Question 4

What are vitamins?

Answer 4

Organic molecules that must be obtained from food

• function as co-enzmes or part of co-enzymes

Question 5

Why can’t you overdoes in water soluble vitamins?

Answer 5

• water soluble mean that the body cannot store it

* therefore excess is excreted in the urine

Question 6

What are Saprobes

Answer 6

Obtains carbon and energy directly from dead organic matter

e.g. bacteria and fungus

Question 7

Detritovores

Answer 7

Obtain energy from the waste products of other organisms

Question 8

Filter Feeders

Answer 8

Trap tiny particles or organisms suspended in water

e.g. primitive fish, molluscs, baleen whales

Question 9

Predators

Answer 9

catch and kill organisms for food

- carnivores, omnivores, herbivores

Question 10

How is a calorie defined in diets?

Answer 10

• 1 Cal = 4.2 KJoules

* 1000Cal = 1Kcal

Question 11

What happens to an animals with insufficient caloric intake?

Answer 11

• considered undernourished

* must metabolise its stored glycogen, fat and finally its own protein

Question 12

What causes the rapid initial weight loss when you fast?

Answer 12

• when not enough calories are consumed, the body first metabolises carbohydrates
• carbohydrates are stores as glycogen and has a very high water content - hence very heavy
• loss of this causes the initial weight loss

Question 13

What is leptin and its function?

Answer 13

• It is a protein
• Involved in the long term regulation of body weigh
• produced primarily by fat cells

Question 14

What happened in mice with mutations on both ob genes?

Answer 14

• unable to produce leptin
• unaware of when sufficient amounts of fat stored
• as a result mice overeat and become obese

Question 15

Where are receptors for leptin found?

Answer 15

• in the regions of the hypothalamus involved in the control of hunger
- ventromedial hypothalamus

Question 16

What is the main cause of obesity?

Answer 16

Mutation in the leptin gene

Question 17

How do some obese people have higher than normal levels of leptin?

Answer 17

• leptin receptors have reduced sensitivity to leptin

* leptin cannot have its normal ‘appetite suppressing’ affects

Question 18

What are essential amino acids and why are they necessary?

Answer 18

• essential amino acids must be obtained through the diet

* have important role in protein synthesis, tissue repair and nutrient absorption

Question 19

Why is Vitamin D necessary?

Answer 19

• affects calcium and phosphorous absorption

Deficiency can lead to rickets

Question 20

Why are fat-soluble vitamins toxic at high levels?

Answer 20

• stored in the liver and excess levels can be toxic

* is not excreted in the urine

Question 21

What is the difference between micro and macronutrients?

Answer 21

Micronutrients - needed in small amounts like vitamins and minerals. Also help in digestion of macronutrients

Macronutrients - to provide energy
• carbohydrates
• proteins
• fats

Question 22

Vitamin B1 deficiency symptoms

Answer 22

• extreme muscle weakness
• irritability
• loss of appetite/weight loss

Question 23

Vitamin C function in the body

Answer 23

Necessary for the growth, development and repair of all body tissues
• immune system
• formation of collagen
• maintenance of cartilage and bones/teeth