Digestion And Absorption Of Carbs(Week 2)

Question 1

What are Two reasons that organisms need to eat.

Answer 1

1. Fuel for ATP production

2. Using inorganic molecules to assemble new molecules

Question 2

Molecules that animals require but cannot make are called essential nutrients. What are the four essential nutrients?

Answer 2

1. Essential amino acids.
2. Essential fatty acids
3. Vitamins
4. Minerals

Question 3

What organs are in the digestive system in relation to the digestion of carbohydrates?

Answer 3

Mouth
Oesophagi
Stomach
Small intestine
Large ingesting
Rectum
Anus

Question 4

Describe the first stage of carbohydrate digestion. (Oral cavity, pharynx and oesophagus)

Answer 4

Salivary glands deliver saliva to lubricants food whilst teeth chew into smaller particles which are exposed to salivary amylase. This enzyme breaks down glucose polymers. The oesophagus moves food down the pharynx by peristalsis.

Question 5

Which bond in in carbohydrates does amylase breakdown?

Answer 5

The linear alpha 1-4 linkage. This leads to various products being formed.

Question 6

Describe the second stage of carbohydrate digestion. (Stomach)

Answer 6

The stomach stores food and secreted gastric juice which converts a meal to acid chyme. This gastric juice is made up of hydrochloride acid and pepsin. Pepsin is released in its inactive form as pepsinogen which has an additional 44 amino acids to pepsin. Pepsinogen secretes hydrogen and chloride ions which form hydrochloride acid. The acid allows pepsinogen to unfold and become the active pepsin enzyme.

Question 7

Describe the third stage of carbohydrate digestion. (The small intestine)

Answer 7

In the duodenum, acid chyme from the stomach mixes with digestive secretions from the pancreas, liver, gallbladder and the SI itself. The brush border in the SI secretes digestive enzymes.

Question 8

What enzymes does the pancreas secrete?

Answer 8

Trypsin
Chymotrypsin
Amylase

Question 9

What are the substrates and products that relate to the enzyme Glucose-amylase?

Answer 9

Substrate: Maltose and maltotriose
Product:Glucose

Question 10

What are the substrates and products that relate to the enzyme Isomaltase?

Answer 10

Substrates: Alpha limit dextrins, Maltose, Maltotriose
Products: Glucose

Question 11

What are the substrates and products that relate to the enzyme Lactase?

Answer 11

Substrates: Lactose
Products: Glucose and Galactose

Question 12

What are the substrates and products that relate to the enzyme Sucrase?

Answer 12

Substrates: Maltose, maltotriose and sucrose
Products: Glucose and fructose

Question 13

Where in the Small intestine does absorption occur and how is the small intestine adapted for its purpose?

Answer 13

It occurs in the duodenum, but absorption of water and nutrients mainly occurs in the jejunum and ileum. The villi and microvilli hugely increase the surface area of the SI increasing the relate of absorption

Question 14

Give an overview of absorption.

Answer 14

Amino acids and sugars pass through the epithelium of the small intestine and enter the bloodstream. The capillaries then converge in the hepatic portal vein and deliver blood to the liver and then to the heart. Dietary fats are broken down into small units that move across the brush border into the epithelial cells, packages in the cytosine and form chylomicrons which move into the lymph system and drain into the blood circulation

Question 15

How are monosaccharides taken into cells from the bloodstream?

Answer 15

Facilitated diffusion by GLUTs

Question 16

Describe the fourth stage of digestion. (Absorption in the large intestine, caecum, colon and rectum)

Answer 16

The caecum connects the small and large intestine