Digestive system

Question 1

What are 2 types of nutrition

Answer 1

Heterotrophic:
Consume nutrients which are organic substances and mineral ions, then absorb into the blood and assimilate them in body cells.
Autotrophic:
Organisms make their own food by carrying out photosynthesis, using raw materials such as CO2 and water

Question 2

What are the 5 processes involving nutrition in the body

Answer 2

Ingestion: Taking in food from the mouth
Digestion: Mechanical and chemical breakdown of large organic insoluble into smaller, more soluble components
Absorption: Taking soluble food through the small intestine by diffusion and active transport into the blood stream
Assimilation: Absorbed food is chemically by the liver before being utilized by the cells of the body and movement of digested food molecules into the cells
Egestion: Solid undigested food leaves body through the anus

Question 3

What is digestion

Answer 3

Chemical and physical breakdown of food
Converts large insoluble molecules into small soluble molecules, which can be absorbed into the blood easily

Question 4

What is mechanical digestion

Answer 4

Physical breakdown of food to help chemical digestion
First is in the mouth, where teeth bite and chew the food into small pieces that have a larger surface area
This means that enzymes can act on food faster
Muscles in the stomach contract to churn up the food

Question 5

What is chemical digestion

Answer 5

Enzymes or biological catalysts are involved
Food is broken into small, soluble particles in order to absorb to the blood
eg. amylase in mouth, pepsin in stomach

Question 6

What does the mouth do in the digestive system

Answer 6

Food is ingested and chewed. Teeth tear and grind food into small pieces. This increases surface area for the action of enzymes
Food is mixed with saliva. Saliva contains mucus which is a slimy substance which helps food to shape into a bolus to be swallowed easily
Saliva contains enzyme amylase to start the digestion of starch into maltose

Question 7

What does the Oesophagus do in the digestive process and what are the 2 sets of muscles in it

Answer 7

It is a muscular tube that pushed food to the stomach by waves of rhythmic contractions called peristalsis
Circular muscles: contracts and make the oesophagus narrower
Longitudinal muscles: contracts and makes the oesophagus wider

Question 8

How does peristalsis work?

Answer 8

When circular muscles contract and longitudinal muscles relax, the gut is made narrower, and the opposite happens the gut becomes wider
Waves of muscle contraction that passes along the gut pushing the food along is called peristalsis
The moment food is swallowed, a flap called the epiglottis closes so that food does enter the trachea
Movement of food in the gut doesn’t depend on gravity

Question 9

What does the stomach do in the digestive process

Answer 9

It is muscular bag towards the left side of the body just below the diaphragm
Mechanical digestion is carried out by the churning action of muscular wall of the stomach
Chemical digestion is started by protease enzyme
When food reaches the stomach gastric acid is released from the stomach lining
Gastric acid contains
1. Pepsin - protease enzyme which breaks proteins down into shorter chains called polypeptides
2. Hydrochloric acid – provide optimum pH 2 for pepsin to work and also helps to kill any ingested bacteria
There are two rings of muscles at the top and bottom, called sphincter muscles which prevent food from leaving the stomach while it is being churned around
After a few hours, the food is now a mushy liquid called chyme
It is then allowed to continue on its journey a bit at a time

Question 10

What is the enzyme reaction in stomach?

Answer 10

Protein–> Polypeptides

Question 11

What is the duodenum and what does it do in the digestive process

Answer 11

First part of the small intestine
When food enters the duodenum a number of secretions are added to it to complete the digestion.
Bile from gall bladder which is made in liver
Pancreatic juice from pancreas
Digestive enzymes from the wall of the duodenum

Question 12

Where is Bile produced, stored
Explain bile salts

Answer 12

It is produced in the liver and stored in the gall bladder
Bile contains no digestive enzymes but it can contains bile salts which play a vital role in fat digestion
Fats and oils don’t mix with water, but the enzyme lipase which digests them needed water in order to work
Bile salts break down the large fat drops into tiny droplets which can mix with water to form an emulsion

Question 13

What are the functions of bile

Answer 13

Bile emulsifies the fat by breaking down into small fat globules which increase the SA so more lipase can work on the fat and breakdown it into fatty acids and glycerol quickly
Bile helps to neutralize the stomach acid to provide the optimum pH for the small intestine enzymes to work best in a slightly alkaline environment

Question 14

What are the pancreatic juice and its role in the digestive process

Answer 14

The pancreas is both exocrine (secret juice through a duct) and endocrine organ (secrete hormones eg. Insulin directly into blood)
It secretes pancreatic juice which enters the duodenum via the pancreatic duct.
Pancreatic juice contains Lipase, Amylase, Trypsin

Question 15

What are digestive enzymes from the walls of the digestive wall

Answer 15

It is secreted by the wall of duodenum and ileum
It contains the enzymes lipase, maltose, peptidase

Question 16

What is the ileum

Answer 16

Last and longer part of the small intestine and highly adapted for the absorption of food from the small intestine to the blood
Digestion is completed and digested food is absorbed to the blood
It is lined up with villi to increase the surface area over which absorption takes place

Question 17

What are villi and its structure

Answer 17

Each villus contains network of blood capillaries- glucose and amino acids in the food absorb to the blood
Contains lacteal tube: fatty acids and glycerol enter this. Lacteals form part of the body’s lymphatic system, which transport a liquid called lymph and eventually drains into the blood system
Surface of villus is made of a single layer of cells called epithelium so short distance of diffusion from the ileum to the blood
Epithelium cells contain large number of mitochondria which supply energy needed for active transport of some substances eg. glucose
Villus contain muscle fibers which contract to move the villus. They are in constant motion, keeping them contact with digested food in the ileum and maintaining steep concentration gradient for diffusion

Question 18

What are adaptations in small intestine for the absorption of digested food

Answer 18

Long tube with microvilli and villi to increase surface area for diffusion of nutrients such as glucose, amino acids can move from villi to blood capillaries by diffusion or active transport
It has rich blood supply/flow to maintain higher concentration gradient to have a continuous flow of nutrients
Villi and capillaries have thin walls, one cell thick to provide short distance for faster diffusion
Villi have lacteals to absorb fatty acids and glycerol from the food

Question 19

What role does the colon have in the digestive process

Answer 19

By the time the food reaches the large intestine most of the digested food and water has been absorbed
Water is reabsorbed here leaving semisolid waste material called faeces
This is stored in rectum until expelled out of the body through the anus

Question 20

Liver, its blood vessels, its 6 functions

Answer 20

Liver is the largest internal organ
Hepatic portal vein carries blood rich in glucose, amino acids, vitamins and minerals from the ileum
Hepatic artery carries oxygenated blood to the lover
Liver breaks some molecules down and building up and storing others so act as main site of assimilation of food
Store excess glucose as glycogen
Making urea- deamination: removal of nitrogen containing part of amino acids, forming urea
Production of bile for emulsification of fat
Detoxification- removal of toxins from the blood
Regulation of blood glucose level in homeostasis- by hormone insulin and glycogen

Question 21

What does pancreas act as

Answer 21

Both exocrine (produce hormones eg. insulin) and endocrine (produce enzymes eg. trypsin, lipase) organ