diet and digestion

Question 1

why do we need energy?

Answer 1

• allows messages to be sent via nerves
• warmth
• growth + repair of tissues
• so muscles can contract
• to fuel internal functions
• movement
• heart can pump blood

Question 2

what is energy content of food measured in

Answer 2

KJ (kilojules)

Question 3

examples of food with large amounts of energy:

Answer 3

• oily fish
• butter
• olive oil

Question 4

examples of food with lower amounts of energy:

Answer 4

• vegetables
• fruit

Question 5

method to find energy in food:

Answer 5

1. fill a boiling tube with 20cm cubed water and measure the temp
2. chose the food + measure the mass of the food
3. light food on fire
4. immediately place food under boiling tube
5. measure temp of water again once food has stopped burning
6. energy = mass water x temp rise x 4.2 / mass food

Question 6

what are the disadvantages to the burning food method to calculate energy?

Answer 6

• lots of heat lost to surroundings
• not much control
• heat not evenly distributed

Question 7

what is an alternative practical to the burning food method to calculate energy?

Answer 7

bomb calorimeter

Question 8

what is digestion?

Answer 8

the chemical and mechanical breakdown of food. it converts large insoluble molecules into smaller soluble molecules that can be absorbed

Question 9

organs present in digestive system

Answer 9

mouth, salivary glands, oesophagus, liver, gall bladder, pancreas, small intestine, stomach, large intestine, appendix, rectum, anus

Question 10

function of salivary glands

Answer 10

produce saliva which contains the enzyme salivary amylase

Question 11

function of the mouth

Answer 11

food is chewed up by teeth here and swallowed. mechanical and chemical digestion occurs

Question 12

function of the oesophagus

Answer 12

tube that connects the mouth to the stomach

Question 13

function of the duodenum

Answer 13

where food comes into contact with bile

Question 14

function of the rectum

Answer 14

where faeces is stored

Question 15

function of the pancreas

Answer 15

produces amylase, lipase and protease enzymes and releases them into the duodenum

Question 16

function of the anus

Answer 16

faeces leaves the body here

Question 17

function of the stomach

Answer 17

contains the enzymes pepsin (a protease) and also hydrochloric acid to kill bacteria

Question 18

function of the ileum

Answer 18

where absorption of the food molecules into the bloodstream takes place

Question 19

function of the liver

Answer 19

produces bile which is used to emulsify large fat globules into smaller droplets

Question 20

function of the colon

Answer 20

water from the waste food is absorbed here

Question 21

function of the appendix

Answer 21

no use in humans except to cause lots of pain if burst

Question 22

adaptations of the villi

Answer 22

• large surface area
  -> villi + microvilli
  -> increase rate of diffusion
• good blood supply
  -> maintain concentration gradient for diffusion
• long
  -> lots of chance for diffusion to occur
• thin/near capillary
  -> short diffusion distance

Question 23

role of the villi

Answer 23

increase surface area of the intestines to allow digested food to be efficiently absorbed into the blood stream and delivered to cells around the body

Question 24

assimilation definition

Answer 24

small food particles are used to build larger food molecules (e.g. amino acids are used to synthesise proteins)

Question 25

absorption definition

Answer 25

small, soluble molecules move from the small intestine into the blood

Question 26

ingestion definition

Answer 26

food enters the digestive system via the mouth

Question 27

egestion definition

Answer 27

removal of undigested food (faeces) from the anus

Question 28

digestion definition

Answer 28

break down large insoluble molecules into small soluble molecules

Question 29

mechanical digestion

Answer 29

teeth break down food into small pieces and peristalsis helps move food along the small intestine

Question 30

chemical digestion

Answer 30

enzymes break down food into small, soluble molecules

Question 31

variables for investigating the effect of temp of the activity of enzymes

Answer 31

independent - temperature
dependent - speed of colour change
control -
pH level
volume of starch
volume of iodine
volume of bacterial amylase

Question 32

investigating the effect of temp of the activity of enzymes

Answer 32

• measure activity of enzyme by looking at speed at which starch disappears
• use iodine to work out when reaction is finished
  -> will turn blue/black when reaction is complete

Question 33

investigating the effect of temp of the activity of enzymes method

Answer 33

1. place single drops of iodine into depressions on tile
2. prepare a water bath for 20, 30, 40, 50, 60, 70 degrees Celsius
3. place 2cm cubed amylase and 2cm cubed starch into test tube and put in water bath
4. after 10 seconds, put one drop onto the iodine , then wait another 10 seconds and put a drop onto the next depression of iodine