NUTRITION AND DIGESTION
How we ingest, digest, absorb and assimilate
what our cells need
SPECIFICATION: BIOLOGICAL MOLECULES 1:
NUTRIENTS
2.5 identify the chemical elements present in
carbohydrates, proteins and lipids (fats and oils)
2.6 describe the structure of carbohydrates,
proteins and lipids as large molecules made up
from smaller basic units: starch and glycogen from
simple sugar; protein from amino acids; lipid from
fatty acids and glycerol
2.7 describe the tests for glucose and starch
SPECIFICATION: BIOLOGICAL MOLECULES 2: ENZYMES
2.8 understand the role of enzymes as biological
catalysts in metabolic reactions
2.9 understand how the functioning of enzymes
can be affected by changes in temperature,
including changes due to change in active site
2.10 understand how the functioning of enzymes
can be affected by changes in active site caused
by changes in pH
2.11 describe experiments to investigate how
enzyme activity can be affected by changes in
temperature.
SPECIFICATION: NUTRITION 1: DIET
2.23 understand that a balanced diet should include
appropriate proportions of carbohydrate, protein,
lipid, vitamins, minerals, water and dietary fibre
2.24 identify sources and describe functions of
carbohydrate, protein, lipid (fats and oils), vitamins
A, C & D, and the mineral ions calcium & iron, water
& dietary fibre as components of the diet
2.25 understand that energy requirements vary with
activity levels, age and pregnancy
2.32 describe an experiment to investigate the
energy content in a food sample
SPECIFICATION: NUTRITION 2: THE ALIMENTARY
CANAL
2.26 describe the structures of the human
alimentary canal and describe the functions of the
mouth, oesophagus, stomach, small intestine,
large intestine and pancreas
2.27 understand the processes of ingestion,
digestion, absorption, assimilation and egestion
2.28 explain how and why food is moved through the
gut by peristalsis
2.31 describe the structure of a villus and explain how
this helps absorption of the products of digestion in
the small intestine
SPECIFICATION: NUTRITION 3: CHEMICAL
DIGESTION
2.29 understand the role of digestive enzymes, to
include the digestion of starch to glucose by
amylase and maltase, the digestion of proteins to
amino acids by proteases and the digestion of
lipids to fatty acids and glycerol by lipases
2.30 understand that bile is produced by the liver
and stored in the gall bladder, and understand the
role of bile in neutralising stomach acid and
emulsifying lipids
Chemical elements in the major nutrients
2.5 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils)
Carbon, C
Hydrogen, H
Oxygen, O
Nitrogen, N
Carbohydrate
✓
✓
✓
✗
Lipid
✓
✓
✓
✗
Protein
✓
✓
✓
✓
Structure of carbohydrates, proteins and lipids
2.6 describe the structure of carbohydrates, proteins and lipids as large molecules made up from
starch and glycogen from simple sugar; protein from amino acids; lipid from fatty acids and glycerol
smaller basic units:
Tests for glucose and starch
2.7 describe the tests for glucose and starch


Starch: iodine solution
turns from yellow-brown to
blue-black
Glucose: Benedict’s solution turns from blue to
brick red (through green, yellow and orange)
Enzymes: biological catalysts speed up
reactions
2.8 understand the role of enzymes as biological catalysts in metabolic reactions
Enzymes: biological catalysts speed up
reactions (2)
2.8 understand the role of enzymes as biological catalysts in metabolic reactions
Enzymes: effect of temperature
2.9 understand how the functioning of enzymes can be affected by changes in temperature, including
changes due to change in active site
.

Below optimum
temperature:
too little kinetic

energy
too few collisions
between enzyme
and substrate
Above optimum
temperature:
enzyme denatured so
active site does not fit
substrate

does not catalyse
reactions any more
Enzymes: effect of pH
2.10 understand how the functioning of enzymes can be affected by changes in active site caused by changes
in pH
This is just an example: The optimum pH in the stomach is not 8, but 3!
Enzyme activity and temperature experiment
2.11 describe experiments to investigate how enzyme activity can be affected by changes in temperature.
Balanced Diet
2.23 understand that a balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre(TA)
A diet that
contains
adequate
amounts of
all the
necessary
nutrients
required for
healthy
growth &
activity.
Balanced Diet
2.23 understand that a balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre(TA)
Balanced Diet
2.23 understand that a balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre(TA)
72% of our body is WATER.
We contain so much water because water:
• Transports nutrients to cells, such as
minerals, vitamins and glucose as part
of our blood
• Part of urine and faeces, which
removes waste from our body
• Is needed for sweat (essential in
controlling our body temperature)
What do you have to eat
2.24 identify sources and describe functions of carbohydrate, protein, lipid (fats and oils), vitamins A, C and D, and the mineral ions calcium and iron, water and dietary fibre as components of
the diet
Component
Function
Example of sources
Carbohydrate
Short-term chemical energy
Bread, potatoes, rice, pasta
Lipids (fats and oils)
Long-term chemical energy
Meat, cheese, eggs
Protein
Growth & repair
Fish, egg
Vitamin A
Eyesight
Carrots, fish liver oil
Vitamin C
Healthy skin + gums
Oranges
Vitamin D
Absorb Calcium
Sunlight, milk
Mineral ions – Fe (iron)
Making haemoglobin in RBC
Spinach, red meat
Mineral ions – Ca (calcium)
Strong bones and teeth
milk
Dietary fiber
Peristalsis; prevent constipation
Vegetables, cereal
Water
Transport system
To sweat
All chemical reactions occur in
water in cytoplasm
Not just drinks; also fruits like
watermelon
Not all bodies are Energy (J) Equal
2.25 understand that energy requirements vary with activity levels, age and pregnancy (TA)
Person
Energy needed per day (kJ)
Newborn baby
2000
Age 2
5000
Age 6
7500
Girl age 12-14
9000
Boy age 12-14
11000
Girl age 15-17
9000
Boy age 15-17
12000
Female office worker
9500
Male office worker
10500
Heavy manual worker
15000
Pregnant woman
10000
Breast-feeding woman
11300
Bodies use different amounts of energy
2.25 understand that energy requirements vary with activity levels, age and pregnancy (TA)
Energy requirements vary according to several factors:
• Age: growing people require more energy than others.
• Gender: on average, males require more energy than
females.
• Pregnancy: pregnant women require more energy to
nourish themselves and the baby.
• Activity levels: more active people require more
energy as they use up more energy throughout the day.
Name that structure
2.26 describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas
game
Describe the function
2.26 describe the structures of the human alimentary canal and describe the functions of the mouth, oesophagus, stomach, small intestine, large intestine and pancreas
• Functions
Mouth
• Teeth chew & grind to increase surface area
• Salivary glands produce saliva -> moistens food, making it easier to
swallow
• Chemical digestion by amylase breaks down starch into maltose
Oesophagus
• Food is moved by peristalsis
Stomach
• Produces acid: HCl (kills bacteria)
• Produces protease (pepsin) enzymes
• Churns food to increase surface area
Small intestine
• Produces carbohydrase (maltase) and protease (trypsin)
• Absorbs digested food
Pancreas
• Produces carbohydrase (amylase), protease (trypsin) & lipase
enzymes
Large intestine
• Absorbs water
Rectum / anus
• Stores faeces / opens so egestion can happen
Flow Chart of Nutrition and Digestion
2.27 understand the processes of ingestion, digestion, absorption, assimilation and egestion
Ingestion
• Taking food into
the body
Digestion
Absorption
• The breakdown of large
insoluble molecules into
small soluble molecules
so they can be absorbed
into the blood
• The process of
absorbing nutrients
into the body after
digestion
Egestion
• Getting rid of
undigested/unwan
ted food
Assimilation
• Using food
molecules to build
new molecules
Flow Chart of Nutrition and Digestion
2.27 understand the processes of ingestion, digestion, absorption, assimilation and egestion
Digestion can be mechanical or chemical
Mechanical Digestion: digestion by physically breaking food into smaller pieces (i.e. not
using enzymes) to make it easy to move and increase the surface area. Carried out by:
• mouth and teeth chewing food
• stomach churning food
Chemical Digestion: digestion using enzymes
Where it is
made
Where it works
Enzyme
Substrate
Products
Salivary Glands
Mouth
Amylase
Starch
Maltose
Stomach cells
Stomach
Protease
Protein
Amino Acids
Liver
Small Intestine
Bile Salts
Fat
Fat droplets
Pancreas
Small Intestine
Small Intestine
Small Intestine
Amylase
Protease
Lipase
Maltase
Protease
Starch
Protein
Lipids
Maltose
Protein
Maltose
Amino Acids
Glycerol & Fatty acids
Glucose
Amino Acids
Peristalsis
2.28 explain how and why food is moved through the gut by peristalsis
Food is moved the digestive
system by a process known as
peristalsis.
This is the contraction of two
sets of muscles in the walls of
the gut.
1) One set runs along the gut
2) The other set circles it.
Their wave-like contractions
create a squeezing action,
moving down the gut.
Digestive Enzymes
2.29 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases and the digestion of lipids to fatty acids and
glycerol by lipases
Enzymes involved in respiration and making new molecules work inside cells.
Digestive enzymes are produced and released by specialised cells and work
outside the cells.
Different enzymes
(Different enzymes catalyse different digestion reactions)
Digestive Enzymes
2.29 understand the role of digestive enzymes, to include the digestion of starch to glucose by amylase and maltase, the digestion of proteins to amino acids by proteases
Digestive Enzymes
2.29 understand the role of digestive enzymes, to include the digestion of lipids to fatty acids and glycerol by lipases
Bile starts the digestion of lipids
2.30 understand that bile is produced by the liver and stored in the gall bladder, and understand the role of bile in neutralising stomach acid and emulsifying lipids
After the stomach, food travels to the small intestine. The enzymes in
the small intestine work best in alkaline conditions, but the food is
acidic after being in the stomach.
• Bile alkaline so it
neutralizes stomach acid
• Bile is produced by the
liver and stored in the gall
bladder.
• Bile is secreted into the
small intestine, where it
emulsifies (splits up fats)
• Splitting fats increases
the surface area for
lipases to work.
Absorption in the small intestine
2.31 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine
The villus
2.31 describe the structure of a villus and explain how this helps absorption of the products of digestion in the small intestine
Where small soluble nutrients are absorbed into the blood.
Adaptation
Explanation
Thin wall
Wall of villus is 1 cell thick, which speeds the rate of
diffusion of molecules into the blood
Rich blood supply
Absorbed molecules are carried away fast. So there is a
low concentration of food molecules in the blood, which
maintains a high concentration gradient
Intestine length
Roughly 7m long, which increases the surface area
Surface Area
Villi and microvilli increase the surface area of the small
intestine by 1000x
How much energy is in that peanut?
2.32 describe an experiment to investigate the energy content in a food sample.(TA)
Change in temperature x mass of water x 4.2
mass of food
There are problems with using this set-up:
Not all the food burns
Water loses heat to environment