The document provides information about calories, kilojoules, macronutrients (carbohydrates, proteins, lipids), vitamins, minerals, digestion, and the functions of the liver and digestive system. It states that a calorie is the amount of energy needed to increase the temperature of 1 gram of water by 1°C, while a kilojoule is the International System unit of energy. Carbohydrates, proteins and lipids contain different elements and are the building blocks of cells, tissues and a source of energy. Vitamins and minerals are required in small amounts for chemical reactions and maintaining health. The digestive system breaks down food through a multi-step process involving mechanical and chemical breakdown to absorb nutrients. The

1. CALORY: 1 cal= 4,187 j. It’s not very used now. It
expresses THE ENERGETIC POWER OF FOOD. It’s
the amount of Caloric Energy necessary to increase in
1°C the temperature of 1 gram of What water
is a calorie?
KJ: derived unit of energy or work in the International
System of Units, it’s the amount of E by completely
oxidizing 180 gram of glucose

3.  We need food for 1) energy.
2) for growth provides the substances
needed for making new cells/tissues
 3) for replacement of worn and damaged
tissues

4. CARBOHYDRATES PROTEINS LIPIDS
Elements they
contain
C,H,O C,H,O,N,S C,H,O
Smaller
molecules of
which they are
made
Glucose/simple sugar Amino acids (3) fatty acids and (1)
glycerol
Solubility in H2O Monosaccharides YES
Polysaccharides NO
YES NO
Food that
contains them
Bread, cereals, deserts,
potatoes, rice, pasta,
jam, sweets, lettuce
Meat, fish, chicken, egg
white, milk, cheese,
pork, peas, beans and
cereals
Butter, oils, fat meat,
junk food, egg yolk

5. Why animals
need them
Easily available
energy (16kj/g)
Making
CELLS,ANTIBODIES
, ENZYMES; used
for ENERGY if all
the stores have run
out (17kj/g)
*Source of
ENERGY (37kj)
*LONG TERM
storage of E in fat
depots
*insulation
(adipose tissue)
*part of cell
membrane and
membrane
systems
Things to
remember
ProteinsAminoaci
ds bloodstream
build up different
proteins
(cytoplasm/enzyme
s)
aminoacids not
usedLiVERremo
val of amino group
(-NH2) 
Glycogen Stored
or OXIDIZED for E
SUGAR
GLUCOSE

7. Why do we need vitamins and
minerals?
Mineral Found in Why it is needed Deficiency disease
IRON in RED meat, eggs, bread,
spinach, lentils
haemoglobin carries O2
round the body  when
destroyed stored in the
LIVER
 needed in MUSCLES and
ENZYME SYSTEM
ANEMIA  lack of red blood
cells less O2
CALCIUM milk, cheese
not soluble in water=> not
absorb needs vitamin D and
bile salts
*hardens bones and teeth/
*part of blood
clotting(plasma)/
*needed for chemical changes
in MUSCLES and transmission
ofNERVE IMPULSES
brittle bones and teeth
IODINE SEA fish, shellfish and most
vegetables
part of the Thyroxine
molecule hormone
produced by Thyroid gland
GOITRE sweeling of the neck
and slow metabolism
PHOSPHORUS Milk, cheese,meat and fish Needed for Calcium phosphate
of the bone and DNA
brittle bones and teeth

8. What are the vitamins?
1) organic substances quite unrelated to each other in structure
2) Characteristics: * not broken down for E
*not built into the body structure
*essential in small quantities
*needed for chemical reactions associated with
enzymes
3) They can be: WATER soluble (green leaves, fruits, grains) or FAT
soluble (animal fat or vegetable oils)

9. Vitamin Found in Why it is needed Deficiency disease Notes
A (RETINOL)
FAT SOLUBLE
A (CAROTENE)
WATER SOLUBLE
Butter, margarine,egg
yolk, milk, liver
Green vegetables and
carrots
*Keep the cells lining
the respiratory system
healthy
*make pigment in the
rod cells in the retina,
needed for seeing in
dim light
*Keratomalacia
(ulceration of the
cornea), night blindness
*infections of the cells
lining the respiratory
syst
*stored in the LIVER
Can’t be stored
B 1-2-6-9-12
FOLIC ACID
Water soluble
Wholemeal bread,
brown rice, yeast, liver
Involved in chemical
reactions FOLIC ACID
very imp in
pregnancybirth
disease like spine bifida
NERVOUS SYST
BERI-BERI :diet based
on polished rice causing
muscular weakness and
paralysis
10 or more vitamins B
come all together
C (ascorbic acid)
WATER SOLUBLE
Grapes, potatoes,
citrics, brown rice
Keeps tissues in good
repair (connective
tissues&blood vessels)
Acts as catalyst in cell
respiration
SCURVY: causes pains in
joints and muscles
bleeding gums
Only in fresh food, can’t
be stored, daily intake
is needed
D (Calciferol)
FAT SOLUBLE
Butter, milk, egg yolk,
cheese, liver, fish liver
oil
Helps Calcium and
phosphate to be used
for making bones
Helps absorption of
Calcium from intestine
RICKETS (bones are soft
and deformed)
OSTEOMALACIA
Can be made by the
skin when sunlight
shines on it
K Green vegetables,
made by a bacteria
living in the intestine
Plays a part in the
blood-clotting process
Unlikely to be lacking
except in people whose
intestinal bacteria have
been reduced by
antibiotics

10. Water functions

11.  In our cells, chemical reactions take place
in water
 Waste chemicals are diluted in water in
order to be passed out of our bodies
 Blood transport substances dissolved in
water
Why do we need water?

12. Can we digest
fibre??
NOOOOOO
To digest fibre, the enzyme cellulase must be present to break
down cellulose, which compose the cell wall. In our digestive
system, we can't synthesise this enzyme. Thus, we can't digest
fibre
What is the
function of fibre?
To keep the digestive system healthy
and functioning properly. Fibre aids and speeds up
the excretion of waste and toxins from the body,
preventing constipation. It stimulates peristalsis
and help retain water

15.  ENERGY REQUIREMENTS per day => 12000kj (=2800cal)
For *keeping our internal body processes working
*keeping our body temperature
*meeting the needs of work and activities
8 hours asleep 2400 kj
8 hours awake (inactive) 3000 kj
8 hours physically active 6600 kj
Balanced diet
Total 12000 kj
BASAL METABOLISM 
2400 kj (574cal in 8 hours of
sleep) maintains circulation/
breathing/body temperature/
brain function/chemical
processes in liver and other
organs

16. Special NEEDS
PREGNANCY proteins, calcium, vitamin D, folic Acid
LACTATION  proteins, vitamins, calcium
GROWING CHILDREN  calcium, iron, vitamin D, vitamin A (disease
resistance)
MALNUTRITION
insufficient, excessive or imbalanced comsuptiom of nutrients
MARASMUS no food intake,
E deficency
KWASHIORKORpot belly/
no proteins

17. Digestion
 Digestion is the breakdown of large food
molecules into small food mollecules in
the digestive system, so that they can be
absorbed into the bloodstream and carried
to every cell of the body.

18. Digestive system
 Digestive truct
Esophagus
Stomach
Small intestines
Large intestines
Rectum and anus
 Glands
Salivary glands
Liver
Gallbladder
Pancreas

19. Path of Food Mouth--chewing
Pharynx--conscious swallowing
Esophagus--transport to stomach
Stomach--mechanical
and chemical breakdown
Small Intestines--
chemical digestion and absorption
Large Intestines--
resorb water, form feces
Rectum---collect and expel feces

20. MOUTH
Mechanical and
chemical digestion
start in the mouth.
Saliva contains the enzyme amylase ( it breaks down starch into
sugar).
Saliva also contains mucus which lubricates the food and helps it
pass down the oesophagus.
Saliva lubricates
and stick the
small pieces
togetherbolus

21. Chewing and
swallowing
SWALLOWING: Food passes from the MOUTH to the PHARYNX and into the ESOPHAGUS
1 The tongue presses UPWARDS and BACK against the roof of the mouth
2 The SOFT PALATE closes the NASAL CAVITY
3 The LARYNX cartilage is pulled upwards so that the glottis is under the back of the tongue
4 The GLOTTIS is partly closed
5 The EPIGLOTTIS shuts down to help prevent food from going down the WINDPIPE
The beginning is VOLUNTARY, once food gets to the back of the mouth  REFLEX ACTION

22. Peristalsis
The oesophagus has circular muscles in the
wall. These muscles contract behind the
bolus to push it along and the muscles in
front of the food relax. This way food passes
along the oesophagus to thestomach. This
movement is known as peristalsis.
http://www.passmyexams.co.uk/GCSE/biology/digestive_system.html

23. Enzymes in digestion.
Enzymes are chemicals that break down
large food molecules into small food molecules.

24. STOMACH FUNCTION
–Mechanical and chemical breakdown
of food
Protein
breakdown-pepsin
secreted by
epithelial lining
◦ Acidic
conditions--for
pepsin to work and
to kill bacteria
The gastric juices contain protease enzymes (PEPSIN) and hydrochloric acid

25. STOMACH
Food+ GASTRIC JUICE=
◦ From esophagus
(cardiac orifice
or lower
esophageal
sphincter)
◦ To small
intestine (pyloric
sphincter)
CHYME

26. SALIVA + Amylase
Chewing
Esophagus Stomach
PERISTALSIS
Gastric juices: Pepsin+
Hydrochloric acid
Pancreatic juice
(TRYPSIN+PANCREATIC
AMYLASE+LIPASE)+
SODIUM
HYDROGENCARBONATE
Small Intestine-
DUODENUM
Bile
Small Intestine-
Illeum
Absorption
Liver
Assimilation of produtcs
EGESTION
KIDNEYS
LARGE INTESTINE
Colon absorbs FATTY
ACIDS, BILE SALTS;
WATER

27. INTESTINES
 Small Intestine
 Large Intestines
Absorption of
nutrients
Reabsorption of
water
Duodenum / Ileum
Cecum, colon, rectum and anal canal.
the ascending colon, the transverse colon, the descending colon,
and the sigmoid colon.

29. Small Intestine:
Modifications for absorption
dense capillary
network
Digested food passes
to the blood to be
taken to the liver and
then distributed round
the body
Microvilli:
Increases surface
area  the larger
the surface, the
faster the
absorption
thin epithelium
increases contact,
fluids can pass
easily to reach the
capillaries
Length
It gives plenty of
time for digestion
to be completed
and for digested
food to be
absorbed

30. *They work in stages and different parts of the canal  e.g: starch  MALTOSE  GLUCOSE (SALIVA/PANCREAS)
protein  PEPTIDE  Amino acid (AA) (STOMACH)
 Fats  LIPASE  GLYCEROL+ FATTY ACIDS
*TYPES: 1) CARBOHYDRASES  digest CH e.g  AMYLASE => MALTOSE  MALTASE => GLUCOSE
2) LIPASES  digest FATS into=> fatty acids and glycerol
3) PROTEASES  digest proteins into POLIPEPTIDES => Amino acid (AA)
*

31. PROTEASES are produced in an inactive form + MUCUS
* PEPSIN is produced as PEPSINOGEN and becomes PEPSIN when it
encounters HYDROCHLORIC ACID
* TRYPSIN is produced as TRYPINOGEN and becomes TRYPSIN when it
encounters ENTEROKINASE (produced by duodenum lining)
BRAIN
nerve impulses
GASTRIN  when food reaches
the stomach, circulates in the
blood to maintain the gastric
secretion
SECRETIN
stimulates secretion of
ENTEROKINASE and SODIUM
HYDROCARBONATE

32. Interesting Facts about the
Digestive System…
•We eat about 500kg of food per year.
•We produce 1.7 litres of saliva each day.
•In the mouth, food is either cooled or warmed to a more suitable temperature.
•The oesophagus is approximately 25cm long.
•Muscles contract in waves to move the food down the esophageus. This means that food would get to a
person's stomach, even if they were standing on their head.
•An adults stomach can hold approximately 1.5 litres of material and produces about 2.5 litres of gastric
juice everyday.
•In an average person, it takes 8 seconds for food to travel down the food pipe, 3-5 hours in small intestine and 3-4
days in the large intestine.
•The human body takes 6 hours to digest a high fat meal and takes 2 hours for a carbohydrate meal.
•Every day 11.5 litres of digested food, liquids and digestive juices flow through the digestive system, but only
100mls is lost in faeces.
•Most of us pass somewhere between 200 and 2,000 ml of gas per day. These emissions are composed of five
gasses: nitrogen (N2), oxygen (O2), carbon dioxide (CO2), hydrogen (H2), and methane (CH4).

34. INGESTION
DIGESTION
ASSIMILATION
ABSORPTION
EGESTION
D
U
O
D
E
N
U
M
I
L
E
U
M
AMYLASE
Salivary/pancreatic
PEPSIN
TRIPSIN
BILE salts
LIPASE
MALTOSE
PEPTIDES
MALTOSE
GLUCOSE
AA

35. ILEUM ABSORPTION
GLUCOSE and AA  Epithelial cells =>Capillaries =>VEINS =>HEPATIC
PORTAL VEIN => LIVER => BLOOD CIRCULATION
GLYCEROL+ FATTY ACIDS  LACTEALS => Lymphatic system =>
bloodstream
HOW  water/alcohol => OSMOSIS
Amino acids/ salts/sugars =>ACTIVE TRANSPORT
FAT soluble VITAMINS =>ACTIVE TRANSPORT (+fat droplet)
WATER soluble VITAMINS => DIFFUSION
CALCIUM IONS => need VITAMIN D => ACTIVE TRANSPORT

36. ASSIMILATION : uptake and use of
food
STORAGE
GLUCOSE  ENERGY from respiration *GLYCOGEN in LIVER (Short
term storage) and MUSCLE
*FAT  fat depots
FATS  to form some cell structures (membranes)
or as a source of ENERGY *LONG-TERM STORAGE
 FAT DEPOTS
ADIPOSE TISSUE
(round kidneys/under skin)
AMINO ACIDS  build up proteins forming
tissues/enzymes *NOT STORED in the
body DEAMINATED (-NH2)

37. redish-brown organ which lies beneath the
diaphram and overlaps the stomach partially
ALL THE BLOOD FROM THE BLOOD
VESSELS OF THE ALIMENTARY CANAL
PASSES THROUGH THE LIVER, ADJUSTING
ITS COMPOSITION BEFORE JOINING
GENERAL CIRCULATION
Functions: 1) REGULATION OF BLOOD SUGAR: removes excess glucose and stores it as
GLYCOGEN (normal level 80/150mg) or from GLYCOGEN to GLUCOSE maintaining
HOMEOSTASIS (internal environment within narrow limits) and the composition of the
BODY FLUIDS
2) PRODUCTION OF BILE  BILIRUBIN
pigment from breakdown of haemoglobin .
BILE contains bile salts (for digestion of fats)
3)STORAGE OF IRON
4)DEAMINATION  conversion of useless AA to glycogen
removing the amino group (-NH2)Ammonia (poisonous)
UREA excreted by the KIDNEYS
5) MANUFACTURE OF PLASMA PROTEINS
6) DETOXIFICATION  ALCOHOL/MEDICINES
7) STORAGE OF VITAMINS A AND D

38. PART OF
CANAL
JUICE SECRETED ENZYMES SUBSTANCE PRODUCT OTHER
SUBSTANC
ES IN THE
JUICES
FUNCTION OF THE
OTHER
SUBSTANCES
MOUTH Saliva amylase starch maltose - -
PHARYNX - - - - - -
STOMACH Gastric juice Pepsin proteins Poly
peptides
Hydro
chloric
acid
Gives acidity
for the pepsin
to work
Kills bacteria
DUODENUM *pancreatic
juice
Amylase
Lipase
trypsin
Starch
Fats
Proteins and
Polypeptides
Maltose
Fatty acids/
glycerol
Sodium
hydrogen
carbonate
Neutralises
acidity of chyme
Makes the
environment
alkaline
* Bile (liver) Bile salts
&pigments
Emulsify fats
Excretory
product
ILEUM - Maltase
Sucrase
Lactase
Peptidase
Lipase
Maltose
Sucrose
Lactose
Polypeptides
Emulsify fats
Glucose
Glucose &
Fructose
Galactose&
Glucose
Aminoacids
Fatty acids/
glycerol

40. Overview of the Digestive System
1
- the first part of the digestive system, where food enters the body. Chewing and salivary enzymes in
the mouth are the beginning of the digestive process (breaking down the food).
- glands located in the mouth that produce saliva. Saliva contains enzymes that break down
carbohydrates (starch) into smaller molecules.
- the long tube between the mouth and the stomach. It uses rhythmic muscle movements (called
peristalsis) to force food from the throat into the stomach.
- rhythmic muscle movements that force food in the esophagus from the throat into the stomach.
Peristalsis is involuntary - you cannot control it. It is also what allows you to eat and drink while
upside-down.
- a large organ located above and in front of the stomach. It filters toxins from the blood, and makes
bile (which breaks down fats) and some blood proteins.
- a sack-like, muscular organ that is attached to the esophagus. Both chemical and mechanical
digestion takes place in the stomach. When food enters the stomach, it is churned in a bath of acids
and enzymes.
2 6 1 3 4 5
Salivary glands / Stomach / Mouth / Esophageus / Peristalsis / Liver

41. Overview of the Digestive System
1
- the first part of the digestive system, where food enters the body. Chewing and salivary enzymes in
the mouth are the beginning of the digestive process (breaking down the food).
2
- glands located in the mouth that produce saliva. Saliva contains enzymes that break down
carbohydrates (starch) into smaller molecules.
- the long tube between the mouth and the stomach. It uses rhythmic muscle movements (called
peristalsis) to force food from the throat into the stomach.
- rhythmic muscle movements that force food in the esophagus from the throat into the stomach.
Peristalsis is involuntary - you cannot control it. It is also what allows you to eat and drink while
upside-down.
- a large organ located above and in front of the stomach. It filters toxins from the blood, and makes
bile (which breaks down fats) and some blood proteins.
- a sack-like, muscular organ that is attached to the esophagus. Both chemical and mechanical
digestion takes place in the stomach. When food enters the stomach, it is churned in a bath of acids
and enzymes.
Salivary glands / Stomach / Mouth / Esophageus / Peristalsis / Liver
1
3
4
5
6
2 6 1 3 4 5

42. - food in the stomach that is partly digested and mixed with stomach acids. It goes on to the small
intestine for further digestion.
- a small, sac-like organ located by the duodenum. It stores and releases bile (a digestive chemical
which is produced in the liver) into the small intestine.
- a digestive chemical that is produced in the liver, stored in the gall bladder, and secreted into the
small intestine.
- an enzyme-producing gland located below the stomach and above the intestines. Enzymes from
the pancreas help in the digestion of carbohydrates, fats and proteins in the small intestine.
- the first part of the small intestine; it is C-shaped and runs from the stomach to the jejunum.
Overview of the Digestive
System 2
4 5 1 2 3
Pancreas / Duodenum / Chyme / Gall bladder / Bile

43. Overview of the Digestive
System 2
- food in the stomach that is partly digested and mixed with stomach acids. It goes on to the small
intestine for further digestion.
2
- a small, sac-like organ located by the duodenum. It stores and releases bile (a digestive chemical
which is produced in the liver) into the small intestine.
- a digestive chemical that is produced in the liver, stored in the gall bladder, and secreted into the
small intestine.
- an enzyme-producing gland located below the stomach and above the intestines. Enzymes from
the pancreas help in the digestion of carbohydrates, fats and proteins in the small intestine.
- the first part of the small intestine; it is C-shaped and runs from the stomach to the jejunum.
4 5 1 2 3
Pancreas / Duodenum / Chyme / Gall bladder / Bile
1
3
4
5

44. The Digestive System

45. Answers