Chapter 6 life processes 1 (introduction, nutrition and digestion)

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LIFE PROCESSES
Looking at living things

Living things
 Although all living things look different from each other, they
all have seven things in common.
 These seven things are called life processes.
 Something is only alive if it does all seven processes.

 Animals move their
whole bodies to get
from one place to
another.
 Plants turn towards
the light and their
roots grow down
into the soil.

 Animals have babies.
 New plants grow
from seeds.

3
All living things are
sensitive

 All living things respond
to changes. Living things
notice changes in their
surroundings and react
to them.
 Eg. Plants grow towards
the light.
 Eg. People react to the
temperature around
them.

4
All living things need
nutrition

 Food is used to provide energy.
 Green plants make their own
food using sunlight.
 Animals eat plants or other
animals.

 Waste substances
must be removed
from the body.
 Plants and animals
both need to get rid
of waste gas and
water.

 Plants and animals
use the oxygen in
the air to turn food
into energy.

 Babies grow into
adults.
 Seedlings grow into
plants.

The seven life processes
1 Move
2 Reproduce
3 Sensitive
4 Nutrition
5 Excrete
6 Respire
7 Grow

Use the first letter from each process to help you
remember them.
Move
Reproduce
Sensitive
Nutrition
Excrete
Respire
Grow
They spell MRS NERG

This is MRS NERG !
Can you remember what each
of the letters in her name
stand for ?

Move
Reproduce
Sensitive
Nutrition
Excrete
Respire
Grow

Nutrients :-
The components of food like carbohydrates, fats,
proteins vitamins and minerals are called nutrients.
Nutrients help living organisms :-
i) To build their bodies.
ii) To grow.
iii) To repair the damaged parts of their bodies.
iv) To provide energy to carry out life processes.

The mode of taking food by an organism
and its utilization in the body is called
nutrition.
Modes of nutrition :- There are two
main modes of nutrition in living
organisms. They are autotrophic
nutrition and heterotrophic nutrition.
i) Autotrophic nutrition :- is nutrition in
which organisms can prepare their own
food.
Organisms which can prepare their own
food are called autotrophs.
ii) Heterotrophic nutrition :- is nutrition
in which organisms get their food
directly or indirectly from plants.
Organisms which get their food directly
or indirectly from plants are called
heterotrophs.
nutrition

What is photosynthesis?
 Plants make their own food. This process is
called photosynthesis.

Where does photosynthesis occur?
 Photosynthesis occurs in the leaves of a plant.

What is needed for photosynthesis to
occur?
 Light is needed for photosynthesis to occur. The
plant’s leaves use the light to make a sugar called
glucose.

Why do plants need glucose?
 Glucose is the food for the plant. It gives the plant
energy to grow.

How much glucose does a plant make?
 Plants make enough glucose to be used during the night and
on cloudy days when they don’t get sunlight. The extra
glucose is stored in the plant’s leaves and other parts.

How does photosynthesis help us?
 During the process of photosynthesis, oxygen is
produced. We use this oxygen to breathe.

Photosynthesis - Food making process in plants :-
Photosynthesis is the process by which plants prepare their own
food by using sunlight, water, carbon dioxide and chlorophyll.
Photosynthesis take place in the leaves.
i) Sunlight is obtained from the sun.
ii) Water is absorbed by the roots and transported to the leaves.
iii) Carbon dioxide is taken from the air through small pores in
the leaves called stomata.
iv) Chlorophyll are the green pigments present in the leaves.

Chlorophyll uses the energy from sunlight to prepare food by using water and
carbon dioxide. The food prepared is carbohydrate which is then converted into
starch. During photosynthesis oxygen is released.
Equation of photosynthesis :-
Sunlight
Carbon dioxide + Water Carbohydrate + Oxygen
Chlorophyll

Synthesis of proteins :-
The soil has some bacteria which convert nitrogen from the air into usable
nitrogen in the soil. Farmers also add fertilisers containig nitrogen into the
soil. Plants absorb this nitrogen from the soil along with water and other
constituents to prepare proteins and fats.

Outline
I. Photosynthesis
A. Introduction
B. Reactions
II. Cellular Respiration
A. Introduction
B. Reactions

Photosynthesis
 Method of converting sun energy into chemical energy usable by
cells
 Autotrophs: self feeders, organisms capable of making their own
food
– Photoautotrophs: use sun energy e.g. plants photosynthesis-makes
organic compounds (glucose) from light
– Chemoautotrophs: use chemical energy e.g. bacteria that use sulfide or
methane chemosynthesis-makes organic compounds from chemical
energy contained in sulfide or methane

Photosynthesis
 Photosynthesis takes place in specialized structures inside plant
cells called chloroplasts
– Light absorbing pigment molecules e.g. chlorophyll

Overall Reaction
 6CO2 + 12 H2O + light
energy → C6H12O6 + 6O2+ 6H2O
 Carbohydrate made is glucose
 Water appears on both sides because 12 H2O molecules are required and 6
new H2O molecules are made
 Water is split as a source of electrons from hydrogen atoms releasing O2 as a
byproduct
 Electrons increase potential energy when moved from water to sugar
therefore energy is required

Light-dependent Reactions
 Overview: light energy is absorbed by chlorophyll molecules-this
light energy excites electrons and boosts them to higher energy
levels. They are trapped by electron acceptor molecules that are
poised at the start of a neighboring transport system. The
electrons “fall” to a lower energy state, releasing energy that is
harnessed to make ATP

Energy Shuttling
 Recall ATP: cellular energy-nucleotide based molecule with 3
phosphate groups bonded to it, when removing the third
phosphate group, lots of energy liberated= superb molecule for
shuttling energy around within cells.
 Other energy shuttles-coenzymes (nucleotide based
molecules): move electrons and protons around within the cell
NADP+, NADPH NAD+, NADP FAD, FADH2

Light-dependent Reactions
 Photosystem: light capturing unit, contains chlorophyll, the light capturing
pigment
 Electron transport system: sequence of electron carrier molecules that
shuttle electrons, energy released to make ATP
 Electrons in chlorophyll must be replaced so that cycle may continue-these
electrons come from water molecules, Oxygen is liberated from the light
reactions
 Light reactions yield ATP and NADPH used to fuel the reactions of the Calvin
cycle (light independent or dark reactions)

Calvin Cycle (light independent or “dark” reactions)
 ATP and NADPH generated in light reactions used to fuel the
reactions which take CO2 and break it apart, then reassemble the
carbons into glucose.
 Called carbon fixation: taking carbon from an inorganic molecule
(atmospheric CO2) and making an organic molecule out of it
(glucose)
 Simplified version of how carbon and energy enter the food
chain

Harvesting Chemical Energy
 So we see how energy enters food chains (via autotrophs) we can
look at how organisms use that energy to fuel their bodies.
 Plants and animals both use products of photosynthesis (glucose)
for metabolic fuel
 Heterotrophs: must take in energy from outside sources, cannot
make their own e.g. animals
 When we take in glucose (or other carbs), proteins, and fats-these
foods don’t come to us the way our cells can use them

Cellular Respiration Overview
 Transformation of chemical energy in food into chemical energy
cells can use: ATP
 These reactions proceed the same way in plants and animals.
Process is called cellular respiration
 Overall Reaction:
– C6H12O6 + 6O2 → 6CO2 + 6H2O

Cellular Respiration Overview
 Breakdown of glucose begins in the cytoplasm: the liquid matrix
inside the cell
 At this point life diverges into two forms and two pathways
– Anaerobic cellular respiration (aka fermentation)
– Aerobic cellular respiration

C.R. Reactions
 Glycolysis
– Series of reactions which break the 6-carbon glucose molecule down into
two 3-carbon molecules called pyruvate
– Process is an ancient one-all organisms from simple bacteria to
humans perform it the same way
– Yields 2 ATP molecules for every one glucose molecule broken down
– Yields 2 NADH per glucose molecule

Anaerobic Cellular Respiration
 Some organisms thrive in environments with little or no oxygen
– Marshes, bogs, gut of animals, sewage treatment ponds
 No oxygen used= ‘an’aerobic
 Results in no more ATP, final steps in these pathways serve ONLY to
regenerate NAD+ so it can return to pick up more electrons and hydrogens in
glycolysis.
 End products such as ethanol and CO2 (single cell fungi (yeast) in beer/bread)
or lactic acid (muscle cells)

Aerobic Cellular Respiration
 Oxygen required=aerobic
 2 more sets of reactions which occur in a specialized structure
within the cell called the mitochondria
– 1. Kreb’s Cycle
– 2. Electron Transport Chain

Kreb’s Cycle
 Completes the breakdown of glucose
– Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen
atoms end up in CO2 and H2O
– Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to
produce NADH and FADH2
 Production of only 2 more ATP but loads up the coenzymes with
H+ and electrons which move to the 3rd stage

Electron Transport Chain
 Electron carriers loaded with electrons and protons from the Kreb’s
cycle move to this chain-like a series of steps (staircase).
 As electrons drop down stairs, energy released to form a total of
32 ATP
 Oxygen waits at bottom of staircase, picks up electrons and
protons and in doing so becomes water

Energy Tally
 36 ATP for aerobic vs. 2 ATP for anaerobic
– Glycolysis 2 ATP
– Kreb’s 2 ATP
– Electron Transport 32 ATP
36 ATP
 Anaerobic organisms can’t be too energetic but are important for
global recycling of carbon

Other modes of nutrition in plants :-
Parasitic plants :- are plants which do not have chlorophyll
and cannot prepare their own food. They get their food
from other plants called host . Eg :- Cuscuta ( Amarbel)

Insectivorous plants :- are plants which feed on insects. Eg:- Pitcher plant. The
leaf of the pitcher plant is modified into a pitcher. The end of the pitcher has a
lid which can open and close. When an insect enters the pitcher, the lid closes.
The insect is then digested by digestive juices inside the pitcher. Other
example is Venus flytrap, Nepenthes, Serracenia and Cephalotus

Saprotrophs :- are plants which do not have chlorophyll and cannot prepare their
on food. They get their food from dead and decaying organic matter. Eg :-
mushroom, bread mould etc. They produce digestive juice on the dead and
decaying organic matter and convert it into a solution and then absorb the
nutrients from the solution.

Symbiotic relationship :- Some plants live together and share shelter and
nutrients. Eg :- lichens. In lichens, an alga and a fungus live together. The
fungus provides shelter, water and minerals to the alga. The alga provides
food to the fungus which it prepares by photosynthesis.

How food is absorbed?
Mechanisms for the movement of nutrients into a
body system

Types of Nutritional Gain
 Holozoic nutrition
 method by which humans and other mammals feed
 Saprotrophic nutrition
 method by which fungi and many prokaryotes feed
 Parasitic nutrition
 method of feeding which has evolved in many different groups of
organisms, including various kinds of worms and fungi and a few
plants.

Glucose
 indirect active
transport
 involving the co-
transport of sodium
ions.
 Then facilitated
diffusion and simple
diffusion ,into the
tissue fluid inside
the villus and then
into blood capillary.

Amino-acids
In a fetus a newly born baby ,
some entire undigested
proteins can be absorbed by
pinocytosis.
 This is how babies are able to
absorb some of their mother’s
antibodies from the milk. This can
also happen to a small extent in
adults.
Absorbed into the villus cells by active
transport and pass out of the opposite side
by diffusion.

Fatty acids and glycerol
 Easily absorbed across the cell surface membrane
of the villus by simple diffusion.
 Once inside the cells, they are taken to the smooth
endoplasmic reticulum, then to the Golgi
apparatus, where they are surrounded in a coat of
protein.
 These tiny structures ranging from 100 to 600nm
in diameter ,are moved out of the villus by
exocytosis.
 Too big for blood so they absorb into the lymph
inside the lacteals from a milky emulsion, which is
what gives these structures their name.
 (‘Lact’ means ‘to do with milk’).

Vitamins
 Absorbed in the small intestine
 The fat-soluble vitamins A, D, and E can simply cross the cell
surface membranes by diffusion
 The water –soluble vitamins, such as vitamin C and the many
types of B vitamins are moved across the cells surface
membranes by specific transport.
 Vitamin B can only be adsorbed in combination with intrinsic factor.

Water and Inorganic Ions
 Considerable amounts of sodium, chloride, calcium, and irons
are also adsorbed in small intestine
 Calcium is helped by the presence of vitamin D.
 Iron is helped by citrate ions and ascorbic acid, both of which
is found in citrus fruits.
 Why fresh fruits and vegetables in the diet can help to prevent
anemia.
 On the other hand, drinking to much tea can hinder irons absorption,
because tannins in the tea react with irons to produce compounds
which cannot be adsorbed.

Liquid vs. Pill
Vitamin Filtering Begins

Liquid vs. Pill
Pill Vitamin Looses 0.8 Ounces In Filtering Process

Liquid vs. Pill
Liquid Vitamin Looses 0.2 Ounces In Filtering Process

Liquid vs. Pill
Pill PillLiquid Liquid

Nutrient Requirements
• Humans require eight essential amino acids.
• All are available in milk, eggs, or meat, but not in all
vegetables.
• Thus, vegetarians must eat a mix of foods.

Heterotrophic Nutrition: When an
organism takes food from another
organism, it is called heterotrophic
nutrition. Different heterotrophic
organisms follow different methods to
take and utilize food. Based on this,
heterotrophic nutrition can be divided
into two types:

(a) Saprophytic Nutrition: In saprophytic nutrition,
the digestion of food takes place before ingestion of
food. This type of nutrition is usually seen in fungi and
some other microorganisms. The organism secretes
digestive enzymes on the food and then ingests the
simple substances. Saprophytes feed on dead
materials and thus help in decomposition dead
remains of plants and animals.

(b) Holozoic Nutrition: In holozoic nutrition, the
digestion of food follows after the ingestion of food.
Thus, digestion takes place inside the body of the
organism. Holozoic nutrition happens in five steps, viz.
ingestion, digestion, absorption, assimilation and
egestion.

• Describe the functions of main regions of the alimentary
canal and the associated organs: mouth, salivary glands,
oesophagus, stomach, duodenum, pancreas, gall
bladder, liver, ileum, colon, rectum, anus, in relation to
ingestion, digestion, absorption, assimilation and
egestion of food, as appropriate.
• Functions of a typical amylase, protease and lipase
(listing the substrate and end-products)

 Holozoic nutrition: feeding on ready-
made complex organic matter.

 The taking in of food (chemical
energy) by the body &
converting it into living matter

INGESTION
DIGESTION
ABSORPTION
ASSIMILATION
EGESTION
Taking in food
Breakdown of complex
food substances into smaller
soluble food substances
Digested food is absorbed
Into body cells
Absorbed food is use to
provide energy or form
new protoplasm
Removal of undigested food
5 processes in digestion

 Feeding/ Ingestion – intake
of food into the mouth.

 Digestion – large food molecules are
broken down into small, soluble and
diffusible molecules.
 2 types: Physical and chemical
digestions

1. Physical digestion refers to the
mechanical break up of food into
small particles which increases
its surface area for chemical
digestion. (E.g. Chewing,
stomach churning). It also mix
the digestive enzymes with the
food particles

1. Chemical digestions – breaking
of biomolecules like proteins,
starch and fats into small soluble
molecules which can be absorbed
by the cells. It involves digestive
enzymes and chemical reactions
like hyrolysis.

Why must food molecules be
broken down into smaller, simpler
forms before it can be absorbed by
the cells for other uses?
Cell membranes are
partially permeable
and only allow small
molecules to pass
through.

 Absorption – digested
food materials are taken
into the body cells.

 Assimilation – absorbed
food materials are converted
into new protoplasm or
used to provide energy.

 Egestion – elimination of
undigested food materials
(faeces)
Do not
confuse
Ingestion
with
Egestion!!!

Starch
Proteins PROTEASE
Lipids/ Fats
AMYLASE
LIPASE fatty acids &
glycerol
amino acids
maltose

The Digestive
System
Consists of:
1) The gut or alimentary
canal (9 m) from mouth
to anus.
2) Glands (A cell, tissue,
or organ that secretes a
chemical substance).
3) Associated organs.

1. Food enters through the mouth. This
process is called ingestion.
2. Teeth cuts food into small pieces. This
increases surface area to volume ratio
for enzyme to act more efficiently.

1. Salivary glands produce saliva to
moisten food.
2. Saliva also contains salivary amylase to
break down starch to maltose.
3. pH of saliva is neutral (around pH 7).

Starch Maltose
Salivary Amylase
Salivary amylase is active at pH 7.

1. Tongue rolls food into boli.
2. Food is swallowed and enters
the pharynx.

• Made up of a tubular
gut called the
alimentary canal.
• Food travels through
our body along the
alimentary canal
which is a continuous
tube beginning at the
mouth and ending at
the anus.
• The parts of the gut
includes: mouth,
pharynx, oesophagus,
stomach, small
intestine, large
intestine and anus.
mouth
stomach
oesophagus
small intestine
pharynx
large intestine
anus
Rectum

 Mouth & salivary glands
 Pharynx, Oesophagus
 Stomach
 Small intestine- duodenum &
ileum
 Associated organs-liver, gall
bladder, pancreas
 Large intestine- colon, rectum
 Anus

mouth
stomach
oesophagus
duodenum
pharynx
colon/ large intestine
anus
liver
gall bladder
pancreas
ileum
rectum
jejunum
salivary gland

• Nutrition (Definition)
• 5 Processes of Nutrition
• Digestive Enzymes
• Alimentary Canal
• Alimentary Canal & Accessory Organs
What we learn today.

liver
gall bladder
pancreas
ileum
rectum
jejunum
salivary gland
colon/ large intestine
anus
duodenum
oesophagus
mouth
pharynx
stomach

GI (gastrointestinal) tract = alimentary canal

 Digestion is the breakdown
of large, complex organic
molecules into smaller
components that can be
used by the body.
 Molecules need to be small
enough to diffuse across
plasma membranes.

 Ingestion – this is the consumption of or taking in of
nutrients.
 Digestion – the chemical breakdown of large organic
molecules into smaller components by enzymes.
 Absorption – the transport or delivery of digested nutrients to
body tissues.
 Assimilation – absorbed food materials are converted into new
protoplasm or used to provide energy.
 Egestion – the elimination of food waste materials from the
body.

 Food enters the human
digestive tract through the
mouth or oral cavity.
 Humans are considered
chunk feeders because they
consume chunks of food
that are then mechanically
broken down.

 The human digestive tract
is often referred to as the
alimentary canal.
 The alimentary canal of a
normal adult is
approximately 6.5 to 9
meters long.

 Mouth
◦ mechanical digestion
 teeth
 breaking up food
◦ chemical digestion
 saliva
 amylase
 enzyme digests starch
 mucin
 slippery protein (mucus)
 protects soft lining of digestive system
 lubricates food for easier swallowing
 buffers
 neutralizes acid to prevent tooth decay
 anti-bacterial chemicals
 kill bacteria that enter mouth with food

 Physical breakdown of food
begins with the teeth grinding
the food and increasing its
surface area. An increase
surface area allows for easier
chemical digestion
 Bacteria living in the mouth can
feed off of nutrients sticking to
the teeth and cause tooth decay.

 Saliva is released from the
salivary glands and begins
chemical digestion of
starches. Saliva contains
the enzyme salivary
amylase which breaks down
starches into simpler
carbohydrates.

 As the food particles
dissolve in the saliva they
penetrate the cells of the
taste buds located on the
tongue and cheeks.
 Humans can differentiate
between sweet, sour, salty
and bitter.

 Saliva also lubricates the
food and helps to form a
bolus, the ball of food that
is swallowed.

 The bolus of food moves
down the esophagus
propelled by wave-like
muscular contractions
known as peristalsis.
 Peristalsis moves food all
the way through the
gastrointestinal tract.

mouth
break up food
digest starch
kill germs
moisten food

 Chemical and
mechanical
digestion.
 Food is chewed
(masticated)
mechanically.
 A bolus (lump) is
formed with saliva
and the tongue.

Food is taken into the body through the mouth. This process is
called ingestion. In the mouth the food is broken down into smaller
pieces by the teeth. The mouth has salivary glands which secrete
saliva. The saliva breaks down starch into sugars. The tongue helps
to mix the food with saliva and swallow the food.

Babies do not have teeth. Humans grow two sets of teeth. The first
set of teeth begins to grow during infancy. This set of teeth is
called milk teeth. These fall off between the ages of six and eight.
The second set of teeth, which replaces the milk teeth, is called
the permanent teeth. This set lasts throughout our life, unless it falls
off during old age.
Teeth help in breaking down the food into smaller particles so that
swallowing of food becomes easier. There are four types of teeth in
human beings. They are incisors, canines, permolars and molars.

 The incisor teeth are used for cutting the food.
 The canine teeth are used for tearing the food and for cracking
hard substances.
 The premolars are used for coarse grinding of food.
 The molars are used for fine grinding of food.
 Number of teeth
Type of teeth Lower jaw Upper jaw Total
Incisors 4 4 8
Canines 2 2 4
Premolars 10 10 20
molars

Dental Formula
 Dental formula for milk teeth in humans is 2120/2120. It means that each half of upper
jaw and lower jaw has 2 incisors, 1 canine and 2 premolars. Molars are absent in milk teeth.
There are 20 teeth in the milk teeth set.
 Dental formula for permanent teeth in human is 2123/2123. It means that each half of
upper jaw and lower jaw has 2 incisors, 1 canine, 2 premolars, and 3 molars.
 The dental formula in dogs (carnivore) is 3142/3143
 The dental formula in rabbits (herbivore) is 2033/1023

Structure of Tooth
The vertical section of tooth shows the following parts
• The crown − the part lying above the gums
• The neck − it connects the crown with the root
• The root − it lies buried inside the gums and supports the tooth
The white part of the tooth is called the enamel, it consists of calcium salts.
Inner to the enamel is the dentine which is a solid tissue and contains strands of
cytoplasm in it.
The dentine encloses a cavity known as the pulp cavity. This cavity supplies the tooth
with nerves and blood capillaries.
At the root of the tooth is a bone like material called the cement which holds the
tooth firmly to the socket.

Tooth decay
A number of bacteria are present in our mouth, though
not all of them are harmful. However, irregular and
improper cleaning of teeth can lead to the growth of
several harmful bacteria in our mouth. These bacteria
break down the sugar present in leftover food
particles and release acids in the mouth, which damage
the teeth. This is known as tooth decay. This condition
can lead to severe toothache. It can also result in
untimely loss of teeth.
Tooth decay can occur because of consuming
chocolates, sweets, cold drinks, and other sugar
products.

How can tooth decay be prevented?
Tooth decay can be prevented by
maintaining oral hygiene, which includes
the proper cleaning of teeth. Teeth must
be brushed twice a day after meals
using dantun or dental floss.

The tongue has taste buds to detect different tastes of food. The
different regions of the tongue detect different tastes.

 Epiglottis
◦ flap of cartilage
◦ closes trachea (windpipe) when swallowing
◦ food travels down esophagus
 Peristalsis
◦ involuntary muscle contractions to move food along

1. Chewing a saltine? -
2. Saliva breaking the saltine down into molecules
of glucose? -
3. Your tongue breaking pieces of a hamburger
apart?
4. Pepsin (an enzyme) in your stomach breaking
the hamburger into amino acids?

 The back of the
throat.
 Larynx- passage
for air, closes
when we
swallow.
 Is approximately
15cm long.

 Groups of
specialized
secretory cells.
 Found in the
lining of the
alimentary canal
or accessory
organs.

 series of involuntary
wave-like muscle
contractions which
move food along the
digestive tract
Peristalsis

 The stomach acts as a
temporary storage site for food.
Food usually spends about 4
hours in the stomach. It has
ridges which allow it to expand
to store about 1.5 litres of food.
 The stomach is also the site of
initial protein digestion.

 Movement of food into and out of the
stomach is controlled by circular
muscles known as sphincters.
 One at the top of the stomach allows
food from the esophagus to enter and
prevents food from going back up into
the esophagus.
 Another located at the bottom slowly
releases partially digested food into
the small intestine. The partially
digested food is called chyme.

 Millions of cells lining the stomach secrete various fluids
known collectively as gastric fluids.
 Gastric fluid consists of mucus, hydrochloric acid,
pepsinogens and other substances.
 Mucus coats and protects the lining of the stomach.
Hydrochloric acid kills any harmful substances that have
been ingested and it also converts pepsinogen into pepsin.
 Pepsin is a protein digesting enzyme that breaks large
protein chains into smaller chains.

 The pH environment of the
stomach normally ranges
between 2.0 and 3.0 on the
pH scale.
 The high acidity allows
pepsin to work and makes
the HCL effective at killing
pathogens

 An stomach ulcer is a lesion in
the lining of the stomach. It
occurs when the protective
mucus lining breaks down and
the cell membranes are exposed
to the HCl and pepsin
 Most stomach ulcers are linked
to the bacterium shown on the
right known as Heliobacter
pylori.

 An endoscope (shown on the
right) can be used to view
things such as stomach ulcers
or as shown below, a tumor
growing in the large intestine.
 The endoscope can also extract
small pieces of tissue for a
biopsy.

 Food is temporarily
stored here.
 Gastric juices are
secreted.
 Has layers of
muscle that line the
inside.
 Mechanically and
chemically breaks
down food.

 Functions
◦ food storage
 can stretch to fit ~2L food
◦ disinfect food
 HCl = pH 2
 kills bacteria
 pepsin
 enzyme breaks down proteins
But the stomach is made out of protein!
What stops the stomach from digesting
itself?
mucus secreted by stomach cells protects
stomach lining

stomach
kills germs
break up food
digest proteins
store food
sphincter
sphincter
mouth
break up food
digest starch
kill germs
moisten food

 Secreted by the stomach.
 Acidic (pH 1.5-2.5) (HCl).
 Pepsin- an enzyme that
breaks down large
proteins into amino
acids.
 Food is further broken
down into a thin liquid
called chyme.

Pancreas
Gall Bladder
Spleen

 Pouch structure located near the liver which
concentrates and stores bile
 Bile duct – a long tube that carries BILE. The
top half of the common bile duct is associated
with the liver, while the bottom half of the
common bile duct is associated with the
pancreas, through which it passes on its way
to the intestine.

 Bile emulsifies lipids (physically breaks apart
FATS)
 Bile is a bitter, greenish-yellow alkaline fluid,
stored in the gallbladder between meals and
upon eating is discharged into the duodenum
where it aids the process of digestion.

 An organ which secretes both digestive enzymes
(exocrine) and hormones (endocrine)
 ** Pancreatic juice digests all major nutrient types.
 Nearly all digestion occurs in the small intestine &
all digestion is completed in the SI.

 Digestive enzymes
◦ digest proteins
 trypsin, chymotrypsin
◦ digest starch
 amylase
 Buffers
◦ neutralizes
acid from
stomach

 Function
◦ produces bile
 bile stored in gallbladder until needed
 breaks up fats
 act like detergents to breakup fats
bile contains
colors from old
red blood cells
collected in liver
=
iron in RBC rusts &
makes feces brown

pancreas
produces enzymes to
digest proteins & starch
stomach
kills germs
break up food
digest proteins
store food
mouth
break up food
digest starch
kill germs
moisten food
liver
produces bile
- stored in gall bladder
break up fats

 The intestines are named
for their diameter, not
length.
 The small intestine is up to
7 m in length but only 2.5
cm in diameter.
 The large intestine is only
1.5 m in length but 7.6 cm
in diameter.

 In mammals the length of the
small intestine is directly related
to their diet.
 Due to the fact that meats are
easier to digest than plant
materials, carnivores (lion) will
have a shorter intestine than
herbivores (rabbit). The length
of the digestive tract of
omnivores falls somewhere in
the middle.

 The majority of chemical
digestion occurs in the first of
three sections of the small
intestine known as the
duodenum.
 This section also contains an
opening from the bile duct and
pancreatic duct through which
bile and pancreatic enzymes
enter the small intestine.

 Food enters the small intestine
as a semi-solid mixture known
as chyme. The chyme is acidic
due to the HCl in the stomach
so it needs to be neutralized.
 The presence of chyme in the
small intestine triggers the
conversion of prosecretin into
secretin which is absorbed into
the blood stream and carried to
the pancreas

 Most chemical
digestion takes place
here.
 Simple sugars and
proteins are absorbed
into the inner lining.
 Fatty acids and
glycerol go to
lymphatic system.
 Lined with villi, which
increase surface area
for absorption, one
cell thick.

 Function
 major organ of digestion & absorption
◦ absorption through lining
 over 6 meters!
 small intestine has huge surface area = 300m2
(~size of tennis court)
 Structure
◦ 3 sections
 duodenum = most digestion
 jejunum = absorption of nutrients & water
 ileum = absorption of nutrients & water

 1st section of small intestines
◦ acid food from stomach
◦ mixes with digestive juices from:
 pancreas
 liver
 gall
bladder

stomach
kills germs
break up food
digest proteins
store food
mouth
break up food
digest starch
kill germs
moisten food
pancreas
produces enzymes to
digest proteins & starch

 Much absorption is thought to occur directly through
the wall without the need for special adaptations
 Almost 90% of our daily fluid intake is absorbed in the
small intestine.
 Villi - increase the surface area of the small intestines,
thus providing better absorption of materials

 Absorption through villi & microvilli
◦ finger-like projections
◦ increase surface area for absorption

 The pancreas is an accessory
organ of the digestive system.
It releases chemicals to aid in
digestion.
 Secretin will stimulate the
pancreas to release a solution
containing bicarbonate ion into
the small intestine where it will
neutralize the acidic chyme and
raise the pH from 2.5 to 9.0.
This inactivates the pepsin.

 The pancreas also releases digestive enzymes that break
down the three macromolecules: carbohydrates, lipids and
proteins.

 Trypsinogen, a protein-
digesting enzyme is released
into the small intestine where it
is convertes into trypsin and it
breaks down large protein
chains into smaller chains.
 The final step in protein
digestion occurs with the
release of erepsins from the
pancreas and they break the
smaller chains into individual
amino acids.

 Amylase enzymes are released
from the pancreas that break
large carbohydrate chains into
small chains called
disaccharides.
 Then the small intestine
releases disaccharide enzymes
which break those small chains
into individual sugars.

 The pancreas also releases
enzymes known as lipases that
break down fats into fatty acids
and glycerol.
 The lipases include pancreatic
lipase and phospholipase.
 Before lipids can be broken
down by lipases they must first
be emulsified.

 The liver is a large
accessory organ of the
digestive system that is
constantly producing a
fluid known as bile.
 Bile is stored in the gall
bladder until it is needed in
the small intestine.

 The presence of lipids in the
small intestine trigger the
release of the hormone
cholecystokinin (CCK) which
triggers the release of bile from
the gall bladder.
 Bile contains bile salts that
emulsifies fats which means it
breaks them into smaller
droplets so they can be
digested.

 Bile contains cholesterol
which can acts as a binding
agent and cause bile salts
to crystallize into
gallstones.
 Gallstones can block the
bile duct and inhibit fat
digestion while causing a
lot of pain.

 Jaundice is a yellow
discoloration of the skin and
tissues caused by a collection of
bile pigments in the blood.
 The pigments are a result of the
liver breaking down hemoglobin
from red blood cells and the
products are stored in the gall
bladder.

 The liver is also able to detoxify
many substances in the body by
making them soluble and they
can then be dissolved in the
bloodstream and eliminated in
urine.
 One example would be alcohol.
Alcohol can damage liver cells
which are replaced by
connective tissues and fat. The
result is cirrhosis of the liver
(shown left).

 Chemical digestion of
nutrients is completed by
the time it reaches the
large intestine.
 Now that nutrients are
small enough they need to
be absorbed into the blood
stream so they can diffuse
inside cells.

 The large intestine or colon
stores waste products long
enough so that water can
be reabsorbed from the
wastes.
 Along with the water, some
inorganic salts, minerals
and vitamins are absorbed.

 The large intestine is home
to several different types of
bacteria.
 These bacteria use waste
materials to synthesize
vitamins B and K. This is
an example of a symbiotic
relationship.

 Cellulose is a long chain
carbohydrate found in the
cell wall of plant cells.
 Humans cannot digest
cellulose however it
provides bulk which
promotes the movement of
the waste products out of
the colon.

 Cellulose is more commonly
known as fiber. Fiber helps to
remove wastes and therefore
toxins from the body.
 If you have a diet low in fiber
you will have fewer bowel
movements which means toxins
remain in your body for longer
periods of time.

 Most nutrients are absorbed in
the small intestine.
 The small intestine is lined with
millions of small finger-like
projections known as villi. The
villi increase the surface are of
the small intestine which
increases it’s ability to absorbed
digested nutrients.

 Each villus contains a capillary
network along with a lacteal.
 End products of protein and
carbohydrate digestion enter
the capillary network.
 End products of fat digestion
are absorbed into the lacteal.
The lacteal is a vessel of the
lymphatic system.

 Function
◦ re-absorb water
 use ~9 liters of water every
day in digestive juices
 > 90% of water reabsorbed
 not enough water absorbed
 diarrhea
 too much water absorbed
 constipation

 Solid materials pass
through the large intestine.
 These are undigestible
solids (fibers).
 Water is absorbed.
 Vitamins K and B are
reabsorbed with the water.
 Rectum- solid wastes exit
the body.

 Living in the large intestine is a community
of helpful bacteria
◦ Escherichia coli (E. coli)
 produce vitamins
 vitamin K; B vitamins
 generate gases
 by-product of bacterial metabolism
 methane, hydrogen sulfide

 Last section of colon
(large intestines)
◦ eliminate feces
 undigested materials
 extracellular waste
 mainly cellulose
from plants
 roughage or fiber
 masses of bacteria

 ULCERS – erosion of the surface of the
alimentary canal generally associated with
some kind of irritant

 CONSTIPATION – a
condition in which the
large intestine is emptied
with difficulty.
 Too much water is
reabsorbed
 and the solid waste
hardens

 DIARRHEA – a gastrointestinal
disturbance characterized by
decreased water absorption and
increased peristaltic activity of the
large intestine.
 This results in increased, multiple,
watery feces.
 This condition may result in severe
dehydration, especially in infants

 APPENDICITIS – an inflammation of the appendix due to
infection
 Common treatment is removal of the appendix via surgery

 GALLSTONES – an accumulation of
hardened cholesterol and/or calcium
deposits in the gallbladder
 Can either be “passed” (OUCH!!) or
surgically removed

 ANOREXIA NERVOSA - a psychological
condition where an individual thinks they
appear overweight and refuses to eat.
 Weighs 85% or less than what is
developmentally expected for age and height
 Young girls do not begin to menstruate at the
appropriate age.

 HEART BURN – ACID from the stomach
backs up into the esophagus.

Chapter 6 life processes 1 (introduction, nutrition and digestion)

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Chapter 6 life processes 1 (introduction, nutrition and digestion)