ENERGY IN FOOD
Enzymes and PH
Digestive System
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 Organisms
must obtain energy to carry
out life processes
 Amount of energy in food is measured in
Calories
 Food also contains raw materials
(nutrients) used to build/repair body
tissues
2
 Nutrients
1.
2.
3.
4.
5.
6.
supplied by food:
Water
Carbohydrates
Lipids
Proteins
Vitamins
Minerals
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 Breaks
up food – physically & chemically
 Stores food for a short time
 Absorbs digested nutrients and passes
them into circulatory system
 Stores & eliminates undigested materials
from body
4
 Types
1.
2.
of digestion:
Mechanical – physical breakdown of
food by non-chemical means
Chemical – the use of enzymes & other
chemicals to break down food
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 Consumers
must be able to break down
food into molecules that can be absorbed
& used by cells
 In many multicellular organisms, this is
accomplished by a digestive system
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 Enzyme
– specialized proteins that act as
biological catalysts
 Catalyst – substance that speeds up
chemical reactions & remains unchanged
by the reaction
 All the activities of living things are
controlled by chemical reactions
 Without enzymes, these reactions would
not happen and the organism would die
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 Activation
energy – amount of energy
needed to get a chemical reaction started
 Chemical reaction – the breaking down
and/or forming of new compounds
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 Are:
a 3-dimentional protein
 Have: a specific area that attaches to the
chemical compound undergoing a
change (active site)
 Fit: like a puzzle piece to one type of
compound (substrate)
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 Need:
specific pH range
 Require:
constant body temperature to
work correctly
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 When
the enzyme bids with its specific
substrate, changes occur in the enzyme
at the active site
 This change is called induced fit and it
enhances the ability of the enzyme to
break down the substrate
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 Denature
– a change in the shape of an
enzyme; caused by change in pH or fever
 If the enzyme is missing or denatured,
the reaction cannot happen
 Example: lactose intolerance
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Inhibitors – keep something from working correctly
 Competitive:
 Allosteric
• Chemicals that
• Chemicals that bond
resemble the enzyme’s
normal substrate
• Compete with
substrate
to a another part of the
enzyme
• Changes shape of
active site
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Pathway of the Digestion
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 Digestion
1.
2.
begins in the mouth with:
Mechanical – teeth and tongue
chop/mix food
Chemical – salivary glands add enzyme
amylase to break down starches into
simple sugars
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 Food
moves into pharynx at back of
throat; opening for 2 tubes that lead to 2
systems
1. Esophagus – digestive
2. Trachea – respiratory
 Epiglottis – flap of
tissue that covers
opening not being used
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 Peristalsis
– one way movement of
materials through digestive system;
controlled by smooth muscle contraction
 Food moves down esophagus into
stomach:
1. Has a pH of 2 (hydrochloric acid)
2. Secretes enzyme pepsin (acts on
proteins)
3. Mechanical & physical digestion
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 After
~2 hours, food leaves stomach and
enters small intestine:
1. 7 m long – 2.5 cm diameter
2. Multiple enzymes secreted to break
down lipids and nucleic acids
3. Other enzymes used to complete break
down of carbs and proteins
4. Most absorption of nutrients occurs
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 Anatomy
inside of small intestine:
• Villi – fingerlike projections that absorb
nutrients from small intestine
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 Accessory
1.
2.
3.
organs of small intestine:
Pancreas – secretes enzymes that work
on carbs, protein and lipids; helps
regulate blood sugar; also secretes
sodium bicarbonate that neutralizes
stomach acid
Liver – produces bile to dissolve fats
Gall bladder – stores bile
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 Accessory
organs of digestive system:
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 After
4-6 hours what is left of your food
enters large intestine:
1. ~1.5 m long – 6 cm diameter
2. 3 sections – cecum, colon & rectum
3. Absorbs water and salts
4. Colonies of E.coli break down rest of
undigested material and produce
Vitamin K (needed for blood clotting)
5. Solid waste is stored in rectum &
excreted though anus
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 Anatomy
of large intestine:
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