Transcript Enzymes and the digestive system

Enzymes and the digestive
system
2.1 Enzymes and digestion
21/07/2015
1
Settler Activity: Can you find today's
16 key words?
O
L
E
S
A
R
D
Y
H
O
B
R
A
C
E
E
E
N
I
T
S
E
T
N
I
L
L
A
M
S
S
T
N
O
I
T
S
E
G
E
Q
U
A
R
A
O
A
S
S
I
X
B
T
A
E
M
Y
Z
N
E
P
F
N
A
K
T
B
F
Z
D
U
N
T
S
T
H
N
U
E
H
C
A
M
O
T
S
S
F
L
O
A
G
E
R
S
D
I
L
A
Y
F
S
E
I
R
G
A
E
C
E
B
D
P
I
O
K
N
B
P
P
U
I
V
N
R
E
C
T
U
M
N
U
R
A
E
S
D
N
A
L
G
Y
R
A
V
I
L
A
S
T
N
H
O
P
H
Y
D
R
O
L
A
S
E
E
N
E
W
E
C
B
H
Y
D
R
O
L
Y
S
I
S
T
E
N
I
T
S
E
T
N
I
E
G
R
A
L
A
A
B
S
O
R
P
T
I
O
N
I
O
N
T
21/07/2015
2
Learning Objectives
All students should be able to:
• Define digestion.
• Give the structure and function of the major
parts of the digestive system.
• Understand how the digestive system breaks
down food both physically and chemically.
• Understand the role of villi and microvilli.
• Outline the role of enzymes in digestion.
Specification reference: 3.1.2
21/07/2015
3
Success Criteria
• I can rearrange fragments of a sentence to give the
correct definition of digestion.
• I can label the digestive system.
• I can name the structures of the digestive system when
given their function and vice versa.
• I can draw a labelled diagram of the lining of the small
intestine and answer questions related to its key
features.
• I can answer exam questions on digestion and digestive
enzymes.
21/07/2015
4
Starter Activity: Can you rearrange
these fragments of a sentence to give
the correct definition of digestion?
hydrolysed by
Digestion
Digestion is
the
process in which large
and
assimilated.
molecules
are
hydrolysed
by
enzymes
molecules which
molecules are
into small molecules which can be
enzymes
which large
absorbed and assimilated.
can be
into small
21/07/2015
absorbed
is the process in
5
Activity 1: The human digestive system
• The human digestive system is made up of a long
muscular tube and its associated glands.
• The glands produce enzymes that break down
large molecules into small ones ready for
absorption.
• The digestive system therefore provides an
interface with the environment because food
substances enter the body through it.
Missing words: small interface glands enter
enzymes muscular large absorption
21/07/2015
6
Activity 2: Can you label the human
digestive system?
X
W
A
V
B
C
U
D
T
E
F
G
S
R
Q
21/07/2015
P
O
N
M
H
I
J
K
L
7
Activity 4: Question 1
• Which parts of the digestive system
does the food pass through?
• Mouth, oesophagus, stomach, small
intestine (duodenum, jejunum,
ileum), large intestine (caecum,
colon, rectum), anus.
21/07/2015
8
!!!
• The contents of the intestines are
NOT inside the body! Molecules
and ions only truly enter the body
when they cross the cells and
cell-surface membranes of the
epithelial lining of the intestines.
21/07/2015
9
???
Activity 5: How well do you
know the major parts of the
digestive system?
???
21/07/2015
10
This part is the final section of
the intestines. The faeces are
stored here before
periodically being removed
via the anus in a process
called egestion.
RECTUM
21/07/2015
11
These are situated near the
mouth. They pass their
secretions via a duct into the
mouth. These secretions
contain the enzyme amylase,
which breaks down starch
into maltose.
SALIVARY
GLANDS
21/07/2015
12
This part is a muscular sac with an
inner layer that produces enzymes.
Its role is to store and digest food,
especially proteins. It has glands
that produce enzymes which digest
protein. Other glands in its wall
produce mucus. The mucus
prevents this organ being digested
by its own enzymes.
STOMACH
21/07/2015
13
This is a large gland situated
below the stomach. It
produces a secretion. This
secretion contains proteases to
digest proteins, lipase to digest
lipids and amylase to digest
starch.
PANCREAS
21/07/2015
14
LARGE
INTESTINE
This part absorbs water. Most of
the water that is reabsorbed
comes from the secretions of the
many digestive glands. The food
within this part therefore becomes
drier and thicker in consistency and
forms faeces.
21/07/2015
15
This is a long muscular tube. Food is
further digested here by enzymes that are
produced in its walls and by glands that
pour their secretions into it. The inner
walls of this organ are folded into villi,
which gives them a large surface area. The
surface area of these villi is further
increased by millions of tiny projections,
called microvilli, on the epithelial cells of
each villus. This adapts this organ for its
purpose of absorbing the products of
digestion into the bloodstream.
SMALL
INTESTINE
21/07/2015
16
The lining of the small intestine
21/07/2015
17
This part carries food from
the mouth to the stomach.
It is therefore adapted for
transport rather than for
digestion or absorption. It is
made up of a thick muscular
wall.
OESOPHAGUS
21/07/2015
18
Activity 6: Question 1
• Can you distinguish between the terms
‘absorption’ and ‘assimilation’?
• Taking soluble molecules into the
body. (Absorption)
• Incorporating absorbed molecules
into body tissues. (Assimilation)
21/07/2015
19
!!!
• All organisms are made up of the
same biological molecules and
therefore our food consists almost
entirely of other organisms or parts
of them. We must first break them
down into molecules that are small
enough to pass across cell surface
membranes.
21/07/2015
20
Activity 6: Question 2
• Unscramble the anagrams to reveal
the two stages of human digestion.
breakdown)
•(Physical
Hysipalc robewkand
•(Chemical
Halcmice digestion)
tindogies
21/07/2015
21
Activity 7: Physical Digestion
• If the food is large, it is broken down into
smaller pieces by means of structures such as
the teeth. This not only makes it possible to
ingest the food but also provides a large
surface area for chemical digestion. Food is
churned up by the muscles in the stomach
wall and this also physically breaks it up.
Missing words: surface area physically
stomach teeth chemical ingest large
muscles
21/07/2015
22
Activity 8: Chemical Digestion
• This breaks down large, insoluble molecules into smaller, soluble
ones. It is carried out by enzymes.
• All digestive enzymes function by hydrolysis (the splitting up of
molecules by adding water to the chemical bonds that hold them
together). The general term for such enzymes is hydrolases.
• Enzymes are specific and so it follows that more than one enzyme
is needed to break down a large molecule. Usually one enzyme
splits a large molecule into sections and these sections are then
hydrolysed into smaller molecules by one or more additional
enzymes.
Missing words: specific enzymes hydrolysed hydrolysis smaller
large additional insoluble soluble hydrolases splits
21/07/2015
23
Activity 9: Question 1
• Can you name the three different
types of digestive enzyme?
1. These
breakdown carbohydrates,
Carbohydrases
ultimately to monosaccharides.
2. These
breakdown lipids (fats and oils)
Lipases
into glycerol and fatty acids.
3. These breakdown proteins, ultimately
Proteases
to amino acids.
21/07/2015
24
Chemical digestion continued...
• Once the large food molecules have been hydrolysed into
monosaccharides, glycerol, fatty acids and amino acids,
they are absorbed by various means from the small
intestine into the blood.
• They are carried to different parts of the body and are
often built up again into very large molecules, although
these are not necessarily of the same type as the molecules
from which they were derived.
• These molecules are incorporated into body tissues and/or
used in processes within the body.
This is called
assimilation.
Missing words: fatty acids, tissues, large,
monosaccharides, glycerol, amino acids, assimilation,
derived, blood,
21/07/2015
25
Plenary Activity: Answer these 4
questions under test conditions!
1. State one way in which the stomach is adapted:
a) To churn food
b) To prevent the enzymes it produces from
digesting the surface of the stomach.
2. What is hydrolysis?
3. Which two structures produce amylase?
4. Suggest a reason why the stomach does not
have villi or microvilli.
21/07/2015
26
Answers
1.
a. By having a muscular wall.
b. By secreting mucus.
2. Hydrolysis is the breakdown of molecules by the
addition of water to the bonds that hold these
molecules together.
3. Salivary glands, pancreas
4. Villi and microvilli increase surface area to speed
up the absorption of soluble molecules. As the
food in the stomach has not yet been broken
down into soluble molecules they cannot be
absorbed and so villi and microvilli are
unnecessary.
21/07/2015
27
Learning Objectives
All students should be able to:
• Define digestion.
• Give the structure and function of the major
parts of the digestive system.
• Understand how the digestive system breaks
down food both physically and chemically.
• Understand the role of villi and microvilli.
• Outline the role of enzymes in digestion.
Specification reference: 3.1.2
21/07/2015
28