Title: Unit 2: The continuation of life
1Unit 2 The continuation of life
Higher Human Biology
- Chapter 22
- Delivery of Materials to cells (NUTRIENTS)
2- To understand how nutrients are delivered by the
bloodstream to every living cell in the body..
- Explain how glucose and amino acids, the end
products of digestion of carbohydrates and
proteins, are absorbed into the blood stream. - Identify the parts of a villus and explain how it
is adapted to its function. - Describe the role of the lacteal in transport of
absorbed lipid.
3Preparation for nutrient absorption
Food is moved along the alimentary canal from the
mouth, to the small intestine by peristalsis.
As this happens digestive enzymes breakdown..
View the Peristalsis animation
http//www.westga.edu/lkral/peristalsis/
4SG Revision Labelling exercise
Rectum
Large intestine
Gall bladder
anus
liver
Oesophagus
Salivary glands
Small intestine
stomach
appendix
mouth
Pancreas
5Enzymes Scholar Activity
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7Digestive Enzymes revision
Digestive enzymes at various parts of the
digestive system act on different types of food
molecule
81. Small Intestine
91. Small Intestine
The small intestine is well suited to food
absorption because
3. Each villus has a lacteal blood capillary
network for efficient transport of absorbed
substances
10(No Transcript)
112. Absorption of nutrients
- Glucose and amino acids, the soluble end products
of carbohydrate and protein digestion, are
absorbed into the epithelial cells from where the
pass directly into the blood capillaries. - The products of lipid digestion also pass to
epithelial cells but instead of blood capillaries
enter the central lacteal.
122. Absorption of nutrients
- Nutrients requiring no digestion by enzymes are
also absorbed by the lining of the small
intestine. These include calcium, iron and many
vitamins. - Remember Vit B12 can only be absorbed if
intrinsic factor (a poly peptide made by the
stomach) is present to stimulate endocytosis by
the membrane of the epithelial cells.
132. Absorption of nutrients
Absorbed into blood
large insoluble food molecules
small soluble molecules
B L O O D
Glucose
Carbohydrates
amino acids
Proteins
fatty acids and glycerol phosphates
Lipids
Absorbed into lacteal
Nutrients that dont need to be digested (e.g.
calcium, iron vitamins) by enzymes are also
absorbed by the small intestine.
14- To understand how nutrients are delivered by the
bloodstream to every living cell in the body.
- Carry out an experiment to examine the effects of
bile salts - i) as an emulsifier and
- ii) on the activity of lipase
15Bile salts
Bile salts are.
Produced in the liver
Stored in the gall bladder.
Pass into the small intestine via the bile duct
16Bile salts help us break down fat
- Bile is necessary for efficient digestion of
lipids. During a meal, bile is secreted from the
gallbladder into the small intestine. In the
small intestine, bile helps to break dietary fat
into smaller particles, a process called
emulsification. Emulsified fat can be more easily
acted upon by digestive enzymes. Without bile,
digestion and absorption of fat is incomplete.
17Investigating the effect of bile salts as an
emulsifier
Lipids are, insoluble in water and less dense
than water (so float).
Shaken
Emulsifier a substance that preserves emulsion.
18Discussion
- In test tube A, when the layers are shaken
vigorously, the become mixed forming an EMUSION
of tiny oil droplets. - This does not last long the oil droplets settle
to the top into two distinct layers again.
- In test tube B, when the layers are shaken
vigorously, they again form EMUSION. - However in this case the emuslsuin does not
separate into two separate layers.
19Conclusion
- An EMULSIFYER is an agent which reserves an
emulsion. From this experiment it can be
concluded that bile salts act as an emulsifier.
20Action of Bile Salts
Bile salt molecule
- Tail
- lipid soluble
- hyrdophobic (water-hating)
- Head
- water soluble
- hyrdophilic (water-loving)
When shaken, with a lipid, the bile salt molecule
becomes attached to the lipid with the lipid
soluble tails pointing in to the centre.
The heads are negatively charged so the lipid
droplets repel each other and dont rejoin. This
is emulsification.
21FYI What are Gallstones
- Gallstones form when bile hardens into a small
pebble-like substance that can grow as big as a
golf ball due to high cholesterol, too much
bilirubin, or inadequate bile salts.
In the event, when gallstones clog these ducts,
it causes inflammation to the gallbladder wherein
if it stays there for a longer period of time, it
can result to a severe damage or infection to the
gallbladdder, liver or pancreas.
22Lipase
- A digestive enzyme made in the pancreas
- Active in the small intestine where it catalyses
the breakdown of lipid molecules by cleaving off
the first and third fatty acid molecules.
23Lipase
SUBSTRATE
END PRODUCTS
24Investigating the effect of bile salts on the
action of lipase
Shaken alkali added to make pH 7
then left for 30 mins in water bath at 37C
pH 4
pH 5
pH 7
25Investigating the effect of bile salts on the
action of lipase
- Here the lipid substrate is being used in olive
oil. - After 30 minutes the contents of tubes A and B
are found to show a drop in pH indicating the
presence of acidic conditions. - It is therefore concluded that lipase has
promoted the breakdown of lipid to fatty acids in
tubes A and B.
26Significance of the control tube
- Since no change in pH is found to occur in tube
C, it is concluded that lipase is required to
catalase the digestion of lipid and that bile
salts alone are unable to bring about the
digestive reaction
Comparing tube A and B
- A has undergone a greater drop in pH than B. It
is therefore concluded that more digestion of
lipid to fatty acids occurs when bile salts are
present.
27Why do bile salts aid digestion by lipase?
Bile salt molecules maintain an emulsion of lipid
droplets. This increases the relative surface
area of the lipid exposed to the lipase enzyme,
so increases the number of substrate molecules
that the enzyme can act on, thus aiding
digestion.
28Absorption of the end products of lipid digestion
Following digestion, monoglycerides and fatty
acids, the end products of lipid digestion,
combine with bile salts to form tiny
water-soluble particles called micelles.
Micelles move to the surface of the intestinal
epithelium, which has microvilli.
Fatty acids and monoglyceride molecules leave the
micelles and diffuse through the cell membrane
into the epithelium.
29Video Micelles
30Absorption of the end products of digestion
After passing through the epithelium of the
microvilli, the monoglycerides fatty acids pass
into the cells endoplasmic reticulum to be built
back into lipid molecules (triglycerides).
They are then coated with lipoprotein and move
out of the cell by exocytosis.
They get absorbed by the lacteal and are
transported via the lymphatic system to the blood.
31Task Torrance-TYK pg169 Qu 1-3
32- To understand how nutrients are delivered by the
bloodstream to every living cell in the body.
- Explain why the liver needs a dual blood supply
- Analyse data on the composition of plasma of
hepatic artery, hepatic vein and hepatic portal
vein.
334. The Liver
Hepatic vein carries deoxygenated blood from the
liver to the vena cava
Hepatic artery carries oxygenated blood to liver
Hepatic portal vein carries deoxygenated blood to
the liver directly from the gut
34Portal System
- The portal system is circulation where blood in a
capillary bed (e.g. gut) passes through a vein
(e.g. hepatic portal vein) and into a second
capillary bed (e.g. liver) before returning the
normal circulation system. - This prevents the end products of digestion
entering directly into the circulation system.
They are passed through the liver instead, which
removes anything toxic by metabolism or excretion
and converts nutrients into useable or stored
forms .
35Composition of plasma
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Hepatic vein contains normal blood plasma
concentrations of glucose amino acids high
urea concentration
Hepatic artery contains blood with all essential
nutrients normal urea concentration
Hepatic portal vein contains blood plasma with
high concentrations of the end products of
digestion normal urea concentration
- In liver
- excess glucose stored as glycogen
- excess amino acid converted to urea
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385. Role of the Liver in MetabolismA.
Carbohydrate metabolism
- Animals gain glucose by eating carbohydrates.
The liver regulates the concentration of the
glucose in the blood (blood sugar). - After a carbohydrate rich meal, blood entering
the liver by the hepatic portal vein contains a
concentration of glucose in excess of the bodies
immediate requirements. - In response to the hormone insulin from the
pancreas, an enzyme in the liver promotes the
conversion glucose to glycogen
395. Role of the Liver in MetabolismA.
Carbohydrate metabolism
- Up to 100g of excess glucose is stored in the
liver as glycogen. Any more excess glucose is
stored as lipids in the bodys fat reserves. - If glucose is needed the glycogen breaks down
releasing the glucose into the bloodstream. - When the bloods sugar level is low, a different
hormone called glucagon is secreted by the
pancreas. - This activates a different enzyme in the liver
which promotes the conversion of glycogen to
glucose. - Glucose is then released into the blood stream
for use by living cells.
405. Role of the Liver in MetabolismB. Lipids
Liver cells remove certain lipid molecules from
blood and alter them to make other lipids e.g.
cholesterol.
- Cholesterol in cell membranes needed to make
steroid hormones are synthesised in liver - Excess cholesterol is processed by the liver
excreted in bile
Lipoproteins - formed in the liver
41Fat-soluble vitamins are stored in liver cells
e.g. Vitamins A, D, E K
Image sources www.nlm.nih.gov
42Image sources www.nlm.nih.gov
43Image sources www.nlm.nih.gov
445. Role of the Liver in MetabolismC. Proteins
3 types of plasma proteins are made in the liver.
The amino acids needed for this are absorbed from
the bloodstream by liver cells.
Albumins Cause osmotic return of water from
tissue fluid in capillary beds
Globulins Cause transport of lipids and
fat-soluble vitamins
Fibrinogen Have an essential role in clotting of
blood .
Transaminase enzymes in liver cells can convert
one amino acid to another. So even when amino
acids arent obtained from food, many can be
synthesised by the liver cells.
456. Fate of absorbed materials
Material Use In Body Fate of Excess
Carbohydrate Glucose used by cells to obtain energy (for aerobic respiration) Stored as glycogen in liver and muscles as fat in fatty tissues
Lipids Used by cells as a source of energy Converted back to lipid stored in fatty (adipose) tissue
Proteins Amino acids used for protein synthesis (e.g. to produce enzymes, hormones, antibodies) NOT STORED some used as an energy source by cells following deamination in liver (converted to urea)
466. Fate of absorbed materials D. Vitamins
minerals
Some vitamins minerals absorbed from food play
a key role in enzyme reactions
- Metal ions
- Zinc
- Iron
- Copper
- Magnesium
Enzyme activators
Co-factors
Co-enzyme a small non-protein co-factor
composed of an organic substance (e.g. a
vitamins).
Iron the co-factor responsible for activating
the enzyme catalase.
Vitamin B an essential component of co-enzymes
acts as hydrogen carriers during aerobic
respiration
47- What is the function of villi?
- What is the name given to the central lymph
vessel in a villus? - Which foodstuffs are transported by lacteals.
- What substances are required for the proper
absorption of vit B12. - What is the name of the process in which amino
acids are broken down in the liver? - What is the toxic end-product of this process?
- Where is bile stored?
- What is the prime function of bile?
- What vitamins can be stored in the liver?
48- To increase the surface area of the small
intestine for the absorption of food. - Lacteal
- Fats.
- Intrinsic Factor
- Deamination
- Urea
- In the gall bladder
- Bile emulsifiers (breaks up) fats.
- A,B12 and D
49Label the diagram best you can to describe the
blood flow to the Liver
50Liver Morton sheet
Pulmonary Artery
Pulmonary Vein
Aorta
Vena cava
Hepatic Artery
Hepatic Vein
Hepatic Portal Vein
51Label A, B and C and organ X, try other bits if
you can
52Class Worksheet
Aorta
Hepatic Artery
Hepatic Vein
Vena Cava
Gall bladder
Hepatic Portal Vein
53Essay Questions 2005
- Describe the functions of the liver under the
following headings - Production of urea. (2)
- Metabolism of carbohydrates. (5)
- Breakdown of red blood cells. (3)
54Task Torrance-TYK pg172 Qu 1-4
55Task Torrance AYK pg173-4 Qus 1-4
56Humour?