Unit 2: The continuation of life

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Unit 2 The continuation of life
Higher Human Biology

• Chapter 22
• Delivery of Materials to cells (NUTRIENTS)

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• Learning Intentions

• Success Criteria

• 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.

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Preparation 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/
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SG Revision Labelling exercise
Rectum
Large intestine
Gall bladder
anus
liver
Oesophagus
Salivary glands
Small intestine
stomach
appendix
mouth
Pancreas
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Enzymes Scholar Activity
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Answers Scholar Activity
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Digestive Enzymes revision
Digestive enzymes at various parts of the
digestive system act on different types of food
molecule
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1. Small Intestine
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1. 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
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(No Transcript)
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2. 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.

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2. 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.

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2. 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.
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• Learning Intentions

• Success Criteria

• 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

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Bile salts
Bile salts are.
Produced in the liver
Stored in the gall bladder.
Pass into the small intestine via the bile duct
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Bile 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.

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Investigating 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.
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Discussion

• 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.

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Conclusion

• An EMULSIFYER is an agent which reserves an
  emulsion. From this experiment it can be
  concluded that bile salts act as an emulsifier.

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Action 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.
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FYI 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.
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Lipase

• 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.

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Lipase
SUBSTRATE
END PRODUCTS
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Investigating 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
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Investigating 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.

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Significance 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.

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Why 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.
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Absorption 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.
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Video Micelles
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Absorption 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.
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Task Torrance-TYK pg169 Qu 1-3
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• Learning Intentions

• Success Criteria

• 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.

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4. 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
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Portal 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 .

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Composition of plasma
Try the scholar activity http//courses.scholar.h
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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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Scholar Activity
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Answers Scholar Activity
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5. 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

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5. 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.

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5. 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
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Fat-soluble vitamins are stored in liver cells
e.g. Vitamins A, D, E K
Image sources www.nlm.nih.gov
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Image sources www.nlm.nih.gov
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Image sources www.nlm.nih.gov
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5. 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.
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6. 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)
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6. 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
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1. What is the function of villi?
2. What is the name given to the central lymph
   vessel in a villus?
3. Which foodstuffs are transported by lacteals.
4. What substances are required for the proper
   absorption of vit B12.
5. What is the name of the process in which amino
   acids are broken down in the liver?
6. What is the toxic end-product of this process?
7. Where is bile stored?
8. What is the prime function of bile?
9. What vitamins can be stored in the liver?

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1. To increase the surface area of the small
   intestine for the absorption of food.
2. Lacteal
3. Fats.
4. Intrinsic Factor
5. Deamination
6. Urea
7. In the gall bladder
8. Bile emulsifiers (breaks up) fats.
9. A,B12 and D

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Label the diagram best you can to describe the
blood flow to the Liver
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Liver Morton sheet
Pulmonary Artery
Pulmonary Vein
Aorta
Vena cava
Hepatic Artery
Hepatic Vein
Hepatic Portal Vein
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Label A, B and C and organ X, try other bits if
you can
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Class Worksheet
Aorta
Hepatic Artery
Hepatic Vein
Vena Cava
Gall bladder
Hepatic Portal Vein
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Essay 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)

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Task Torrance-TYK pg172 Qu 1-4
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Task Torrance AYK pg173-4 Qus 1-4
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Humour?