Unit 2: The continuation of life Chapter 22: Delivery of Materials to cells (NUTRIENTS)...

Unit 2: The continuation of life

Chapter 22:

Delivery of Materials to cells (NUTRIENTS)

21/04/23 Mrs Smith Ch22 The delivery of nutrients to cells

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Higher Human Biology


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Learning Intentions

To understand how nutrients are delivered by the bloodstream to every living cell in the

body..

Success Criteria1. Explain how glucose and amino

acids, the end products of digestion of carbohydrates and proteins, are absorbed into the blood stream.

2. Identify the parts of a villus and explain how it is adapted to its function.

3. Describe the role of the lacteal in transport of absorbed lipid.

Preparation for nutrient absorptionPreparation for nutrient absorptionFood is moved along the alimentary canal from the mouth, to the small intestine by peristalsis.

View the Peristalsis animation: http://www.westga.edu/~lkral/peristalsis/

As this happens digestive enzymes breakdown…..

large insoluble food molecules

small soluble molecules21/04/23 3Mrs Smith Ch22 The delivery of

nutrients to cells

mouth

anus

stomach

Large intestineGall bladder

Salivary glandsSmall intestine

Oesophagus

Rectum

Pancreas

liver

appendix

SG Revision: Labelling exerciseSG Revision: Labelling exercise

21/04/23 4Mrs Smith Ch22 The delivery of nutrients to cells

Enzymes: Scholar Activity


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http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=e6928e85-bb13-a0f0-102d-f1072a4fcd30

Answers Scholar Activity


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http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=e6928e85-bb13-a0f0-102d-f1072a4fcd30

Digestive Enzymes: revisionDigestive Enzymes: revisionDigestive enzymes at various parts of the digestive system act on different types of food molecule…

Small Intestine21/04/23 7Mrs Smith Ch22 The delivery of

nutrients to cells

1. Small Intestine1. Small Intestine


1. Small Intestine1. Small IntestineThe small intestine is well suited to food absorption because:

3. Each villus has a lacteal & blood capillary network for efficient transport of absorbed substances

1. It is long 2. It has a folded inner lining covered in villi

…So has a large surface area for absorption

4. The lining of each villi is one cell thick – so nutrients can pass through easily 21/04/23

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Epithelial cells, bearing microvilli, project into the lumen of the gut

Intestinal gland

between the villi; contains

enzyme secreting cells and hormone releasing cells


• 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 nutrients2. 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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Glucose

amino acids

fatty acids and glycerol

phosphates

BLOOD

Carbohydrates

Proteins

Lipids

large insoluble food molecules small

soluble molecules

Absorbed into blood

Absorbed into lacteal

digestion

Nutrients that don’t need to be digested (e.g. calcium, iron & vitamins) by enzymes are also absorbed by the small intestine. 21/04/23 13Mrs Smith Ch22 The delivery of

nutrients to cells


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Learning Intentions


body.

Success Criteria4. Carry out an experiment to

examine the effects of bile salts

i) as an emulsifier and

ii) on the activity of lipase

Bile saltsBile salts

Bile salts are….

Stored in the gall bladder.

Pass into the small intestine

via the bile duct

Produced in the liver


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 Investigating the effect of bile salts as an emulsifieras an emulsifier

Lipids are, insoluble in water and less dense than water (so float).

A B A B A BOlive oil

Water Bile salts solution

Emulsification – oil

droplets in water

Olive oil

WaterBile salts act as an emulsifier so oil still emulsified

Shaken

Emulsifier = a substance that preserves emulsion.21/04/23

17Mrs Smith Ch22 The delivery of

nutrients to cells

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.


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• 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.

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 SaltsAction of Bile SaltsBile 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.

Droplet of lipid

Bile salt molecule acting as an emulsifier

The heads are negatively charged

so the lipid droplets repel each other and

don’t rejoin. This is emulsification. 21/04/23 20Mrs Smith Ch22 The delivery of

nutrients to cells

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.

21/04/23Mrs Smith Ch22 The delivery of

nutrients to cells21

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.

LipaseLipaseA digestive enzyme made in the pancreasActive in the small intestine where it catalyses the breakdown of lipid

molecules by cleaving off the first and third fatty acid molecules.


LipaseLipaseSUBSTRATE END PRODUCTS

Lipid molecule (triglyceride)

+

monoglycerideFree fatty

acids

LIPASE


Investigating the effect of bile salts on Investigating the effect of bile salts on the action of lipase the action of lipase

A B C A B CShaken + alkali

added to make pH 7

then left for 30 mins in water

bath at 37˚C

Olive oil

Lipase

Water Bile salts

Bile salts

Universal indicator

pH 4 pH 5 pH 7

Acid conditions due to breakdown of lipids to fatty acids by lipase

No digestion from

bile salts alone

Lower pH shows bile salts aid digestion of

lipid to fatty acid21/04/23 24Mrs Smith Ch22 The delivery of

nutrients to cells

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


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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.

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.

Droplet of lipid

Bile salt molecule acting as an emulsifier

Why do bile salts aid digestion by Why do bile salts aid digestion by lipase? lipase?


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.

Absorption of the end products of lipid digestion Absorption of the end products of lipid digestion

Fatty acids and monoglyceride molecules leave the micelles and diffuse through the cell membrane into the epithelium.

21/04/23 28

Video: Micelles


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Absorption of the end products of digestionAbsorption of the end products of digestion

They are then coated with lipoprotein and move out of the cell by exocytosis.

Lipid molecule (triglyceride)

fatty acidsmonoglyceride

+

After passing through the epithelium of the microvilli, the monoglycerides & fatty acids pass into the cell’s endoplasmic reticulum to be built back into lipid molecules (triglycerides).

E.R.

Lipoprotein coat

Exocytosis

Absorbed by lacteal

They get absorbed by the lacteal and are transported via the lymphatic system to the blood.

21/04/2330Mrs Smith Ch22 The delivery of

nutrients to cells

Task: Torrance-TYK pg169 Qu 1-3



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Learning Intentions


body.

Success Criteria5. Explain why the liver needs a dual

blood supply

6. Analyse data on the composition of plasma of hepatic artery, hepatic vein and hepatic portal vein.

4. The Liver4. The Liver

Hepatic artery carries oxygenated blood to liver

Hepatic vein carries

deoxygenated blood from the liver to the

vena cava

Hepatic portal vein carries deoxygenated blood to the liver directly from the gut


Portal SystemPortal SystemThe 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 .


Composition of plasmaComposition of plasma

In liver:• excess glucose stored as glycogen• excess amino acid converted to urea

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

Hepatic vein contains normal blood plasma concentrations of glucose & amino acids+ high urea concentration

Try the scholar activity:http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=8f30977c-4cb9-fe59-4dfa-86bf98b62bdd

21/04/23

35Mrs Smith Ch22 The delivery of

nutrients to cells

Scholar Activity


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Try the scholar activity:http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=ae01a001-7a3a-b119-c268-9aa0c7ae8160

Answers: Scholar Activity


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Try the scholar activity:http://courses.scholar.hw.ac.uk/vle/scholar/session.controller?action=viewContent&contentGUID=ae01a001-7a3a-b119-c268-9aa0c7ae8160

Image source: .biomed.brown.edu

5. Role of the Liver in Metabolism5. Role of the Liver in MetabolismA. Carbohydrate 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


Image source: .biomed.brown.edu

5. Role of the Liver in Metabolism5. Role of the Liver in MetabolismA. Carbohydrate 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 body’s fat reserves.

• If glucose is needed the glycogen breaks down releasing the glucose into the bloodstream.

• When the blood’s 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.

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

5. Role of the Liver in Metabolism5. Role of the Liver in MetabolismB. LipidsB. Lipids


Image sources: www.nlm.nih.gov

Fat-soluble vitamins are

stored in liver cells

e.g. Vitamins A, D, E &

K21/04/23 41Mrs Smith Ch22 The delivery of nutrients to cells

Image sources: www.nlm.nih.gov 21/04/23 42Mrs Smith Ch22 The delivery of

nutrients to cells

Image sources: www.nlm.nih.gov 43

3 types of plasma proteins are made in the liver. The amino acids needed for this are absorbed from the bloodstream by liver cells.

Transaminase enzymes in liver cells can convert one amino acid to another. So even when amino acids aren’t obtained from food, many can be synthesised by the 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 .

5. Role of the Liver in Metabolism5. Role of the Liver in MetabolismC. ProteinsC. Proteins


6. Fate of absorbed materials6. Fate of absorbed materialsMaterial 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

LipidsUsed 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)21/04/23 45Mrs Smith Ch22 The delivery of

nutrients to cells

Metal ions• Zinc• Iron• Copper• Magnesium

Enzyme activators

Some vitamins & minerals absorbed from food play a key role in enzyme reactions:

= Co-factors

Iron = the co-factor responsible for

activating the enzyme catalase.

Co-enzyme = a small non-protein co-factor composed of an organic substance (e.g. a vitamins).

Vitamin B = an essential component of

co-enzymes: acts as hydrogen carriers

during aerobic respiration

6. Fate of absorbed materials6. Fate of absorbed materialsD. Vitamins & mineralsD. Vitamins & minerals


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. Lacteal3. Fats.4. Intrinsic Factor5. Deamination6. Urea7. In the gall bladder8. 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

21/04/23 49

Liver – Morton sheet

21/04/23 50

Pulmonary Artery Pulmonary Vein

Vena cava

Hepatic Vein

Aorta

Hepatic Artery

Hepatic Portal Vein

Label A, B and C and organ X, try other bits if you can

21/04/23 51

Class Worksheet


Gall bladder

Hepatic Vein

Vena Cava

Hepatic Artery

Aorta

Hepatic Portal Vein

Essay Questions: 2005

Describe the functions of the liver under the following headings

1.Production of urea. (2)

2.Metabolism of carbohydrates. (5)

3.Breakdown of red blood cells. (3)


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Task: Torrance-TYK pg172 Qu 1-4


Task: Torrance AYK pg173-4 Qu’s 1-4



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Humour?

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Unit 2: The continuation of life Chapter 22: Delivery of Materials to cells (NUTRIENTS)...

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