Digestion
-
Upload
marthese-azzopardi -
Category
Business
-
view
1.721 -
download
0
description
Transcript of Digestion
![Page 1: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/1.jpg)
DIGESTION
![Page 2: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/2.jpg)
Digestion is the process by which
insoluble food, consisting of large molecules is broken down into soluble compounds
![Page 3: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/3.jpg)
What are starch, proteins & fats broken down into?
enzyme
enzyme
enzyme
STARCH
PROTEIN
FAT
Glucose
Amino acids
Fatty acids & glycerol
![Page 4: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/4.jpg)
Why must food be digested?
Blood Blood
Blood
Food in intestine
Food in intestine
Food in intestine
1
3
2
Wall of intestine
To be small enough to be absorbed
through the wall of intestine.
enzyme
![Page 5: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/5.jpg)
Digestion starts at
the mouth and ends
at the
……………….anus
![Page 6: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/6.jpg)
Food is broken down by two actions:
1. PHYSICAL /MECHANICAL
2. CHEMICAL
![Page 7: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/7.jpg)
1. PHYSICAL DIGESTION by: teeth peristalsis of the alimentary
canal
Chewing (mastication)
![Page 8: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/8.jpg)
Why is it important to break down food physically?
To increase the surface area for enzyme action.
![Page 9: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/9.jpg)
Question: SEP, 2009
Give TWO reasons why food must be masticated before swallowed. (4)1. Increased surface area for enzymes to act
quickly.2. Easier to manipulate by tongue to form a
bolus.
![Page 10: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/10.jpg)
2. CHEMICAL DIGESTION by: enzymes
Digestive enzymes are the chemicals that break large insoluble food molecules into smaller soluble molecules.
![Page 11: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/11.jpg)
Four stages in feeding & digestion:
1. Ingestion
2. Digestion
3. Absorption into the bloodstream
4. Egestion
![Page 12: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/12.jpg)
Digested food is absorbed & then assimilated by the cells
Digestive system
Circulatorysystem
Body cell
Absorption
Assimilation
![Page 13: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/13.jpg)
Digestive tract is also called:
Alimentary canal / tract Gut
![Page 14: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/14.jpg)
Mucus is produced throughout the gut:
For lubrication To protect gut wall
from digestive enzymes
![Page 15: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/15.jpg)
Fig. 1 The human digestive system.
![Page 16: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/16.jpg)
The 1st stage of nutrition:
2. Digestion
1. Ingestion
3. Absorption4. Egestion
![Page 17: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/17.jpg)
DIGESTION IN THE MOUTH
![Page 18: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/18.jpg)
salivary glands produce SALIVA (pH = 7-8)
![Page 19: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/19.jpg)
Salivation is a reflex action which is triggered by:
Sight
Smell Thinking
of food
![Page 20: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/20.jpg)
mucus water sodium hydrogen
carbonate salivary amylase
(ptyalin [old term])
Saliva contains:
![Page 21: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/21.jpg)
Functions of mucus in saliva:1. lubricates the food2. sticks the food particles together
bolus
![Page 22: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/22.jpg)
Salivary amylase
![Page 23: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/23.jpg)
In swallowing, food is directed into the gullet / oesophagus
![Page 24: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/24.jpg)
A person cannot breathe while swallowing. Why?
1. The soft palate closes the nasal cavity .
2. The epiglottis closes the trachea.
![Page 25: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/25.jpg)
Swallowing
![Page 26: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/26.jpg)
Peristalsis: wave-like motions of the alimentary
canal which move the food forwards
1
2
BolusDigestive tract
Wave ofcontraction
Wave ofrelaxation
Bolusmoves
2
![Page 27: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/27.jpg)
Peristalsis:
![Page 28: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/28.jpg)
Peristalsis is possible as gut wall is muscular
contraction of circular & longitudinal muscles alternate to push food
![Page 29: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/29.jpg)
Food is pushed when:
What does the longitudinal muscle
do at the same time?
Circular muscle above bolus CONTRACTS
Relaxes
![Page 30: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/30.jpg)
Food reaches the stomach
![Page 31: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/31.jpg)
The stomach stores food for some time & releases it slowly
Food stays for 2-6 hours in the stomach
Chyme: creamy liquid leavingthe stomach
![Page 32: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/32.jpg)
Food remains inside stomach due to contraction of two sphincters
Cardiac sphincter
Oesophagus
Duodenum
Pyloric sphincter
Layers of muscleChurning due to:
Lining of mucus
![Page 33: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/33.jpg)
Which sphincter is contracted?
Cardiac sphincter:Pyloric sphincter: contracte
drelaxes to let chyme into the duodenum
![Page 34: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/34.jpg)
Gastric glands
secrete gastric juice
![Page 35: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/35.jpg)
What happens to food inside the stomach?
![Page 36: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/36.jpg)
Gastric juice contains:1. HYDROCHLORIC ACID2. PEPSIN 3. RENNIN
What is the pH in the stomach?
1-2
![Page 37: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/37.jpg)
Functions of hydrochloric acid:
1. creates the optimum pH for pepsin
Pepsinogen(inactive form)
Pepsin(active enzyme)
3. kills bacteria taken in with the food
2. HCl
![Page 38: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/38.jpg)
Excessive production of gastric juice: burning sensation
![Page 39: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/39.jpg)
Gastric juice enters oesophagus: not enough mucus to protect wall
![Page 40: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/40.jpg)
Remedy for burning sensation in throat and chest:
1. Drink milk2. Take antacids
![Page 41: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/41.jpg)
Doctors can see the stomach lining by using an:
endoscope
oesophagus
![Page 42: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/42.jpg)
Stomach ulcers due to: little mucus in stomach
![Page 43: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/43.jpg)
Pepsin is a protease: breaks:
Polypeptides
Proteins
![Page 44: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/44.jpg)
Which conditions are needed for a piece of meat to be digested?
Pepsin in acidic conditions
![Page 45: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/45.jpg)
Question: MAY,2009
The following diagram represents the protein found in egg white. Each circle represents an amino acid. Complete the diagram below to show how pepsin breaks down the protein found in egg white.
[Idea is that short chains representing polypeptides are made.] (Do NOT accept individual amino acids represented as single circles or dipeptides represented as a pair of circles)
![Page 46: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/46.jpg)
Question: MAY, 2012
List TWO reasons why amylase does not act on starch in the stomach. (2)i. pH in stomach is not optimum for amylaseii. there is no enzyme in the stomach to break
starch
![Page 47: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/47.jpg)
Some substances that are absorbed by the stomach:
ethanol vitamins certain salts and drugs some water glucose
How did I get drunk so
quickly?
![Page 48: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/48.jpg)
Rennin is an enzyme found in the stomach of young
children Function:
Soluble protein in milk
Changes into insoluble protein
Pepsin then acts on the insoluble
protein
![Page 49: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/49.jpg)
In cheese-making, rennet [contains rennin] is added to milk
![Page 50: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/50.jpg)
THE INTESTINES:
Small intestine
Large intestine
1.5 m long
7 m long
![Page 51: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/51.jpg)
The small intestine is composed of:
duodenum & ileum
![Page 52: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/52.jpg)
Two functions of the small intestine:
1. digestion is completed2. digested food is absorbed
Bloodstream
Products of digestion
![Page 53: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/53.jpg)
Duodenum U-shaped first part of small intestine (most digestion
occurs here) about 25 cm long
![Page 54: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/54.jpg)
The duodenum receives secretions from the:
Pancreas[pancreatic juice via the pancreatic duct]
Liver[bile via the bile duct]
![Page 55: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/55.jpg)
DIGESTION IN THE DUODENUM
![Page 56: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/56.jpg)
Where is bile:i) made? ii)stored?
![Page 57: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/57.jpg)
Made in liver
Stored in gall
bladder
![Page 58: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/58.jpg)
Bile:
has no enzymes consists of:
water sodium chloride bile salts bile pigments
pH = 8
![Page 59: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/59.jpg)
Functions of Bile: dilutes contents from stomach creates optimum pH for pancreatic enzymes
to work in duodenum contains bile salts which emulsify fats
Bile salts
![Page 60: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/60.jpg)
Bile salts emulsify fats i.e.: break large fat globules into smaller globules
Emulsificationof fats
What is the benefit of emulsification?The surface area where lipase can act is increased.
![Page 61: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/61.jpg)
A person had his gall bladder removed. Explain why the doctor told him to limit fats in the diet.
Fats cannot be emulsified; difficult to digest fats by lipase.
![Page 62: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/62.jpg)
Three enzymes in pancreatic
juice:
Pancreatic amylaseTrypsin
Pancreas
Lipase
Action of each
enzyme:
![Page 63: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/63.jpg)
lipase +
fat moleculeglycerol fatty
acids
starch molecule
amylasemaltose
proteins & polypeptides
trypsin
peptides
![Page 64: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/64.jpg)
Question: MAY, 2012
Bile and pancreatic juice are involved in digestion of fats.a) Describe the role of both secretions in this
process. (4) b) Explain why bile must be released before
pancreatic juice for the efficient digestion of fats. (2)
![Page 65: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/65.jpg)
DIGESTION IN THE ILEUM
![Page 66: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/66.jpg)
The wall of the ileum has
intestinal glands that produce
intestinal juice
![Page 67: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/67.jpg)
Enzymes in intestinal juice
SUBSTRATE ENZYME END PRODUCT
Peptides Peptidase Amino acidsLipids Lipase Fatty acids &
glycerolMaltose Maltase Glucose + glucoseSucrose Sucrase Glucose + fructoseLactose Lactase Glucose + galactose
![Page 68: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/68.jpg)
Remember:
Pepsin
Amino acids
Peptides
Polypeptides
Proteins
Trypsin
Peptidase
![Page 69: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/69.jpg)
Remember: Digestion of starch
Starch
Maltose
Maltose(in ileum)
Glucose
Pancreatic Amylase
Salivary Amylase(In Mouth)
No digestion of starch in stomach (amylase is denatured)
Maltase
![Page 70: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/70.jpg)
Digestion is complete in the ileum. What happens to the
digested food?
![Page 71: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/71.jpg)
Model of the ileum showing numerous villi
Villus: a finger-like projection
![Page 72: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/72.jpg)
Villi contain blood & lymph vessels
![Page 73: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/73.jpg)
Structure of a villus
![Page 74: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/74.jpg)
A villus is adapted for absorption
![Page 75: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/75.jpg)
The ileum is adapted to absorb digested food
by providing a LARGE surface area: Folded walls Has villi Has microvilli
![Page 76: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/76.jpg)
Ileum is adapted for absorption:
1. Ileum is long: more time for digestion a greater surface area for absorption
2. Villi: increase surface area for absorption
3. Microvilli in epithelium: increase surface area for absorption
4. Epithelium is very thin: soluble products of digestion pass through quickly
5. Dense capillary network: removes the digested food
![Page 77: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/77.jpg)
THE LARGE INTESTINE
![Page 78: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/78.jpg)
The large intestine is composed of:
1.Caecum
Anus
2. Appendix
4. Colon
3. Rectum
![Page 79: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/79.jpg)
Material in the large intestine consists of:
water mucus dead cells undigested matter
Most of the undigested matter is cellulose. Why is this so?
![Page 80: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/80.jpg)
![Page 81: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/81.jpg)
Function of the:
Colon: absorbs water
Rectum: stores FAECES before being expelled through the ANUS
![Page 82: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/82.jpg)
The 4th stage of feeding & digestion:
4. Egesting
![Page 83: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/83.jpg)
Egestion / Defaecation
the process of removing faeces
I really have to go to the bathroom!
![Page 84: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/84.jpg)
Caecum & Appendix are
Large in herbivores Vestigial in humans:[small & no function]
Caecum
Appendix
![Page 85: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/85.jpg)
Question: SEP, 2011
Humans are omnivores.Do not depend only upon vegetation for nutrients.A large caecum is found in herbivores and is full of bacteria that produce cellulase to digest cellulose.
Explain why the caecum / appendix in humans is small and non-functional. (4) Human Rabbit
![Page 86: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/86.jpg)
Ingestion(2 L) Salivary gland secretions
(1 L)
Gastric secretions(2 L)
Pancreatic secretions(1.2 L)
1% infaeces
Small intestinesecretions(2 L)
Bile(0.7 L)
Although 8.9 L of water are ingested or secreted daily,
the faeces are dry.Explain.
![Page 87: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/87.jpg)
Ingestion(2 L) Salivary gland secretions
(1 L)
Gastric secretions(2 L)
Pancreatic secretions(1.2 L)
Absorbed in the small intestine &
colon.
1% infaeces
Small intestinesecretions(2 L)
Bile(0.7 L)
![Page 88: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/88.jpg)
ASSIMILATION OF DIGESTED FOOD
FOOD USE STOREGlucose
Respiration Glycogen or Fat
Fats
Respiration, to build cell structure, as a store of energy
Fat
Amino acids
Build proteins for cell structures, enzymes
CANNOT BE STORED – ARE DEAMINATED & USED IN RESPIRATION
![Page 89: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/89.jpg)
Deamination occurs in the liver
AMMONIA
AMINO ACIDis broken into two:
The rest is used for energy
Part with nitrogen forms:
UREA
![Page 90: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/90.jpg)
Question: MAY, 2007
Write the correct term for each of the following processes:i) the breakdown of excess amino acids
Deamination
ii) rhythmical muscular contractions that push food along the digestive systemPeristalsis
![Page 91: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/91.jpg)
iii) the elimination of indigestible food from the bodyEgestion / Defaecation
iv) the passage of digested food through the gut wall in the blood stream.
Absorption
![Page 92: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/92.jpg)
BLOOD SUPPLY OF THE LIVER
![Page 93: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/93.jpg)
Oxygenated blood from heartBlood from
digestive system
HEPATIC PORTAL VEIN
HEPATIC ARTERY
LIVER
HEART
HEPATIC VEINto heart
GUT
Blood supply to and away from the liver
![Page 94: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/94.jpg)
Write an account of a controlled experiment you would perform to show the action of the enzyme amylase on starch. (6) [MAY, 1997]
Two spotting tiles are prepared with a drop of iodine solution in each hole.
An equal volume of starch is placed into two separate test tubes, labelled A and B.
12
![Page 95: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/95.jpg)
An equal volume of amylase is placed into two separate test tubes, labelled C and D. Test tube C is boiled for 5 minutes to denature the enzyme and so act as a control.
All four test tubes are placed in a water bath at 37C for 5 minutes to acclimatise.
3
4
![Page 96: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/96.jpg)
Starch in test tube A is poured into amylase in test tube D, mixed and the stop watch is started.
5
After 30 seconds, a drop of the mixture is taken and added to one of the drops of iodine solution on the spotting tile. This is repeated until a yellow colour appears.
6
![Page 97: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/97.jpg)
Starch in test tube B is poured into amylase in test tube C, mixed and the same method is repeated.
7
8Contents in test tube:i) D give a yellow colour with
iodine solution after a few minutes
ii) C continues to give a blue-black colour after 30 minutes.
![Page 98: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/98.jpg)
9 The results show that amylase breaks down starch.
10If Benedict’s solution is added to the contents of test tubes C and D and heated for a few minutes, a brick red colour is obtained only in test tube D [unboiled amylase]. This shows that when starch breaks down, reducing sugars are formed.
C D
![Page 99: Digestion](https://reader031.fdocuments.us/reader031/viewer/2022013003/547be06cb4af9f73098b4d4c/html5/thumbnails/99.jpg)
THE END
I HAVE SO
MUCH TO
DIGEST!!