Digestive System

Question 1

What is digestion?

Answer 1

The breaking down of the nutrients (food/macro nutrients) we eat into simpler organic compounds that can be absorbed by the body

Question 2

What are the two processes in digestion?

Answer 2

Mechanical
Chemical (involving digestive enzymes)

Question 3

Name the three mechanical processes in the mouth

Answer 3

-Swallowing
-Chewing

Question 4

Name the enzyme that performs chemical digestion in the mouth, and its products

Answer 4

EZYME: Salivary Amalyse
PRODUCTS: Polysaccharides (starch) -> disaccharides (maltose/sugar)

Question 5

Define peristalsis

Answer 5

Wave like contraction of the muscular wall of the alimentary canal that pushes food along the digestive tract

Question 6

Name the two mechanical processes in the stomach:

Answer 6

-Muscular churning mixes food with gastric juices (forms chyme)
-Rennin (infants only) curdles milk

Question 7

Name the substances involved in chemical digestion in the stomach and describe their roles and products.

Answer 7

HCl - Activates perpinsogen (-> pepsin)
ENZYME: Pepsin
PRODUCTS: Proteins -> peptones

Question 8

What absorption occurs in the stomach?

Answer 8

Limited absorbtion of water, glucose, alcohol and some drugs

Question 9

Name the mechanical processes that occur in the Duodenum

Answer 9

Bile salts emulsify fats (reduces large fat globules to small droplets, increasing surface area for enzyme action)

Question 10

Name the enzymes that performs chemical digestion in the duodenum, and its products

Answer 10

ENZYME: Amalyse
PRODUCT: Disaccharides -> glucose
EZYME: Lipase
PRODUCT: Fats + oils -> fatty acids + glycerol
ENZYME: Trypsin
PRODUCT: Peptones -> polypeptides

Question 11

Name the mechanical processes that occur in the Small Intestine

Answer 11

Absorbtion:
-Glucose, amino acids, water + minerals are absorbed into the blood capillaries
-Fatty acids + glycerol are absorbed into the lacteals (forming chyle)

Question 12

Name the enyzmes that performs chemical digestion in the Small Intestine, and its products

Answer 12

ENZYME(s): Maltase, Lactase, Sucrase
PRODUCT: Glucose
ENZYME: Lipase
PRODUCT: Fatty acids + glycerol
ENZYME: Peptidases
PRODUCT: Polypeptides -> amino acids

Question 13

State the processes that occur in the Large Intestine

Answer 13

-Further absorption of water + some salts
-Bacterial activity - trillions of resident bacteria in large intestine; several roles in addition to digesting cellulose in plant foods + synthesising some vitamins (e.g. folic acid)

Question 14

State the processes that occur in the Liver

Answer 14

-Deaminates amino acids
-Converts glucose to glycogen
-Produces bile
-Stores iron, and vitamins A, B12, D, E & K
-Synthesises vitamin A & plasma proteins
-Detoxifies drugs (including alcohol) and other toxins
-Stores Glycogen

Question 15

What is the Alimentary Canal

Answer 15

The alimentary canal is the continuous tube that runs from the mouth to the anus. Together with associated organs such as the pancreas and the gall bladder, the alimentary canal makes up the digestive system.
The lining of the alimentary canal is the surface through which nutrients are absorbed

Question 16

Describe the characteristics of the Oesophagus

Answer 16

The oesophagus is a tube about 23–25 cm long that connects the pharynx to the stomach. The wall of the oesophagus, like the rest of the alimentary canal, has a double layer of muscle. Circular muscle has muscle fibres arranged in a circle, and longitudinal muscle has fibres arranged along the length of the canal

Question 17

How does the Oesophagus move food?

Answer 17

As the lump of food enters the pharynx and oesophagus, the circular muscle behind it contracts to narrow the tube. The contraction of successive bands of circular muscle causes the constriction to move in a wave called peristalsis. This movement pushes the food in front of it, assisted by the secretion of mucus that lubricates the inner lining

Question 18

State the enzymes present in pancreatic juice

Answer 18

-Pancreatic Amalyse
-Trypsin
-Pacreatic Lipases
-Ribonuclease
-Deoxyribosnuclease

Question 19

What is the purpose of the large intestine?

Answer 19

Moves material at a slow rate (18-24 hours) for elimination from the body. During this, excess water is absorbed to solidify material and bacteria breaks down remaining oraganic compounds for absorption through the walls into the blood

Question 20

How does the Small Intestine maximise absorption?

Answer 20

-Large surface area (villi, microvilli)
-One cell thick walls
-Rich blood supply (capillaries + Lacteals)
-Efficient transport mechanisms
-Facilitated by length

Question 21

What does HCl do in the Stomach?

Answer 21

-Converts the enzyme pepsinogen into the active form, pepsin
-Denature proteins (easier for enzymes to break down)
-Maintains PH for optimal functioning of enzymes + kills harmful microorganisms that may enter with food

Question 22

What is Bile?

Answer 22

-Produced by the liver
-Stored in the gallbladder
-Secreted into the small intestine via the common bile duct
-Bile salts necessary for mechanical digestion of fats (act as a detergent + emulsify fat, breaking them down into tiny droplets)
-Form of mechanical digestion

Question 23

What is coeliac disease?

Answer 23

People are unable to tolerate the protein gluten (found in wheat, rye, barley). If consumed immune system attacks and damages/kills villi.

Question 24

What is Constipation?

Answer 24

-a condition characterized by infrequent or difficult bowel movements, often involving hard, dry stools that are painful to pass, and a feeling of incomplete evacuation
-caused by insufficeint fibre/water intake (results in excessive water absorption)

Question 25

What is diarrhoea?

Answer 25

-the frequent passage of loose, watery stools, often accompanied by other symptoms like stomach cramps and nausea -leads to dehydration (water absorption<)

Question 26

What are the 4 activities of the digestive system?

Answer 26

1. Ingestion of food (mechanical digestion, chemical digestion) 2. Movement along the alimentary canal 3. Absorption of nutrients/water 4. Elimination of waste

Question 27

How are nutrients absorbed in the small intestine?

Answer 27

Simple sugars and amino acids are absorbed into blood capillaries by active transport. Fatty acids and glycerol are absorbed into lacteals (lymph capillaries) by simple diffusion, and then transported to the blood via the lymphatic system.

Question 28

What is bowel cancer (colorectal cancer), and what are its main risk factors?

Answer 28

Starts in the large intestine (colon) or rectum. It typically begins as a small growth called a polyp that can become cancerous over time. Risk Factors: Diet: Low-fiber, high-fat diet, and excessive red/processed meat consumption. Age: Risk increases after age 50. Family History: Family history of colorectal cancer or polyps. Genetic Conditions: Conditions like familial adenomatous polyposis (FAP) and Lynch syndrome increase risk. Inflammatory Bowel Disease (IBD): Conditions like Crohn's disease and ulcerative colitis increase risk.

Question 29

What are the key functions of the liver in digestion and metabolism?

Answer 29

The liver plays a crucial role in digestion, metabolism, and detoxification. Its main functions include: Bile Production: The liver produces bile, which helps emulsify fats in the small intestine, aiding in fat digestion. Detoxification: It detoxifies harmful substances like alcohol and drugs by breaking them down into non-toxic compounds. Glycogen Storage: The liver stores glucose in the form of glycogen, releasing it into the bloodstream when needed to maintain blood sugar levels. Protein Synthesis: It synthesizes plasma proteins, including albumin (important for maintaining blood volume) and clotting factors. Deamination: The liver deaminates amino acids, removing the amino group, which is converted to urea and excreted in the urine. Storage of Nutrients: It stores iron, and vitamins A, D, E, K, and B12 for future use

Question 30

What is the role of the gall bladder?

Answer 30

Store and concentrate bile produced by the liver, and subsequently release it into the small intestine to act as an emulsifying agent that aids in the mechanical digestion of lipids.

Question 31

State some functions of vitamins in human nutrition

Answer 31

-Act as coenzymes for many of the chemical reactions of metabolism -VITAMIN D prevents osteoporsis -VITAMIN A rquired for normal growth of cells

Question 32

State some functions of minerals in human nutrition

Answer 32

-Essential for metabolism because they may be part of the enzymes -May function as cofactors for enzymes -May be part of substances, such as ATP -CALCIUM necessary for normal bone growth (development of teeth, heart, never, muscle), main mineral stored within bone

Question 33

Explain how reducing carbohydrate and lipid consumption may prevent body fat accumulation in terms of metabolism

Answer 33

1. Carbohydrate and lipid intake: Carbohydrates and lipids provide glucose and fatty acids, which the body uses for energy. 2. Energy metabolism: Any excess glucose or fatty acids that are not needed immediately for energy are converted into stored fat in adipose tissue. 3. Reduced intake: When carbohydrate and lipid consumption is reduced, there is less material available for the body to convert into stored fat. 4. Energy balance: If energy intake drops below energy expenditure, the body begins breaking down its existing fat stores for energy rather than adding more. 5. Result: This helps prevent the accumulation of additional body fat and supports maintaining a healthy body weight.

Question 34

Outline how the structure of the stomach allows it to function in digestion

Answer 34

1. Muscular Wall (Mechanical Digestion) Structure: Stomach wall has three muscle layers – circular, longitudinal, and oblique. Function: These muscles contract to churn and mix food with gastric juices, turning it into chyme. 2. Mucosa & Gastric Glands (Chemical Digestion + Protection) Structure: The mucosa contains gastric pits with gastric glands. Function – Chemical Digestion: Glands release gastric juice containing acid and enzymes. The acidic pH (2–3) activates pepsin, which begins protein digestion into polypeptides. Function – Protection: Acid kills bacteria. Mucus protects the stomach lining from the acid. 3. Pyloric Sphincter (Movement Control) Structure: A thickened ring of circular muscle at the base of the stomach. Function: Controls the release of chyme into the duodenum and prevents movement unless pushed by peristalsis. 4. Stomach Shape & Lining (Storage + Limited Absorption) Structure: J-shaped organ with a thick mucus lining. Function: Stores large amounts of food. Mucus prevents most absorption, although alcohol and some drugs (e.g., aspirin) can be absorbed.

Question 35

What is the lock-and-key model used for? Outline the model.

Answer 35

Used to describe and explain how enzymes function in chemical reactions. *Components: The enzyme acts upon a molecule called the substrate. * Analogy: The model posits that the shape of the enzyme (the key) is always complementary to the shape of the substrate (the lock). * Binding: Because their shapes fit exactly, the enzyme and the substrate combine. * Complex Formation: The part of the enzyme molecule that combines with the substrate is called the active site. When the enzyme and substrate are combined, they form an enzyme–substrate complex.