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Y3 Biology > 5. Human Digestive System > Flashcards

5. Human Digestive System Flashcards

1
Q

Digestion

Definition

A

Digestion is the process that breaks down complex food substances into simple, soluble molecules that are small enough to be absorbed into body cells

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2
Q

Physical Digestion

Definition

A

Physical Digestion is the mechanical breakdown of food into smaller particles to increase the surface area to volume ratio, for a higher rate of chemical digestion by digestive enzymes

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3
Q

Chemical Digestion

Definition

A

Chemical Digestion is the breakdown of large food molecules into small soluble molecules, catalysed by digestive enzymes through hydrolytic reactions

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4
Q

Ingestion

Digestion

A

Ingestion is the act of taking food into the mouth

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5
Q

Types of digestion in the mouth

A

Chewing - physical digestion
Salivary amylase - chemical digestion

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6
Q

Saliva

Produced where? Contains what? Function?

A

Produced by salivary glands in the mouth
Contains salivary amylase to digest starch into maltose
Help to soften and moisten food

Saliva has a pH of 6.5 - 7.5

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7
Q

Salivary Amylase

Found where? Function?

A

Found in saliva
Digests starch into maltose

Maltose is a dissacharide made up of 2 glucose molecules

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8
Q

Peristalsis

Definition & function

A

Peristalsis is the wave-like, rythmic, muscular contractions of the wall of the alimentary canel.
It functions to mix and propel food down the alimentary canel.

The alimentary canel is the digestive tract from the mouth to the anus

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9
Q

Stomach

What is it?

A

A elastic, muscular bag with thick muscular walls

Stomach has pH 2

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10
Q

Gastric Juice

Produced where? Contains what?

A

Secreted by gastric glands, when the bolus enters the stomach
Contains mainly hydrochloric acid, pepsin & rennin

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11
Q

Hydrochloric acid in the stomach

Function

A
  1. Provide an acidic medium suitable for the action of enzymes in the stomach
  2. Kills bacteria
  3. Changes inactive forms of enzymes to active forms: converts pepsinogen to pepsin
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12
Q

Pepsin

Found where? Function?

A

Found in gastric juice
Digests proteins into chains of polypeptides

Polypeptides are long chains of amino acids

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13
Q

Rennin

Found where? Function?

A

Found in gastric juice
Converts soluble milk protein caseinogen into insoluble caesin, causing coagulation of milk

Coagulation: process of a liquid changing to a solid/semi-solid state

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14
Q

Types of digestion in the stomach

A

Churning - physical digestion
Pepsin - chemical digestion

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15
Q

Churning

What is it? Function?

A

A form of physical digestion in the stomach

Function is to:
1. Mix food with gastric juice
2. Breakdown food into smaller pieces to increase the surface area to volume ratio, for a higher rate of chemical digestion by digestive enzymes

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16
Q

What are the 3 sections of the small intestine?

A

Duodenum, jujenmum & ileum

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17
Q

Types of digestion in the small intestine

A

Emulsification of fats by bile - physical digestion
8 types of digestive enzymes - chemical digestion

18
Q

Enzymes secreted by the pancreas

& their functions

A

Pancreatic amylase - digests starch into maltose
Trypsin - digests proteins into polypeptides
Pancreatic lipase - digests fats into fatty acids + glycerol

19
Q

Enzymes secreted by intestinal glands

A

Maltase - digests maltose into glucose
Sucrase - digests sucrose into glucose + fructose
Lactase - digests lactose into glucose + galactose
Peptidase - digests polypeptides into amino acids
Intestinal lipase - digests fats into fatty acids + glycerol

20
Q

Gall bladder

Function

A

Stores bile produced by the liver temporarily
Secretes bile into the duodenum via the bile duct

21
Q

Undigested and unabsorbed matter in the large intestine

Components

A

Consists of a mixture of water, bile pigments, dead cells from intestinal lining, dead & live bacteria, and mainly cellulose from plant cells

22
Q

Large Intestine

Function

A

Large intestine functions to absorb water (by osmosis) and mineral salts (by facilitated diffusion or active transport) from undigested matter into the blood stream

23
Q

Egestion

Definition

A

Egestion is the elimination of undigested material from the alimentary canal.

24
Q

4 adaptations of the small intestine

A
  1. Small intestine is long: To provide sufficient time for absorption of nutrients to take place
  2. Inner walls of the small intestine have many transverse folds bearing many finger-like projections called villi. Each villus possesses numerous microvilli: To increase the surface area to volume ratio for faster absorption of digested food substances by diffusion
  3. The epithelium of the villus is 1 cell thick: To reduce the distance for digested products to diffuse into the cappilaries and lacteal, for faster absorption of digested food substances by diffusion
  4. The small intestine consists of a dense network of blood capillaries and lacteal within the villi: The continuous transport of digested food substances away from the small intestine maintains a steep concentration gratident, for faster absorption of digested food substances by diffusion
25
Q

What is absorbed in the small intestine

A

Monosaccharides, amino acids, fatty acids, glycerol, water

26
Q

How are glucose and amino acids absorbed in the small intestine?

A

Absorbed by facilitated diffusion or active transport (depending on the concentration gradient) into the blood capillaries of the villi

27
Q

How are fatty acids and glycerol absorbed in the small intestine?

A

Absorbed by simple diffusion into the epithelial cells of the villi, where they recombine to form minute fat globules, which then diffuse into the lacteal

28
Q

Where are glucose and amino acids transported after being absorbed?

A

Blood capillaries join to form venules which then join to form the hepatic portal vein. The hepatic portal vein carries glucose and amino acids to the liver to be processed.

29
Q

Assimilation

Definition

A

Assimilation is the utilisation of absorbed nutrients and how the body deals with excess nutrients.

30
Q

Usage of glucose

A

Glucose is a substrate for respiration, to release energy for all cell activities

31
Q

What happens to excess glucose?

& What hormone stimulates this reaction?

A

Excess glucose is converted into glycogen by liver cells, and stored in the liver
This is stimulated by insulin (a hormone), produced by the pancreas

32
Q

What happens when there is a lack of glucose in the blood?

& What hormone stimulates this reaction?

A

Glycogen is converted into glucose by liver cells when the blood glucose level is low
This is stimulated by glucagon (a hormone), produced by the pancreas

33
Q

Usage of amino acids

A

Used in the synthesis of new cells, for growth and repair of worn-up cells
To synthesise important proteins: enzymes, hormones, antibodies, transport & structurual proteins

34
Q

What happens to excess amino acids?

A

Excess amino acids are deaminated in the liver
The amino group is removed and converted into urea
The remaining carbon residue is converted into glucose

35
Q

Usage of lipids

A

Maintain cell membranes (phospholipid bilayer)
Produce steriods hormones
Protect vital organs
Where there is an inadequate supply of glucose and glycogen, fats will be broken down in the liver to provide energy

36
Q

What happens to excess lipids?

A

Excess fats are stored in apidose cells
Fat droplets can collect in the cytoplasm, increasing in size and number to form one large globule of fat, pushing the cytoplasm into a thin layer, and the nucleus to one side
Groups of apidose cells form apidose tissue

37
Q

Liver

6 main functions

A
  1. Bile production
  2. Regulation of blood glucose (homeostasis)
  3. Protein synthesis of proteins in blood
  4. Deamination of excess amino acids
  5. Breakdown of red blood cells
  6. Detoxification
38
Q

Bile

Produced where? What is it? Function?

A

Produced by liver, stored in gall bladder temporarily, secreted into the duodenum via the bile duct

A thick, yellowish-green fluid
Contains bile salts and bile pigemtns
Alkaline - neutralises chyme from the stomach
Emulsifies fats - increase surface area to volume ratio for a higher rate of chemical digestion by lipases

39
Q

Breakdown of red blood cells by the liver

A

The liver breaks down haemoglobin in red blood cells and stores the released iron, to be reused

40
Q

Detoxification of blood by liver

A

The liver converts harmful substances into harmless ones
Enzymes (alcohol dehydrogenase) break down alcohol into acetaldehyde, which can be futher broken down into glucose
Catalase breaks down hydrogen peroxide (toxic by-product of celluar activities) into water and oxygen

41
Q

Effects of excessive alcohol consumption

A

Alcohol is a depressant (slows down brain and nervous
system)
- reduced self control
- longer reaction time
- cirrhosis of the liver

Y3 Biology (10 decks)

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