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Semester One Biology > Digestion > Flashcards

Digestion Flashcards

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0
Q

What are the common requirements for all organisms?

A 
Energy
Oxygen
Water
Nutrients
Waste removal 
Reproduction
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1
Q

What are autotrophs?

A

They are organisms that can make their own organic molecules, including glucose, from inorganic molecules; including photosynthetic and chemo synthetic organisms.

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2
Q

What are heterotrophs?

A

Organisms that must obtain organic compounds by eating other organisms or their products.

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3
Q

Role of carbohydrates.

A

Energy source (ATP)
Storage for energy
Structural component (cellulose) of the cell walls of plants
As a part of the receptors on the cell membranes of cells

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4
Q

Lipids are an important….

A

…energy store in animals, and they are required for cell membranes, hormones and vitamins.

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5
Q

Amino acids are required for…

A

…protein synthesis.

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6
Q

Essential amino acids are?

A

Nine amino acids that need to be included in our diet because we do not synthesise them ourselves yet they are essential to our diet.

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7
Q

What are vitamins?

A

Vitamins are a diverse group of organic compounds that are required in very small amounts for particular cell processes.
Not used for energy.

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8
Q

Where are vitamins synthesised?

A

In plants and some simple animals and organisms.

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9
Q

Vitamins are important because….?

A

They are needed to make particular enzymes.

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10
Q

The number of nutrients required by mammals include?

A

9 essential amino acids
13 vitamins
Around 20 mineral

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11
Q

What is digestion?

A

It is the breakdown of food into a form that can be used by an organism for metabolism; involves mechanical and chemical breakdown.

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12
Q

What happens when we eat food?

A

The food doesn’t become part of our body until it has been absorbed by the cells lining the walls of our intestine.
Digested food passes into the bloodstream and carried throughout the body.
If food is not absorbed it continues through the intestine and is passed out as faeces (egestion).

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13
Q

What is excretion?

A

The removal of substances that were once part of the body, and occurs largely in the kidneys.

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14
Q

What is chemical digestion?

A

The action of enzymes in breaking down complex compounds into simple compounds that can be used by organisms for metabolism.

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15
Q

Why are enzymes important in digestion?

A

Because they greatly increase the rate of breakdown of food molecules.

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16
Q

What is hydrolysis?

A

A chemical reaction that involves the splitting of a molecule by the addition of a water molecule at a particular point.

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17
Q

What are the three main kinds of digestive enzymes? And what do they act on?

A

Amylase- act on carbohydrates
Protease- act on proteins
Lipase- act on lipids

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18
Q

How are digestive enzymes made?

A

They are manufactured by specific cells in the gut wall, and by the salivary glands and the pancreas.

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19
Q

What is the importance of pH in digestion?

A

Because enzymes are proteins, they are sensitive to changes in the pH of a solution. Altering the pH changes the shape of protein molecules, which in turn alters their chemical properties. Enzyme can’t bind to its substrate.

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20
Q

What is extracellular digestion?

A

Chemical digestion in which the enzymes are secreted int a cavity where digestion takes place.
The enzymes split the food molecules and the resulting smaller molecules are absorbed.
Eg: starfish

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21
Q

What is intracellular digestion

A

Chemical digestion in which the cell of the gut surrounds and digests food particles.

Cells engulf small pieces of food so that they are contained in a membrane-bound food vacuole within the cell.
Enzymes are released into the vacuole, the food is digested, and the resulting small molecules pass through the vacuole membrane and into the cytosol.
Type and size of food digested by intracellular digestion is limited.

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22
Q

What is the relationship between SA:V ratio and digestion?

A

Digestion is much faster if food is in small pieces and the enzymes have a proportionally larger area to act upon.

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23
Q

What is physical digestion?

A

The breakdown of food by physical means.

Physical digestion is when we break down large substances into smaller ones, in order to increase the surface area of the food so therefore the enzymes can act upon the substance quicker.

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24
Q

What are the examples of physical digestions we have?

A

Teeth grind food into small particles which can be swallowed. This happens before digestion occurs.

Physical digestion also includes peristalsis which helps move food down the digestive tract and the muscular churning of food within the stomach which helps mix food substances with digestive juices and acid.

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25
Q

To improve efficiency of digestion….

A

…this physical breakdown should take place before chemical digestion.

26
Q

What is bile?

A

Bile is a secretion produced by the liver, stored in the gall bladder and released into the small intestine.

27
Q

What does bile do?

A

It acts as an emulsifying agent, physically breaking up large fat droplets into smaller droplets, to increase the surface are of food being digested.

28
Q

Characteristics of these highly efficient digestive systems include:

A
  • effective mechanisms for capture and preliminary handling of food.
  • appropriate physical breakdown of food
    a one-way gut with separation of tasks along its length.
  • efficient transport and storage of ingested food.
  • efficient sequential release of digestive enzymes.
  • an adequate surface area for maximal absorption of nutrients and water.
  • efficient egestion of unwanted materials.
29
Q

Why is mucus secreted in the digestive tract?

A

To protect the lining of the gut and to lubricate food for easier passage.

30
Q

Mouth and mouth cavity.

What does saliva do?

A

Physical digestion with teeth.
Chemical digestion starts here with salivary amylase, the enzyme that breaks down CHO (starch).
Saliva is neutral or slightly alkaline (basic) because amylase is active under alkaline conditions.
Saliva also lubricates food to prevent abrasive damage to the lining of the oesophagus.
Food is swallowed after chewing.

31
Q

When the food is swallowed what happens?

A

Deliberately swallowing food triggers a reflex with the back of your tongue.
Swallowing causes the reflexive opening of both upper and lower oesophageal sphincter a to receive the food.
The reflexes that occur are important because when swallowing the food passes down the throat and crosses the airway between the nose and lungs.

32
Q

What interferes with the general functioning of the reflexes?

A

Anaesthetics

33
Q

Oesophagus

A

The oesophagus transports food by peristalsis from the mouth to the stomach.
Assisted by gravity.
Occurs more slowly if lying down.
No enzymes are produced.
It produces large amounts of mucus to lubricate food as it passes down.
The sphincter at the bottom end of the oesophagus closes when the food enters the stomach. This prevents the stomach contents passing back into the oesophagus which can burn the oesophagus and lead to serious medical conditions. Eg: GORD

34
Q

What is peristalsis?

A

It is the muscular ‘squeezing’ of the oesophagus that pushes the food down into the stomach.

35
Q

Stomach

A

Is an important food storage organ.
Whilst food is stored in the stomach is is changed into chyme - a soft semi-fluid mixture, by a combination of mechanical churning and chemical breakdown.
Glands in the wall of the stomach release hydrochloric acid, pepsinogen and gastric lipase.
Hydrochloric acid splits pepsinogen to form pepsin, enzyme that begins the digestion of protein into peptides. HCl acid also produces the ideal pH (1-3) for pepsin activity.
Gastric lipase begins he digestion of fats into fatty acids and glycerol.
Layer of mucus to protect the lining of the stomach.
Very little absorption occurs in the stomach. Apart form alcohol.

36
Q

Small intestine

A

Important exchange organ.
Long, large. Thus well suited to absorption.
‘Small’ refers to the diameter of this region of the intestine.
Not a small inner surface coz there is millions of tiny folds called villi which increase it’s surface area and further increased by microvilli on the exposed surface cells lining the lumen.
Thin lining allows rapid transfer of nutrients and well supplied with blood and lymphatic vessels.
Partially digested food is moved through by peristalsis.

37
Q

The first part of the small intestine is called?

A

Duodenum

38
Q

Duodenum

A

Small amounts of chyme are released intermittently from the stomach into the first part of the SI, the duodenum.
Digestion and absorption of food is usually extended over about 2-4 hours.
Receives pancreatic enzymes, bile to emulsify fats, and intestinal enzymes secreted by the cells in the lining.
Bile is alkaline. It neutralises the acid from the stomach and produces favourable pH for the duodenal enzymes.
These enzymes complete the digestion of CHO into simple sugars, proteins into AA’s and fats in FF’s and glycerol.

39
Q

Some nutrients pass through the wall of the small intestine by….

A

Diffusion along the concentration gradient.

However this is not sufficient to transfer and provide for our nutritional needs.

40
Q

Nutrients are mostly absorbed by…

A

…active processes, and against the concentration gradient, and considerable energy is expanded in the process.

41
Q

Which type of substance need active transport to absorb them?

A

Amino acids
Simple sugars (monosaccharides)
Vitamins
Mineral

42
Q

What is able to diffuse easily through the intestinal cells, cell membranes?

A

Fats (fatty acids and glycerol). Are lipid soluble molecules.

43
Q

The rest of the small intestine called the?

A

Ileum

44
Q

What are lacteals?

A

Capillaries of the lymphatic system near the intestine, and have a milky appearance due to their high fat content after a fatty meal.

45
Q

Water

A 
Most water (90-95%) is absorbed in the SI.
Passive absorption osmotically
46
Q

Large intestine

What is the colon and what does it do?

A

The colon is the first part of the large intestine.
Salts are actively absorbed
Water is passively absorbed osmotically
No digestive enzymes are secreted.
Bacteria can digest fibre producing fatty acids that can be absorbed into the gut.
This provides insufficient energy for humans.
Bacteria is the main source for gas production.

47
Q

The remainder of the colon, the rectum.

A

Involved in storing faeces which are normally about 75% water and 25% solid matter (dead bacteria and indigestible fibre).

48
Q

Large intestine

A

Movement is less efficient than the small intestine.
Walls are thinner and more easily stretched, providing a large capacity for storage.
When distended (swollen), peristalsis is less effective for moving the contents along.
Fibre, which adds bulk and volumes to faeces, gives peristalsis a firmer material upon which to work.
2 sphincters control defaecation.
The internal sphincter is under involuntary reflex control and responds to distension of the rectum.
The external sphincter is under voluntary control in humans over about 2 years of age.

49
Q

What so cellulose?

A

A complex CHO molecule that is very strong; forms pant cell walls.

Most herbivores surprisingly can’t digest cellulose.

50
Q

What is cellulase?

A

Enzyme that breaks down cellulose. Produced by only a few microorganisms, some of which live as symbionts in the guts of herbivores.

51
Q

How do lots of herbivores such as cows, koalas and kangaroos digest their plant food?

A

They set up a symbiotic partnership, called mutualism, with organisms that can produce the enzyme.

In this partnership, the microorganisms live in the intestine of the host.
They receive shelter and free food for themselves and in return, convert cellulose into simpler molecules that their host can absorb.
They also supply important vitamins.

52
Q

The breakdown of cellulose must occur…

A

Anaerobically by fermentation. In the fermentation chamber.

53
Q

What are hindgut fermenters?

A

Are herbivores that ferment plant based food in a specialised area towards the back of the intestinal tract.

54
Q

Where does hindgut fermentation occur?

A

In the caecum, an enlarged pouch where the small and large intestines join and/or the first part of the colon.
Region where the most absorption occurs.

54
Q

Examples of hingut fermenters?

A

Horses
Koala
Wombat
Rabbits

55
Q

In hindgut fermenters….

A

The digestion products are not completely absorbed.

56
Q

What are foregut fermenters?

A

are mammals that break down plant based food by fermenting it in a specialised stomach prior to digestion, often using bacteria.

57
Q

In foregut fermenters, the fermentation chamber is located…… And in ruminants it is called the?

A

Before the stomach

The rumen

58
Q

What is rumination?

A

When food is regurgitated back into the mouth for further physical breakdown.

59
Q

What is regurgitated food called?

A

Cud

60
Q

What is one advantage of foregut fermenters?

A

That the products of digestion by microorganisms are available for absorption along the entire length of the small intestine

61
Q

Examples of foregut fermenters…

A

Kangaroos, cows, llama, sheep, cattle

Semester One Biology (4 decks)

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