Digestion Flashcards

1
Q

Why do animals eat?

A

To obtain energy
To maintain cellular metabolism
To allow growth and reproduction

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2
Q

What type of trophs are all animals?

A

Heterotrophs

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3
Q

What do animals extract from food?

A
Proteins
Carbs
Fat
Ions
Trace elements
Water
Vitamins
Essential amino acids
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4
Q

What type of teeth do carnivores have?

A

Enlarged canines for gripping killing and tearing prey

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5
Q

What type of teeth do herbivores have?

A

Incisors and canines to tear plants

Large molars and premolars to grind plant matter

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6
Q

What type of teeth do omnivores have?

A

Multipurpose teeth

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7
Q

What are gastroliths?

A

Stomach stones used to grind food

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8
Q

Describe the structure of the human digestive system

A
Mouth
Stomach
Small intestine
Large intestine 
Rectum
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9
Q

What is the mouth for?

A

Responsible for breaking up large amounts of food and mixing it with saliva

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10
Q

What is the stomach for?

A

Responsible for mechanical mixing of food with stomach acid

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11
Q

What is the small intestine for?

A

Responsible for further mixing and absorption of nutrients and is aided by bile and pancreatic juice

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12
Q

What is the large intestine for?

A

Responsible for absorbing water and forming stool

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13
Q

What is the rectum for?

A

Responsible for storing stool before expulsion

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14
Q

What are the salivary glands for?

A

Secrete liquid and enzymes (salivary amylase) into the oral cavity for chemical digestion

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15
Q

How does the stomach digest?

A

In anticipation as well as the arrival of food, it releases HCl and pepsin
Coordinated contractions of muscle layers lead to mixing of food creating chyme

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16
Q

Where does chyme go after the stomach?

A

Released into small intestine duodenum via the pyloric sphincter

17
Q

How does HCl chemically digest food?

A

Denatures proteins by breaking electrostatic interactions in the tertiary structure
Also sterilises food

18
Q

Where does the HCl and pepsinogen come from?

A

Gastric pits are deep folds of the stomach mucosal epithelium

19
Q

How does HCl activate pepsinogen?

A

Pepsinogen is an inactive precursor enzyme that is activated by HCl into pepsin

20
Q

Describe the mucus-bicarbonate barrier

A

Bicarbonate neutralises the acid

Mucus is a physical barrier

21
Q

What happens when chyme enters the duodenum?

A

Digestive enzymes are released from the pancreas and gallbladder and bicarbonate is released to neutralise the acid

22
Q

What is gastrin?

A

A hormone produced by G cells and is innervated by the postganglionic fibres of the vagus nerve during parasympathetic stimulation

23
Q

What is secretin?

A

A hormone that is produced by S cells and inhibits the production of gastrin and neutralises the duodenum pH

24
Q

What is cholecystokinin?

A

A hormone that stimulates the release of bile and pancreatic juice

25
Q

What are the 3 parts of the small intestine?

A

Duodenum
Jejunum
Ileum

26
Q

How does absorption happen in the small intestine?

A

Na+/K+ ATPase generates a chemical gradient for Na+ and this requires energy
The gradient is used to cotransport other substrates into the luminal membrane
The interstitial membrane contains transporters (uniporters) which releases the substrates

27
Q

How are fats digested?

A

Fats are emulsified into micelles through bile in the intestinal lumen
Pancreatic lipase hydrolyses the micelles into fatty acids and monoglycerides
They enter the cell by diffusion
Are resynthesised into triglycerides in the endoplasmic reticulum
Triglycerides are packaged with cholesterol and phospholipids in protein-coated chylomicrons
Chylomicrons are enclosed in vesicles and leave the cell by exocytosis and enter the lymphatic system

28
Q

Where does the absorbed material go?

A

Transported by the portal vein to the liver for detoxification

29
Q

What happens in the large intestine?

A

No digestive enzymes but bacterial digestion occurs

Salt and water are absorbed

30
Q

What is aldosterone?

A

A steroid hormone that stimulates the absorption of Na+ and water

31
Q

What is the appendix for?

A

A reservoir for beneficial microorganisms

32
Q

Describe fermentation in the cecum in herbivores?

A

A microbial fermentation chamber called the cecum extends from the large intestine for bacterial digestion

33
Q

What is coprophagy and why is it practiced?

A

Nutrient absorption in the cecum is inefficient so some eat waste to redigest and get more nutrients