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Wjec Biology Unit 2 > 2.4 > Flashcards

2.4 Flashcards

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1
Q

Description of autotrophic nutrition

A

Synthesis of complex organic chemicals from inorganic substances using an energy source

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2
Q

Description of photoautotrophic

A

Uses light energy to combine inorganic substances into complex organic chemicals.

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3
Q

Description of chemoautotrophic

A

Uses chemical energy, from chemicals such as hydrogen sulphide, to combine inorganic substances into complex organic chemicals.

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4
Q

Description of heterotrophic

A

Cannot synthesise its own complex organic chemicals; it must digest organic chemicals produced by other organisms and use the products of digestion to synthesis their own organic chemicals.

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5
Q

Description of holozoic nutrition

A

Absorption of organic matter followed by internal digestion of the organic
chemicals within the organism.

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6
Q

Description of parasitic nutrition

A

Living in or on another host organism, whereby nourishment is obtained from a host organism, usually to the detriment / harm of the host; the host usually derives no benefit.

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7
Q

Ectoparasites

A

Live on outside of a host organism

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8
Q

Endoparasites

A

Live inside a host organism

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9
Q

What is symbiosis/ mutualism

A

Many organisms live in / on other organisms in a relationship that provides benefit to both organisms.

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10
Q

How do photoautotrophs work

A

Carry out photosynthesis
Carbon dioxide + water —> glucose and oxygen
Uses energy from photons of light and transfers light energy into chemical energy

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11
Q

Primary host

A

Where sexual reproduction occurs

Human

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12
Q

Secondary host

A

Where larval/ intermediate forms of the parasite are found

Pig or cow

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13
Q

Steps of a parasite taking over

A
  1. Eggs released into the environment in faeces
  2. Secondary host eat vegetation contaminated with tapeworm eggs
  3. Eggs hatch and larvae burrow through gut wall - then carried by blood around the body
  4. Larvae develop into cysts in muscle
  5. Humans eat undercooked/raw meat and get infected
  6. Scolex develops and attaches to wall of small intestine
  7. Adults grow to 5 cm longer and can survive for many years
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14
Q

Adaptations of the tapeworm

A
  1. Head = scolex and is embedded in gut wall and has hooks and suckers to prevent it being dislodged by peristalsis
  2. No digestive system or mouth - tapeworm only needs to absorb nutrients already digested
  3. Flat body - large surface area for absorption of nutrients
  4. Each proglottid covered in a thick cuticle thats resistant to action of digestive enzymes
  5. Proglottids secrete mucus and enzyme inhibitors to reduce risk of digestion
  6. Anaerobic respiration- no oxygen in gut lumen
  7. Contains male and female reproductive organs - can self-fertilise
  8. Each proglottid contains about 50,000 eggs - increasing chance of being infected by another host
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15
Q

What kind of parasite are headlouse

A

Ectoparasite

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16
Q

What does it mean that headlouse are obligate parasites

A

They have only live in human hair

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17
Q

Obligate parasite

A

Has to live on a host plant to survive

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18
Q
A
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19
Q

Buccal cavity

A

Mechanical and chemical digestion
Lips, tongue and teeth work together
• receive food, cut and chew food, mix with saliva and form bolus
Salivary glands
• slightly acidic, contains salivary amylase

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20
Q

Oesophagus

A

Straight narrow tube with muscular wall
Carries food to stomach by peristalsis
Epiglottis - closes to prevent food from entering the trachea and lungs

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21
Q

Peristalsis in oesophagus

A

Waves of contraction of muscles in gut wall which push forward through the whole gut

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22
Q

How does the stomach carry out chemical and mechanical digestion

A

Chemical
• action of enzymes and hydrochloric acid
Mechanical
• muscles contract and relax to mix food and gastric juice to increase surface area of particles

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23
Q

What cells secrete pepsinogen

A

Xymogenic

Chief cells

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24
Q

What is pepsinogen

A

Precursor of pepsin
Digestion of protein into polypeptides
Digestion of milk protein

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25
Q

What cells secrete hydrochloric acid

A

Oxyntic cells

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26
Q

Function of hydrochloric acid in the stomach

A

Provides optimum pH for enzymes
Denature proteins
Softens connective tissues in food
Activates pepsin

27
Q

What cells secrete mucus in stomach

A

Goblet

Neck cells

28
Q

Why is mucus needed in stomach

A

Forms a barrier between stomach lining and gastric juice

Prevents self-digestion of stomach walls and glands

29
Q

What is the small intestine comprised of

A

Duodenum and ileum

30
Q

Duodenum

A

First part of small intestine
Receives secretions from accessory organs (bile and pancreatic juice)
Folded wall (VILLI)- increase SA for final stages of digestion and absorption
Base of villi - intestinal glands- crypts of LieberKühn
Brunner’s Glands - secrete alkaline fluid and mucus to neutralise acid chyme from stomach

31
Q

Ileum

A

Where digestion completed
Main site of absorption
5m long - takes long time to pass through ileum - increases time available for digestion and absorption
Villi - increase SA - rich blood supply to remove products of digestion
Most water absorbed in ileum

32
Q
A
33
Q

Large intestine

A

First part = caecum
No role in human digestive system
Appendix in caecum - no known role
Undigested food and remaining water and minerals first pass into colon

34
Q

Colon

A

Main part of large intestine
Absorbs rest fo water and mineral salts
Vitamins produced by microorganisms in colon absorbed into blood
Semi-solid mass of undigested food - faeces

35
Q

Rectum

A

Last part of large intestine

Muscular tube that temporarily stores faeces before eliminated from body

36
Q

Anus

A

Made from sphincter muscles

Control defaecation occurs

37
Q

Accessory organs

Liver

A

Liver
• bile produced by breaking down haemoglobin
• receives almost all products of digestion carried there by hepatic portal vein
• store excess glucose as glycogen
• remove amino groups and convert into urea
• store vitamins

38
Q

Accessory organs

Gall bladder

A

Stores bile

Secreted into duodenum via bile duct

39
Q

Accessory organs

Pancreas

A

ENDOCRINE
• secretes insulin and glucagon for control of blood glucose levels
EXOCRINE
• secretes pancreatic juice ( mix of enzymes, enzyme precursors, sodium hydrogen carbonate) which are carried by pancreatic ducts to duodenum

40
Q

What are the layers in the gut wall

A 
Serosa
Longitudal and circular muscle layers
Submucose
Muscularis mucosa
Mucosa
41
Q

Serosa in gut wall

A

a layer of connective tissue carrying blood vessels, lymphatic vessels and nerves.

42
Q

Longitudinal and circular muscle layers in gut wall

A

Responsible for peristalsis

43
Q

Submucosa in gut wall

A

Generally carries the main arterioles and venules

Contain glands

44
Q

Muscularis mucosa in gut wall

A

Thin lager of muscle involved in moving the inner wall of the gut

45
Q

Mucosa in gut wall

A

covered by a layer of epithelial cells; some of these produce mucus and others are responsible for the final stages of digestion and absorption of nutrients.

46
Q
A
47
Q

How are duodenum and ileum adapted to increasing efficiency of digestion and absorption

A

Folds in wall to increase SA
inner surface further folded into villi
Surface of epithelial cells covering villi further folded into microvilli

48
Q

How has the villi adapted to increase the efficiency of digestion and absorption

A
  • rich capillary network to absorb and remove products of digestion and maintain concentration gradient
  • lacteals - absorb products of fat digestion and maintain concentration gradient
  • thin - reduce diffusion distance
  • microvilli - increase SA
  • many mitochondria- ATP for active transport
49
Q

pH of mouth

A

Varies depending on food eaten

6.5 - 7.5

50
Q

pH of stomach

A

Upper - 4.0-6.5
Lower - 1.5-4.0
Less acidic where food enters from oesophagus

51
Q

pH of duodenum

A

7.0-8.5
Start - acidic
Brunner’s glands secretions neutralise acid and increases pH

52
Q

pH of ileum

A

4.0-7.0

Fatty acids and amino acids lower it

53
Q

pH of colon

A

4.0-7.0

Varies on food and action of bacteria

54
Q

Digestion of starch

A

Digestion of it starts in mouth and duodenum
Salivary and pancreatic amylase
STARCH ——–> MALTOSE
digestion of disaccharides into monosaccharides takes place on surface of epithelial cells covering villi
Enzymes embedded in cell membranes

55
Q

Digestion of protein

A
  • Involves breaking long polypeptide chains into amino acids and dipeptides that can be absorbed
  • Some protease enzymes secreted as inactive precursors to prevent autolysis
  • begins in stomach
  • pepsinogen activated by HCl to form the endopeptidase enzyme = pepsin
  • in duodenum - trypsinogen activated by enterokinase to form trypsin (endopeptidase)
  • pancreas and intestinal glands secrete exopeptidase
  • final digestion of dipeptides into amino acids takes place through enzymes embedded in cell membrane of epithelial cells in ileum
56
Q

Endopeptidase

A

Hydrolyse peptide bonds between amino acids in the middle of a polypeptide chain
Non-terminal peptide bonds
PROTEIN —> POLYPEPTIDES + PEPTIDES
happens before digestion by an exopeptidase to increase rate of digestion of proteins

57
Q

Exopeptidase

A

Break peptide bonds between amino acids at the ends of peptide/polypeptide chains
Terminal peptide bonds
PEPTIDES —> AMINO ACIDS + DIPEPTIDES
wont hydrolyse a dipeptide

58
Q

Lipid absorption

A

Digested by lipases
LIPID —> FATTY ACIDS + GLYCEROL
bile emulsified lipids by breaking large globules of fat into small droplets
This increases SA for lipase action
Also allows very small droplets of fat to be directly absorbed into blood stream

59
Q

How are glucose and amino acids absorbed into ileum by villi

A

Active transport
Diffusion
Co-transport
Into capillaries
Then carries in hepatic portal veins to liver
Disaccharides and dipeptides absorbed into epithelial - digested intracellularly
Amino acids and monosaccharides- pass into capillaries

60
Q

What is glucose used for after being absorbed

A

For energy release in respiration
Some converted into glycogen in liver and muscles
Excess stored in fat cells

61
Q

What is amino acids used for after being absorbed

A

For protein synthesis
Excess cannot be stored - deaminated and converted to urea
Remainder converted to carbohydrates and stored

62
Q

How are fatty acids and glycerol absorbed into ileum

A

Separately into epithelial cells
Reassembled into triglycerides
Some pass into lacteal then lymphatic system to blood stream opening at thoracic duct
Some short-chain fatty acids diffuse directly into blood in capillaries

63
Q

What are lipids used for after being absorbed

A

Produce cell membranes and hormones

Excess stored as fat

64
Q

How is water absorbed in the digestive system

A

Most absorbed into bloodstream in ileum

Remainder of water and mineral salts and vitamins secreted by microorganisms in colon are absorbed by colon

Wjec Biology Unit 2 (5 decks)

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