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Wjec Biology Unit 2 > 2.4 > Flashcards

2.4 Flashcards

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
What cells secrete hydrochloric acid
Oxyntic cells
26
Function of hydrochloric acid in the stomach
Provides optimum pH for enzymes Denature proteins Softens connective tissues in food Activates pepsin
27
What cells secrete mucus in stomach
Goblet | Neck cells
28
Why is mucus needed in stomach
Forms a barrier between stomach lining and gastric juice | Prevents self-digestion of stomach walls and glands
29
What is the small intestine comprised of
Duodenum and ileum
30
Duodenum
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
Ileum
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
33
Large intestine
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
Colon
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
Rectum
Last part of large intestine | Muscular tube that temporarily stores faeces before eliminated from body
36
Anus
Made from sphincter muscles | Control defaecation occurs
37
Accessory organs | Liver
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
Accessory organs | Gall bladder
Stores bile | Secreted into duodenum via bile duct
39
Accessory organs | Pancreas
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
What are the layers in the gut wall
``` Serosa Longitudal and circular muscle layers Submucose Muscularis mucosa Mucosa ```
41
Serosa in gut wall
a layer of connective tissue carrying blood vessels, lymphatic vessels and nerves.
42
Longitudinal and circular muscle layers in gut wall
Responsible for peristalsis
43
Submucosa in gut wall
Generally carries the main arterioles and venules | Contain glands
44
Muscularis mucosa in gut wall
Thin lager of muscle involved in moving the inner wall of the gut
45
Mucosa in gut wall
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
47
How are duodenum and ileum adapted to increasing efficiency of digestion and absorption
Folds in wall to increase SA inner surface further folded into villi Surface of epithelial cells covering villi further folded into microvilli
48
How has the villi adapted to increase the efficiency of digestion and absorption
* 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
pH of mouth
Varies depending on food eaten | 6.5 - 7.5
50
pH of stomach
Upper - 4.0-6.5 Lower - 1.5-4.0 Less acidic where food enters from oesophagus
51
pH of duodenum
7.0-8.5 Start - acidic Brunner's glands secretions neutralise acid and increases pH
52
pH of ileum
4.0-7.0 | Fatty acids and amino acids lower it
53
pH of colon
4.0-7.0 | Varies on food and action of bacteria
54
Digestion of starch
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
Digestion of protein
* 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
Endopeptidase
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
Exopeptidase
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
Lipid absorption
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
How are glucose and amino acids absorbed into ileum by villi
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
What is glucose used for after being absorbed
For energy release in respiration Some converted into glycogen in liver and muscles Excess stored in fat cells
61
What is amino acids used for after being absorbed
For protein synthesis Excess cannot be stored - deaminated and converted to urea Remainder converted to carbohydrates and stored
62
How are fatty acids and glycerol absorbed into ileum
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
What are lipids used for after being absorbed
Produce cell membranes and hormones | Excess stored as fat
64
How is water absorbed in the digestive system
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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