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A level Biology > Nutrition ( Component 3 ) > Flashcards

Nutrition ( Component 3 ) Flashcards

1
Q

Define autotrophic

A

An organism that produces its own food - it manufactures complex organic compounds from simpler inorganic molecules such as water and carbon dioxide

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2
Q

What are the two types of autotrophic organisms ?

A

Photoautotrophic
Chemoautoptrophic

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3
Q

What is a phototrophic organism ?

A

Organism that obtains its nutrition through photosynthesis ( uses light energy )

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4
Q

What is a chemoautotrophic organism ?

A

Organism that obtains its nutrition through inorganic molecules, such as sulfur, in the absence of light

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5
Q

Define heterotrophic

A

An organism that cannot produce its own food. It obtains energy by feeding on organic compounds produced by other organisms - consume complex organic food material.

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6
Q

What is a saprotroph / saprobiont ?

A

A heterotrophic organism that feeds by extracellular digestion and absorbs the soluble products by digestion eg fungi and bacteria

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7
Q

What is meant by the term “ holozoic “ ?

A

Describes a heterotrophic organism that internally digests food substances

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8
Q

What is meant by the term “ parasitic “ ?

A

Describes a heterotrophic organism that lives on or in a host and takes nourishment at the expense of the other organism ( eg mosquito )

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9
Q

Describe extracellular digestion by saprotrophs / saprobionts

A

Release enzymes which catalyse the breakdown of dead plant and animal material into simpler organic matter. They feed by secreting enzymes onto the food material outside the body and then absorb the soluble products across the cell membrane by diffusion. This is called extracellular digestion

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10
Q

What processes does holozoic nutrition involve ?

A

Ingestion, digestion, absorption, assimilation and egestion

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11
Q

Define ingestion

A

The process by which organisms take food into their bodies

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12
Q

Define digestion

A

The process by which large, insoluble molecules are broken down into smaller, soluble molecules that can be absorbed across cell membranes

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13
Q

Name the two types of digestion

A

Mechanical and chemical

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14
Q

What is mechanical digestion ?

A

Type of digestion that involves physically breaking down food material into smaller pieces to increase total SA for chemical digestion

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15
Q

What is chemical digestion ?

A

The process by which large, insoluble molecules are broken down into smaller, soluble molecules using enzymes

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16
Q

What is assimilation ?

A

The synthesis of biological compounds from absorbed simpler molecules

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17
Q

Define absorption

A

The movement of useful substances into the bloodstream

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18
Q

Define egestion

A

The removal of undigested waste material from the body

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19
Q

Describe briefly nutrition in unicellular organism eg amoeba

A

Food particles are absorbed and digestion is carried out intracellularly
Food particles are ingested, digested and the waste egested.

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20
Q

Describe, in detail, how unicellular organisms obtain nutrients

A

Ingestion via phagocytosis
Intracellular digestion ( using hydrolytic enzymes ) breaks down large, insoluble molecules into smaller, soluble molecules
Products of digestion pass into cytoplasm by diffusion and active transport
Undigested material removed by exocytosis

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21
Q

How would you describe the gut in simple organisms ?

A

In simple organisms, feeding on only one type of food, the gut is undifferentiated.

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22
Q

What is a hydra ?

A

A small, multicellular freshwater organism of the phylum Cnidaria

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23
Q

Describe the structure of Hydra

A

Basic, undifferentiated sac like gut
Single opening, surrounded by tentacles, that serves as a mouth and anus
Single gut cavity ( known as the enteron )

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24
Q

Outline the process of digestion in Hydra

A

Hydrolytic enzmyes secreted into the enteron by endodermis
Extracellular digestion partially digests food molecules
Partially digested food transported, via phagocytosis, into endodermal cells where intracellular digestion takes place
Undigested material egested from enteron via single opening

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25
Describe the shape of the gut in more complex organisms
Tube like with two openings, a mouth for ingestion and anus for egestion - evolved a specialised gut for the digestion of food. Tube gut that is divided into various parts along its length and each part is specialised to carry out particular functions.
26
What type of diet is the human gut adapted to ?
An omnivorous diet consisting of plant and animal material - a more varied diet
27
What are the four tissue layers surrounding a central cavity in the gut wall ?
serosa, longitudinal muscle layer, circular muscle layer, submucosa and mucosa.
28
What is the epithelium ?
A single layer of cells that line the gut wall
29
Describe the structure of the mucosa layer of the gut wall
Mucous membrane lining the gut wall Contains glands that secrete digestive enzymes, mucus, and an acid or alkaline liquid that provides an optimum pH
30
Describe the structure of the sub mucosa layer of the gut wall
Layer of connective tissue below the mucous membrane Contains blood vessels and lymph for the transport of digestion product and glands that secrete an alkaline fluid
31
Describe the muscle layer in the human gut
A layer of circular and longitudinal muscles between the submucosa
32
Explain the action of circular and longitudinal muscles in peristalsis
The contraction of the circular muscle behind the bolus of food and the relaxation of the longitudinal muscle in front forces food down the gut
33
What is peristalsis ?
Peristalsis is the involuntary contraction and relaxation of longitudinal and circular muscles throughout the digestive tract which allows food to move down the gut
34
What is the role of cellulose fibre ?
Cellulose fibre is required to provide bulk and stimulate peristalsis.
35
What is the buccal cavity ?
The oral cavity through which food enters the body
36
What type of digestion takes place in the buccal cavity ?
Mechanical digestion and chemical digestion of starch
37
What is the normal pH range in the buccal cavity ?
6.5 to 7.5
38
What is the function of the teeth ?
Crush and grind food into smaller pieces - used in mechanical digestion in order to increase surface area for enzyme action.
39
What is the tongue ?
A muscular organ in the buccal cavity that is vital in the chewing and swallowing of food
40
Describe the function of the salivary glands
Secrete amylase, mineral ions and mucus into the buccal cavity
41
What is the function of the oesophagus ?
Carries food from the buccal cavity to the stomach by peristalsis
42
Describe the different structures in the stomach and state their roles : rugae, cardiac sphincter, pyloric sphincter, goblet cells
Rugae = ridges to help with mechanical breakdown of food Cardiac sphincter : relaxes at upper end, allowing food to enter Pyloric sphincter : relaxes to allow food to exit the stomach into duodenum Goblet cells : secrete mucus to protect stomach wall from enzymes and acid
43
Describe the processes that take place in the stomach
Mechanical digestion ( mixing and grinding ) and chemical digestion of protein - oxynotic cells kill most bacteria in the food, provide optimum pH for enzymes and activate pepsinogen
44
What type of glands are found in the stomach ?
Gastric glands
45
Describe the function of gastric glands
Secrete endopeptidases, hydrochloric acid and an alkaline mucus into the stomach
46
What is the normal pH of the stomach ?
2
47
What is the role of the liver ?
Secrete bile into the small intestine via the gallbladder and bile duct
48
Describe the composition and function of bile
Consists of bile salts and an alkaline fluid Neutralises stomach acid, providing an ideal pH for lipase
49
Where is most of the water reabsorbed ?
Most water is reabsorbed, along with soluble nutrients, in the small intestine.
50
What happens to the remaining water that is not reabsorbed by the small intestine ?
The colon absorbs the remaining water, together with vitamins (secreted by microorganisms in the colon) in order to produce solidified faeces.
51
What passes along the colon to be egested as faeces ?
Residues of undigested cellulose, bacteria and sloughed cells pass along the colon to be egested as faeces.
52
State the two main divisions of the small intestine
Duodenum Ileum
53
What is the role of Brunner's glands and where are they located ?
Found in the submucosa of the duodenum. Secrete mucus for lubrication and protection, secrete alkaline juice which helps maintain the optimum pH for the functioning of the enzymes in this area
54
What is the duodenum ?
The first section of the small intestine where proteins and lipids are hydrolysed, has alkaline pH to neutralise acidity of products from stomach
55
What is the ileum ?
The second section of the small intestine that serves as the main site of absorption of the products of digestion
56
What is the normal pH range of the small intestine ?
7 to 8
57
What is the pancreas and where is it located ?
A large gland situated behind the stomach
58
Describe the role of the pancreas
It secretes enzymes and an alkaline fluid into the duodenum via the pancreatic duct
59
What is the large intestine also called ?
Colon
60
Describe the function of the colon
Reabsorbs water and minerals from the waste material
61
What is the rectum ?
The segment of the large intestine that stores faeces prior to egestion
62
What is the anus ?
Site of egestion of faeces
63
What is the role of the number of different glands in the body
To produce digestive secretions
64
Where are the glands ( that produce digestive secretions ) found and what is the difference between them ?
Some of these glands are found in the wall of the gut with the secretions passing directly into the gut cavity. Other glands are found outside the gut with the secretions passing along ducts into the gut cavity.
65
What do animals with a varied diet require and why ?
Animals with a varied diet require more than one type of enzyme to carry out the digestion of the different food substrates and usually more than one type of enzyme is needed for the complete digestion of a particular food.
66
What is the role of saliva ?
Contains salivary glands, that secrete amylase, mineral ions and mucus into the buccal cavity. Contains mineral salts which maintain alkali condition and lysozome which kills bacteria
67
What is the role of mucus ?
Lubrication and protection
68
Which enzymes are involved in carbohydrate digestion and where are they found ?
Amylase : saliva and pancreatic juice Maltase, sucrase, lactase : membrane of epithelial cells of the small intestine
69
What are the substrates and products of the carbohydrases ?
Amylase hydrolyses starch into maltose Maltase hydrolyses maltose into alpha glucose Sucrase hydrolyses sucrose into glucose and fructose Lactase hydrolyses lactose into glucose and galactose
70
What is the optimum pH of amylase ?
pH 8
71
Which enzymes are involved in protein digestion and what are their roles ?
Endopeptidases : hydrolyse non terminal peptide bonds within a protein to form smaller peptides - hydrolyse peptide bonds within the protein/polypeptide molecule, adjacent to specific amino acids, and form peptides Exopeptidases : hydrolyse the terminal peptide bonds of a protein to form dipeptides and amino acids - hydrolyse the terminal peptide bonds of peptides, from the free amino end or the free carboxyl end.
72
Give 2 examples of endopeptidases
trypsin pepsin
73
How is trypsin produced
Secreted by the pancreas as inactive trypsinogen Enterokinase converts inactive trysinogen into active trypsin in the duodenum
74
Name the active form of pepsin
Pepsinogen
75
Where is pepsinogen secreted from ?
Gastric glands
76
How is inactive pepsinogen converted into its active form, pepsin ?
Hydrochloric acid converts inactive pepsinogen into active pepsin
77
Where are the lipids digested ?
Small intestine
78
What must happen before lipids can be digested ?
The lipids must be emulsified by bile salts produced by the liver. This breaks down large fat molecules into smaller, soluble molecules called micelles, increasing the SA
79
How are lipids hydrolysed ?
Lipases hydrolyse lipids into monoglycerides, fatty acids and glycerol
80
Where are lipases found ?
In pancreatic juice
81
State the processes by which absorption takes place in the ileum
Simple diffusion Facilitated diffusion Active transport Osmosis
82
Which molecules are absorbed by simple diffusion in the ileum ?
Monoglycerides, fatty acids and glycerol
83
Why can monoglycerides, fatty acids and glycerol be absorbed via simple diffusion ?
They are non polar molecules so can easily diffuse across the membrane of the epithelial cells
84
What happens to the monoglycerides, fatty acids and glycerol once they are absorbed into the cells ?
They are reformed into triglycerides, absorbed into the lacteals and transported via the lymphatic system into the blood.
85
How are amino acids absorbed from the lumen of the gut ?
Via active transport into epithelial cells and then into the bloodstream by facilitated diffusion
86
Which molecules rely on co transport from the lumen of the gut into the cytoplasm of the epithelial cells ?
Glucose and other monosaccharides
87
Explain how sodium ions are involved in co transport
Na+ ions are actively transported out of the cell into the lumen, creating a diffusion gradient. Nutrients are then taken up into the cells along with Na+ ions.
88
How do monosaccharides pass from the epithelial cells into the bloodstream ?
Via facilitated diffusion
89
Explain the site and mechanism of final digestion and absorption of dipeptides and disaccharides ( summary )
Digestion on the membranes of epithelial cells covering the villi Absorption of amino acids by active transport into the epithelial cells and facilitated diffusion into the capillaries Absorption of glucose and other monosaccharides into epithelial cells by co transport (with sodium ions) and then into capillaries by facilitated diffusion. Glucose and amino acids are transported via Hepatic portal vein to the liver. Fatty acids and glycerol diffuse into the epithelial cells, where they are reassembled into triglycerides. These then pass into the lacteal and are carried via the lymphatic system to the blood at the thoracic duct
90
What is a parasite ?
An organism that lives on or in a host and takes nourishment at the expense of another organism. They are organisms that live on (ectoparasites) or in (endoparasites) another organism, called the host, and obtain nourishment at the expense of the host. This usually causes damage to the host organism.
91
Name the two different types of parasite
Ectoparasites Endoparasites
92
What are ectoparasites and give an example ?
Parasites that live on the host eg Head louse , Pediculus Humanus
93
What are endoparasites and give an example ?
Parasites that live in the host eg Port tapeworm , Taenia solium
94
How does the head louse feed and transfer from one host to another ?
Feeds by sucking blood from the host's scalp It has claws to hold onto the hairs and lays eggs which are glued to the base of hairs Transfers between host by direct contact
95
Head louse adaptations
Claws – to attach to hairs/ prevent removal from scratching Gut – feeds by holozoic nutrition Piercing mouthparts - feeds on blood Male and Female individuals – A mate is easy to find.
96
Where does the pork tapeworm live ?
Primary host - adult tapeworm lives in human gut Secondary host - larval form can develop in pigs
97
Primary vs Secondary Host
Primary host : where parasite undergoes sexual reproduction / adult form exists Secondary host : where parasite undergoes asexual reproduction / only larval forms exist
98
How can humans and pigs become infected by the Pork Tapeworm ?
Humans become infected by consuming undercooked pork ( containing larval forms of the tapeworm ) Pigs may become infected by ingesting contaminated faeces
99
How does the Pork tapeworm feed ?
Absorbs pre digested nutrients in the gut through its cuticle
100
How is the pork tapeworm adapted to living in the gut ?
Thick cuticle Secretes anti enzymes that prevent its digestion by host enzymes Scolex has strong suckers and hooks for attachment to gut wall Long, thin body provides large SA:V ratio for absorption Produces large number of eggs that pass out in faeces to increases chances of infecting secondary host
101
Head Louse summary from spec
The head louse (Pediculus) is an example of an ectoparasite which feeds by sucking blood from the scalp of the host. It has claws to hold onto the hairs and lays eggs which are glued to the base of hairs. Transfer between hosts is direct contact.
102
Port Tapeworm summary from spec
Taenia solium is an example of an endoparasite. The adult tapeworm lives in the gut of humans - the primary host; a larval form develops in pigs – the secondary host. Infection of humans occurs when a person eats undercooked pork containing live larval forms. The gut is a hostile environment due to the presence of various secretions and peristalsis. The tapeworm has adapted to living in the gut by having a thick cuticle, produces anti-enzymes, and a scolex to attach to the gut wall. Taenia solium has a reduced gut and feeds by absorbing pre-digested nutrients through its cuticle. To increase the chances of infecting a secondary host it produces large numbers of eggs that pass out in the faeces.

A level Biology (10 decks)

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