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Biology A- Level > Component 3 - Nutrition > Flashcards

Component 3 - Nutrition Flashcards

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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

Name the two types of autotrophic
organisms.

A

● Photoautotrophic
● Heterotrophic

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3
Q

What is a photoautotrophic organism?

A

An organism which obtains its nutrition
through photosynthesis.

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4
Q

What is a chemoautotrophic organism?

A

An organism which 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.

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6
Q

What is a saprotroph?

A

An organism that feeds by extracellular
digestion, e.g. fungi.

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7
Q

Describe extracellular digestion by
saprotrophs.

A

● Release enzymes which catalyse the
breakdown of dead plant and animal
material into simpler organic matter
● Absorb the products of digestion

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8
Q

What is meant by the term ‘holozoic’?

A

Describes a heterotrophic organism that
internally digests food substances.

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9
Q

What processes does holozoic nutrition
involve?

A

Ingestion, digestion, absorption,
assimilation and egestion.

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10
Q

Define ingestion.

A

The process by which organisms take
food into their bodies.

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11
Q

Define digestion.

A

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

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12
Q

Name the two types of digestion.

A

● Mechanical digestion
● Chemical digestion

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13
Q

What is mechanical digestion?

A

● Type of digestion that involves physically
breaking down food material into smaller pieces
● Increases the total surface area for chemical
digestion

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14
Q

What is chemical digestion?

A

A type of digestion that involves breaking
down large, insoluble molecules into
smaller, soluble molecules using enzymes.

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15
Q

What is assimilation?

A

The synthesis of biological compounds
from absorbed simpler molecules.

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16
Q

Define egestion.

A

The removal of undigested waste
material from the body.

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17
Q

Describe 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 the cytoplasm by diffusion and
active transport
● Undigested material removed by exocytosis

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18
Q

What is a Hydra?

A

A small, multicellular, freshwater
organism of the phylum Cnidaria.

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19
Q

Describe the structure of Hydra.

A

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

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20
Q

Outline the process of digestion in
Hydra.

A

● Hydrolytic enzymes secreted into the enteron by the 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 the enteron via the single
opening

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21
Q

Describe the shape of the gut in more
complex organisms.

A

Tube-like with two openings, a mouth for
ingestion and anus for egestion.

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22
Q

State the names of the different layers of
the gut wall.

A

● Epithelium
● Mucosa
● Submucosa
● Muscle layer
● Serosa

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23
Q

Describe the structure of the mucosa
layer of the gut wall.

A

● Mucous membrane lining the gut wall
● Contains glands that secrete digestive
enzymes, mucus, and an acid or alkaline liquid
that provides an optimum pH

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24
Q

Describe the structure of the
sub-mucosa layer of the gut wall.

A

● 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

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25
Q

Explain the action of circular and
longitudinal muscles in peristalsis.

A

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.

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26
Q

What is the serosa?

A

The tough, protective layer that
surrounds the gut.

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27
Q

Which type(s) of digestion take place in
the buccal cavity?

A

Mechanical digestion and chemical
digestion of starch.

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28
Q

What is the normal pH range of the
buccal cavity?

A

pH 6.5 to 7.5

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29
Q

What is the function of the teeth?

A

Crush and grind food into smaller pieces,
increasing its surface area.

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30
Q

Describe the function of salivary glands.

A

Secrete amylase, mineral ions and
mucus into the buccal cavity.

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31
Q

What is the function of the oesophagus?

A

Carries food from the buccal cavity to the
stomach by peristalsis.

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32
Q

Describe the processes that take place
in the stomach.

A

Mechanical digestion (mixing and grinding)
and chemical digestion of protein.

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33
Q

What type of glands are found in the
stomach?

A

Gastric glands

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34
Q

Describe the function of gastric glands.

A

Secrete endopeptidases, hydrochloric
acid and an alkaline mucus into the
stomach.

35
Q

What is the normal pH of the stomach?

A

2

36
Q

What is the role of the liver?

A

Secretes bile into the small intestine via
the gallbladder and bile duct.

37
Q

Describe the composition and function
of bile.

A

● Consists of bile salts and an alkaline fluid
● Neutralises stomach acid, providing an
ideal pH for lipase

38
Q

State the two main divisions of the small
intestine.

A

● Duodenum
● Ileum

39
Q

What is the duodenum?

A

The first section of the small intestine
where proteins and lipids are hydrolysed.

40
Q

What is the ileum?

A

The second section of the small intestine
that serves as the main site of absorption
of the products of digestion.

41
Q

What is the normal pH range of the small
intestine?

A

7 to 8

42
Q

What is the pancreas and where is it
located?

A

A large gland situated behind the
stomach.

43
Q

Describe the role of the pancreas.

A

It secretes enzymes and an alkaline fluid
into the duodenum via the pancreatic
duct.

44
Q

What is the large intestine also called?

A

Colon

45
Q

Describe the function of the colon.

A

Reabsorbs water and minerals from the
waste material.

46
Q

What is the rectum?

A

The segment of the large intestine that
stores faeces prior to egestion.

47
Q

Which enzymes are involved in
carbohydrate digestion? Where are they
found?

A
  • Amylase in saliva and pancreatic juice
  • Maltase, sucrase, lactase on the
    membrane of the epithelial cells of the small
    intestine
48
Q

What are the substrates and products of
the carbohydrases?

(4 of them)

A

● Amylase hydrolyses starch to maltose
● Maltase hydrolyses maltose to alpha-glucose
● Sucrase hydrolyses sucrose to glucose and fructose
● Lactase hydrolyses lactose to glucose and galactose

49
Q

What is the optimum pH of amylase?

A

8

50
Q

Which enzymes are involved in protein
digestion? What are their roles?

A

● Endopeptidases - hydrolyse non-terminal peptide
bonds within a protein to form smaller peptides
● Exopeptidases - hydrolyse the terminal peptide bonds
of a protein to form dipeptides and amino acids

51
Q

Give some examples of endopeptidases.

A

● Trypsin
● Pepsin

52
Q

Describe how trypsin is produced.

A

● Secreted by the pancreas as inactive
trypsinogen
● Enterokinase converts inactive trypsinogen into
active trypsin in the duodenum

53
Q

Name the inactive form of pepsin.

A

Pepsinogen

54
Q

Where is pepsinogen secreted from?

A

Gastric glands

55
Q

Describe how inactive pepsinogen is
converted into its active form, pepsin.

A

Hydrochloric acid converts inactive
pepsinogen into active pepsin.

56
Q

Where are lipids digested?

A

Small intestine

57
Q

What must happen before lipids can be
digested?

A

They must be emulsified by bile salts
produced by the liver. This breaks down large
fat molecules into smaller, soluble molecules
called micelles, increasing the surface area.

58
Q

How are lipids digested?

A

Lipases hydrolyse lipids into
monoglycerides, fatty acids and glycerol.

59
Q

Where are lipases found?

A

In pancreatic juice.

60
Q

State the processes by which absorption
takes place in the ileum.

A

● Simple diffusion
● Facilitated diffusion
● Active transport
● Osmosis

61
Q

Which molecules are absorbed by simple
diffusion in the ileum?

A

Monoglycerides, fatty acids and glycerol.

62
Q

Why can monoglycerides, fatty acids and
glycerol be absorbed via simple
diffusion?

A

They are non-polar molecules so can
easily diffuse across the membrane of
the epithelial cells.

63
Q

What happens to monoglycerides, fatty
acids and glycerol once they are
absorbed into cells?

A

They are reformed into triglycerides,
absorbed into the lacteals and transported
via the lymphatic system into the blood.

64
Q

How are amino acids absorbed from the
lumen of the gut?

A

Via active transport into epithelial cells
and then into the bloodstream by
facilitated diffusion.

65
Q

Which molecules rely on co-transport
from the lumen of the gut into the
cytoplasm of the epithelial cells?

A

Glucose and other monosaccharides.

66
Q

Explain how sodium ions are involved in
co-transport.

A

Sodium ions (Na+) 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.

67
Q

How do monosaccharides pass from the
epithelial cells into the bloodstream?

A

Via facilitated diffusion.

68
Q

Describe the adaptations of herbivores to
a high cellulose diet.

A

● Long gut
● Loose articulation of the lower jaw
● Horny pad on the upper jaw
● Specialised dentition for grinding tough plant material

69
Q

Describe how the dentition of a herbivore
is adapted to its diet.

A

● Small, flat incisors on lower jaw for cutting grass against upper horny pad
● Diastema between incisors and premolars - separates fresh grass from the
cud and enables manipulation of food by the tongue
● Premolars and molars have a large surface area and sharply ridged biting
surfaces for grinding plant material

70
Q

What are ruminants?

A

Mammals that digest plant material slowly in a
specialised four-chambered stomach and
regurgitate it to chew it again, enabling the
efficient breakdown of fibre.

71
Q

Name the four chambers of the ruminant
stomach.

A

● Rumen
● Reticulum
● Omasum
● Abomasum

72
Q

Describe the rumen.

A

The first stomach of a ruminant. It
contains mutualistic bacteria that are
able to hydrolyse cellulose into glucose.

73
Q

Describe the adaptations of carnivores to
a high protein diet.

A

● Short gut
● Powerful jaw muscles
● Specialised dentition for cutting and tearing meat

74
Q

Describe how the dentition of a carnivore
is adapted to its diet.

A

● Sharp incisors to remove flesh from bone
● Large, pointed canines required to grip and kill prey
● Sharp carnassials (modified premolars and molars) to slice and
shear meat
● Molars with sharp, flattened edges to crush bone

75
Q

What is a parasite?

A

An organism that lives on or in a host
and takes nourishment at the expense of
the other organism

76
Q

Name the two types of parasite.

A

● Ectoparasites
● Endoparasites

77
Q

What are ectoparasites? Give an
example.

A

Parasites that live on the host e.g. Head
louse, Pediculus humanus.

78
Q

What are endoparasites? Give an
example.

A

Parasites that live in the host e.g. Pork
tapeworm, Taenia solium.

79
Q

How does the head louse feed and
transfer from one host to another?

A

● Feeds by sucking blood from the host’s scalp
● Transfers between hosts by direct contact

80
Q

Where does the pork tapeworm live?

A

● Primary host - adult tapeworm lives in
the human gut
● Secondary host - larval form can develop
in pigs

81
Q

How can humans and pigs become
infected by the pork tapeworm?

A

● Humans become infected by consuming undercooked
pork (containing larval forms of the tapeworm)
● Pigs may become infected by ingesting
contaminated faeces

82
Q

How does the pork tapeworm feed?

A

Absorbs pre-digested nutrients in the gut
through its cuticle.

83
Q

How is the pork tapeworm adapted to
living in the gut?

A

● 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 proves large surface-area-to-volume ratio for
absorption

Biology A- Level (11 decks)

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