ch6 nutrition in humans

Question 1

holozoic nutrition

Answer 1

-take in complex food and digest inside the body
-ingestion, digestion, absorption, assimilation, egestion

Question 2

saprophytic nutrition

Answer 2

-fungi and bacteria (saprophytes)
-break down food outside the body
-absorb soluble nutrients into the body
-digestion, absorption, assimilation

Question 3

parasitic nutrition

Answer 3

-parasites
-live on or inside body or other organisms and obtain food from them
-absorption, assimilation

Question 4

5 main processes of human nutrition

Answer 4

-ingestion: take in food through mouth
-digestion : food is broken down into small soluble food molecules
-absorption: food molecules enter circulatory system
-assimilation: absorbed food molecules are taken up by cells for metabolism
-egestion: undigested and unabsorbed materials are removed as faeces

Question 5

state of food throughout the alimentary canal

Answer 5

mouth cavity: solid
stomach: semi-solid
duodenum: thick liquid
ileum: thinner liquid
colon: semi-solid
rectum: harder pellet

Question 6

4 types of teeth

Answer 6

-incisor: for biting and cutting food, chisel-shaped with flat sharp edges, one root

-canine: tearing flesh, pointed and curved, one root

-premolar: crushing and grinding food, broad top with cusps, one or two roots

-molar: crushing and grinding food, broad top with cusps, two or three roots

Question 7

milk teeth

Answer 7

-dental formula: 2102/2102
-total number of teeth: 20

Question 8

permanent teeth

Answer 8

-dental formula: 2123/2123
-total number of teeth: 32

Question 9

structure of teeth and uses

Answer 9

enamel:
-outermost layer, non-living, made mainly of calcium salts
-hardest tissue in our body -> protects the tooth fro wearing down as a result of chewing

cementum:
-attaches the tooth to the jawbone through the periodontal membrane

dentine:
-bone-like substance, large amt of calcium salts
-living tissue containing living cytoplasm

pulp cavity:
-contain living cells, blood vessels, nerve fibres
-blood vessels supply oxygen and nutrients, and remove wastes
-nerve fibres detect temperature and pressure

Question 10

physical and chemical digestion in the mouth cavity

Answer 10

physical: chewing (mastication)
chemical: catalysed by enzyme in saliva

Question 11

physical and chemical digestion in stomach

Answer 11

physical: churning
chemical: catalysed by enzyme in gastric juice

Question 12

physical and chemical digestion in small intestine

Answer 12

physical: emulsification by bile
chemical: catalysed by enzymes in pancreatic juice and enzymes on intestinal wall

Question 13

mouth cavity
substances in saliva and uses

Answer 13

substances in saliva:
-salivary amylase: carbohydrase, catalyses breakdown of starch into maltose

-mucus: sticky, bind food particles together, moistens and lubricates the food -> easier to chew and swallow

-water: dissolves soluble substances -> taste food

Question 14

swallowing

Answer 14

-tongue rises to push the bolus towards the pharynx
-soft plate moves up to prevent the bolus from entering the nasal cavity
-larynx rises so that the epiglottis covers the opening to the trachea
-bolus enters oesophagus

Question 15

peristalsis

Answer 15

-moving food from the oesophagus to rectum
-muscles layers in walls of oesophagus contract alternatively -> wave-like movement to push the food down

Question 16

stomach
substances in gastric juice and uses

Answer 16

pepsin:
-protease which catalyses the breakdown of proteins into peptides
-acidic medium

hydrochloric acid:
-provides an acidic medium for action of pepsin
-kills most bacteria in food
-denaturing of protein ingested

mucus:
-protects the stomach wall from being damaged by pepsin or hydrochloric acid

Question 17

small intestine
substances in bile and uses

Answer 17

bile:
-green alkaline fluid produced by liver
-temporarily stored in gall bladder
-released through bile duct
-no digestive enzyme

bile contains:
bile salts:
-emulsify lipids into small droplets (physical digestion)
-facilitates chemical digestion by increasing surface area of lipids for lipase to act on

bile pigments:
-not part of digestion
-waste product formed from breakdown of haemoglobin
-excreted as faeces

sodium hydrogencarbonate:
-neutralises the acidic chyme -> protect the small intestine from being damaged
-provides alkaline medium

Question 18

small intestines
substances in pancreatic juice and uses

Answer 18

pancreatic juice:
-produced by pancreas
-released through pancreatic duct

pancreatic juice contains:
pancreatic amylase:
-carbohydrase which catalyses the breakdown of remaining starch into maltose
- starch+water -pancreatic amylase-> maltose

pancreatic lipase:
-catalyses breakdown of lipids into fatty acids and glycerol
- lipids+water -pancreatic lipase-> fatty acids+glycerol

proteases:
-catalyses the breakdown of proteins into peptides, and peptides into amino acids
- proteins+water-proteases->peptides
- peptides+water-proteases-> amino acids

sodium hydrogencarbonate:
-neutralises acidic chyme
-provides alkaline medium

Question 19

small intestine
intestinal juice

Answer 19

intestinal juice:
-produced by glands in wall of small intestine
-slightly alkaline
-mainly consists of water, mucus, sodium hydrogencarbonate

Question 20

small intestine
epithelium

Answer 20

epithelium of small intestines have specialized cells that have enzymes embedded in their cell membranes

enzymes:
carbohydrases:
-catalyses breakdown of disaccharides into monosaccharides
-maltose -maltase-> glucose
- sucrose-sucrase-> glucose+fructose
- lactose-lactase-> glucose+galactose

proteases:
-catalyses breakdown of peptides into amino acids

Question 21

structure of small intestine

Answer 21

wall:
-circular muscles and longitudinal muscles are present in the wall
-inner wall is highly folded

villi:
-finger-like projections
-each villus has lacteal
-lacteal is surrounded by network of capillaries

epithelium:
-one-cell thick
-large number of microvilli

Question 22

uses of liver
carbohydrate metabolism:

Answer 22

-main site for storage of glycogen
-regulating blood glucose level
-after a meal: blood glucose level rises -> liver converts glucose to glycogen -> glycogen is stored in liver
-glucose level falls between meals: glucose in blood is used by cells in respiration -> liver converts stored glycogen back to glucose and releases into blood

Question 23

uses of liver
lipid metabolism

Answer 23

-converts excess carbohydrates and amino acids into lipids -> transported and stored in adipose tissue

Question 24

uses of liver
amino acid metabolism

Answer 24

-excess amino acids are broken down through deamination
-amino group is removed and converted into urea -> excreted in urine
-remaining part is converted into carbohydrates and lipids
-synthesises non-essential amino acids

Question 25

uses of liver
breakdown of old RBC and storage of iron

Answer 25

-breaks down old RBC
-stores iron released from breaking down RBC
-iron is used for making new RBC

Question 26

uses of liver
storage and production of vitamins

Answer 26

-stores lipid-soluble vitamins (A, D)
-carotene is changed to vitamin A

Question 27

uses of liver
production of bile

Answer 27

-bile is produced in the liver
-bile is released into the duodenum for emulsification

Question 28

uses of liver
detoxification

Answer 28

-detoxification: liver cells contain enzymes which break down certain mild toxic substances (alcohol, drugs) into harmless substances
-harmless substances pass out of body

Question 29

adaption of small intestine for absorption

Answer 29

-long intestine -> sufficient time for complete digestion and absorption
-inner wall is highly folded, many villi and microvilli -> increase surface area
-thin epithelium (one-cell thick) -> short distance for diffusion of food molecules into the blood -> rapid absorption
-la teal and capillaries allow absorbed food molecules to be carried away rapidly -> steep concentration gradient -> increases rate of diffusion
-peristalsis brings food molecules into close contact with the villi -> steep concentration gradient -> increases rate of diffusion

Question 30

absorption in the large intestine

Answer 30

-remaining water, minerals, vitamins are absorbed
-farces are formed
-remains passes through colon too slowly: larger portion of water absorbed -> constipation
-remains passes through colon too fast: smaller portion of water absorbed -> diarrhea

Question 31

assimilation

Answer 31

refer to textbook p6-31