Transcript Ch 5 Heterotrophs are consumers

HETEROTROPHS
(CONSUMERS)
The nutritional requirements of a
heterotroph include ....
• Carbohydrates and lipids
• Amino acids
• Vitamins and minerals
* Water (an inorganic molecule) is also required.
Carbohydrates
• an immediate source of energy: glucose is
broken down to produce ATP (cellular
respiration)
• stored in animals and fungi as glycogen
Lipids
• an important energy store in animals
• required for cell membranes, hormones and
vitamins
Amino acids
• required for protein synthesis
• The 9 essential amino acids - not always able
to be made by animals so must be included in
the diet
• not stored, so must be eaten regularly
• found in milk, eggs and meat
The 9 essential amino acids
Isoleucine
Fish, cheese, seeds and nuts, lentils
Leucine
Grains, cereals, nuts, soybeans, lentils and beans, corn
Lysine
Fish, potatoes, lentils and beans
Methionine
Fish, soybeans, cottage cheese, yoghurt, pumpkin seeds,
sesame seeds
Phenylalanine
Cheese, wheat germ, oat flakes
Threonine
Wheat germ, many nuts, beans and seeds
Tryptophan
Pineapple, yoghurt, bananas, unripened cheese
Valine
Soy flour, raw brown rice, cottage cheese, fish, seeds and nuts,
lentils, mushrooms
Histidine
Meat and dairy products (infants cannot synthesise histidine so
they must obtain it from their diet)
Vitamins
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diverse group of organic molecules
required in very small amounts
mammals need 13 different types
obtained from the diet for mammals & most animals
not used to supply energy
synthesised by plants, some microorganisms and some simple animals
may be fat or water soluble
excess water soluble vitamins may be excreted
excess fat soluble vitamins are retained in the body – may build up to
toxic levels
• named alphabetically
• if lacking, may result in diseases eg pernicious anaemia, scurvy, beriberi
Vitamin
deficiency
After
treatment
Minerals:
• inorganic
• include Ca, P, Mg, Fe, Na, K, I
• found in the cytosol of cells, structural
components such as bone & in the molecules
of many enzymes and vitamins
• if lacking, may cause diseases such as rickets,
osteoporosis
Daily nutritional requirements of
humans
Key questions 1 – 3
Food must be digested
• Digestion – breakdown of organic food into
molecules small enough to be able to pass through
membranes and into cells.
• Small food particles increase the total area available
for enzyme action.
• Digested food passes into the bloodstream and is
carried throughout the body.
• Unabsorbed food is passed out as faeces (egestion).
Chemical digestion
• Process of breaking apart complex molecules
into simple molecules.
• Can be extracellular or intracellular.
• Carried out by enzymes.
• 3 main kinds of enzymes:
 amylases (act on carbohydrates)
 proteases (act on proteins)
 ligases (act on lipids)
Digestive enzymes
• Produced at different sites along the digestive
system.
• specific cells in the gut wall
• salivary glands
• pancreas
• Different ones may act together to progressively
break a molecule down
• Sensitive to pH
Enzymes
• Each enzyme reacts with only one kind of substrate.
• The active site of an enzyme matches the shape of a
particular substrate and the two are able to come
close together (lock and key theory).
Extracellular digestion
Albany pitcher plant
• Chemical digestion in which enzymes are secreted into a cavity
where digestion takes place
• For example, in the central cavity – lumen – of the small
intestine.
• Mammals and most other animals rely on some form of
extracellular digestion.
• Also carried out by starfish, carnivorous plants, fungi.
Fungus on log
Starfish turning stomach
inside out; releasing
enzymes into mollusc;
digesting tissues of mollusc;
absorbing digested foods
through stomach wall.
Intracellular digestion
• Chemical digestion in which a cell
surrounds and digests food
particles.
• The food is contained in a
membrane-bound food vacuole
within the cell.
• Enzymes are released into the
vacuole; food is digested; small
molecules created; pass through
vacuole membrane into cytosol.
FOOD ENGULFED
VACUOLE
ENZYMES
DIGESTION
CYTOSOL
Physical digestion
• Breakdown of larger molecules into smaller
ones.
• Improves the efficiency of chemical
digestion.
• Does NOT chemically change the food
molecules.
• May involve structures like
– teeth
– muscles (eg in the stomach)
– a gizzard (+ pebbles!).
Key questions 4 - 6
DIGESTIVE SYSTEMS IN MAMMALS
TEETH
CARNIVORE
DIGESTIVE
SYSTEM
HERBIVORE
OMNIVORE
Importance of teeth in mammals
Incisors: generally used to get food
into the mouth; sharp edges to cut
chunks of food from larger pieces.
Canines: pointed; tear food and
shear through bone and sinew
(carnivores)
Molars: back teeth; ridged surface
to grind food to make it easier to
swallow.
Premolars: between canines and
molars; used for rolling and crushing
food.
Human molar: ~2/3 of tooth
embedded in jaw.
Human digestion activity
An up close and personal,
fun, informative exploration
of the human digestive
system!
Human digestive system
Human digestion timeline
• Food takes, on average, 24
hours to pass through the
digestive system.
• Stomach ~ 1 – 4 hours.
• Small intestine ~ 4 hours.
• Large intestine ~ 10 – 15
hours
Mouth and mouth cavity
• Physical digestion by
teeth.
• Chemical digestion starts
with salivary amylase –
breaks down starch.
• Saliva lubricates food to
protect oesophagus.
• Chewed food (a rounded
mass called a bolus) is
swallowed into the
oesophagus –
coordinated reflexes.
• General anaesthetics
interfere with
oesophageal reflexes.
• pH ~ 6 - 8
Choking occurs if the epiglottis
doesn’t shut properly so food goes
down the trachea rather than the
oesophagus.
Oesophagus
• Soft, muscular tube ~23 cm long (adult).
• Transports food (bolus) from mouth to
stomach by peristalsis.
• Peristalsis – muscular ‘squeezing’ of the
oesophagus.
• Food is pushed along when muscles above
the food contract.
• Contraction moves like a wave along the
oesophagus.
• Secretes lots of mucus (for lubrication) but
NO enzymes.
• Special sphincters – rings of muscle – at
either end of the oesophagus, control the
passage of substances into the stomach.
Stomach
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Expanded part of the gut, just below the diaphragm.
About the size of a large banana (when empty); volume of ~ 50 mL.
Readily stretches (muscles in the wall) up to 1.5 L when food is swallowed.
As it stretches, nerve endings activate a reflex action that leads to the secretion
of gastric juices.
Gastric juice – mixture of mucus, enzymes, hydrochloric acid and water –
secreted by different kinds of cells in the stomach wall.
Chyme – thin, soupy mixture containing swallowed food, saliva and gastric
juices.
pH ~ 1 – 3
Digestion of protein begins in the stomach.
More carbohydrate in the food, the sooner it leaves the stomach.
More fat in the food, the longer it stays in the stomach.
Meals rich in proteins stay longer than carbohydrates but less than fatty meals.
During digestion in the stomach, hormones are also produced in the stomach
wall, then transported to other parts of body – eg pancreas and gall bladder –
to signal food is in stomach and will shortly enter small intestine.
Small intestine
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~ 6.2 m long, 2.5 cm in diameter.
3 main regions: duodenum, jejunum and ileum.
Food remains for 3 – 6 hours.
Digestion here relies on secretions from the
intestine as well as secretions from 3 organs that
lead into it: pancreas, liver and gall bladder.
• Villi increase the surface area for absorption.
Duodenum
Damaged villi – caused by
• 25 cm long
coeliac disease.
• First part of small intestine
• Secretions from the pancreas enter via the
pancreatic duct.
• Bile (emulsify fats) enters from the liver. Bile is
alkaline – neutralises stomach acid.
• Duodenal enzymes complete the digestion of
carbohydrates into simple sugars, proteins into
amino acids and fats into fatty acids and
glycerol.
Pancreas
• Important gland
• Produces the hormones insulin and glucagon
• These hormones are important in regulating blood
glucose.
• Pancreatic secretions include:
– bicarbonate to neutralise acid from stomach
– amylases to digest carbohydrates
– protein digesting enzymes
– lipases to digest fats and phospholipids
– nucleases to digest nucleic acids
Cystic fibrosis
Daily pills to treat CF
Disease in which the affected person produces abnormal secretions from
several glands, including the pancreas.
Liver and gall bladder
Healthy liver cells
Gall stones (blue) – bile contains cholesterol.
Sometimes this cholesterol crystallises to from gall
stones. These may block ducts from liver and gall
bladder.
Cirrhotic liver cells –
damaged by excess
alcohol consumption
People who drink alcohol excessively are
prone to severe and often fatal liver
disease. Liver enzymes have to break
down alcohol rather than carry out
normal levels of cellular respiration.
Jejunum and ileum
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Jejunum ~ 2.5 m long.
Ileum ~ 3.6 m long.
Food moves along these parts of the small intestine.
Pancreatic enzymes still act on undigested food.
Extra enzymes are also secreted to complete the
digestion of protein as well as carbohydrates.
Absorption in small intestine
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Villi – special structures lining the walls of the intestine.
Increase surface area.
Amino acids, glucose, fructose, galactose, glycerol and fatty acids are absorbed across the
cells of each villus.
Much of the absorption is by diffusion. Active transport also occurs.
~ 90% of absorption of nutrients takes place in the small intestine (rest in stomach and large
intestine.)
Digestion overview
Large intestine
• ~ 1.5 m long, about 6.5 cm in diameter.
• Two main parts – colon and rectum.
• Undigested food, dead cells from the wall of the intestine and the remains
of enzymes pass through these sections.
• Bacteria in the colon digest ~ 30 – 40% of fibre into fatty acids; important
source of vitamin K and B12.
• These bacteria can be destroyed by large doses of antibiotics.
• Water and electrolytes such as sodium or chloride are absorbed by the
walls of the colon.
• No enzymes are secreted.
• Rectum – last 20 cm of colon.
• Contents of the rectum = faeces.
Ulcerative colitis
• Long-lasting disease which results in
inflammation of the intestines.
• Normally treatable without drastic surgery.
• Ileostomy – removal of the large intestine
and rectum.
• Drainable bag is placed over the end of the
small intestine brought out through the small
intestine.
• Appliance has to be emptied into the toilet 4
– 5 times a day.
• Completely changed every two days.
Alcohol
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Different types of alcoholic drink contain different amounts of pure alcohol.
Alcohol in the blood
• Rate of removal of alcohol from the blood is ~ 15mg/100mL/hour
• Alcohol increases the risk of having an accident when driving.
• Concentration and judgement abilities are impaired.
HERBIVORES
- utilise cellulose – broken down by fermentation.
Hindgut fermenter
Hindgut fermenter
Foregut fermenter
Food and energy storage
When food is not available, an
animal draws on its own stores to
meet its nutritional and energy
needs.
Platypus: stores fat for the winter
in its tail.
Carbohydrate storage in animals is
glycogen.
Rest of our energy reserves are
stored as fats.
Shorn sheep – need to eat more to
maintain their body temperature.
Daily energy requirement
Average daily consumption according to age, weight and sex.