Lecture 19 and 20- Digestion and absorption Flashcards
What organisms are autotrophs?
Most plants,
Some archaea, bacteria and protists
What are autotrophs?
Organisms that synthesise their own necessary nutrients from inorganic compounds
What do heterotrophs depend on?
Organic synthesis carried out by autotrophs to derive their own nutrients
What have heteotrophs evolved to exploit autotroph resources?
Adaptations
What is a calorie?
A unit of heat energy
1 calorie is the energy needed to raise one gram of water by one degree celsius
What many calories are their in a Joule?
0.239 calories = 1 J
What is the metabolic rate of an animal a measure of?
The energy needs of an animal that are met by food intake and digestion
What are energy budgets constructed with?
Calories consumed
Calories expended
What is the basal metabolic rate for the average human adult female?
1300-1500kcal per day
What is the basal metabolic rate for the average human adult male?
1600-1800 kcal per day
What do energy budgets show?
How animals use their resources. Cost- benefit model can be applied to analyse behavior.
Give an example of territorial behavior.
African sunbirds feed on the specific nectar
The birds are only territorial if the food resource was rich enough to support cost of aggressive behavior.
How is food stored between meals?
Carbohydrates as glycogen in muscle and liver
Fat stores
How much energy is stored in glycogen?
About 1 days worth of basal energy requirments
What is the advantage of storing energy as fat rather than glycogen?
More energy per gram- little water- more compact.
What can be metabolised for energy but is not used as a energy storage compound?
Protein
What is undernourishment?
Too little food taken in. Body metabolises its own molecules.
- Protein is lost rapidly to protein synthesis
- Glycogen and fat are broken down
- Decreased protein use
What can decreased protein cause?
Edema- a sign of kwashiorkor
What is kwashiorkor?
Caused by chronic protein deficiency
Protein synthesis in the liver stops, decreased blood proteins, fluid enters the interstital spaces
What is overnourishment?
More food is taken in than needed and stored as increased body mass
- Glycogen reserves are built
- Extra molecules are converted to body fat
What molecule do animals derive from the metabolsim of most food?
The acetyl group, CH3CO-
What is the acetyl group used for?
Supply carbon skeleton and build complex molecules
What are amino acids used for?
Building blocks of proteins
What name is given to amino acids that cannot be synthesized in the human body?
Essential amino acids (8 in humans)
Why are proteins digested before being used in the body?
- Proteins are not easily absorbed by the gut
- Protein structure/function vary by species (not optimal)
- Immune system would attack protein molecules entering the gut
What name is given to fats that cannot be synthesized by an organism?
Essential fatty acids
What essential fatty acid do humans require?
Linoleic acid
What is linoleic acid used for?
Synthesize other unsaturated fatty acids
Other than essential fatty acids and amino acids, what must an animal derive from their diets?
Macronutrients
Micronutrients
Vitamins
Name some macronutrients
Calcium, chlorine, magneisum
Name some micronutrients
Iron, iodine, chromium, fluorine
What are vitamins?
Carbon compounds that cannot be synthesized
- Species specific
- Water or fat soluble
- 13 in total
What is calcium used for?
Calcium phosphate is the principle structural material in teeth and bones
Muscle contraction, neuronal function and other intracellular functions
What does nutrient deficiencies lead to?
Malnutrition
Chronic malnutrition leads to deficiency disease
What causes scurvy?
Lack of vitamin C
What causes anemia?
Lack of iron (oxygen-binding)
What does vitamin D do and what can a deficiency lead to?
Helps to absorb phosphate and calcium
Rickets
How else can a deficiency be acquired?
Inability to absorb a nutrient
What is pernicious anemia?
Vitamin B12 is not absorbed in the stomach
What are the 5 adaptations animals have to feed?
Mechanical Biochemical Physiological Behavioral Microbial
How have herbivores adapted to eating difficult to digest, low energy content food?
- Spend a long time feeding
- Physical adaptations- elephant trunk, giraffe neck, mouthparts in invertebrates, tooth shape
How have carnivores adapted to ingest and digest food?
-Adaptations to detect, capture, kill and ingest prey
What adaptation have bats evolved to aid obtaining food?
Echolocation
What adaptation have snakes evovled to aid obtaining food?
Jacobson’s organ, hinged jaw, venom
What are the three layers of the general mammalian tooth?
- Enamel
- Dentine
- Pulp cavity
What is the enamel of a tooth?
Composed of calcium phosphate
Covers crown of tooth
What is the dentine of a tooth?
A layer between the crown and root
What is the pulp cavity?
A layer within the dentine
Contains blood vessels, nerves, cells that produce dentine
What are the 4 types of tooth?
Canines
Incisors
Premolars
Molars
What are canines used for?
Ripping and tearing
What are incisors used for?
Cutting
What are premolars used for?
Shearing
What are molars used for?
Grinding
What is the simplest digestive system?
A gastrovascular cavity- seen in cnidarians
How do animals digest their food?
Extracellularly
What are tubular guts?
A mouth takes in food, waste is eliminated through an anus. Different regions of the gut are specialized
How is food broken up at the anterior end of the gut?
Teeth in vertebrates
Radula in snails
Mandibles in arthropods
Birds- stones in the gizzard
What are storage chambers that allow for gradual digestion?
Stomachs and crops
Where are most nutrients, water and ions absorbed?
Midgut
What is the function of the hindgut?
To recover ions and water
Store feces
What helps with the expulsion of feces?
Muscular rectum near anus
What lives in the hindgut of many species?
Colonies of endosymbiotic bacteria
What is the role of endosymbiotic bacteria in the hindgut?
Help break down food
Such as in leeches
What other adaptations are there to increase absorbance efficiency in animal guts?
- Increased surface area: folds called villi, microvilli
- Slow food passage using cecal or spiral valves
- Long intestine
What adaptations have worms evolved to increase gut surface area?
Longitudinal infolding of intestinal wall
What do proteases break down?
Bonds between amino acids
What enzymes break down fats?
Lipases
What enzymes break down peptides?
Peptidases
What is zymogen?
Inactive form of digestive enzymes- cannot act on cell that produced it
What happens when zymogen is secreted into the gut?
It is activated by another enzyme
Why is the cell lining of the gut not digested?
It is protected by a mucus covering.
What is in the rumen and reticulum of a ruminant’s stomach?
Abundant cellulose-fermenting microorganisms
What happens to the contents of the rumen periodically?
Regurgitated for rechewing
Where does the fermented food pass into next?
The omasum
Where it is concentrated by water absorption
Where does the contents of the omasum pass next?
The abomasum- the true stomach
What is digestion governed by?
Neuronal and hormonal control
What responses are unconscious reflexes?
Swallowing, salivating
What do unconscious reflexes do?
Coordinate digestion
What type of nervous system does the digestive tract have?
Independent (intrinsic) nervous system
Neuronal messages do not have to be processed by the CNS
(Parasympathetic nervous system)
What is secretin?
Produced in the duodenum
Causes pancreas to secrete digestive juices
What enzyme in the small intestine causes the gall bladder to release bile, stimulates the pancreas, slows stomach and release digestive enzymes>
Cholecytokinin
What is cholecytokinin released in response to?
Undigested fats and proteins in the chyme
What hormone is secreted by the stomach?
Gastrin
What is gastrin released into?
The blood
What gastrin stimulate?
Stimulates secretion of HCl and pepsin and increases motility of stomach
What is the absorptive state?
The period following a meal when food is in the gut and nutrients are being absorbed
What is the post absorptive period?
Stomach and small intestine are empty, body metabolism relies on internal energy reserves
What is gluconeogenesis?
Conversion of amino acids and other molecules into glucose in the liver
What is the function of a lipoprotein?
Aid fat transport in the blood
What is the structure of a lipoprotein?
Hydrophobic fat core covered by a hydrophilic protein
What are the largest lipoproteins in the blood?
Chylomicrons (produced in the intestine)
How does the liver control fat metabolsim?
Production of lipoproteins
How are lipoproteins classified?
According to density
Fat- low density
Protein- high density
What is the function of high density lipoproteins?
Remove cholesterol from tissues and carry to liver to synthesize bile
What is the composition of HDL’s?
50% protein
35% lipid
15% cholestrol
What is the function of LDLs?
Transport cholesterol around body for biosynthesis and storage
What is the function of very low density lipoproteins?
Contain mostly triglyceride fats, transport to fat cells in adipose tissues
What hormones control fuel metabolism?
Insulin and glucagon.
When is insulin released by the pancreas?
During the absorptive period when blood glucose rises
What does insulin do?
Promotes uptake and utilisation or storage of glucose and glycogen
Where does insulin act?
Skeletal muscle, adipose tissue, liver
What happens when glucose in blood falls?
Glucagon is released- liver breaks down glycogen and begins gluconeogenesis
What part of the brain controls food intake?
The hypothalamus
What does the hypothalamus do?
Provides signals on hunger or satiety and governs how much food is eaten
What hormone does the stomach release to govern hunger?
Ghrelin promotes hunger
What hormone provides feedback information to the brain about body fat reserves?
Leptin
What produces leptin?
Body fat cells
