Exam 2

Study of chemical compounds that compose the bodies of animals and how animals obtain and synthesize these compounds from their environments

Nutrition

Which are the most abundant macromolecules?

proteins and lipids

Study of energy available from foods

Nutrition

Which atoms form the building blocks of macromolecules?

carbon, hydrogen, oxygen

Which atoms are additional/do not directly form the building blocks?

nitrogen, calcium, phosphorus

What composes 50% of organic matter in mammals?

proteins

What are the roles of proteins in the body?

• structure (structural proteins)

• function (enzymes and proteins for locomotion)

All amino acids contain which atom?

nitrogen

16% of proteins are ________

nitrogen

What do animals do with unused amino acids?

digest them by stripping the nitrogenous containing amino groups (-NH2)

• stripped nitrogen excreted

• nitrogen free carbon chains used for biosynthesis or catabolic energy

Essential amino acids

amino acids that cannot be adequately synthesized are must be acquired fully formed from food or other outside source

“Just in time strategy”

strategy employed by animals to synthesize nonessential amino acids when needed, using other amino acids as amino-group donors

• bc the body does not store excess amino acids

Which macromolecules are as abundant as proteins?

lipids

Which are predominantly non-polar molecules composed largely by carbon and hydrogen?

Lipids

Describe lipids chemically

fatty acids: hydrocarbons on backbone of carbon chain

What kind of lipids are fats and oils?

triacylglycerides/triglycerides

Functions of lipids

• storage

• membranes

• decreasing water evaporation

Saturated fatty acids

all bonds btwn carbon atoms = single

Unsaturated fatty acids

one or more bonds btwn carbon = double

Which are essential fatty acids and why?

Omega 3 and omega 6

• bc many animals dont have the enzymes needed to create double bonds at these positions = these fatty acids cannot be synthesized

How do essential fatty acids differ from essential amino acids?

• essential amino acids = specific compounds

• essential fatty acids = can modify longer fatty acids w double bonds at omega 3 or 6 to synthesize shorter essential fatty acids

Which macromolecules are less abundant than proteins and lipids, but can be common when provide structural support?

Car

Functions of carbohydrate

• structural

• storage via glycogen

• energy transport (ex. glucose)

Why is using glycogen, a carbohydrate, for energy storage less efficient than lipids?

Molecules of glycogen are highly hydrated in the tissues of living animals, and because of the added weight of their water of hydration, they yield a low amount of energy per unit of total weight

Essential carbohydrates

none!

Which carbohydrates cannot be digested by most animals?

cellulose and chitin

Small compounds that are required in small amounts, but animals cannot synthesize them

Vitamins

Which compounds are not used as building blocks, and act as co-factors for enzymes for regulatory funcion?

Vitamins

Describe why vitamin A/retinol is important and how animals get it:

• need for photon absorbing structures (vision)

• need to eat carotenoids to liberate vitamin A, bc animals did not evolve own photon absorbing structure, instead reused systems from plants

What is the general term that refers to the other chemical elements required by animals?

Minerals

40% of proteins are ________ which mammals must obtain from _____

metalloproteins (containing zinc, iron, etc.)

• diet

Which mineral must be obtained for thyroid hormone synthesis?

Iodine

Which mineral must be obtained for the synthesis of phospholipids, nucleic acids, and bone?

Phosphorus

Feeding

process of selection, acquisition, and ingestion of food items

What is the feeding process of an animal shaped by?

• feeding apparatus (morphology)

• behavior (foraging strategies, prey choice)

What is the relationship between feeding and nutritional state?

feeding is under negative feedback from nutritional state

• nutritional needs met = feeding can decrease

• nutrition deficient = feeding behavior and choices shift

Radula

a specialized feeding structure: chitinous ribbon with teeth

• scrapes or rasps food

  • adapted to diet (grazing vs predatory snails)

How are insect mouthparts specialized feeding structures? What is this an example of?

They have the same basic segments, but highly modified = example of divergent evolution

• chewing - grasshoppers

• piercing-sucking - mosquitos

• siphoning - butterflies

• sponging - flies

The poisons used by many predators, such as scorpions, spiders, many snakes, many coelenterates, are made of ________.

proteins

What are the compounds within the tissues of organisms, that deter comsuption?

secondary compounds, secondary metabolites, allelochemicals

Suspension feeding

feeding on objects suspended in water

In which type of feeding do predators feed on very tiny organisms but in big numbers? What does this allow the predator to do?

Suspension feeding

• allows predator to feed lower on the food chain = gain access to higher food productivity

• whales, clams, oysters

What is the ecological role of suspension feeders?

strongly couples primary production to higher trophic levels

• can structure entire communities ex. bivalve beds

What is the food collection mechanism employed by suspension-feeding whales based on?

Baleen plates

• made mostly of keratin, hang from upper jaw on 2 sides of head, each plate oriented perpendicular to longitudinal axis of whale’s body

Symbiosis

close, often long term, beneficial association btwn species

What can Nutritional symbiosis provide?

• novel metabolic capabilities

  • ex. cellulose digestion, photosynthesis, chemosynthesis

• expand range of usable substrates

Foregut, midgut, and hindgut fermenters are in _________ w microbes.

symbiosis

What are the 3 main ways symbiosis occurs?

1. heterotrophs + photosynthetic autotrophs

2. heterotrophs + chemosynthetic autotrophs

3. heterotrophic microbial populations in animals

   1. ex. herbivores (fermenters)

Describe the symbiosis btwn corals and algae:

Corals = heterotrophs

Algae (zooxanthellae) = autotrophs

• coral gain energetic needs bc they are poor feeders and the food is not nutritious

• algae gains nitrogen, carbon dioxide, phosphorus protection, and stable position for photosynthesis

Where can corals thrive bc of their symbiosis?

nutrient-poor tropical waters

Describe the symbiosis btwn tube worms and chemosynthetic bacteria:

Tube worms = heterotrophs

Chemosynthetic bacteria = autotrophs

• form hydrothermal vent worms

• bacteria are sulfur-oxidizing chemoautotrophs

  • tube worms gain organic nutrients (can’t feed independently)

  • bacteria gain hydrogen sulfide, oxygen, protection, and stable environment inside the trophosome

Which symbiotic organisms demonstrate a complete replacement of a digestive system by symbiosis?

tube worms and chemosynthetic bacteria

Fermentation

enzyme-catalyzed reactions without O2 as final electron acceptor

Which organisms are invoved in fermentation?

microbes

What is absorbed by the host as major energy source, in symbiotic relationships btwn heterotrophs and microbes?

Short-chain fatty acids (SCFAs): acetate, propionate, butyrate

Foregut fermenter

concamerations in esophagus and stomach

• ruminants

• animals absorb SCFAs and digest microbes later

• cows, sheep, goats

Hindgut fermenter

concamerations in intestines and cecum (hindgut)

• fermentation after small intestine

What are the advantages of foregut fermentation?

• microbes digest cellulose → SCFAs absorbed in foregut

• microbial protein flows to small intestine → host digests microbes = high quality protein source

• detoxification of some plant compounds before absorption

What are the tradeoffs of foregut fermentation?

• slower throughput

• requires complex regulation of rumen environment (pH, motility, gas removal)

Examples of hindgut fermenters

horses, rabbits, elephants, many rodents

Advantages of hindgut fermentation

• faster throughput of food

• can process large volumes of low-quality forage

Tradeoffs of hindgut fermentation

• microbial protein mostly lost in feces (unless coprophagy)
  less opportunity to detoxify before absorption

The breakdown of food molecules by enzyme action into smaller chemical components, that an animal can distribute to tissues of body.

Digestion

Intracellular digestion

within cell via specialzied cells

• sponges, coelenterates, flatworms, molluscs

Extracellular digestion

via extracellular body cavity like lumen of stomach

Absorption in animals

entry of molecules into living tissues of an animal from outside those tissues

What are the 4 main components of the vertebrate digestive tracts?

1. headgut

2. foregut

3. midgut

4. hindgut

Headgut

head & neck (mouth, pharynx)

• Function = capture, engulfing, preparation of food

Foregut

esophagus & stomach, crop (storage), gizzard (grinding)

• Function = move food headgut -> foregut (esophagus), initiation of protein breakdown and storage

Which part of the vertebrate digestive tract is where the pH is 0.8 and why?

foregut

• bc pepsins are secreted here

Midgut

first segment of intestine (small intestine)

• function = principal site of digestion and absorption of proteins, carbohydrates, and lipids

Hindgut

second segment of intestine (large intestine)

• function = needed to store wastes btwn defecations and complete absorption of needed water before elimination

Arthropod digestion resembles vertebrates in that it is mainly ______ and food is moved thru digestive tract by _______.

• extracellular

• muscular contraction

Function of pancreas

exocrine secretion into midgut

• secretes digestive enzymes (proteases, amylase, lipase, nucleases) often as zymogens (inactive precursors)

Zymogens

inactive precursors of enzymes

Function of Biliary system (liver + gallbladder)

• produces and stores bile

• bile salts = amphipathic = emulsify lipids, increase surface area for lipases

How are the secretions of the pancreas and biliary system integrated?

secretin and CCK hormone coordinate pancreatic and biliary secretions with chyme entering small intestine

How are muscles in the gut wall arranged?

into 2 layers:

1. longitudinal muscle (outer, shortens gut when it contracts)

2. circular muscles (inner, constricts gut when it contracts)

Which muscles shorten the gut when they contract?

longitudinal muscles outer layer of gut wall muscles

Which muscles constrict gut when they contract?

circular muscles, inner layer of gut wall muscles

The coordinated pattern of contraction of longitudinal muscles in differenct sections creates which movement?

peristalsis (Wave)

The constriction of circular muscles creates which part of gut motility, pushing the contents in the gut back and forth?

segmentation

Digestion is carried out by which enzymes? How?

Hydrolytic enzymes

• catalyze macromolecules by hydrolytic reactions (split H2O)

Are the digestive (hydrolytic) enzymes specific or general?

specific to certain chemical bounds

Isoenzymes

different forms of same enzymes, conserved across animals and expressed in different regions of digestive tract within same animal

Intraluminal enzymes

secreted into lumen of body cavity, poured onto the food (ex. pepsin)

Membrane-associated enzymes

located in the apical membranes of the epithelial cells so their catalytic sites are exposed to the gut lumen

• finish digestion b4 absorption

• ex. peptodases

Intracellular enzymes

digestive enzymes in the cell

Disaccharidases: function, type of enzymes, examples

break down disaccharides into 2 monosaccharides

• membrane associated enzymes

• ex. sucrose and lactase

Polysaccharides: function and examples

usually broken down into disaccharides

• Cellulase

• Chitinase

• Amylase

Amylase

breaks down (polysaccharides) carbs, including starch and glycogen

What are the 2 major groups of enzymes which digest proteins?

• endopeptidases

• exopeptidases

Endopeptidases

break down amino chains in middle

Exopeptidases

break terminal amino acids from amino chain

When the protein enzymes are intraluminal, why are they synthesized in inactive forms (proenzymes or zymogens), then activated when they arrive at the location of digestion?

the digestive enzymes have the potential to attack the animal’s own body substance

Which enzymes digest protein in the stomach?

• pepsinogens → pepsins (activated by low pH of stomach)

• endopeptidases = cleave internal peptide bonds

Which enzymes digest proteins in the small intestine lumen?

• pancreatic proteases (secreted as zymogens)

  • ex. trypsinogen, chymotrypsinogen

• endo- and exopeptidases generate oligopeptides + free amino acids

Which enzymes digest proteins in the brush border and intracellularly?

• membrane bound peptidases → di- and tripeptides, amino acids

• intracellular peptidases complete digestion after uptake

Why are there fewer enzymes for lipids?

they have fewer types of chemical bonds compared to proteins

Emulsifying

breaking large fat droplets into many smaller ones so enzymes can digest lipids efficiently in a water environment