Chapter 40 - Animal Metabolism, Nutrition, and Digestion

Question 1

True or False: The biology of an animal is in large part shaped by the type of food the animal consumes

Answer 1

True. Additionally, the chemical reactions by which it breaks down its food is closely linked to the energy and nutrients contained in that food/diet

Question 2

True or false: The food that an animal eats also affects its place in an ecosystem

Answer 2

True. Animals that feed on plants exist in larger numbers, while larger animals that feed on smaller animals exist in smaller numbers.

Question 3

True or False: The biochemical pathways that make up animal metabolism are not conserved among organisms.

Answer 3

False. Biochemical pathways are highly conserved across diverse groups of organisms.

Question 4

What are the three main molecules that most animals rely on for growth and development?

Answer 4

Carbs, fats, and proteins

Question 5

How are food sources broken into biologically useful forms? What is involved?

Answer 5

ATP. It is the most common one used by animals and the breakdown of carbs, fats and proteins produce ATP using a linked set of chemical reactions.

Question 6

What is a catabolic reaction?

Answer 6

A reaction that breaks down food sources to fuel the energy needs of a cell

Question 7

What is an anabolic reaction?

Answer 7

A reaction that results in net energy storage within cells and the organism.

Question 8

Describe the breakdown of carbohydrates in the body (sugars and starches)

Answer 8

In the absence of O2: glycolysis/anaerobic respiration -occurs in cytosol of the cell -Results in 2 pyruvate and 2 ATP per glucose molecule If O2 not present or only in small amts: fermentation into lactic acid -production of ATP by anaerobic metabolism for rapid but short-term energy for cell and organism In presence of O2: aerobic metabolism/cellular respiration -occurs in mitochondria of cell for steady supply of ATP for long term energy -pyruvate processed by citric acid cycle -in redox rxns, NADH and FADH2 produced, enter e-transport chain in inner mitochondrial membrane -e-transport chain couples transfer of e- to pumping of H+ across inner mitochondrial membrane, H+ electrochemical gradient which enables synthesis of ATP by oxidative phosphorylation -Result is consumption of O2 and production of H2O

Question 9

What are the total counts of molecules formed in aerobic respiration? In anaerobic respiration?

Answer 9

Per glucose molecule: Aerobic: 32 ATP - 42% efficiency Anaerobic: 2 ATP

Question 10

What happens to the remaining energy that is not converted to ATP in a usable form?

Answer 10

It is converted to heat and either dissipated or used to warm the animal.

Question 11

What happens to the glucose that is not metabolized by the body?

Answer 11

It is stored in the form of glycogen, primarily in liver and muscles.

Question 12

Explain how lipids are broken down in the animal body.

Answer 12

They are broken down to glycerol and free fatty acids, and enter glycolysis or citric acid cycle -yield ATP by mitochondrial electron transport Alternatively, they can be stored as fat (fat tissue in the body), which is efficient because it yields more than twice the energy supply per unit weight. They are broken down in the same way as lipids.

Question 13

Why are proteins a significant energy source for animals, and how are they broken down in the body?

Answer 13

-Proteins are necessary for building and maintaining body, make up enzymes and structural elements of cells and tissues -proteins reserves are broken down mainly from muscles to form ATP -Proteins–>Amino Acids–> Citric Acid Cycle–>ATP by mitochondrial electron transport

Question 14

What is the sequence of energy reserves that the body pulls from in a fasting state?

Answer 14

1. Carbohydrates - spared for brain and nervous system because nerve cells rely on glucose for ATP 2. Fats - long term energy supply (most humans have enough fat for 5-6 days before moving onto protein) 3. Protein - to synthesize glucose for brain and nervous system -liver eventually starts to synthesize glucose to help brain cells in prolonged fasting

Question 15

What is metabolic rate and how is it measured?

Answer 15

It is an animal’s overall rate of energy use, and it’s measured by the animal’s rate of O2 consumption, which in turn reflects the aerobic production of ATP

Question 16

What does the metabolic cycle during physical activity look like? How does it differ between types of activity?

Answer 16

Activity level of the organism - from rest to activity, metabolic rate and O2 consumption increase to meet demand for ATP -Ex: in muscle cells phosphocreatine is hydrolyzed to get ATP from ADP. Rxn is followed by rapid production of ATP by anaerobic glycolysis -rely on these short bursts from anaerobic glycolysis for quick intense activity -Long-term sustainable energy: O2 consumption levels off after initial increase and at this point animal’s need for energy met by aerobic respiration -For prolonged or intense activity: can’t get ATP by aerobic metabolism alone. Requires greater reliance on anaerobic glycolysis to produce ATP, results in buildup of lactic acid and decrease in pH forces animal to decrease activity. Acidity of blood (metabolic acidsos) results in fatigue. -End of activity: animal’s O2 consumption declines but not immediate return to resting level. Recovery metabolism where cells re-make depleted ATP to pay back “debt” , associated with elevated breathing and heart rates.

Question 17

What does the metabolic cycle for activity look like on a graph?

Answer 17

Starting from rest, the slope is very steep and levels off. O2 debt is created. During recovery, slope is downward curve while body “pays back” debt.

Question 18

How does body temperature limit activity levels in predator and prey?

Answer 18

Since a byproduct of metabolism is the generation of heat, animals can disspiate heat through various mechanisms. However, some animals store heat such as the cheetah, and only dissipate it after a chase. This raises the internal body temp of the cheetah so the run can only be short even though they are fast, and must rest for long periods of time between sprints. Therefore, cheetahs are limited in amt of time and distance covered by body temp.

Question 19

Is metabolic rate affected by body size? If so, how?

Answer 19

Yes, larger animals at rest consume more energy and have higher metabolic rates than smaller animals. BUT basal and metabolic rates do not increase linearly with an animals mass. It increases with animal mass raised to 3/4 power. Therefore, the avg rate of energy consumed per gram of body tissue is less in larger animals. The larger the organism, the lower the metabolic rate per gram of body tissue. It’s highly conserved acorss diverse organisms.

Question 20

How is metabolic rate affected by internal body temperature?

Answer 20

• thermoregulation affects rates of chemical rxns which determines how fast fuel can be broken down for ATP
• endotherms - animals that produce most of own heat as byproducts of metabolic rxns

these maintain constant body temp that is higher than environment, function of homeostasis (e.g. mammals, birds) - “warm-blooded animals”

Have higher metabolic rate than ectotherms and are therefore more active animals

-ectotherms - regulate body temp by behavorial means (moving into/out of sun), temp of animals fluctuate with environment (e.g. fish, amphibians, reptiles, invertebrates) - “cold-blooded animals”

Can’t sustain prolonged activity although they can achieve activity levels similar to endotherms when at similar body temp - but, require less food

-keep in mind that “cold-blooded” animals can have higher internal temp than “warm-blooded”

Question 21

What is the digestive process in single-celled protists?

Answer 21

Intracellular digestion - obtain food particles by phagocytosis, and food broken down in lysosomes containing hydrolytic enzymes fuse with food vacuoles and food products of broken down and absorbed into cell for use.

Question 22

What is the most common digestive process in animals?

Question 23

What is the gut/digestive tract?

Answer 23

Passages that connect the mouth, digestive organs, and anus. It can be specialized for different functions such as storage, chemical breakdown, aandabsorption of released nutrients, and elmination of waste.

Question 24

What are the digestive tracts of animals divided into?

Answer 24

Foregut - mouth, esophagus, stomach/crop for initial storage and digestion

Midgut- small intestine where remainder of digestion and most nutrient absorption takes place. Organs secrete enzymes to break down macromolecules

Hindgut - Large intestine and rectum. Water and minerals reabsorbed leaving feces. Rectum stores waste and defecates feces

Question 25

Describe the digestive process in the foregut.

Answer 25

Digestion begins in mouth - animals manipulate food in buccal cavity and break down food mechanically. Mammals secrete amylase (enzyme breaks down carbs)

• Tongue manipulates food and moves it into position for maceration
• Bolus is moved to rear of mouth cavity by tongue, swallowing controlled by autonomic nervous system and involves sealing off of epiglottis, contraction of pharynx- once initiated, swallowing reflexes occur without voluntary control. Bolus enters esophagus.
• senses of food send signals to brain and stimulate appetite, secretion of HCl, pepsin (breaks down proteins), food enters stomach, HCl activates pepsin to cleave amino acids and killing pathogens
• cells release gastrin in response to food in stomach - positive feedback to increase production of HCl , gastrin absorbed in small intestine and recirculated to cells in stomach, which increases gastrin secretion. If pH too low, gastrin secretion inhibited by negative feedback.

Question 26

What is the purpose of the gizzard and in which animals can it be found?

Answer 26

It’s a compartment with thick muscular walls, found in birds, alligators, crocodiles, earthworms to help break food mechanically into smaller pieces.

Question 27

Explain the digestive process of the midgut.

Question 28

What causes ulcers?

Question 29

What is involved in the stomach’s mechanical breakdown of food?

Answer 29

Stomach walls contract:

• peristalsis: muscular contraction that move food toward base of stomach
• pyloric sphincter opens and allows small amounts of digested food to enter small intestine- regulates rate of digestion and absorption
• stomach also stores food for about 4 hours in humans, or longer in carnivorous animals that consume large and infrequent meals

Question 30

Describe the digestive processes of the midgut.

Answer 30

• food enters small intesting where primary fat digestion begins and protein and carb digestion continue
• chyme enters duodenum from stomach where most food digestion occurs
• jejunum and ileum carry out most nutrient absorption
• accessory organs: liver and pancreas
  liver: produces bile composed of salts, acids, bicarb ions to break up fat into smaller lipids by emulsification. Bile produced by liver to be stored in gallbladder, and enter duodenum to do work. CCK causes gallbladder to contract to release bile into duodenum. Lipases break up lipids better to be absorbed across wall and into bloodstream

Pancreas: both endocrine (dir. into blood) and exocrine gland (dir. into ducts). Produces lipase, trypsin (breaks down proteins), bicarb ions (neutralize acid) stimulated by secretin released by duodenum to allow for enzymes to work.

-Final digestion: jejunum and ileum. HIghly folded villi and microvilli to increase surface area for absorption of nutrients

Question 31

How are roducts of digestion abosorbed across microvilli?

Answer 31

Cells that line small intestine are connected by tight junctions that connect microvilli to prevent leaking between cells .

Question 32

What is the function of the microvilli of the cells lining the small intestine?

Question 33

Why are some people lactose intolerant?

Question 34

How are nutrient molecules transported into the small intestine?

Answer 34

1. Nutrient molecule enters intestinal cell along with Na+, driven by Na+ concentration difference between lumen of intestine and cytoplasm of cell
2. Na+ concentration is kept low inside cell by action of Na+ -K+ ATPase pump (3 Na out, 2 K+ in)
3. Nutrient molecule exits intestinal cell passively by transport protein (fats do not require carrier but diffuse across lipid membrane and transported to bloodstream).

Question 35

Describe what happens in the hindgut during the digestion process.

Answer 35

• Water and minerals are reabsorbed in the large intestine or colon
• contents form a semisolid feces
• feces stored in rectum until periodically eliminated through anus

Question 36

What kinds of bacteria reside in the small and large intestine and what purpose do they serve?

Answer 36

E. Coli is the principle bacteria in the intestines, they aid in the digestion of host’s gut contents, and provide nutrients and certain vitamins like biotin and vitamin K that animal can’t produce itself. They also produce gases like methane and hydrogen sulfide that are expelled when foods can’t be digested by the stomach but can be digested by the bacteria.

Question 37

What is the digestive tract composed of?

Answer 37

From inside layer to outside:

• lumen - central space through which things travel
• mucosa - inner tissue layer that has secretory and absorptive functions
• submucosa - layer that contains blood vessels, lymph vessels, nerves
• circular muscle - contracts to reduce size of lumen
• autonomic nerves that regulate peristalsis
• longitudinal muscle - shortens small sections of the gut
• serosa - outer layer of cells and connective tissue
• mesentery - membrane that supports gut in abdominal cavity through which blood vessels, nerves, and lymph travel to supply gut

Question 38

How do the digestive tracts of plant-eating animals reflect their diets?

Answer 38

• herbivores must be able to digest cellulose and other plant compounds but lack cellulase, the enzyme that breaks down cellulose
• herbivores have specialized compartments in digestive tract which have large bacterial populations and do produce cellulase
• ruminants have 4-chambered stomach to enhance function of gut bacteria

Question 39

How does a 4-chambered stomach function? Which animals have this digestive structure?

Answer 39

1. Rumen - anaerobic bacteria break down cellulose - rumen contents frequently regurgitated for repeated chewing. Bacteria break down food by fermentation, and produce CO2 and methane
2. Reticulum - more bacteria - bacteria synthesize their own amino acids because plants harbor lots of nitrogen and make their proteins
3. Omasum - food and bacteria travel here and water is absorbed
4. Abomasum - Protein digestion - acid and protease kill bacteria, nutritional products absorbed in small intestine.

Animals: cattle, sheep, goats

Question 40

What is hindgut fermentation and and what animals use it?

Answer 40

Mammalian herbivores such as koalas, rabbits, horses digest by hingut fermentation.

-it occurs in the colon and in the cecum (chamber of large intestine) - fermentation products already passed through small intestine, it’s less efficient because those nutrients don’t have a chance to get absorbed.