Exam 1 Physio

What is animal physiology?

The study of how animals function

What two questions does physiology try to answer?

1) what is the mechanism by which a function is accomplished?

2) why did a particular mechanism come to be?

Define mechanism

an interaction of components that results in a particular function

Why is physiology important?

In understanding :

-the fundamental biology of all animals

-human health/disease

-health/disease of nonhuman animals of importance in human affairs

What does it mean, "animals are structurally dynamic?"

The atoms and molecules that make up animals undergo dynamic exchange with the environment throughout life

Say a species is a temperature regulator and the average body temperature of the species is 38 deg C when the external temperature is 38 deg C. What is the average body temperature of this species when the external temperature is −10 deg C? Why?

The average body temperature is still 38 deg C because being a temperature regulator means the species regulates its temperature to be at a constant value despite changes in the external temperature.

Say an aquatic species is a Mg2+ concentration conformer and the blood concentration of Mg2+ is 1 mM when the external Mg2+ concentration is 1 mM. What is blood concentration of this species when the external Mg2+ concentration is 125 mM? Why?

The blood concentration of Mg2+ would be 125 mM because being a Mg2+ concentration conformer means the species conforms its concentration to that of the external environment.

Look at the data points for the species of dikdik and African buffalo on the graph of body weight vs. gestation duration on slide #7 in the lecture "Animals and Environments". Which species likely has the larger brain? Which likely has a smaller rate of energy use? How did you infer this?

African buffalo likely have larger brains and dikdiks likely have smaller rates of energy use. Similar to gestation duration, brain size and rate of energy use are also directly correlated with body size. Since African buffalo are of a larger size than dikdiks, it is therefore likely that they have greater gestation duration, larger brain sizes, and greater rates of energy use.

Say a population of 1,000 laboratory-raised fruit flies has two alleles of the gene that codes enzyme X: 40% of the population has allele A and 60% has allele B. The fruit fly population is then allowed to reproduce for approximately 100 generations inside a refrigerated unit kept at 10 deg C (room temperature is usually about 22 deg C). Afterward, 20% of the population has allele A and 80% has allele B. Has evolution occurred? Why or why not? Is the change in the frequency of genes for enzyme X likely due to natural selection, genetic drift, or something else?

Evolution has occurred because the frequency of the alleles in the population has changed over time. This change is likely due to natural selection. Since the fruit flies were being housed in an experimentally controlled environment and environmental stress was being applied in the form of unnaturally cold temperature, it is likely that the change in frequency of alleles of the gene coding enzyme X is an adaptation to living in cold conditions. Allele B—the allele that increased in frequency over time—likely changed the function of enzyme X in a manner that increased the likelihood of survival and reproduction in the population of fruit flies.

Why do Antarctic species of fish have a greater percentage of unsaturated phospholipids in their cell membranes than tropical species of fish?

Unsaturated phospholipids (i.e., more double bonds in the hydrocarbon tails) increase fluidity of cell membranes. On the other hand, decrease in temperature decreases membrane fluidity. The higher proportion of unsaturated phospholipids in Antarctic fish as compared to tropical fish is likely an adaptation to counteract decreased membrane fluidity in cold environments.

Regarding enzymes, what is the difference between turnover number and substrate affinity?

Substrate affinity is a measure of the ease with which substrate molecules can bind to enzyme molecules, whereas turnover number is an enzyme's rate of conversion of substrate molecules to product molecules under the assumption that all substrate-binding sites on the enzyme are filled by substrate.

What is similar between an isozyme and an interspecific enzyme homolog of lactate dehydrogenase? What is different between them?

Isozymes and interspecific enzyme homologs of lactate dehydrogenase are similar in that they all catalyze the same reaction—in this case, the conversion of pyruvic acid to lactic acid. Isozymes and interspecific enzyme homologs of lactate dehydrogenase are different in that isozymes are within the same species whereas interspecific enzyme homologs are in different species.

Say the intracellular concentration of O2 is 2 mM and the extracellular concentration starts at 10 mM. Then, a sudden influx of O2 raises the extracellular concentration to 18 mM. Does this sudden influx of O2 change the rate of diffusion of O2? If so, by how much? In which direction does O2 diffuse?

Diffusion always goes in the direction of high concentration to low concentration. Since the extracellular concentration of O2 is greater than the intracellular concentration, O2 will diffuse into the cell.

Say a hypothetical cell membrane consists only of phospholipids—no membrane proteins. The extracellular osmotic pressure is 400 mOsm and the intracellular osmotic pressure is 350 mOsm. Will osmosis occur? Why or why not? If so, in which direction?

H2O is capable of diffusing through the cell membrane—even a membrane composed entirely of phospholipids. Since there is an osmotic pressure difference across the membrane, osmosis will occur, and it will occur in the direction toward greater osmotic pressure. So, in this case, osmosis will occur out of the cell. (Recall: greater osmotic pressure = greater solute concentration = less water concentration.)

Say animal X was only fed dietary carbohydrates and lipids. Could it synthesize proteins in its body from these nutrient sources? Why or why not? Say animal Y was only fed dietary protein. Could it synthesize carbohydrates in its body from this nutrient source? Why or why not?

No, animal X could not synthesize proteins using only dietary carbohydrates and lipids. The amino acids that the animal uses to create new proteins ultimately comes from ingesting other proteins. Yes, animal Y could synthesize carbohydrates using only dietary protein. There are no essential carbohydrates. All carbohydrates can be synthesized from dietary protein—or the glycerol of dietary lipids, for that matter.

Describe how the monosaccharide, glucose, is absorbed from the lumen of the small intestine into the extracellular fluid.

a) Na+-K+ pump in the basal membrane of the intestinal epithelial cell creates low concentration of Na+ inside the cell. b) Na+-glucose cotransporter (SGLT) in the apical membrane of the intestinal epithelial cell uses the energy from allowing Na+ to flow down its concentration gradient (high Na+ in the lumen; low Na+ in the cell) to transport glucose from the lumen into the cell (low glucose in the lumen; high glucose in the cell). c) Glucose transporter (GLUT; a type of facilitated diffusion) in the basal membrane of the intestinal epithelial cell transports glucose down its concentration gradient from inside the cell (high glucose) to the extracellular fluid (low glucose).

Describe how triglycerides are digested in the small intestine

Triglycerides are digested into free fatty acids and monoglycerides by lipases in the small intestine. Since triglycerides are hydrophobic, they tend to lump together into large fat droplets, limiting the surface area for lipases to act on. The liver secretes bile salts into the small intestines in order to emulsify large fat droplets into many smaller fat droplets, thereby increasing the surface area available for lipase enzymatic activity.

Summarize the main functional product of each of the four stages of aerobic catabolism. (Don't simply give a detailed description of the stages.)

a) Glycolysis: pyruvic acid, which gets fed into the Krebs cycle.

b) Krebs cycle: NADH2 and FADH2, which are utilized to power the electron-transport chain.

c) Electron-transport chain: H+ concentration gradient between the mitochondrial matrix and intermembrane space, which is used to power ATP synthase. d) Oxidative phosphorylation: ATP, produced by ATP synthase.

a) Where is O2 specifically used in the aerobic catabolic pathway?

a) O2 is consumed at the end of the electron-transport chain.

b) How does lactate dehydrogenase (LDH) allow glycolysis to continue in the absence of O2?

b) NAD is used during glycolysis. In the absence of O2, NAD becomes depleted because all of it is transformed to NADH2. LDH allows glycolysis to continue in the absence of O2 by combining NADH2 with pyruvic acid—the end-product of glycolysis—to produce NAD (and lactic acid). This newly produced NAD molecule can then be recycled back into the biochemical reactions of glycolysis.

Summarize the mechanisms by which ATP is produced for a bout of heavy submaximal exercise, from the beginning to midway through the exercise.

At the beginning of heavy submaximal exercise, most ATP is produced by non-steady-state means of ATP production: aerobic catabolism using internal O2 stores, creatine phosphate, and anaerobic glycolysis. ATP production via creatine phosphate and aerobic catabolism using internal O2 stores is used up within seconds. In the meantime, the rate of ATP production via aerobic catabolism using external O2 ramps up, with ATP production via anaerobic glycolysis filling in the gap of needed ATP (oxygen deficit). By midway through the exercise, the rate of aerobic catabolism using external O2 has increased to the point that it is sufficient to completely meet ATP needs.

You are wandering in the wilderness, hungry and cold. You find two caves of the same dimensions. In one cave there is 600 kg moose and in the other cave are 100,000 6-gram mice. Both species are friendly and they have an unlimited supply of food.

Which cave would you enter to warm up quickly?

Explain why. Include in your answer reference to differences in mass specific metabolic rates and surface:area ratio.

Based on what you know about thermal properties and animal heat budgets, describe two mechanisms by which heat can be transferred to your body from other animals in your cave.

A) Befriend the mice.

B) 100,000 six gram mice is equal to 600 kg. However, because of the allometric relationship between body size and metabolic rate, the mass specific metabolic rate of a small mouse is greater than a large moose. So, 600 kg of mice are generating more heat per g of tissue. The smaller mice also have a greater surface area: volume ratio, so they are losing heat at a faster rate. All things being equal, the mouse cave will be warmer.

C) There are actually three: Conduction if you snuggle, or more slowly if the air in the cave is still Convection if the air is moving from all the activity Infrared radiation from mouse bodies to your body

Two swallows begin their migration from N Africa to the English channel and beyond One is small, one is larger. Both carry identical proportional lipid stores of 10% their body mass. Which will run out of fuel first?

The small bird will use up its energy faster because its metabolic rate per body mass is higher, and the weight - specific cost of transport increases as size decreases. This is an allometric pattern seen within fliers, swimmers and runners

what does it mean, “animals are organized systems that require energy to maintain their organization?”

an organized, structurally dynamic system always requires energy

even though atoms and molecules are replaced, the spatial arrangements of molecules in an animal remains relatively constant

Homeostasis definition

The collection of regulated factors in an animal kept at their set points via negative feedback control systems

negative feedback definition

control system that responds to changes in a regulated factor to move the level of the factor back to its set point

Regulation advantages and disadvantages

Disadvantages: uses up energy - internal environment always pulled toward the external environment

advantages: allows animals to exists in a wider range of environments

Conformity advantages and disadvantages

disadvantages: restricts animal to environments tolerated by cells

advantages: does nit use energy

What does it mean, “time and body size are fundamental significance to all animals”

The physiology of animals changes on different time scales

Acute response

response to external environment changes within first few minutes or hours

chronic response

response to external environment changes after a few days or weeks

Evolutionary response

response to external environment changes

changes to genotype frequency over a population of animals

developmental response

internally programmed change

genetically programmed changes in an animal;s phenotype from conception to senescence

biological clock

internally programmed change

mechanisms that give organisms an internal capability of tracking time

features of animals of overriding importance

1) animals are structurally dynamic

2) animals are organized systems that require energy to maintain organization

3) time and body size are fundamental significance to all animals

environment definition

the chemical and physical and biotic components of an organism’s surroundings

3 big factors of the environment

temperature, oxygen, and water

temperature definition and why is it important to environment

the amount of kinetic energy per molecule

molecule interactions can behave differently at extreme highs and lows

Oxygen definition and why is it important to environment

O2→ need for oxygen is usually due to the need to get rid of excess H+ during cellular respiration

H+ combines /w oxygen to form h2O

water definition and why is it important to environment

1) H2O abundanr

2) litter ganger existsed for an animal to become dehydrated or overhydrated

it can be a harmess byproduct when combined w oxygen

% atmosphere O2 and aerated rivers

21% atmosphere and 3-5% of O2/liter as atmosphere in river

evolution

a change of gene frequencies in a population over time

Mechanisms by which evolution can occur

natural selection, genetic drift,

natural selection

an increase in the frequency of genes that produce phenotypes that raise the liklihood animals will survive and reproduce

adaptation

an evolved trait that confers greater possibility of survival and reproduction than other available alternative traits

not all traits are adaptation!

genetic drift

gene frequencies altered by chance

Pleiotropy

control of 2 or more seemingly unrelated traits by a single allele of a gene

• one trait may be strongly favored by natural selection while other potentially decreases fitness

How can you asses whether a trait is an adaptation?

1) the comparative method

2) laboratory populations subjected to environmental stress

The comparative method

identifying adaptations by comparing mechanisms between related and unrelated species in a similar and dissimilar environment

laboratory populations subjected to environmental stress

changes in gene frequency can be observed in laboratory ini fast-breeding organisms (fruit flies or C. elegans)

Cell membrane characteristics

6-8 nm thick

compartmentalizes intra and extracellular fluid

Receives and transmits signals that arrive at cell surface

Some organelles are also enclosed by membrane

Phospholipid bilayer

amphipathic - what part of membrane is amphipathic

polar and nonpolar regions

phospholipid

leaflet

each lipid layer

what does a double covalent bond do to hydrocarbon tain

imparts a bend in tail structure

resists crystallization → increases fluidity

saturated hydrocarbon

no double bond → decrease fluidity

unsaturated hydrocarbon

one or more double bonds → increased fluidity

what other molecules so membranes contain other than phospholipids

Carbohydrates (glycolipids, glycoproteins, etc)

Other lipids ( sterols → cholesterol, cholesterol esters)

eppithelium

a sheet of cells that covers a body surface or organ, or lines a cavity

simple epithelium

single layer of cells

apical surface

faces into cavity or open space

basal surface

faces toward tissue to which epithelium is attached

basement membrane

thin, permeable sheet of extracellular matric ppositioned beneath basal surface

3 ways epithelia classified

cubiodal, columnar, or squamous

adjacent cells in epithelium are joined by:

tight junctions, desmosomes, gap junctions

tight junctions (septate)

neighboring cell membranes tightly join or fuse

forces extracellular substances to pass thru epithelium transcellularly

segregates proteins on apical surface of basal surface

desmosomes

spots where glycoproteins from neighboring cells strongly link together (interlock)

gap junction

connexin proteins linked between neighboring cells forming coontinousous channel linking cytoplasms

enzymes

protein catalysts speed chem reactions without being altered themselves

important for regulating cell metabolism and signaling

enzymes reduce activation energy of reaction

Why does a chemical reaction even occur?

to attain a state of lower Gibbs free energy in molecules

For a reaction to proceed, the free energy of the substrate must surpass the activation energy

How does a substrate molecule attain energy to exceed the activation energy

from the kinetic energy of random collisions with other molecules

reduced activation energy means →

greater turnover number (kcat)

turnover number

# of substrate molecules converted to product per second by each enzymes molecule when bound to the enzyme

Law of mass action

reactions proceed in the direction to attain chemical equilibrium

How fast is the reaction velocity of its kineteics

depends on

1) number of substrate molecules

2) affinity between enzyme and substrate

3) number of enzyme molecules

4) kcat

maximum velocity

Vmax = (# enzyme molecules) x kcat

hyperbolic kinetics

one substrate-binding site or multiple sites that do not affect one another

sigmoid kinetics

2 or more substrate binding sites that affect one another

Hyperbolic kinetic described by what equation

Michaelis-Menten equation

V= (Vmax [S]) / ([S] + Km)

S is concentration of substrate and Km is the half-saturation constant

Large Km→

low affinity

small Km

high affinity

Allosteric modulation

may either increase or decrease the affinity between substrate and enzyme

Two important ways Enzymes regulate cell function (fast and slow)

1) the types and amounts of enzymes determine whcig metabolic pathways are active in the cell (SLOW)

2) the rates at which metabolic pathways operate can be controlled by modulating the function of the enzymes existing in the cell at any given time (FAST)

Expression of gene influenced by ____

transcription factors

ectracellular signal molecules bind w ____

receptor proteins

most receptors embedded in cell membrane

4 types of receptor proteins

1) ligand gated channels

2) enzyme/enzyme linked receptor

3) intracellular receptor

4) G-protein coupled receptor

What receptors often trigger signal cascades

G-prot coupled and enzyme/enzyme linked

signal cascades allow ____

enormous amplification of the signal

cell membranes and epithelia both allow ___

control over exchange of materials

isoenzyme

different molecular forms of an enzyme within the same species

interspecific enzyme homologs

different molecular forms of an enzyme coded by homologous gene loci in different species

passive transport (need energy? toward/away equil?)

no energy, toward equilibrium

active transport (need energy? toward/away equil?)

Needs energy, away from equilibrium

diffusion transport arsing from…

1) the kinetic energy of solute particles

2) the statistical tendency of those particles to move from areas of high concentration to areas of low concentration

Which particles can easily diffuse thru the cell membrane and which cannot

Nonpolar and small polar can diffuse thru, ions and molecules too large and polar cannot

direction and rate of diffusion for ions relies on____

both concentration gradient and the electrical gradient

molecules that cannot easily diffuse doen the concentration gradient use ____

transporter proteins

Where does energy come from for transporter proteins?

random kinetic energy → not ATP

Primary active transport

transporter proteins draw energy direvtly by hydrolyzing ATP (an ATPase)