Principles of Physiology Exam 1

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Krogh's principle


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89 Terms

Krogh's principle

for every biological problem there is an organism on which it can be most conveniently studied

Bergman's rule

larger species will be found in colder climates; species of smaller sizes will be found in warmer climates

Body Size and Complexity

complexity increases with body size to increase internal surface area ratio

Basal Metabolic Rate (BMR)

metabolic rate when organism is at rest (energy needed for vital processes)

Mass-Specific Metabolic Rate (MSMR)

BMR divided by organism's mass

BMR vs Mass

allometric relationship- nonlinear correspondence between BMR and mass

Surface Area and Volume

SA:V ratio gets smaller as volume increases at much faster rate than surface area; having more SA means higher rate of exchange across cell membrane

Pros and Cons of being large

Pros: maintains body temp more easily, have more inert tissue, greater cell specialization Cons: move slower, more easily targeted by predators, require carefully maintained environment


maintained via negative feedback loops; equilibrium state


organisms where homeostasis is heavily influenced by environment


organism where homeostasis avoid environmental conditions


organisms where homeostasis is mid affected

Negative Feedback Loops

Give signals to return to systems to norman/baseline, most common, lots of subtypes Antagonistic: usually to effectors with opposite effects Anticipatory: activates corrective response before variable is disturbed (ex. glucose and insulin, thermostat, body temperature)

Feedback Loop terms

Stimulus: initiation event Variable: effect Sensor: detects the change in the variable Integrator: compares against reference value (set point) Effectors: make adjustments to the variable

Positive Feedback Loops

work to enhance or continue change, rare (ex. labor, fight and flight)


DNA/RNA, ATP/NADH DNA/RNA Structure: phosphate group, pentose sugar (deoxyribose), nitrogenous base ATP: 3 phosphate groups, adenine, ribose NADH: same thing lol


Functional: enzymes, transport, channels Signaling: millions of signaling molecules and receptors Immunity: antibodies Energy storage: protein catabolism Structural: microtubules and other filaments 20 different amino acids: categorized into polar charges, polar uncharged, nonpolar (hydrophobic)

Levels of Protein Structure

Primary: sequence of amino acids Secondary: hydrogen bonds, alpha helices, beta sheets Tertiary: noncovalent bonds, just folding Quaternary: multiple subunits together

Heat Shock and Protein Damage

Proteins unfold/misfold at high temperatures Heat shock-proteins interact with other proteins to help them fold correctly


Sugars in single units or chain Energy Storage (glucose): packed together and stored as starch or glycogen Structural (cellulose chitin) Signaling (glycoproteins glycolipids): cell adhesion and recognition (ABO blood types), digestion (absorptive surface)


Fatty acids, triglycerides, phospholipids, cholesterol All are hydrophobic: nonpolar C-H bonds, need help travelling through blood Energy storage: long-term storage (fatty acids, triglycerides) Structural/functional (cell membranes) Has to be transported as triglyceride (glycerol plus fatty acids) Saturated vs Unsaturated fatty acids Structure of phospholipids: polar head face out and nonpolar fatty acid tails face inward Steroids: derived from cholesterol through a series of enzymatic modifications, easily diffuse across cell membranes to bind to intracellular receptors

Central Dogma

Allele of gene transcribed into RNA containing exons and introns that go through exon splicing to get mRNA that is translated into a protein by a ribosome and tRNA


  1. spend 1 ATP to trap glucose in the cell (hexokinase takes glucose and makes glucose 6-phosphate)

  2. rearrange it to prepare for split

  3. spend 1 ATP add a P prepare split

  4. splits into 3 carbon molecules [glyceraldehyde-3-phosphate]

  5. interacts NAD + Pi to create NADH + H+ to add extra phosphate G-3-P (2x)

  6. two P groups transferred to ADP to make 2 ATP (2x) -> 2 pyruvate

Input and Output of Glycolysis

Input: 2 ATP, glucose, NADPi Output: 4 ATP, 2 pyruvate, 2 NADH, H2O Net ATP: 2

Linking Step

Pyruvate to Acetate

  1. move pyruvate from cytosol to mitochondria (gain NADH, convert pyruvate to Acetyl-CoA)

  2. pyruvate travels through transmembrane protein, releases CO2, protonate an NAD to NADH, and is tagged with Coenzyme A to produce Acetyl-CoA

Citric Acid/Krebs Cycle

  1. Acetyl-CoA combines with oxaloacetate and water via Citrate synthase to create Citrate and CoA-SH (makes the 3 C Acetyl-CoA a 6 C Citrate)

  2. Energy-harvesting steps produce: 3 NADH + FADH2 + ATP (2x) (so in total- 6, 2, 2)

  3. overall by this point, 1 glucose molecule has produced: 4 ATP, 10 NADH, 2 FADH2

Anaerobic Respiration

Begins with glycolysis, but pyruvate interacts with lactate dehydrogenase to convert it into lactate; makes less energy but at a faster pace

Electron Transport Chain (Oxidative Phosphorylation)

  1. 10 NADH * 2.5 ATP = 25 ATP

  2. 2 FADH2 * 1.5 ATP = 3 ATP Net 28 ATP

  • proton gradient has high extracellular proton concentration and low intracellular proton concentration; gradient drives ATP synthase

  • waste products: oxygen free radicals (oxygen containing unpaired electrons) search for electron to complete and stabilize atom (can be combated via antioxidants)

Where does each step of glucose metabolism take place?

  1. glycolysis = cytosol

  2. linking step = mitochondrial matrix

  3. krebs cycle = mitochondrial matrix

  4. ETC = mitochondrial inner membrane

Free Radicals

contain an unpaired electron


can donate a spare electron

Fat Catabolism

  1. Lipolysis: triglycerides broken down into free fatty acids

  2. transported into mitochondria- use 2 ATP and CoA to make a fatty Acyl-CoA (activated fatty acid)

  3. carnitine replaces CoA so that it can help long-chain fatty acids across mitochondrial membrane (short chains can cross alone)

  4. Beta Oxidation: snips off two carbon atoms at a time and sends Acetyl-CoA to citric acid cycle

Protein Catabolism

  1. Proteasomes digest chains tagged with ubiquitin

  2. newly broken amino acids can go directly into Krebs cycle

  • glucogenic, ketogenic, and glucogenic/ketogenic

Nucleic Acid Catabolism

  1. glycolysis breaks nucleotides into nucleoside, then separates pentose and base along glycosidic bond

  2. purines turn into uric acid

  3. pyrimidines turn into citric acid cycle intermediates

Fluid Mosaic

  • cell membranes are never static

  • CM composed of phospholipid bilayer (hydrophilic head and hydrophobic tail)

  • Saturated (no double/triple bonds) v Unsaturated (has "kinks" created by double/triple bonds)

  • Membrane fluidity: liquid crystal at high temp, crystal at low temp (can't function properly)

  • Fluidity maintained by cholesterol levels and unsaturated fatty acids

Selective Permeability

  • Permeable: gasses and lipophilic molecules

  • Semipermeable: small uncharged polar molecules

  • Impermeable: large uncharged polar molecules, ions

Simple Diffusion

  • movement of particles from high to low concentrations without protein, no energy or transporters needed, applies to lipid-soluble molecules, driven by concentration gradient

  • Fick's Law: "molar flux due to diffusion is proportional to the concentration gradient" -Osmosis


-movement of a solvent through a semipermeable membrane to equalize the solute concentration (solvent typically water and solute is molecule)

Osmotic Pressure

  • force that must be applied to a solution side to stop movement of water

  • hypoosmotic: low osmotic pressure, low # of solutes in cell, water diffuses out

  • hyperosmotic: high osmotic pressure, high # of solutes in cell, water diffuses in

  • isosmotic: equal osmotic pressure, equal number of solutes, no net movement of water


a measure of osmotic pressure of a given solution (unit = osmoles)


  • same measure as osmolarity BUT only applies to non-permeable solutes; penetrating solutes have NO effect on tonicity

  • hypertonic solution has a higher concentration of solutes outside the cell, water leaves and cell shrinks (plasmolysis)

  • hypotonic solution has a lower concentration of solutes outside the cell, water rushes in and cell expands (cytolysis)

  • isotonic solution has equal concentration outside cell, no net movement of water

Facilitated Diffusion

  • no ATP required, moves down concentration gradient, requires carrier protein (channel)

  • open channels: allows only select molecule to flow through freely

  • gated channels: can open/close in response to various stimuli (voltage, ligand, mechanical)

  • carrier proteins allow molecules through via conformational change; types are uniport, symport, and antiport

Active Transport

  • protein transporter needed, energy is required, molecule moves against concentration gradient

  • primary active transport: uses ATP directly (ex. Na+/K+ ATPase pump)

  • secondary active transport: uses ATP indirectly, couples movement of one molecule to movement of second molecule; can take product of one primary AT and use it in secondary AT

Cell Signaling Basics

  • Signaling cells: send a signal

  • Target cells: receives the signal

Indirect (local and distant) signaling

  1. release of chemical messenger from signaling cell

  2. transport of messenger to target cell

  3. communication of signal to target cell

Water and Lipid Solubility

  • Hydrophobic and lipophilic: not water soluble, dissolves in lipids, ex. steroids, can't be stored, need carrier proteins, can diffuse across cell membrane

  • Hydrophilic and lipophobic: water soluble, does not dissolve in lipid, ex. proteins, can be stored in vesicles, travels freely in blood, can't cross cell membrane but utilizes surface receptors

Ligand-receptor interactions

  • Specificity: receptors bind to only correct shaped ligands

  • Agonists: activate receptors

  • Antagonists: blocks receptors

Regulation of Response

  • can down/up regulate by changing number of receptors on cell (more receptors = more response)

  • number of receptors most directly related to intensity of response

  • Signal transduction pathways increase (amplify) number of molecules affected

Ligand-Gated ion channels

  • ligand binding causes change in receptor shape

  • concentration gradient dictates direction