Krogh's principle
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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
Homeostasis
maintained via negative feedback loops; equilibrium state
Conformers
organisms where homeostasis is heavily influenced by environment
Avoiders
organism where homeostasis avoid environmental conditions
Regulators
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)
Nucleotides
DNA/RNA, ATP/NADH DNA/RNA Structure: phosphate group, pentose sugar (deoxyribose), nitrogenous base ATP: 3 phosphate groups, adenine, ribose NADH: same thing lol
Proteins
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
Carbohydrates
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)
Lipids
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
Glycolysis
spend 1 ATP to trap glucose in the cell (hexokinase takes glucose and makes glucose 6-phosphate)
rearrange it to prepare for split
spend 1 ATP add a P prepare split
splits into 3 carbon molecules [glyceraldehyde-3-phosphate]
interacts NAD + Pi to create NADH + H+ to add extra phosphate G-3-P (2x)
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
move pyruvate from cytosol to mitochondria (gain NADH, convert pyruvate to Acetyl-CoA)
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
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)
Energy-harvesting steps produce: 3 NADH + FADH2 + ATP (2x) (so in total- 6, 2, 2)
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)
10 NADH * 2.5 ATP = 25 ATP
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?
glycolysis = cytosol
linking step = mitochondrial matrix
krebs cycle = mitochondrial matrix
ETC = mitochondrial inner membrane
Free Radicals
contain an unpaired electron
Antioxidant
can donate a spare electron
Fat Catabolism
Lipolysis: triglycerides broken down into free fatty acids
transported into mitochondria- use 2 ATP and CoA to make a fatty Acyl-CoA (activated fatty acid)
carnitine replaces CoA so that it can help long-chain fatty acids across mitochondrial membrane (short chains can cross alone)
Beta Oxidation: snips off two carbon atoms at a time and sends Acetyl-CoA to citric acid cycle
Protein Catabolism
Proteasomes digest chains tagged with ubiquitin
newly broken amino acids can go directly into Krebs cycle
glucogenic, ketogenic, and glucogenic/ketogenic
Nucleic Acid Catabolism
glycolysis breaks nucleotides into nucleoside, then separates pentose and base along glycosidic bond
purines turn into uric acid
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
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
Osmolarity
a measure of osmotic pressure of a given solution (unit = osmoles)
Tonicity
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
release of chemical messenger from signaling cell
transport of messenger to target cell
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