Section II (Chapters 4, 6-9) Flashcards
Why is water a good solvent for electrolytes?
Since they are dipolar molecules, they can form hydrogen bonds easier via uneven electrons
If molecules hydrogen bond with water molecules, it means…
Dissolve readily in water
Hydrogen bonds between water & polar solutes
Continuously dissociate and reform
Water has a high heat of…
Fusion, making it a good thermoregulator
What is a hydrogen bond?
Weak noncovalent interaction between hydrogen of one molecule and more electronegative of acceptor molecule
In a polar environment, molecules can … to form network of hydrogen bonds with water
dissolve
In a nonpolar environment, molecules do…dissolve, which causes them to form
Not, hydration shells
What is osmolality?
Water distributes between compartments according to concentration of solutes (osmolality), moves from component with lower osmolality (lower concentration of solutes) to higher concentration (high osmolality) to achieve balance
What occurs in hyperglycemia?
Excess glucose or ketones in blood increase blood osmolality, pulling extra water into cells with it, thus when passed through kidney, increased water is excreted in urine, leading to overall dehydration of cells
What is pH?
Negative log10 of hydrogen concentration expressed in moles per L (pH = -log[H+])
What is an acid?
Substance that can release hydrogen ions/protons
What is a base?
Substance that can accept hydrogen ions/protons
What is a buffer?
Mixture of undossociated acid and its conjugate base (form of the acid that has lost its proton), resists changes in pH when H or OH are added
What is the pKa?
Negative log of dissociation constant Ka, buffer has greatest buffering capacity when pH is near pKa
What does strong acid mean?
Dissociates completely within water
What is an example of a strong acid?
Sulfuric acid
What is an example of a weak acid?
Lactic acid, citric acid
Interpretation of titration curve
- Midpoint is when 0.5 equivalents of OH have been added and half of conjugate acid is dissociated = pKa
- Adding OH causes shift to right, H dissociates from acid and combines with OH to form water = minimal change in pH
- Adding H causes shift to left, conjugate base A- combine with H to form HA = minimal change in pH
If pH is above pKa…
Basic form
If pH = pKa
Balanced at 50% basic and acidic form (A-/HA = 1)
If pH is below pKa
Acidic form
What is the physiological pH?
7.4
Added OH causes
Dissociation of acid and H to combine in order to form water
What is the Henderson-Hasselbach equation?
pH = pKa + log ([A-]/[HA])
What is the major source of acid?
CO2
Where does CO2 diffuse?
Diffuses into interstitial fluid, then blood plasma, then into RBC
Where does phosphate buffer occur?
All cells
Where does protein buffer occur?
Cells & plasma
What does Aspirin do?
Increases breathing rate and expiration of CO2 to attempt to normalize excess H concentration
What is ketoacidosis?
Insulin supply is inadequate (due to autoimmune destruction of B-cells of pancreas), so body stays in a state similar to fasting even with food ingestion (insulin is not signaling uptake of glucose into tissues, so ketones are still being formed); ketones are weak acids that release anions and hydrogen ions which thereby lower the blood pH
What do we use for PO2 analysis?
Clark electrode
What do we use for PCO2 analysis?
Severinghaus
What is 60% of our body weight?
Water
What does buffer resist?
Changes in pH
How is water distributed?
Intracellular & extracellular components
Acids release
H
Bases accept
H
What does normal metabolism generate?
Metabolic acids, inorganic acids, and CO2
Hemoglobin acts as a
Buffer
Respiratory acidosis
CO2 elimination is inadequate
↑ PCO2
↓ pH because [H+] increases
If chronic, [HCO3 ] increases
Accumulation of CO2, push toward right
Respiratory alkalosis
CO2 elimination is excessive
↑ pH because [H+] decreases
↓ PCO2
If chronic, [HCO3-] decreases
CO2 decrease, push toward left
Metabolic acidosis
↓ pH because [H+] increases
↓ [HCO3 ]
If chronic, PCO2 decreases
Administration of HCO3 can provide temporary palliation.
Accumulation of H in blood
What is the general structure of amino acids?
Carboxylic acid group, amino acid group attached to an alpha-carbon in L configuration, hydrogen atom, and varying side chains
What is the ionization state of amino acids at physiological pH?
They are zwitterions
Amino group + charge, carboxylate group - charge
Why does glycine not fit well into any amino acid classifications?
Small hydrogen chain, which causes the least amount of steric hinderance
Usually found at bends in proteins
Which amino acids are nonpolar hydrophobics?
Alanine, valine, leucine, isoleucine, proline
Which amino acids are uncharged polar?
Serine, threonine, asparagine, glutamine
Which amino acids are considered “sulfur”
Cystine, methionine
Which amino acids are negatively charged (acidic)?
Aspartate, glutamate
Which amino acids are positively charged (basic)?
Lysine, arginine, histidine
Which amino acids are aromatic?
Phenylalanine, tyrosine, trytophan
What are the 9 essential amino acids for the body?
Leucine, isoleucine, lysine, threonine, valine, tryptophan, phenylalanine, methionine, and histidine
Phenylalanine is very… and …
Nonpolar, hydrophobic
Tyrosine has … group that engages in … bonds/hydrophilic
Hydroxyl, hydrogen
Tryptophan is an indole … with … that can hydrogen bond
Ring, nitrogen
What does not occur with the H atoms on the aromatic amino acids?
Hydrogen bonding
Which sulfur amino acid forms disulfide bridges?
Cysteine
What occurs when a pH is higher than 10 in positively charged amino acids?
Lose the proton from NH group
What occurs when a pH is lesser than four in negatively charged amino acids?
Lose the proton from carboxylic acid
Methionine (sulfur) is nonpolar, large, and has a bulky side chain. What does it do in place of forming a disulfide bridge?
Transfers methyl group that was attached to the sulfur atom
What do uncharged amino acids contain?
Hydroxyl or amide group
Asparagine and glutamine are amides of…
Aspartate and glutamate
Where can you find uncharged polar amino acids?
On the surface of water-soluble globular proteins
Nonpolar amino acids…
Cluster together for the hydrophobic effect
What is unique about proline?
An amino acid due to ring involving a-carbon and a-amino group, forms kinks in peptide backbones or restrictions of conformation
What do valine, leucine, and isoleucine exhibit?
High hydrophobicity!
What are the chemical properties of a peptide bond?
- Between carboxylic acid group and amino group of next acid
- Amino group, a-carbon, and carboxyl group form peptide backbone with side chains extending outwards
Primary structure of amino acids can … the translated protein structure …
Alter, therefore alter protein function
What does the primary structure assume?
Trans configuration -> successive alpha-carbons and R groups are on opposite sides
What must remain planar in the primary structure?
Carboxyl & amide groups
What can occur in primary structure?
Variations
What is found in variant regions?
Noncritical variations of the primary amino acid
What is considered a conservation substitution?
Replacing one amino acid with one of a similar structure
If many different amino acid residues are tolerated at a certain position, it is called…
Hypervariable
Regions where binding sites or functional three-dimensional structures are usually…
Invariant
What are common post-translational modifications?
Phosphorylation, oxidation, carboxylation, glycosylation, fatty acylation/prenylation, regulatory modification, oxidation/hydroxylation of proline, selenocysteine
O-glycosylation
Small chains bound to serine or threonine residues by O-linkage, attached in secreted proteins
N-glycosylation
Bound by N-linkage to the amide nitrogen of asparagine, in order to protect from proteolysis or immune attack
Fatty acylation/prenylation
Addition of lipid, found in many membrane proteins
Phosphorylation of hydroxyl group on serine, threonine, or tyrosine by protein kinase
Large, bulky, negatively charged group created altering structure and activity
Where does acetylation occur?
Lysine residues of histone proteins in chromatin
Adenosine diphosphate ribosylation
Transfer of ADP ribose from NAD+ to arginine, glutamine, or cysteine residue, regulating the activity
Carboxylation of gamma-carbon of glutamate
Attaching clot to surface; mediated by calcium ions binding two negatively charged carboxyl groups to phospholipids of cell membrane