Chapter 3 part 1 Flashcards
What are the characteristics of an amino acid structure?
Has an amino group at the first end, an alpha carbon, an R group, & an alpha carboxyl group
All 20 aa share the same ________________ backbone
Nitrogen-carbon-carbon backbone
What are the two types of covalent bonds between amino acids in proteins?
- Peptide bonds
- Disulfide bonds
Peptide bonds
Links amino acids together into polypeptides chains
Disulfide bridges
Bridges between cysteine R groups
Polypeptides are formed by linking amino acids together in __________ bonds
Peptide
A peptide bond is formed between the ___________ group of one amino acid & the alpha-amino group with the loss of ________
Carboxyl group, water
In a polypeptide chain the ___________ pattern from the amino acid is known as the backbone of the polypeptide
N-C-C-N-C-C (A single amino acid is known as a reisdue)
The ________________ is the 1st end made during polypeptide synthesis& the carboxyl terminus last
Amino acid terminus
The ________________ residues is always written first
Amino terminal
Proteolysis (Proteolytic cleavage)
Hydrolysis of a protein by another protein
Proteolytic enzyme (Protease)
Hydrolysis of a protein by another protein
____________ can form disulfide bonds (sulfur-sulfur bonds) with each other
Cysteines
When cysteine becomes disulfide-bonded to one another its called ___________ instead of cysteine
Cystine
Proteins fold into a unique 3D structure so that it can _____________ properly
function
Denatured proteins
Improperly folded that are non-functional
Denaturation
Refers to the disruption of a protein’s shape without breaking peptide bonds
Proteins are denatured by what conditions?
- Urea- which disrupts hydrogen bonding interactions
- Extreme pH
- Extreme temperature
- Changing salt concentration (tonicity)
Primary (1) structure
Linear sequence of amino acid residues( & peptide bonds determines its structure)
Secondary (2) structure
Contains hydrogen bonds between backbone groups
Secondary structure is the initial folding of a polypeptide chain into shapes stabilized by ____________ bonds between backbone NH & CO groups
Hydrogen bonds
Secondary structure contains what 2 types of motifs?
- Alpha helix
- Beta pleated sheets
Parallel beta pleated sheets
Have adjacent polypeptides strands running in the same direction
Anti-Parallel beta-pleated sheets
Polypeptides strands running in opposite directions
If a single polypeptide folds once & forms a beta-pleated sheet with itself it would be _________________
Antiparallel
Tertiary (3) structures are stabilized by _________________ interactions
hydrophobic/hydrophilic
Secondary structures such as ___________ fold into 3 structures driven by the interation of the R groups with eaxh toeher & water
Alpha helices
In forming the 3 structures the hydrophobic R groups fold into the interior of the protein & the hydrophilic R groups tend to be exposed to water or the surface of the protein and this process is known as what?
Hydrophobic effect
Quaternary (4) structure involves the interactions between polypeptide _________
Subunits
A subunits is what?
Is a single polypeptide chain that is part of a large complex containing many subunits (a multisubunit complex)
What forces stabilize the 4 & 3 structures?
Non-covalent, interactions, van der waals forces, hydrogen bonds, disulfide bonds & electrostatic interaction stabilize 4 & 3 structures
__________ bonds_ aren’t involved in 4 structures (ex. The difference between 4 disulfide & 3 disulfides bonds is that 4 disulfides are bonds that form between chains that aren’t linked by peptide bonds & 3 disulfides are bonds that form between residues in the same polypeptide
Peptide bonds
Carbohydrates can be broken down to CO2 in a process called _________ which is also the burning or combustion
Oxidation
Monosaccharides (simple sugars)
Is a single carbohydrate molecule (have the general formula CnH2nOn)
What are some examples of monosaccharides?
Fructose, Glucose, & Ribose
Two monosaccharides bonded together form a _______________, a few form an oligosaccharide & many form a polysaccharide
Disaccharide
Glycosidic linkage
The bond between two sugars molecules
What are lipids physiological roles?
- In adipose cells triglycerides (fats) store energy
- In cellular membranes phospholipids constitute a barrier between intracellular & extracellular environments
- Cholesterol is a special lipid that serves as the building block for the hydrophobic steroid hormones
The main characteristic of the lipid is its _________________
hydrophobicity
A hydrophobic molecule is also a _____________ molecule
lipophilic
Hydrophilic molecule is ____________
Lipophobic (lipid-rearing)
Fatty Acids contain _____________ at its end & are usually 14 to 18 carbons long
carboxylic acids
Only ________ numbered fatty acids are made in human cells
Even
Saturated fatty acids
A fatty acid with no double bond
Unsaturated fatty acids
Contain one or more double bonds & are usually cis (or Z)
When fatty acids interact with water (or an aqueous solution) they form a micelle where the long hydrophobic tails are in the center & the hydrophilic head is exposed & the _________________ interactions is the driving force for it
Hydrophobic
The storage form of a fatty acid is _______ which is triacylglycerol or triglyceride
Fat
The triglyceride is composed of ____ fatty acids esterified to a glycerol molecule & glycerol is a 3-carbon triol with the formula HOCH2-CHOH-CH2OH
3
Lipases
Are enzymes that hydrolyzed fats
Triacylglycerols
Are stored in fat cells as an energy source
Fats are more efficient energy storage molecules than carbohydrates for what two reasons?
- Packing
- Energy content
Packing
Their hydrophobicity allows fat to pack together much more closely than carbohydrates. Carbohydrates carry a great amount of water-of-solvation(water molecules hydrogen bonded to their hydroxyl groups)
Energy content
All packing considerations asides, fat molecules store more energy than carbohydrates. In other words, regardless of what you dissolve it in, a fat has more energy carbon-for-carbin than a carbohydrate
Phospholipids form what when interacting with water?
Lipid Bilayer
Double bonds in phospholipids fatty acids tend to ______ membrane fluidity
Increase
_______________ prevents the membrane from solidifying by disrupting the orderly packing of the hydrophobic lipid tails
Unsaturation
Decreasing the length of fatty acids tails also increases _____________
Fluidity
At low temperatures cholesterol ___________ fluidity in the same way as kinks in fatty acid tails, therefore its known as membrane antifreeze
Increase
At high temp, cholesterol keeps fluidity at an _____________
Optimum level
What are the structural determinants of membrane fluidity?
- Degree of saturation
- Tail length
- Amount of cholesterol
A terpene has a general formula ____________, they come from an isoprene units
(C5H8)n
Steroids are similar to________
Fats
All steroids have the basic ______________
tetracyclic ring system (based on the structure of cholesterol)
Cholesterol is a ____________
Steroid (ex. testosterone & estradiol)
Phosphate is also known as _______________
orthophosphate
Two orthophosphates bound together via an anhydride linkage form ___________
Pyrophosphate where the P-O-P bond in Pyrophosphate is an example of a high energy phophosphate bond
What are the 3 reasons that phosphate anhydride bonds store so much energy?
- When phosphates are linked together, their negative charges repel each other strongly
- Orthophsophate has more resonance forms and thus a lower free energy than linked phosphates
- Ortohophoshates has a more favorable interaction with the biological solvent (water) than linked phosphates
Two monosaccharides joined with a ____________ linkage form a disaccharide
Glycosidic linkage (common disaccharides are maltose, sucrose, & lactose)
Glycogen (animals) & starch (plants) are ________ units for glucose & can be broken down for energy
Storage (cellulose is a glucose polymer but its beta linkage prevents digestion)
Lipids are found in triglycerides, ________________, cholesterol, and steroids, and terpenes
Phospholipids
Triglycerides and phospholipids are linear while cholesterol and steroid have _______ structure
Ring
Lipids are _________
Hydrophobic
Triglycerides are used for _________ storage, phospholipids form ________ & cholesterol is the precursor to the steroid hormones
Energy, membranes
The building blocks of nucleic acids (DNA & RNA) are ____________ which are comprised of pentose sugar, a purine or pyrimidine base & 2-3 phosphate units
nucleotides
