1. Biologically Important Molecules Flashcards
(33 cards)
Explain or draw the basic amino acid structure
left - amino group (NH2)
middle - alpha carbon with hydrogen and R group attached
right - carboxyl group (COOH)
What bond connects amino acids?
peptide bond (covalent bond)
How is a peptide bond created?
Free electrons from an amino group attack the center carbon of a carboxyl group in a hydrolysis reaction (water is released).
By convention, polypeptide chains always start with the amino-terminus
Hydrolysis of a protein by another protein (to break that protein down) is called?
proteolysis / proteolytic cleavage.
the enzyme that cuts the protein is called a protease.
What is a thiol group? Which amino acid contains it?
a thiol is a sulfide-containing group (-SH).
Cysteine’s R group is a thiol
What is a disulfide bond? What does it create?
A disulfide bond (covalent) is created by two cysteine groups. When created, cysteine is now called cystine. This covalent bond increases tertiary structure stability.
t or f, denaturation refers to the disruption of proteins shape without breaking peptide bonds.
true! - denaturation does NOT break peptide bonds
what can cause protein denaturation (n=4)?
- urea
- changes in pH extremes
- temperature extremes
- changes in salt concentrations
Explain what each level of protein structure is determined by.
primary - peptide bond sequence
secondary - hydrogen bonds (between backbone NH and CO groups)
tertiary - R-group interactions (hydrophobic, electrostatic, etc.)
note: despite that disulfide bonds are covalent, they are still considered a part of the tertiary structure
quaternary - interactions between polypeptide subunits.
t or f, a peptide bond may form in quaternary structure.
false
carbohydrates may be broken down into CO2 in a process called?
oxidation
what is the general chemical formula for monosaccharides?
CnH2nOn
glucose = C6H12O6
what bond forms between two sugars?
glycosidic linkage (covalent bond) –> formed by a dehydration reaction requiring enzyme catalysis.
t or f, mammals can digest alpha and beta glycosidic linkages.
false - mammals (typically) can only digest alpha linkages.
What are glycogen, starch, and cellulose, briefly?
glycogen - alpha polymer of glucose used in mammals. short with many branches
starch - alpha polymer of glucose used in plants. less branched.
cellulose - beta polymer of glucose that creates cell walls and wood.
what is a fatty acid? how large are they?
long unsubstituted alkane which ends in a carboxylic acid. FAs are typically 14-18 carbons long.
note: only even-numbered fatty acids are made in human cells
what is a saturated fatty acid?
a fatty acid with NO carbon-carbon double/triple bonds. it is saturated with hydrogen molecules.
what are cis (Z) / trans (E) fats?
these are unsaturated fatty acids (they contain one or more double bonds).
cis/Z –> bent fatty acid
trans/E –> not bent (compacts easier)
what is micelle?
the molecule formed when fatty acids interact with water. the carboxyl heads face outwards while the hydrophobic tails point inwards to create a ball.
what is triglyceride?
triglyceride is fat. Three fatty acids are esterified (bonded to) glycerol, forming triglyceride. This is how fatty acids are stored.
what enzyme breaks down triglyceride?
Lipase (hydrolyzes triglycerides)
t or f, fats are more efficient energy storage than carbs.
true.
they pack more tightly due to hydrophobic effects and have more energy per C-C bond
what are phospholipids? What is diglycerol phosphate (DG-P)?
phospholipids create lipid bilayer membranes.
DG-P is essentially glycerol, except instead of three alcohol groups, the third is a phosphate group.
Fatty acids spontaneously form micelles, phospholipids spontaneously form ?
the lipid bilayer which makes membranes
