AP Biology U1 Quiz

Biochem

Controlled Experiment

Compares an experimental group to a control group to isolate the effect of the independent variable on the dependent variable

Positive control

Treated with a method already known to produce an expected result

Negative control

Set up to show no change/effect; treated the same as other groups. but without active treatment

Null hypothesis

Hypothesizes there is NO relationship between the observed pphenomenon and the independent variable being changed

Elements of a good graph

Title, labeled axes with units (independent variable on x-axis, dependent on y-axis), frame, index marks, line doesn’t start at origin if data doesn’t start there.

Covalent Bonds

form the stable backbone of macromolecules

Weak bonds(H-bonds, ionic bonds)

determines 3D shape and flexibilityin biological molecules, allowing for interactions between them.

Why water is polar

Oxygen is more electronegative than hydrogen (unequal sharing; O is partially negative, H is partially positive)

Cohesion

H-bonds hold water molecules to each other

Adhesion

H-bonds let water stick to other polar surfaces

High surface tension

Strong H-bonds at the surface resist breaking

Expansion upon freezing

Ice is less dense, floats, insulates water below

Water versatility as solvent

Polarity lets water pull apart other polar/charged molecules.

Water high specific heat

water resists temperature change, stabilizing environments for aquatic life

Hydrophilic

Polar/charged, dissolves in water (water loving)

Hydrophobic

Nonpolar, doesn’t dissolve in water (water fearing)

How is carbon used

Basis for chain, branch, and ring diversity (the backbone structure of most molecules)

Hydroxyl

-OH

Carbonyl

C=O

Carboxyl

-COOH (acidic, donates H+)

Amino

-NH2 (basic, accepts H+)

Sulfhydryl

-SH (forms disulfide bonds, Hydrophobic)

Phosphate group

-OPO3²- (negatively charged)

Methyl

-CH3 (nonpolar, affects shape/function)

main elements in Carbohydrates

CHO

Building blocks of Carbohydrates

Monosaccharide, disaccharide, polysaccharide

Bond in disaccharide

Glycosidic bond

Elements in Lipids

CHO(P in phospholipids; can include N or S in complex lipids)

Mostly nonpolar C-H bonds

Building blocks for Lipids

Glycerol (head) and fatty acid (tails)

Saturated fatty acids

only single carbon-carbon bonds, create straight chains that pack tightly together

Unsaturated fatty acids

Contain one or more double carbon=carbon bond, creating kinks that prevent tight packing (bends at double bond)

Triglyceride

3 fatty acid chains attached to one glycerol molecule (long term energy storage)

Phospholipids

Composed of glycerol, two fatty acids, and a phosphate group (bilayer of all cell membranes)

elements in Proteins

CHON(S)

Protein building blocks

Amino acid monomers

What bonds amino acid monomers

peptide bonds

Main elements in nucleic acids

CHONP

parts of a nucleotide

nitrogenous base, pentose sugar (5-carbon sugar), and phosphate group

building blocks of nucleic acids

nucleotides

Dehydration synthesis

builds polymers and releases water

Hydrolysis

breaks polymers apart, uses water

Monosaccharides

energy source; carbon skeleton for other molecules

Disaccharides

two mono saccharides joined by glycosidic linkage

Polysaccharides

storage (starch, glycogen) or structure (cellulose, chitin)

Starch

alpha linkages, coiled/helical, branched, good for compact storage and easily hydrolyzed

Cellulose

Beta linkages, alternating glucose flips 180, straight chains, many H-bonds between chains strong microfibrils, structural cell walls

Why lipids don’t dissolve in water

nonpolar c-h bonds can’t h-bond with water, water excludes them

Fats (triglycerides)

1 glycerol + 2 fatty acid tails + 1 phosphate group

energy storage, insulation, cushioning

Phospholipids

1 glycerol + 2 fatty acid tails + 1 phosphate group, Hydrophilic head and hydrophobic tails (forms membranes)

Steroids

four fused carbon rings

function in membranes/as hormones

Saturated fatty acids:

no double bonds, straight tails, pack tightly (less fluid more solid at room temp)

Unsaturated fatty acids:

double bonds, kinks, cant pack tightly, more fluid

Temperature effects on membrane fluidity

higher temp means more kinetic energy means tails move apart means more fluid

lower temp means less kinetic energy means tighter packing means more rigid gel like

DNA functions

stores/passes genetic info, the recipe

RNA functions

helps use DNA’s instructions to make proteins (transfers DNA recipe)

Linkage

phosphodiester bonds form sugar phosphate backbone

5’ end

free phosphate group

3’ end

free hydroxl group

Synthesis direction

always 5’ —> 3’

Antiparallel structure

two strands of nucleotides run in opposite directions to be held together by hydrogen bonds between complementary bases

DNA

deoxyribose (thymine) double stranded for stable storage

RNA

ribose (uracil), single stranded for protein synthesis

DNA vs RNA

DNA sugar missing one oxygen atom

RNA has extra oxygen hydrogen group in sugar

Amino acid structure

Central alpha carbon + amino group (-NH2) + carboxyl group (-COOH) + H atom + R group

R group vategories

Nonpolar (hydrophobic)

polar (hydrophilic)

Acidic (negative)

Basic (positive)

Protein: primary structure

Linear sequence of amino acids

Secondary structure

local folding (alpha helix or beta pleated sheet) via backbond H-bonds

Tertiary structure

Overall 3D shape of one chain - stabilized by hydrophobic interactions, disulfide bridges, ionic bonds, and hydrogen bonds between R groups

Quaternary structure

two + folded polypeptide chains join into one functional protein

Denaturation causes

heat, pH changes, chemicals, agitation

Effect of denaturation

loss of function due to shape change, unfolding causes it to stop working

Primary structure stays intact but folding destroyed

hydrophobic side exposed to water will caue it to refold or bury hydrophobic r group internall disrupting H-bonding and other interactions