AP Bio Midterm- Unit 1

Which of the following molecules is polar?
They are both polar.

Which of the functional groups affects the expression of genes when bound to DNA or on proteins bound to DNA?

A compound contains hydroxyl groups as its predominant functional group. Therefore this compound…
a.) lacks asymmetric carbon and is probably a fat or lipid
b.) should dissolve in water
c.) should dissolve in a nonpolar solvent
d.)will not form hydrogen bonds with water

In what way do testosterone and estradiol differ from each other?
different functional groups @ same carbon skeleton

Which is a false statement concerning amino groups?
a. are basic with respect to pH
b. are found in amino acids
c. contain nitrogen
d. are nonpolar

How common are the elements living systems are made out of?
Living organisms are 96% (carbon, hydrogen, oxygen and nitrogen) 4%- (calcium, phosphorus, potassium and sulfur)
other 20 elements are less than 1%

Of 92 natural elements, 20-25% are essential (orgs need to live a healthy life)

Why do atoms bond?
Atoms bond because their outer electron shell (valence shell) must be filled in order for an atom to be stable, this requires either giving or taking electrons, which requires bonding to another atom.

What causes molecular polarity?
Polarity results from the uneven partial charge distribution between various atoms in a compound. Atoms, such as nitrogen, oxygen, and halogens, that are more electronegative have a tendency to have partial negative charges. Atoms, such as carbon and hydrogen, have a tendency to be more neutral or have partial positive charges.

When you have a very electronegative (need for electrons) with one that’s not so, you end up with a partial negative and positive charge

How does the type of bonds present in a substance influence the chemical and physical properties of that substance?
ex: saturated fatty acids have no double bounds between carbons which lets them pack solidly at room temperatures, why they are usually solids (butter, lard)
unsaturated fats: have some double bounds, which results in kinks and they cannot pack tightly, therefore are usually liquids (oils)
Phospholipids- hydrophilic polar head with phosphate group and fatty acid tails= hydrophobic…membranes are hydrophobic and only allow certain molecules in

How do properties of water or sodium chloride show emergent properties?
Water- Hydrogen bonds, the polarity of the bonds allows the molecules to form hydrogen bonds with each other.

What is cohesion?
linking of “like” molecules, hydrogen bonds form between molecules…EN Oxygen with + H. (TO EACHOTHER)

What is adhesion?
clinging of one substance to another…to another polar substance (use their very EN and + charge to cling)

What is transpiration?
movement of water molecules up thin xylem tubes and evaporation from stomata in plants

Specific heat in Water-
amount of heat required to raise or lower temp of substance by 1 C. Water has a high specific heat due to the H bonds, H is very attracted to the EN oxygen and it takes more E to break that bond

Water as the “universal solvent”
substance that dissolves another substance
w/ any other polar molecule…H attracts the – charge of other and O attracts +

NaCl emergent properties-
Na is a metal and Cl is a poisonous gas, but together they make something we can eat.

Why are radioactive elements useful for the study of biological systems?
bone scans, kidney scans, and others. Radioactive isotopes and radioactively labeled molecules are used as tracers to identify abnormal bodily processes. This is possible because some natural elements tend to concentrate in certain parts of the body: iodine in the thyroid, phosphorus in the bones, potassium in the muscles. When a patient is injected with a radioactive element, a special camera can take pictures of the internal workings of the organ.

Ionic bonds-
two atoms attract valence elctrons unequally that the more EN atom steals the electron from the less EN atom
ion is the result
+/- charge

Covalent Bonds-
valence electrons are shared by two atoms
nonpolar—electrons shared equally
polar—one atom has greater EN than other, ,unequal share. EN is slightly -, less EN is +

Hydrogen bonds-
relatively weak
form between partially pos charged H atoms and very strongly EN atom of another (N or O)

How do you identify if a substance has ionic or covalent bonds?
nonmetal and metal = ionic,
nonmetal + nonmetal = covalent

What causes radioactivity?
Radioactivity is caused when an atom, for whatever reason, wants to give away some of its energy. It does this because it wants to shift from an unstable configuration to a more stable configuration. The energy that is released when the atom makes this shift is known as radioactivity.

“Expansion with freezing”-
When ice freezes, it expands because the hydrogen bonds
The fact that water expands upon freezing causes icebergs to float. The fact that water reaches a maximum density at about 4°C causes bodies of water to freeze on the top first. Then the further expansion as a part of the phase change keeps the ice floating with some 8% of its mass above the surface. The expansion during the phase change may be shown on a PvT surface, and contrasts with the contraction upon freezing of most substances.
he expansion upon freezing comes from the fact that water crystallizes into an open hexagonal form. This hexagonal lattice contains more space than the liquid state.

Ice with living orgss
Ice is less dense than water, and therefore floats…this way organisms can live in the oceans without freezing

Relationship between disassociation of Water an pH
When water dissassociates, it’s when an H from one H20 attaches to another…makes H30 (hydronium) and leaves OH-. Acid is anything that increases the H, Base is anything that decreases.
pH=-log [ H+]

Why is carbon central to the structure of all biological molecules?
It has 4 valence electrons
form 4 bonds
single or double covalent bonds

What are isomers?
molecules with same molecular formula but diff arrangement
as number C increases, so does # isomers

Hydroxyl group-
polar bonds, H bonds
alcohols like ethanol and methanol
helps dissolve molecules like sugars

Carboxyl group-
carboxylic acids such as fatty acids and suugars
acidic properties because it tends to ionize; source of H ions

Carbonyl group-
ketones and aldehydes like sugars

amino group-
amines like amino acids

organic phosphates, including ATP, DNA and phospholipids

Sulfhydryl group
found in some amino acids
froms disulfide bridges in proteins

Methyl group-
addition of a methyl group affects expression of genes

Why is carbon so great?
VERSATILE–double bonds, covalent and polar bonds
bonds to self and others
4 bonds

Structural Isomers-
same formula, different order

Cis-trans Isomers-
same formula, different positioning around double bond

Enantiomers Isomers-
same formula, mirror image position around central carbon atom

Why does the carboxyl group make something acidic?
because it donates H

Why does amino group act as a base?
Because it picks up Hs from surround

What is the amount of change in chemical structure to have a major effect on an living organism?
in boys and girls, the testosterone and estradiol hormones just have a difference of ONE FUNCTIONAL GROUP

Why do biological systems use L amino acids and D sugars?
more favored..natural selection favored these more…better

Explain the difference between a pH of 8 and a pH of 12, in terms of H conc.
8- conc is lower
12- higher

Study pH

How are macromolecules assembled from monomoers? broken down?
assembled-dehydration reactions, two monomers joined by removing one water molecule
broken down- hydrolysis, water is added to split up molecules

How can you tell if a biological molecule is a carbohydrate?
include simple sugars and polymers like starch
in ratio of 1carbon: 2hydrogen: 1 oxygen

Explain relationship between monosaccharides, disaccharides and polysaccharides, please and thank ya
monosachh-(simple sugars) monomers of carbs (glucose and ribose)
polysacch- polymers of monosacch (starch, cellulose and glycogen)
disaccharide- 2 simple sugars or monosacch, formed by glycosidic linkage (cov bond) between two mono, by dehydrat synthesis to form.

Why are starch and glycogen useful as energy storage molecules, while cellulose is useful for structure and support?
glycogen- stored in liver and muscle cells, hydrolysis of glycogen releases glucuse when demand for sugar increases

starch- polymer of glucose monomers, stock pile for energy, later withdrawn from back

cellulose-polymer of glucose, stronger and used for cell walls.

Why isn’t cellulose easily broken down?
we don’t have correct enzymes to break down
we have starch enzyme, therefore…can’t have cellulose
cows have it…cellulose digesting prokaryotes and protists in their gut..hydrolyze cellulose and convert it to glucose or other things for nourishment

How can you tell a biological molecule is a lipid?
glycerol and three fatty acids
fatty acids=hydrocarbon tail, non polar
saturated–no double bonds
unsat=double bonds
phospholipids=hydrophil polar head, with phosphate group, two HC tails

Starch and Cellulose
both composed of glucose monomers
different ring forms and linkages—> diff functions
we digest starch 1-4 alpha
not cellulose 1-4 beta