Download Biology 3 Winter 2009 First Exam

Biology 3 Winter 2009 First Exam
Name & SID
1A -3 pts. For each of the following elements state how many protons, neutrons and
valence electrons are present in a single atom:
Helium atomic number 2, atomic mass number 3
2 protons, 1 neuton, 2 valence electrons
Chlorine, atomic number 17, atomic mass number 29
17 protons, 12 neutrons, 7 valence electrons
1B – 4 pts Briefly describe the difference between a polar covalent bond and an ionic
bond.
While both are polar, an ionic bond is when two atoms exchange one or more electrons
in order to fill their outermost shell and stick together as a result of their opposite
electrostatic charge. Polar covalent bonds represent unequally shared pairs of electrons
with each atom contributing one electron to the shared pair, but since they are unequally
shared there is a resulting partial charge to the molecule they form.
1C- 3pts What is the difference between a molecule and a compound?
A molecule is any structure that consists of two or more atoms bonded together. A
compound is any molecule with two or more elements in its structure
2A – 4 pts Define the following:
Solute Material that is suspended by solvent in a solution
Solvent the medium into which the solute(s) of a solution are suspended
Hydrophobic Reactive with water
Aqueous solution any solution that has water as its solvent
2B – 4 pts If the atomic mass number of C = 12, H = 1, and O = 16:
What does a mole of methane (CH4) weigh?
= 1x12 + 4x1 = 16 g
How about a mole of ribose (C5H10O5)?
= 5x12+ 10x1 + 5x16 = 150 g
2C – 4 pts Define the following:
Diffusion the net passive movement of material from high to low concentration
Osmosis the diffusion of water across a semi-permeable membrane (not if they do not
properly define diffusion in the answer above they should not receive credit for using it in
the definition of osmosis)
3 – 4 ptsWhat happens when a chemical reaction reaches equilibrium? Either 1) there is
no net change in the [] of reactants & products or 2) the rate of the forward and reverse
reaction are equal
4A – 4pts Sketch the products of the reaction that would join these two molecules making
sure to show all products produced. What is this type of reaction called? What would the
reverse reaction be called?
HO
OH
hydrolysis
HO
HO
OH
Dehydration synthesis
O
OH
+H20
4B – 4pts What is meant by tetravalence with respect to carbon? Why does this
phenomenon make it especially suitable to form the backbone of biological molecules?
Tetravalence refers to the presence of four valence electrons which means that carbon
can form four covalent bonds. This allows it to link with other carbons to form the
backbone of molecules while still having slots left for other functional groups to attach to
4C – 4 ptsLabel the following simple biological molecules:
A = nucleotide, B = amino acid, C = fatty acid, D = simple sugar
4D – 5 pts. Now locate the following functional groups on any of the molecules and
circle and label them (note you only need to circle and label each group once).
Methyl group, hydroxyl group, phosphate group, carboxyl group, amino group
-I’m confident you guys can figure this out
Name & SID
5A – 2pts What makes simple sugars hydrophilic?
They are full of hydroxyl groups which have polar covalent bonds between the oxygen
and the hydrogen making the molecule as a whole polar and reactive with water
5B – 2ptsWhat kind of carbohydrates are starch and glycogen?
They are both polysaccharides
5C – 2pts. What causes starch and glycogen to coil?
The same hydroxyl groups that make starch and glycogen hydrophilic also readily form
hydrogen bonds with each other. Because these bonds are relatively weak, they are only
sufficient to gently coil the molecule via the interaction of non-neighbor monomers.
6A – 3pts Briefly explain the difference between a saturated, mono-unsaturated, and
poly-unsaturated fat.
While all three are triglycerides, they differ in the relative number of carbon to carbon
double bonds in their fatty acid tails. Saturated fats have no carbon to carbon double
bonds and are unkinked. Monounsaturated fats have a single carbon to carbon double
bond in each of their fatty acid tails and thus there is a single kink in each.
Polyunsaturated fats have several carbon to carbon double bonds in their fatty acids tails
and as a result they are highly kinked
6B – 2ptsWhat property do phospholipids share with triglycerides? How do they differ
Both have two fatty acid tails joined to a glycerol backbone and as such will interact with
hydrophobic substances. Phospholipids differ in having a charged polar head on the 3rd
slot of the glycerol backbone as opposed to another fatty acid tail (found in
triglycerides). This aligns on the opposite side of the glycerol backbone and allows
phospolipids to interact with hydrophilic substances as well.
7A – 6 pts Briefly describe (not list) the four possible levels of protein structure.
Primary – the specific sequence of amino acids of a polypeptide
Secondary – the coiling or sheeting of the polypeptide due to hydrogen bonds between
different regions of the backbone
Tertiary – the folding of the polypeptide due to interaction of the R groups of different
amino acids
Quaternary – two or more polypeptides form the final functional protein
7B – 2 pts. With respect to proteins, what is meant by final conformation and denatured?
Final conformation refers to the final functional shape of a protein after it has attained
all the levels of structure.
Denatured refers to the loss of structure and as a result function of a protein
8A – 3pts. What are the three basic components of a nucleotide?
A phosphate, a five carbon sugar, and a nitrogenous base
8B – 2pts How arenucleotides arranged to form polymers (ie what pattern do they take)
The basic pattern of a nucleic acid is an alternating backbone of phosphates and sugars
with nitrogenous bases sticking up from each sugar
8C – 2 pts. What are purines and pyrimidines and how do they differ?
They are both nitrogenous bases found in nucleic acids. Pruines consist of double ringed
structures while pyrimidines have a single ring structure
9A – 3pts What are the three basic components found in any cell?
A plasma (cell) membrane
Genetic material
Cytoplasm
9B – 6 pts. What are the two basic types of cells and how do they differ from each other?
The two basic types of cells are prokaryotes and eukaryotes. Prokaryotes lack a true
nucleus and membranous organelles, eukaryotes have both these features.
10A – 4pts Label the following diagram depicting different mechanisms of transport
across the cell membrane. Be as specific as possible
A = simple diffusion, B = facilitated diffusion via a channel protein, C = Facilitated
diffusion via a carrier protein, D = active transport via a carrier protein.
Name & SID
10B – 2pts.What is the nuclear envelope? What is it primarily made of?
The nuclear envelope is the double membrane that surrounds the nucleus of an
eukaryotic cell. It is made principally of phospholipids
10C 2 pts What is chromatin and where would you find it?
Chromatin is 50% protein and 50% nucleic acid and it would be found within the nucleus
of an eukaryotic cell
10D – 5 pts. Briefly describe the structure and function of the following organelles:
Rough endoplasmic reticulum
Structure: channels of membranous tubes with ribosomes attached to it
Function: internal cell transport and protein synthesis
Smooth endoplasmic reticulum
Structure: channels of membranous tubes with no ribosomes attached to it
Function: internal cell transport and lipid synthesis
Vesicle
Structure: small membranous sac
Function: internal cell transport, storage, endo/exocytosis
Golgi body
Structure: flattened stack of membranous sacs
Function: receiving, shipping, processing and storage of biological molecules
What cellular system are all these a part of?
The endo or cytomembrane system
10E – 3 pts Ribosomes
What is a ribosome made of?
Ribosomal RNA
What function does it serve in a cell?
It is a workbench on which proteins are assembled
Would you find it in a prokaryote or eukaryote?
Both
10F – 3ps. What are the cristae & matrix and what organelle would you find them in?
They are both found in the mitochondrion
Cristae = the infoldings of the inner membrane that dramatically increase surface area
Matrix = cytoplasm like material found within the inner membrane
10G – 3 pts What are the stroma & grana and what organelle would you find them in?
They are both found in the chloroplast
stroma = cytoplasm like material found within the inner membrane
grans = stacks of thylakoids formed by the infolding of the inner membrane