Final - Midterm 1

Question 1

what are the tenets of the cell theory

Answer 1

• all living things are composed of cells
• all cells arise from pre-existing cells
• cells are the structural unit of life

Question 2

which of the following structures is the smallest: eukaryote, prokaryote, nucleus, protein, neuron

Answer 2

protein

Question 3

what are the characteristics of model organisms

Answer 3

• fast generation time
• large number of offspring
• easy to manipulate in the lab
• short lifespan
• fast to mature

Question 4

polar molecules are ______; non polar molecules are _____

Answer 4

hydrophilic, hydrophobic

Question 5

what are characteristics of water

Answer 5

• the water molecule is asymmetric (has a dipole due to differences in electronegativities between H and O)
• covalent bonds in water are polarized
• all 3 atoms can form hydrogen bonds

Question 6

what is a characteristic of hydrogen bonds

Answer 6

hydrogen must be covalently bonded to an electronegative atom in order to form a hydrogen bond

Question 7

what is the hydrophobic effect

Answer 7

aggregation of nonpolar molecules to decrease entropy (disorder) of water

Question 8

which polysaccharide bond cannot be broken by mammalian enzymes that normally digest polysaccharides

Answer 8

Beta (1—>4) glycosidic linkages

Question 9

in a polypeptide, when peptide bonds are formed between adjacent amino acids:

Answer 9

the carboxyl group of one amino acid joins with the carboxyl group of the adjacent amino acid

Question 10

what are domains:

Answer 10

two or more distinct modules that fold up independently of one another that often represent parts of a protein that have a specific function.

Question 11

what are functional groups:

Answer 11

particular groupings of atoms that often behave as a unit and give organic molecules their physical properties, chemical reactivity, and solubility in aqueous solution

Question 12

what varies in biomembranes of cells:

Answer 12

the composition and ratio of lipids and proteins

Question 13

what is an example of an amphipathic molecule

Answer 13

a fatty acid with a polar carbonyl head group and a nonpolar hydrocarbon chain

Question 14

what is a sphingolipid/membrane lipid:

Answer 14

a sphingosine backbone with an attached fatty acid and an attached oligosaccharide

Question 15

what are the building blocks of phosphatidic acid

Answer 15

glycerol, one phosphate group, 2 fatty acid tails

Question 16

what directly or indirectly determines the transition temperature of a molecule

Answer 16

• the chain length of the fatty acids
• whether the fatty acid chains of the lipids are saturated or unsaturated
• the extent to which the fatty acid chains of the lipids contain double bonds

Question 17

a bacterial culture growing at 15C is transferred to a culture room and maintained at a temperature of 40C. what would you expect to see?

Answer 17

enhanced rate of synthesis of saturated fatty acids for membrane incorporation

Question 18

what are lipid rafts

Answer 18

contains higher concentrations of sphingolipids and cholesterol and certain proteins becomes concentrated within them

Question 19

what is the role of acyl transferases in the synthesis of of a membrane lipid in the ER:

Answer 19

add 2 fatty acids to glycerol-3-phosphate

Question 20

the orientation of a protein attached to the plasma membrane via acylation is:

Answer 20

always cytosolic

Question 21

integral membrane proteins can consist of:

Answer 21

• just one transmembrane alpha-helix
• one single polypeptide with multiple membrane spanning alpha helices
• multiple polypeptides with individual membrane spanning alpha helices

Question 22

a molecule normally enters a cell by diffusion through the lipid bilayer. what happens if you artificially reverse the molecules concentration gradient by adding all of the molecule to the inside of the cell at the start of the experiment

Answer 22

the molecule moves out of the cell until equilibrium concentrations have been reached

Question 23

the net driving force of a charged molecule across the plasma membrane consists of:

Answer 23

a combination of concentration and voltage

Question 24

with respect to carriers (transporters):

Answer 24

• molecules go down their concentration gradient
• they alternate between two conformations

Question 25

GLUT4:

Answer 25

is a uniporter

Question 26

an antiport will:

Answer 26

transport one molecule down its concentration gradient and one molecule, in a different direction, against its concentration gradient

Question 27

with respect to the Na+/K+ ATPase:

Answer 27

• K+ is pumped into the cell
• both Na+ and K+ are pumped against their concentration gradients
• it is an example of direct active transport

Question 28

the Na+/glucose symporter moves ____ down its gradient and drives the transport of ____ against its gradient

Answer 28

Na+ ions, glucose

Question 29

potassium and sodium cannot move through the cell membrane into the cell on their own because:

Answer 29

these ions are charged