MIDTERM 1 Flashcards
Which of the following molecules is held together by nonpolar covalent bonds?
NH3, CH4, KCl
CH4
Which of the following molecules is held together by polar covalent bonds?
NH3, CH4, KCl
NH3
Phospholipase is an enzyme that cleaves the phosphate head group off a phospholipid molecule. The plasma membrane is not, however, permeable to the enzyme. Imagine a cell where phospholipid A is present in the layer of phospholipids facing the exterior of the cell, and phospholipid B is present in the layer of phospholipids facing the interior of the cell. After adding phospholipase to the medium in which the cell is growing, what would you expect to find in the fluid surrounding the cell?
The phosphate head group from phospholipid A only
Which one of the following molecules would MOST likely require a transport protein to cross the plasma membrane of a red blood cell?
CO2, C6H12O6, O2, H2O
C2H12O6
Why does a phospholipid on the cytoplasmic side of the cell membrane rarely flip to the extracellular side if both environments are polar?
The two sides have different functions and thus the phospholipid would not function properly.
The cytoplasmic phospholipid is too big to pass through the membrane.
The polar head group cannot pass through the nonpolar interior.
The cholesterol does not allow lipids to move.
The polar head group cannot pass through the nonpolar interior.
In the figure below, the cell is _____ to the solution. If the membrane is permeable to water, but not to solutes, net movement of water will be _____ the cell
Inside cell: 285mM
Solution: 500mM
Hypotonic; out of
Which of the following examples is considered catabolism?
A. hydrolysis of glycogen (a glucose polymer) during activity
B. synthesis of new DNA copies prior to cell division
C. fat cells growing bigger during times of ample nutrition
D. use of fat (triglyceride) stores as a cellular energy source
E. a person losing weight on a calorie restriction diet
A, D, E
Which of the following reactions would you predict could be coupled to ATP synthesis from ADP + Pi?
A. creatine phosphate + H2O → creatine + Pi, ΔG – 10.3 kcal/mol
B. glutamic acid + NH3 → glutamine, ΔG + 3.4 kcal/mol
C. glucose 6-phosphate + H2O → glucose + Pi, ΔG – 3.3 kcal/mol
D. glucose 1-phosphate + H2O → glucose + Pi, ΔG – 5.0 kcal/mol
E. phosphoenolpyruvate + H2O → pyruvate + Pi, ΔG – 14.8 kcal/mol
A, E
delta G < -7.3 kcal/mol
When carbohydrates are oxidized, the C–H bonds of the carbohydrate become C=O bonds of carbon dioxide. Oxidation is defined as a loss of electrons, but carbon does not become positively charged in the process. Why then is this considered oxidation?
A. The shared electrons in C–O bonds spend less time close to the carbon nucleus than the shared electrons in C–H bonds.
B. C=O bonds in CO2 are double bonds, and C–H bonds are single bonds.
C. Electrons in the C=O bonds are higher energy than the electrons in the C–H bonds.
D. The phosphate groups of ATP are ionized, and carbons donate those electrons.
A
Which of the following is/are TRUE regarding redox reactions?
A. If a molecule accepts electrons, it has been reduced.
B. Oxidizing agents accept electrons.
C. Reducing agents accept H atoms.
D. Redox reactions may involve the transfer of hydrogen ions (H+).
E. A molecule that has gained H atoms is said to be reduced.
F. Oxidizing agents accept H+ ions.
A, B, E
Which pair of atoms form a stronger bond? The one with high potential energy or the one with lower potential energy?
Lower potential energy
Which of these bonds/ interactions has the highest potential energy?
Covalent, Ionic, Hydrogen bonds, van der Waals’ forces
van der Waals’ forces (weakest bond)
Rank the following molecules in order of least permeable to most permeable: oxygen, Na+ ion, urea, glucose
Na+ ion, glucose, urea, oxygen
Water travels into a piece of lettuce: the plant cells are ____ compared to the surrounding solution.
Hypertonic, Hypotonic, Isotonic
Hypertonic
Based on the diagram, the concentration of K+ ions should be:
Higher, Lower, The same… inside the cell as outside
Higher
