LS 7A flash cards
45 cards for Cell and Molecular Biology, laid out week by week and timed around your exams. Free on iPhone and the web.
Exam dates
Unblank times your reviews around these. You can always set your own dates in the app.
- FinalThu, Mar 18, 2027A sample date until the Registrar posts the real one
The first 20 cards
Read the question, think of your answer, then open the card.
Week 1 · Water and pHWhat is a hydrogen bond?Show the answerHide the answer
A weak attraction between a hydrogen atom bonded to an electronegative atom (such as O or N) and another electronegative atom nearby.
Week 1 · Water and pHWhy does water dissolve ions and polar molecules so well?Show the answerHide the answer
Water is polar, so its partial charges surround ions and polar groups, stabilizing them in solution.
Nonpolar molecules offer no charges to attract water, so they stay clustered together instead.
Week 1 · Water and pHA solution has [H⁺] = 1 × 10⁻⁴ M. What is its pH?Show the answerHide the answer
pH 4, since pH = -log[H⁺] = -log(10⁻⁴) = 4.
Week 1 · Water and pHHow much more H⁺ is in a solution at pH 3 than one at pH 5?Show the answerHide the answer
100 times more. Each pH unit is a tenfold change in [H⁺], and two units is 10 × 10.
Week 1 · Carbohydrates and lipidsWhat is a dehydration (condensation) reaction?Show the answerHide the answer
A reaction that joins two monomers with a covalent bond and releases a molecule of water.
Hydrolysis is the reverse: water is added to break the bond.
Week 1 · Carbohydrates and lipidsWhat makes a fatty acid saturated?Show the answerHide the answer
It has no carbon-carbon double bonds, so its chain carries the most hydrogens it can.
Straight saturated chains pack tightly, which is why saturated fats tend to be solid at room temperature.
Week 1 · Carbohydrates and lipidsWhat bond links sugars together in a polysaccharide?Show the answerHide the answer
A glycosidic linkage, formed by a dehydration reaction between two sugars.
Week 2 · Protein structureWhat is a protein's primary structure?Show the answerHide the answer
Its sequence of amino acids, joined by peptide bonds.
Week 2 · Protein structureWhat holds alpha helices and beta sheets together?Show the answerHide the answer
Hydrogen bonds between backbone atoms: the C=O of one peptide group and the N-H of another.
Side chains are not involved at this level; their interactions shape tertiary structure.
Week 2 · Protein structureA mutation swaps a buried hydrophobic amino acid for a charged one. What is the likely effect?Show the answerHide the answer
The protein may misfold, because a charged side chain is unstable in the hydrophobic core.
Week 2 · DNA and RNA structureHow do DNA and RNA nucleotides differ?Show the answerHide the answer
DNA has deoxyribose and thymine; RNA has ribose, with an extra 2' hydroxyl, and uracil in place of thymine.
Week 2 · DNA and RNA structureWhat does antiparallel mean for the two strands of DNA?Show the answerHide the answer
The strands run in opposite directions: one 5' to 3', its partner 3' to 5'.
Week 2 · DNA and RNA structureA double-stranded DNA sample is 20% adenine. What percent is guanine?Show the answerHide the answer
30%. A = T = 20%, so G + C = 60%, and G = C = 30%.
Chargaff's rule: in double-stranded DNA, A pairs with T and G pairs with C, so their amounts match.
Week 3 · Membrane structureWhy do phospholipids form a bilayer in water?Show the answerHide the answer
They are amphipathic: hydrophilic heads face the water on both sides while hydrophobic tails cluster inside, away from it.
Week 3 · Membrane structureHow does cholesterol affect membrane fluidity?Show the answerHide the answer
It buffers it: it reduces fluidity at warm temperatures and keeps the membrane from stiffening at cold ones.
Week 3 · Membrane transportWhat is facilitated diffusion?Show the answerHide the answer
Passive movement of a molecule down its concentration gradient through a channel or carrier protein, with no energy input.
Week 3 · Membrane transportA red blood cell is placed in a hypotonic solution. What happens?Show the answerHide the answer
Water moves into the cell by osmosis, so it swells and may burst (lyse).
Week 3 · Membrane transportWhat does the sodium-potassium pump move for each ATP it uses?Show the answerHide the answer
It pumps 3 Na⁺ out of the cell and 2 K⁺ in, both against their gradients.
Week 4 · Free energy and ATPWhat does a negative ΔG tell you about a reaction?Show the answerHide the answer
The reaction is exergonic: it releases free energy and is spontaneous, though not necessarily fast.
Week 4 · Free energy and ATPHow do cells drive an endergonic reaction?Show the answerHide the answer
By coupling it to an exergonic one, usually ATP hydrolysis, so the overall ΔG is negative.
Week by week
The whole deck: 45 cards over 10 weeks. Every week is open from day one.
- 1Chemistry of life7 cards
- Water and pH 4
- Carbohydrates and lipids 3
- 2Proteins and nucleic acids6 cards
- Protein structure 3
- DNA and RNA structure 3
- 3Membranes and transport5 cards
- Membrane structure 2
- Membrane transport 3
- 4Energy and enzymes5 cards
- Free energy and ATP 2
- Enzymes and their regulation 3
- 5Cellular respiration5 cards
- Cellular respiration 5
- 6Photosynthesis3 cards
- Photosynthesis 3
- 7DNA replication3 cards
- DNA replication 3
- 8Gene expression5 cards
- Transcription and RNA processing 2
- Translation and mutations 3
- 9Gene regulation2 cards
- Gene regulation 2
- 10Signaling and the cell cycle4 cards
- Cell signaling 2
- The cell cycle and mitosis 2