AP biology
## Unit 1: Chemistry of Life
1. What types of chemical bonds are responsible for most of water's special properties?
Hydrogen bonds are responsible for water's unique properties. These occur because water is a polar molecule; the slightly positive hydrogen of one molecule is attracted to the slightly negative oxygen of another.
2. How does the specific heat of water affect the environment?
Water has a high specific heat, meaning it resists temperature changes. This helps stabilize ocean temperatures and creates a favorable environment for marine life, while also helping terrestrial organisms regulate their internal body temperatures.
3. What is special about the structure of carbon that makes it important for life?
Carbon has four valence electrons, allowing it to form four covalent bonds. This enables the creation of large, complex, and diverse molecules (chains, rings, and branches) that serve as the backbone for all organic life.
4. What are chemical functional groups?
Functional groups are specific groupings of atoms within molecules that have their own characteristic properties, regardless of the other atoms present in a molecule. They determine how organic molecules interact with other molecules.
5. What functional groups are found on amino acids?
Every amino acid contains an amino group (), a carboxyl group (), and a unique R-group (side chain).
6. What is the important role of ATP in living systems?
ATP (Adenosine Triphosphate) is the primary energy currency of the cell. It stores energy in its phosphate bonds and releases it through hydrolysis to power cellular work, such as muscle contraction or active transport.
7. What is the difference between dehydration (condensation) and hydrolysis reactions?
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Dehydration synthesis: Bonds two monomers together by removing a water molecule.
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Hydrolysis: Breaks the bond between monomers by adding a water molecule.
8. Why can humans digest starch but not cellulose?
Starch and cellulose are both polymers of glucose, but they have different glycosidic linkages. Humans have enzymes (amylase) that can break the -linkages in starch but lack the enzyme needed to break the -linkages in cellulose.
9. What happens when lipids (and phospholipids) are mixed with water?
Lipids are hydrophobic and do not mix with water. Phospholipids are amphipathic; when mixed with water, they spontaneously form a bilayer, with hydrophilic heads facing the water and hydrophobic tails pointing inward, away from the water.
10. What is the structural difference between saturated vs. unsaturated fats?
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Saturated fats: Have no double bonds between carbon atoms in the fatty acid tail, making them straight and able to pack tightly (usually solid at room temperature).
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Unsaturated fats: Have one or more double bonds, creating "kinks" in the tail that prevent tight packing (usually liquid at room temperature).
11. What is the functional difference between saturated vs. unsaturated fats in the membrane of cells?
Unsaturated fats increase membrane fluidity because the kinks in their tails prevent the phospholipids from packing too closely. Saturated fats make the membrane more rigid.
12. What makes each of the 20 amino acids unique?
The R-group (side chain) attached to the central carbon is what differs between the 20 amino acids. These groups can be polar, nonpolar, acidic, or basic, determining how the protein eventually folds.
13. What is the structural difference between the and ends of a nucleic acid?
The end has a phosphate group attached to the 5th carbon of the sugar, while the end has a hydroxyl group () attached to the 3rd carbon. DNA/RNA is always synthesized in the to direction.
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## Unit 2: Cell Structure and Function
14. What are the major differences between prokaryotic vs eukaryotic cells?
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Prokaryotes: No nucleus, no membrane-bound organelles, and are generally smaller.
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Eukaryotes: Have a nucleus (containing DNA), membrane-bound organelles (like mitochondria), and are generally larger and more complex.
15. What structures do plant and animal cells have in common?
Both have a nucleus, cytoplasm, cell membrane, ribosomes, mitochondria, endoplasmic reticulum, and Golgi apparatus.
16. What factor limits the maximum size of a cell?
The surface area-to-volume ratio. As a cell grows, its volume increases faster than its surface area. If the cell is too large, it cannot exchange materials (nutrients in, waste out) fast enough to support its volume.
17. Know the functional role of each part of a eukaryotic cell.
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Nucleus: Stores genetic information.
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Ribosomes: Protein synthesis.
* Rough ER: Modifies proteins; Smooth ER: Lipid synthesis and detoxification.
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Golgi Apparatus: Sorts, tags, and ships proteins.
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Mitochondria: Site of ATP production (cellular respiration).
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Lysosomes: Digests macromolecules and waste.
18. What is the pathway a protein destined to be secreted from a cell takes?
Ribosome Rough ER Transport Vesicle Golgi Apparatus Secretory Vesicle Plasma Membrane.
19. What types of molecules diffuse through the membrane the easiest?
Small, nonpolar (hydrophobic) molecules, such as and , diffuse easiest. Large or charged (polar/ionic) molecules require transport proteins.
20. What is diffusion?
The passive movement of molecules from an area of high concentration to low concentration until equilibrium is reached.
21. What is osmosis?
The diffusion of free water across a selectively permeable membrane.
22. How does solute concentration affect osmosis?
Water moves from areas of low solute concentration (high water) to areas of high solute concentration (low water).
23. What is the difference between hypertonic vs. hypotonic solutions?
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Hypertonic: Higher solute concentration outside the cell; water leaves the cell (cell shrinks).
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Hypotonic: Lower solute concentration outside the cell; water enters the cell (cell swells/bursts).
24. What circumstances require active transport using ATP hydrolysis?
Active transport is required when moving substances against their concentration gradient (from low to high concentration).
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## Unit 3: Cellular Energetics
25. What is the difference between anabolic vs. catabolic metabolic pathways?
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Anabolic: Consumes energy to build complex molecules from simpler ones (e.g., protein synthesis).
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Catabolic: Releases energy by breaking down complex molecules into simpler ones (e.g., cellular respiration).
26. What is the function of enzymes in chemical reactions?
Enzymes act as biological catalysts that speed up reactions by lowering the activation energy required for the reaction to start.
27. What is feedback inhibition?
A metabolic control mechanism where the end product of a pathway acts as an inhibitor for an enzyme early in that same pathway, preventing the cell from wasting resources.
28. During aerobic cellular respiration which chemical compounds are oxidized and which become reduced?
Glucose is oxidized (loses electrons to become ), and Oxygen is reduced (gains electrons to become ).
29. What are the end products of glycolysis?
2 Pyruvate, 2 ATP (net), and 2 NADH.
30. What are the end products of citric acid (Kreb's) cycle?
, ATP, NADH, and .
31. What does the electron transport chain do?
It uses the energy from electrons (donated by NADH and ) to pump protons () across the inner mitochondrial membrane, creating a proton gradient used by ATP synthase to make ATP.
32. What is the sequential pathway electrons travel during aerobic respiration?
Glucose NADH Electron Transport Chain Oxygen ().
33. What energy-extracting step can still occur even if oxygen is absent?
Glycolysis can occur with or without oxygen.
34. What is the function of the fermentation pathway?
To regenerate **** so that glycolysis can continue to produce ATP in the absence of oxygen.
35. What is the relationship between photosynthesis and cellular respiration?
They are inverse processes. The products of photosynthesis (Glucose + ) are the reactants for cellular respiration, and the products of respiration ( + ) are the reactants for photosynthesis.
36. What are the products of the light reactions of photosynthesis?
ATP, NADPH, and (as a byproduct).
37. When is oxygen produced during photosynthesis?
During the light reactions, specifically when water is split () to provide electrons for Photosystem II.
38. What is the sequential pathway electrons travel during photosynthesis?
Photosystem II ETC Photosystem I NADPH.
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## Unit 4: Cell Communication and Cell Cycle
39. What must a target cell have to respond to a signaling molecule?
A specific receptor protein that recognizes and binds to that specific signal molecule.
40. What type of signal transduction proteins add phosphates to target molecules?
Protein kinases.
41. What are the differences between receptor tyrosine kinases, G-protein receptors and ligand-gated ion channels?
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GPCRs: Work with the help of a G-protein that binds GTP.
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RTKs: Form dimers and phosphorylate each other's tyrosines to trigger multiple pathways.
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Ligand-gated channels: Open or close in response to a signal, allowing specific ions to flow through.
42. How do steroid hormones differ from protein hormones in terms of their interaction with their receptors?
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Steroids: Lipid-soluble; they pass through the membrane and bind to intracellular receptors.
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Proteins: Water-soluble; they cannot pass through the membrane and bind to surface receptors.
43. What are second messengers? What are examples?
Small, non-protein, water-soluble molecules or ions that spread a signal throughout the cytoplasm. Examples: cAMP and Calcium ions ().
44. Why are phosphorylation cascades useful in cellular signal transduction?
They allow for signal amplification (one molecule activates many) and provide more opportunities for regulation.
45. Why do not all cells respond to all signal molecules?
Only cells with the specific receptor for that signal can "hear" and respond to it.
46. What is an example of a pair of hormones that work antagonistically to maintain homeostasis?
Insulin (lowers blood glucose) and Glucagon (raises blood glucose).
47. How do Helper T Cells become activated?
They are activated when their receptors bind to an antigen fragment presented on the surface of an antigen-presenting cell (like a macrophage or B cell).
48. How do B cells and cytotoxic T cells respond differently to pathogens?
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B cells: Part of the humoral response; they produce antibodies to neutralize pathogens in body fluids.
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Cytotoxic T cells: Part of the cell-mediated response; they kill infected host cells directly.
49. Why is your second exposure to a pathogen less likely to create symptoms of being sick?
Memory cells (B and T) produced during the first exposure allow for a faster, stronger, and more prolonged secondary immune response.
50. What immune cell type interacts with both B cells and cytotoxic T cells?
Helper T cells.
51. What happens during G1, S and G2 of the cell cycle?
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G1: Cell growth and normal metabolic roles.
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S (Synthesis): DNA replication occurs.
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G2: Final growth and preparation for mitosis.
52. What happens during each of the steps of mitosis?
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Prophase: Chromosomes condense, spindle forms.
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Metaphase: Chromosomes line up at the cell equator.
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Anaphase: Sister chromatids separate and move to opposite poles.
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Telophase: Nuclear envelopes reform around the two new sets of chromosomes.
53. How does the amount of DNA in a cell change as it goes through the different stages and steps of the cell cycle?
DNA amount doubles during the S phase and stays doubled until the end of mitosis (Anaphase/Telophase), where it is split back to the original amount in the two daughter cells.
54. What the difference between chromosomes and sister chromatids?
A chromosome is a single DNA molecule. Sister chromatids are two identical copies of that DNA molecule joined at the centromere after replication.
55. What are cyclins and cdks and what is their functional role?
They are regulatory proteins that control the cell cycle. Cyclins fluctuate in concentration; they bind to Cdks (Cyclin-dependent kinases) to activate them, allowing the cell to pass through checkpoints.
56. What is the role of the mitotic spindle?
It is a structure made of microtubules that organizes and separates the chromosomes during mitosis.
57. What factors lead to the development cancer cells?
Mutations in genes that regulate the cell cycle, such as proto-oncogenes (which become overactive) and tumor-suppressor genes (which become inactive).
58. What features do cancer cells exhibit?
They divide uncontrollably, lack density-dependent inhibition (they pile up), and lack anchorage dependence (they can travel/metastasize).
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## Unit 5: DNA and Replication
59. What experiment did Hershey and Chase do?
They used radioactive isotopes to label DNA () and Protein () in viruses. They found that only the radioactive DNA entered the bacteria, proving DNA is the genetic material.
60. What experiment did Frederick Griffith do?
He discovered transformation. He showed that heat-killed virulent bacteria could pass their "disease-causing" trait to harmless live bacteria when mixed.
61. What experiment did Meselson and Stahl do?
They used nitrogen isotopes to show that DNA replication is semi-conservative, meaning each new DNA molecule consists of one old "parental" strand and one newly synthesized strand.
62. How do the proportions of each type of base in a DNA molecule relate to each other?
According to Chargaff's rules: **** and ****.
63. During DNA polymerization what is the vs orientation of the nucleotides as they are added?
New nucleotides are always added to the hydroxyl end of the growing strand. Therefore, the strand grows in the to direction.
64. What does it mean that DNA strands are antiparallel?
The two strands run in opposite directions; one is while the other is .
65. What is the difference between leading vs lagging strands during DNA replication?
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Leading strand: Synthesized continuously toward the replication fork.
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Lagging strand: Synthesized discontinuously away from the fork in short segments called Okazaki fragments.
66. What is the role of DNA polymerase?
It adds nucleotides to the end of the growing DNA strand and proofreads the new DNA for errors.
67. What is the role of Topoisomerase?
It relieves the "over-winding" or strain ahead of the replication fork by breaking, swiveling, and rejoining DNA strands.
68. What happens during the lytic cycle of a virus?
The virus takes over the host cell's machinery to produce new viruses, then bursts (lyses) the cell to release them.
69. What happens during the lysogenic cycle of a virus?
The viral DNA integrates into the host's genome (as a prophage) and is copied along with the host DNA without killing the cell immediately.
70. Why do RNA viruses have a high rate of mutation?
RNA polymerases (and reverse transcriptase) lack the proofreading mechanisms that DNA polymerases have, leading to more frequent errors during replication.
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