Exam Prep Flashcards
(400 cards)
1
Q
What are the six most abundant elements in living organisms?
A
C, H, O, N, P, S
2
Q
Define homeostasis.
A
The maintenance of a stable internal environment.
3
Q
What is the cell theory?
A
All living things are made of cells; all cells come from preexisting cells.
4
Q
What molecule is the universal genetic material in all cells?
A
DNA
5
Q
What is common descent?
A
The concept that all living things share a common ancestor.
6
Q
What is a genome?
A
The complete set of genetic material in a cell/organism.
7
Q
What distinguishes prokaryotes from eukaryotes?
A
Prokaryotes lack membrane-bound organelles and a nucleus.
8
Q
What process changed Earth’s early atmosphere and enabled aerobic respiration?
A
Photosynthesis (especially by cyanobacteria)
9
Q
What is endosymbiosis?
A
The theory that mitochondria and chloroplasts evolved from engulfed prokaryotes.
10
Q
Define adaptation.
A
A structural, physiological, or behavioral trait that enhances survival/reproduction.
11
Q
What is the biological significance of liposomes?
A
They are models for how membranes could form around early cells.
12
Q
What are three domains of life?
A
Bacteria, Archaea, Eukarya
13
Q
What is the function of ribosomes?
A
Protein synthesis
14
Q
Briefly state the steps from chemical evolution to cells.
A
Simple molecules → complex molecules → polymers → membranes/protocells → cell-like structures
15
Q
Describe multicellularity.
A
An evolutionary innovation where cells specialize and form tissues/organs.
16
Q
What molecule stores information to build proteins?
A
DNA
17
Q
What is the mechanism of evolution by which traits become more common?
A
Natural selection
18
Q
How can we infer evolutionary relationships between organisms?
A
By comparing their DNA/protein sequences (phylogenetic trees)
19
Q
What is selective breeding?
A
Artificial selection of traits by humans.
20
Q
What is photosynthesis’s main global effect?
A
Production of O2 and organic molecules, changing ancient Earth’s conditions.
21
Q
Why is DNA replication necessary before cell division?
A
To ensure each new cell gets a complete genome.
22
Q
What is a mutation?
A
A heritable change in DNA sequence.
23
Q
What property of water helps moderate Earth’s temperature?
A
High heat capacity
24
Q
What is a fossil?
A
Preserved remains or traces of ancient life forms.
25
What is the main evidence for endosymbiotic origin of mitochondria?
Mitochondria have their own DNA, ribosomes, and double membrane.
26
How do viruses differ from cells?
Viruses are not cells; they lack ribosomes, can't reproduce nor metabolize on their own.
27
What is the significance of the ozone layer?
It absorbs UV radiation, allowing life on land.
28
What does the biosphere include?
All living organisms and their environments on Earth.
29
How do unicellular organisms differ from multicellular in terms of complexity?
Unicellular can carry out all necessary functions in one cell; multicellular use specialized cells.
30
How did photosynthesis enable terrestrial life?
By producing O2 for aerobic respiration and an ozone layer for UV protection.
31
What is an isotope?
Atoms of the same element with different numbers of neutrons.
32
What is a covalent bond?
A chemical bond formed by sharing electron pairs.
33
What kind of bond is found within water molecules?
Polar covalent bond
34
What kind of bond is found between water molecules?
Hydrogen bond
35
What is a nonpolar molecule?
A molecule with no charge difference across it (equal sharing of electrons).
36
Define hydrophilic.
“Water loving”—dissolves in or is attracted to water.
37
Define hydrophobic.
“Water fearing”—repels or does not dissolve in water.
38
What is the pH of pure water?
7 (neutral)
39
What is the function of a buffer?
To resist changes in pH.
40
What are the four major classes of biological macromolecules?
Proteins, carbohydrates, nucleic acids, lipids
41
What is the monomer unit for proteins?
Amino acids
42
What is the monomer unit for nucleic acids?
Nucleotides
43
What is the monomer unit for carbohydrates?
Monosaccharides (simple sugars)
44
What type of reaction forms polymers from monomers?
Condensation (dehydration synthesis) reaction
45
What type of reaction breaks polymers into monomers?
Hydrolysis
46
What determines the function of a protein?
Its shape/3D structure, which depends on amino acid sequence.
47
What is primary structure in a protein?
The sequence of amino acids.
48
What is secondary structure in a protein?
Formation of α-helices and β-sheets via H-bonds in the backbone.
49
What is tertiary structure?
The overall 3D folding formed by side-chain interactions.
50
What is quaternary structure?
Association of multiple peptide chains.
51
Define enzyme.
A biological catalyst (usually a protein).
52
What is the “active site” of an enzyme?
The region that binds the substrate and where catalysis occurs.
53
What is the basic structure of a nucleotide?
Sugar (pentose) + phosphate + nitrogenous base
54
Name two pentose sugars found in nucleic acids.
Ribose (RNA), deoxyribose (DNA)
55
What are the base pairing rules in DNA?
A pairs with T; G pairs with C
56
What are the base pairing rules in RNA?
A pairs with U; G pairs with C
57
What is a phospholipid?
A lipid with a hydrophilic head and hydrophobic diglyceride tails; major component of cell membranes.
58
What is the fluid mosaic model?
Describes the cell membrane as a fluid bilayer with proteins embedded throughout.
59
What is the function of cellulose in plants?
Provides structural support (cell wall).
60
What are starch and glycogen used for?
Energy storage (starch in plants, glycogen in animals).
61
What kind of bond joins glucose monomers in cellulose?
β-1,4 glycosidic bond
62
Why are saturated fats solid at room temperature?
Straight hydrocarbon chains pack closely together.
63
Why are unsaturated fats liquid at room temperature?
Kinks from double bonds prevent close packing.
64
What is the role of cholesterol in membranes?
Modulates fluidity and stability of the membrane.
65
What is chitin?
A structural polysaccharide in arthropod exoskeletons and fungi cell walls.
66
What is a glycoprotein?
A protein with covalently bonded carbohydrate(s), often involved in cell recognition.
67
What is denaturation?
Loss of protein’s 3D shape (and often function), due to pH, temperature, etc.
68
What is a prion?
A misfolded protein that can cause other proteins to misfold, associated with diseases.
69
What are nucleic acid chains linked by?
Phosphodiester bonds
70
What makes a molecule amphipathic?
It contains both hydrophobic and hydrophilic regions.
71
Describe the structure of a monosaccharide.
Simple sugar with formula (CH2O)n, often forming ring structures in aqueous solutions.
72
What polymer does RNA never form?
Double helix; it's typically single-stranded.
73
What is the function of rRNA?
Forms part of the ribosome.
74
What is the function of tRNA?
Transfers amino acids during protein synthesis.
75
What are van der Waals forces important for?
Stabilizing interactions between hydrophobic regions of proteins/molecules.
76
What does it mean for a reaction to be “spontaneous?”
It has a negative ΔG (releases free energy), but not necessarily rapid.
77
What is a transition state?
High-energy, unstable intermediate during reaction.
78
Define kinetic and potential energy
Kinetic = energy of movement; Potential = stored energy.
79
What role does water’s high heat of vaporization play in homeostasis?
Allows effective cooling via evaporation (sweating).
80
What type of isomer are glucose and galactose?
Structural isomers (same formula, different arrangement).
81
How do environmental pH and temperature affect enzyme function?
Enzymes have an optimal pH and temperature; extremes denature enzymes.
82
What is feedback inhibition in a metabolic pathway?
The end product inhibits an enzyme at the pathway's start.
83
What is the difference between prosthetic groups, cofactors, and coenzymes?
Prosthetic group = tightly bound, nonprotein helper; cofactor = inorganic ion, often transient; coenzyme = organic molecule, loosely bound, helps with enzyme reaction.
84
How does competitive inhibition work?
Inhibitor binds the enzyme’s active site, competing with substrate.
85
How does noncompetitive inhibition work?
Inhibitor binds elsewhere, changes enzyme conformation, reducing activity.
86
What is allosteric regulation?
A regulator binds a site other than the active site, changing enzyme activity.
87
What is the primary structure of DNA?
The sequence of nucleotides.
88
What is the secondary structure of DNA?
Double helix.
89
What type of bond forms between the base pairs in DNA?
Hydrogen bonds.
90
What is the main energy currency of the cell?
ATP (adenosine triphosphate)
91
What structure controls what enters or leaves the cell?
Cell (plasma) membrane
92
What are the two main components of cell membranes?
Phospholipids and proteins
93
What is selective permeability?
Allowing some substances to cross the membrane more easily than others.
94
What is simple diffusion?
Movement of molecules from high to low concentration, without energy input or transporter.
95
What is osmosis?
Passive diffusion of water, from high to low water potential (usually low to high solute).
96
Define hypotonic, hypertonic, isotonic.
Hypotonic: lower solutes than cell (water in); Hypertonic: higher solutes (water out); Isotonic: equal solutes (no net water movement).
97
What is facilitated diffusion?
Passive transport via protein channels or carriers; for ions/polar molecules.
98
What is active transport?
Movement against concentration gradient, requiring ATP energy (e.g., Na+/K+ pump).
99
What is exocytosis?
Vesicle fusion with cell membrane, releasing contents.
100
What is endocytosis?
Membrane pinches in to bring material into the cell.
101
What is the major function of ribosomes?
Protein synthesis
102
What is the function of the rough endoplasmic reticulum?
Protein synthesis and modification for export or insertion into membranes.
103
Function of smooth ER?
Lipid synthesis and detoxification
104
Function of the Golgi apparatus?
Protein modification, sorting, and packaging
105
What is the function of lysosomes?
Intracellular digestion of macromolecules and damaged organelles.
106
What is the function of mitochondria?
Site of cellular respiration, ATP production.
107
What is the function of chloroplasts?
Site of photosynthesis.
108
What is the function of the cytoskeleton?
Network of fibers for shape, support, movement.
109
List 3 main fibers of the cytoskeleton and their functions.
Actin (microfilaments - cell shape/movement); intermediate filaments (mechanical strength); microtubules (movement, transport, cell division).
110
What happens to an animal cell in a hypertonic solution?
It loses water and shrivels (crenates).
111
What are tight junctions?
Seal adjacent animal cells, prevent passage of molecules.
112
What are desmosomes?
Anchor animal cells together, allow some flexibility.
113
What are gap junctions?
Protein channels between animal cells for communication.
114
What are plasmodesmata?
Plant cell wall channels for cytoplasmic exchange.
115
What are integrins?
Membrane proteins connecting the cytoskeleton to the ECM.
116
What types of signals can animal cells receive?
Physical (light, temperature, pressure) and chemical (hormones, neurotransmitters).
117
What are the four types of cell signaling?
Autocrine, paracrine, juxtacrine, endocrine
118
What is a signal transduction pathway?
Series of molecular events from signal at membrane to cell response.
119
What is a ligand?
A specific molecule that binds to a receptor.
120
What are three main types of cell-surface receptors?
Ion channel, protein kinase, GPCR
121
What is a second messenger? Give an example.
Small molecule relaying/amplifying signals (e.g., cAMP, Ca2+, IP3, DAG)
122
What does the G in “G protein” stand for?
Guanine (GDP/GTP binding protein).
123
What triggers G protein activation?
Ligand binding to its GPCR.
124
What is the function of kinases?
Enzymes that transfer phosphate groups.
125
What is the function of phosphatases?
Enzymes that remove phosphate groups.
126
How does epinephrine trigger both increased heart rate and liver glucose release?
Acts through different GPCR subtypes and downstream pathways in different cell types.
127
What is cAMP synthesized from?
ATP, by adenylyl cyclase.
128
What is Ca2+'s role in signaling?
Acts as a universal second messenger, triggers exocytosis, contraction, etc.
129
What breaks down cAMP?
Phosphodiesterase.
130
How are receptor binding and ligand affinity measured?
By the dissociation constant (KD); lower KD = higher affinity.
131
What is meant by signal amplification?
One signal sets off a cascade, producing many final effect molecules.
132
What is gene expression?
The process of transcribing DNA to RNA and (when required) translating RNA to protein.
133
What is the main component of plant cell walls?
Cellulose
134
Why do plant cells not burst in hypotonic solution?
Their cell wall prevents lysis; instead, turgor pressure increases.
135
Define osmoregulation.
Regulation of water and solute concentrations.
136
What is bulk flow?
Movement of fluids down pressure gradients; e.g., xylem sap movement.
137
What’s the basic difference between carrier and channel proteins?
Carriers bind/conformationally change; channels create a pore for flow.
138
What process uses vesicles to move material out of a cell?
Exocytosis
139
Where does transcription take place?
Nucleus (eukaryotes); cytosol (prokaryotes)
140
Where does translation take place?
Cytosol (on ribosomes)
141
What is the role of mRNA?
Determines order of amino acids in proteins.
142
What is positive feedback?
A process whose product increases its own production.
143
What is negative feedback?
A process whose product inhibits its own production.
144
Why do multicellular organisms need cell communication?
To coordinate tissue/organ function and responses to stimuli.
145
In plants, what two main tissues conduct water, nutrients, and sugars?
Xylem (water, minerals), phloem (sugars).
146
What defines a stem cell?
A cell capable of both division and differentiation.
147
What are the phases of the animal cell cycle?
G1, S, G2, M
148
What are cyclin-dependent kinases (CDKs)?
Enzymes regulated by cyclins that control cell cycle transitions.
149
What is a checkpoint in the cell cycle?
Control point where the cell assesses readiness to proceed.
150
What is the function of p53 protein?
Tumor suppressor; triggers cell cycle arrest/apoptosis when DNA is damaged.
151
What is mitosis?
Division of the cell nucleus, produces genetically identical diploid cells.
152
What is meiosis?
Two consecutive cell divisions that produce four non-identical haploid gametes.
153
When does crossing over occur?
Prophase I of meiosis
154
What is “independent assortment”?
Random orientation/segregation of chromosomes during gamete formation.
155
What do you call an observable trait?
Phenotype
156
What do you call the underlying genetic composition?
Genotype
157
What is a gene?
A segment of DNA encoding a product (protein or functional RNA).
158
What is Mendel’s Law of Segregation?
Allele pairs separate during gamete formation.
159
What is Mendel’s Law of Independent Assortment?
Genes for different traits segregate independently.
160
Who discovered the laws of inheritance?
Gregor Mendel
161
What does “homozygous” mean?
Having two identical alleles for a gene.
162
What does “heterozygous” mean?
Having two different alleles for a gene.
163
What is a dominant allele?
An allele that determines the phenotype in a heterozygote.
164
What is a recessive allele?
An allele masked by a dominant allele in a heterozygote.
165
What is incomplete dominance?
Heterozygote shows intermediate phenotype (pink snapdragons).
166
What is codominance?
Both alleles are fully expressed (blood type AB).
167
What is the difference between a dihybrid and monohybrid cross?
Monohybrid involves one trait; dihybrid, two.
168
What is pleiotropy?
A single gene affects multiple phenotypic traits.
169
What is epistasis?
One gene masks/changes the effect of another gene.
170
What is a polygenic trait?
Controlled by many genes, showing continuous variation (height, skin color).
171
What is metabolism?
All the chemical reactions occurring in an organism.
172
What is an anabolic reaction?
Builds larger molecules from smaller ones; requires energy.
173
What is a catabolic reaction?
Breaks larger molecules into smaller ones; releases energy.
174
What molecule powers most cellular work?
ATP
175
What are the products of glycolysis?
2 pyruvate, 2 net ATP, and 2 NADH per glucose.
176
Where does glycolysis occur?
Cytoplasm
177
Where does the citric acid (Krebs) cycle occur?
Mitochondrial matrix
178
Where does electron transport/oxidative phosphorylation occur?
Inner mitochondrial membrane
179
What is the final electron acceptor in aerobic respiration?
Oxygen (O2)
180
How much ATP can aerobic respiration yield from one glucose?
~30–32 ATP
181
What is fermentation?
Anaerobic process that regenerates NAD+ (produces lactate or ethanol).
182
Why is O2 needed for full energy extraction from glucose?
It’s required to accept electrons at the end of the electron transport chain.
183
What is substrate-level phosphorylation?
Generation of ATP by direct transfer of phosphate to ADP.
184
What is chemiosmosis?
Using a proton gradient to drive ATP synthesis via ATP synthase.
185
What is the “proton-motive force”?
Electrochemical gradient of H+ across inner mitochondrial membrane.
186
What is UCP1?
Uncoupling protein in brown fat mitochondria; dissipates proton gradient, generates heat.
187
What is lactic acid fermentation?
Pyruvate is reduced to lactate to regenerate NAD+.
188
What causes muscle soreness after intense activity?
Lactate buildup and/or micro-tear/inflammation.
189
What happens in alcoholic fermentation?
Pyruvate is converted to ethanol and CO2, regenerating NAD+.
190
What is β-oxidation?
Breakdown of fatty acids into acetyl-CoA for energy.
191
How is ATP synthesis regulated?
By allosteric regulation of enzymes (e.g., phosphofructokinase), feedback inhibition.
192
In metabolism, what is a coenzyme?
An organic molecule (often derived from vitamins) that assists enzymes (e.g., NAD+, FAD).
193
What is substrate inhibition?
High substrate concentration reduces enzyme activity.
194
What is the function of NAD+ and FAD?
Electron acceptors in redox reactions; become NADH and FADH2.
195
What is a metabolic pathway?
A sequence of enzyme-catalyzed reactions converting a reactant to a product.
196
What is the main regulated step ('committed step') in glycolysis?
Phosphofructokinase-1 (PFK-1).
197
Give an example of an anabolic pathway.
Synthesis of proteins from amino acids.
198
How do competitive enzyme inhibitors function?
Bind active site, blocking substrate.
199
What’s the effect of allosteric activator on enzyme activity?
Binds site other than active site, increases activity.
200
What is Vmax?
Maximum rate of enzyme-catalyzed reaction when all active sites are occupied.
201
What is feedback inhibition?
End product of a metabolic pathway inhibits an earlier-step enzyme.
202
What happens to enzymes at high temperature or extreme pH?
Denaturation (loss of structure and function).
203
How does phosphorylation regulate proteins?
Reversible addition/removal of phosphate groups alters protein activity.
204
What is the role of coenzyme Q (ubiquinone) in the ETC?
Electron carrier in the mitochondrial electron transport chain.
205
What is the function of cytochrome c?
Electron transfer protein in electron transport chain.
206
What is gluconeogenesis?
Formation of glucose from non-carbohydrates (like amino acids).
207
What substrate do plants use for energy at night?
Starch (broken down to glucose).
208
What two processes are linked by the ATP-ADP cycle?
Exergonic (catabolic) and endergonic (anabolic) reactions.
209
Why is O2 essential for survival in aerobic organisms?
Needed for the electron transport chain (ETC) to function.
210
Name a fatal human mitochondrial disorder.
Leigh syndrome
211
What is ATP synthase?
An enzyme that synthesizes ATP, powered by H+ flow down its gradient.
212
What does the term 'oxidative phosphorylation' refer to?
ATP formation via ETC and chemiosmosis using O2 as final electron acceptor.
213
What is the difference between NADH and NADPH?
NADH is used in catabolism/respiration; NADPH in anabolism/photosynthesis.
214
What is a transition state analog?
A molecule resembling the transition state; often an enzyme inhibitor.
215
Give an example of a coenzyme derived from a vitamin.
NAD+ from niacin (vitamin B3).
216
Why are metabolic pathways compartmentalized in eukaryotes?
To increase efficiency, regulation, and separation of incompatible processes.
217
What is the function of pyruvate dehydrogenase?
Converts pyruvate to acetyl-CoA.
218
What is the major waste product of aerobic respiration?
CO2
219
What is the role of substrate-level phosphorylation during glycolysis and the citric acid cycle?
Direct generation of ATP without involvement of ETC.
220
Which molecule 'traps' high energy electrons during glycolysis and the Krebs cycle?
NAD+, FAD
221
What is the ultimate fate of CO2 generated in aerobic respiration?
Exhaled as a waste product.
222
What is the relationship between redox state and metabolic regulation?
High NADH/NAD+ ratio indicates high energy, inhibits NAD-dependent enzymes.
223
Why do cells prefer aerobic respiration over anaerobic fermentation?
Produces much more ATP per molecule of glucose.
224
During intense exercise in humans, why can lactic acid build up?
Oxygen supply can't meet demand, so muscle cells switch to fermentation.
225
What drives electrons through the electron transport chain?
Electronegativity difference between NADH/FADH2 and O2.
226
What is an obligate anaerobe?
Organism that can’t survive in oxygen.
227
What is a facultative anaerobe?
Organism that can use O2 if present, but can survive without it.
228
What’s the difference between endergonic and exergonic?
Endergonic = requires energy input; exergonic = releases energy.
229
If ΔG for a reaction is positive, what must couple to it for the reaction to proceed?
An exergonic reaction (such as ATP hydrolysis).
230
Why does breaking of a phosphoanhydride bond in ATP release so much energy?
Electrostatic repulsion between phosphates, resonance stabilization of ADP and Pi.
231
Where do the light reactions of photosynthesis occur?
Thylakoid membrane of the chloroplast.
232
Where does the Calvin cycle take place?
Stroma of the chloroplast.
233
What are the products of the light reactions?
ATP, NADPH, O2
234
What is the main input for the Calvin cycle (excluding products of light reactions)?
CO2
235
What is rubisco?
The main enzyme for carbon fixation in the Calvin cycle; can also act as an oxygenase.
236
What is photorespiration?
Process where rubisco adds O2 instead of CO2, reducing photosynthetic output.
237
What are C4 plants and how do they minimize photorespiration?
Plants that fix CO2 into four-carbon acids in one cell, release CO2 to Calvin cycle in another cell.
238
What are CAM plants?
Open stomata at night, fix CO2 into acids, store until day for Calvin cycle.
239
What pigment is the primary light absorber in plants?
Chlorophyll a
240
What is the action spectrum?
The range of wavelengths most effective for a process (e.g., photosynthesis).
241
What molecule donates electrons to Photosystem II?
Water (H2O)
242
What is the byproduct when water is split in photosynthesis?
O2
243
What is the main sugar produced by photosynthesis?
Glucose (converted to sucrose and starch)
244
What is the role of bundle sheath cells in C4 plants?
Where the Calvin cycle operates; isolate rubisco from O2.
245
What is the benefit of open stomata for leaves?
Allow CO2 in and O2 out for photosynthesis.
246
What is the risk of open stomata?
Water loss by transpiration.
247
What regulates stomatal opening?
Guard cells (K+ influx and turgor).
248
What is abscisic acid (ABA)?
Plant hormone; triggers stomatal closure during drought.
249
What are three main tissue types in plants?
Dermal, ground, vascular
250
What is meristem?
Plant tissue responsible for growth (apical for length, lateral for thickness).
251
What are xylem and phloem?
Xylem transports water/minerals; phloem transports sugars.
252
What is transpiration?
Process of water movement through plant and evaporation from leaves.
253
What is the cohesion-tension theory?
Explains how water moves from roots to leaves via tension and cohesion in xylem.
254
What is root pressure?
Pressure generated in roots that can push water up xylem.
255
What are lateral roots?
Roots that branch off a main root.
256
What is secondary growth in plants?
Growth in thickness via lateral meristems (vascular cambium).
257
What are annual rings in trees?
Layers of secondary xylem; reflect yearly growth.
258
What is the function of cuticle in leaves?
Waxy layer that prevents water loss.
259
What is a trichome?
Plant hair; used for protection, reflecting light, reducing water loss.
260
What hormone promotes stem elongation?
Gibberellin
261
What hormone promotes cell elongation/phototropism?
Auxin
262
What is apical dominance?
Inhibition of side bud growth by the shoot apex.
263
What is turgor pressure?
Pressure of the cell contents against the cell wall; important for maintaining shape.
264
What is phototropism?
Plant growth toward light.
265
What environmental condition causes starch to be used in plants?
Darkness/night (no photosynthesis).
266
What are bundle sheath cells rich in, structurally?
Chloroplasts (in C4 plants)
267
What kind of root system does a monocot have?
Fibrous root system
268
How does water move from soil to leaves?
Through root hairs → cortex → endodermis → xylem → upward via cohesion-tension.
269
What is the function of parenchyma cells?
Storage, photosynthesis, tissue repair in plants.
270
What are collenchyma cells specialized for?
Flexible support in growing tissues.
271
What are sclerenchyma cells specialized for?
Rigid support in mature plant tissues.
272
What is the role of companion cells in phloem?
Support sieve tube elements, help with loading/unloading sugars.
273
What is the main purpose of the periderm in plants?
Replaces epidermis in roots/stems of woody plants (bark).
274
Why does closing of stomata limit photosynthesis?
Reduces CO2 influx necessary for carbon fixation.
275
What is the source of most dry plant mass?
CO2 from the atmosphere.
276
What structure in the plant is responsible for gas exchange?
Stomata
277
What are lenticels?
Spongy regions in bark for gas exchange.
278
Define the pressure-flow hypothesis.
Sugar transport in phloem occurs from high to low pressure (source to sink).
279
What are transpiration streams mainly composed of?
Water and mineral ions moving up xylem.
280
What are the sources and sinks in plants?
Source: Where sugar is produced (leaves); Sink: Where sugar is used/stored (roots, fruits).
281
What triggers seed dormancy break?
Water, temperature change, light (depends on species).
282
What group of plants use CAM photosynthesis?
Succulents, cacti, some orchids and bromeliads.
283
What is a vascular cambium?
Lateral meristem that produces secondary xylem and phloem.
284
What adaptation do xerophytes have to conserve water?
Thick cuticle, sunken stomata, CAM photosynthesis, extensive roots.
285
What is the maximum theoretical efficiency of converting sunlight to plant dry mass?
~5%
286
What are the four main animal tissue types?
Epithelial, connective, muscle, nervous.
287
What is the role of epithelial tissue?
Barriers, secretion, absorption, protection.
288
What is the main function of connective tissue?
Support, structure, storage, immunity, transport (blood).
289
What is the role of muscle tissue?
Movement (skeletal—voluntary, cardiac—heart, smooth—involuntary organs).
290
What is nervous tissue essential for?
Communication, control, information processing.
291
What is a neuron?
A nerve cell; transmits electrical signals.
292
What is a glial cell?
Non-neuronal cell that supports and nourishes neurons.
293
What is a synapse?
Junction between neurons where signal is transmitted.
294
What is an action potential?
Rapid reversal of membrane potential across a neuron membrane.
295
What ion influx is responsible for depolarization in neurons?
Na+ influx
296
What ion movement repolarizes the neuron?
K+ efflux
297
How is resting membrane potential maintained?
Na+/K+ ATPase pump
298
What is myelin?
Insulating sheath around many axons, speeds up impulse conduction.
299
What is saltatory conduction?
Action potentials 'jump' from node to node on myelinated axons.
300
What is the function of the node of Ranvier?
Gaps in myelin where action potentials are regenerated.
301
What is homeostasis?
Maintenance of stable internal environment.
302
What are sensors in a homeostatic system?
Cells/tissues that detect changes in variables.
303
What is an integrating center?
Processes signals from sensors, initiates response.
304
What is an effector?
Tissue/organ that carries out the response to restore set point.
305
What is negative feedback?
Response reduces the original stimulus.
306
What is feedforward control?
Anticipatory regulation before deviation happens.
307
What is positive feedback used for in animals?
Rapid amplification of a process (e.g., childbirth, blood clotting).
308
What tissue creates force to contract the heart?
Cardiac muscle
309
What carries oxygen in blood?
Red blood cells (hemoglobin)
310
What is adipose tissue’s primary function?
Energy storage, insulation, cushioning.
311
What type of junction links cardiac muscle cells?
Intercalated discs (desmosomes + gap junctions)
312
What is the role of ATP in muscle contraction?
Binds myosin head for release from actin, powers the 'power stroke.'
313
What is the role of Ca2+ in muscle contraction?
Binds troponin, shifts tropomyosin, exposing actin binding sites.
314
Which muscle types are voluntary?
Skeletal
315
What is a neurotransmitter?
Chemical that transmits signals across a synapse.
316
What neurotransmitter is released at neuromuscular junctions?
Acetylcholine (ACh)
317
What does acetylcholinesterase do?
Breaks down acetylcholine in the synaptic cleft.
318
What is the main function of sensory neurons?
Connect sensory input to the nervous system.
319
What does the central nervous system comprise?
Brain and spinal cord
320
What does the peripheral nervous system comprise?
All nerves outside CNS
321
What are afferent and efferent neurons?
Afferent: to CNS; Efferent: from CNS to effectors.
322
What does a reflex arc involve?
Sensory input → interneuron → motor output (without brain).
323
Why do mammals require oxygen for survival?
For aerobic respiration (maximal ATP production).
324
Which hormone triggers uterine contractions at labor?
Oxytocin
325
What are pacemaker cells?
Specialized cardiac muscle cells that initiate heartbeats.
326
What is spatial summation in neurons?
Multiple synapses stimulate a postsynaptic neuron simultaneously.
327
What is temporal summation?
Several impulses from the same synapse in rapid succession.
328
What is a tripartite synapse?
Synapse that includes presynaptic, postsynaptic neuron, and an astrocyte.
329
What is the function of the blood–brain barrier?
Protects brain from toxins/pathogens, formed by astrocytes.
330
What are endocrine glands?
Ductless glands that secrete hormones into blood.
331
What are exocrine glands?
Glands with ducts that secrete externally (e.g., sweat, digestive).
332
What are paracrines and autocrines?
Paracrine: local signaling; Autocrine: self-stimulation.
333
What is the effect of insulin?
Lowers blood glucose by stimulating uptake/storage in tissues.
334
What does glucagon do?
Raises blood glucose by stimulating glycogen breakdown.
335
What tissue acts as a major glucose sensor in mammals?
Pancreatic beta cells.
336
Which enzyme 'fixes' atmospheric CO2 in the Calvin cycle?
Rubisco.
337
Why is rubisco’s oxygenase activity a problem?
Leads to photorespiration, wasting energy and reducing sugar production.
338
What is the function of phytochrome in plants?
Detects red/far-red light; regulates seed germination, flowering.
339
How does ABA affect water stress in plants?
Triggers stomatal closure to conserve water.
340
What is classical conditioning, in animal behavior?
Learning to associate a neutral stimulus with a meaningful one.
341
What is the central dogma of molecular biology?
DNA → RNA → Protein.
342
What is a locus?
The specific location of a gene on a chromosome.
343
What is genetic recombination?
Exchange of genetic material between homologous chromosomes during meiosis.
344
What is epigenetics?
Changes in gene expression not due to changes in DNA sequence (e.g., methylation).
345
What is a mutation 'hotspot'?
Region of DNA more prone to mutation.
346
Define pleiotropy.
When one gene affects multiple traits.
347
What is a quantitative trait?
Shows continuous variation; influenced by multiple genes and environment.
348
What is incomplete penetrance?
Not all individuals with a genotype display the phenotype.
349
What does variable expressivity mean?
Degree/severity of phenotype varies among individuals with the same genotype.
350
What does 'linked genes' mean?
Located on the same chromosome; inherited together more often.
351
What is the role of mitochondria in apoptosis?
Release factors that activate cell death pathways.
352
What is a prion disease?
Disease caused by infectious, misfolded proteins (e.g., mad cow, Creutzfeldt-Jakob).
353
What are operons?
Clusters of genes under the control of one promoter in prokaryotes.
354
What is the difference between positive and negative gene regulation?
Positive: activator increases transcription; Negative: repressor decreases it.
355
What is a lac operon?
Set of E. coli genes for lactose metabolism; inducible.
356
What is trp operon?
Tryptophan synthesis genes in E. coli; repressible.
357
What is a plasmid?
Small, circular DNA in bacteria; can carry antibiotic resistance in cloning.
358
What is the significance of recombinant DNA technology?
Allows genes to be transferred between organisms; basis of genetic engineering.
359
What is a selectable marker?
Gene introduced into an organism that confers a trait for selection (e.g., antibiotic resistance).
360
What is transformation in bacteria?
Uptake of foreign DNA from the environment.
361
What is conjugation in bacteria?
Direct transfer of DNA between bacteria via mating pili.
362
What is transduction?
DNA transfer by virus between bacteria.
363
What is a gene family?
Group of related genes with similar sequences/functions from gene duplication.
364
What are pseudogenes?
Nonfunctional gene sequences resembling functional genes.
365
What is genomic imprinting?
Expression of gene depending on parental origin.
366
What are telomeres?
Repetitive DNA at chromosome ends; protect from degradation.
367
What is the role of telomerase?
Enzyme that extends telomeres; active in stem/cancer cells.
368
What is apoptosis?
Programmed cell death.
369
What is necrosis?
Accidental cell death due to injury.
370
What is aneuploidy?
Abnormal chromosome number (e.g., trisomy 21 = Down Syndrome).
371
What is polyploidy?
More than two sets of chromosomes.
372
What is a karyotype?
Ordered display of chromosomes from a cell.
373
What is the role of cyclins in the cell cycle?
Activate CDKs for cell cycle transitions; levels fluctuate.
374
What is a checkpoint?
A control point in the cell cycle where process can be halted for repair.
375
What is cancer?
Disease of unregulated cell division.
376
What are oncogenes?
Mutated genes that promote cell division, cancer.
377
What are tumor suppressor genes?
Genes that prevent uncontrolled division; mutations lead to cancer.
378
What is a proto-oncogene?
Normal gene regulating cell growth; can mutate to oncogene.
379
What does p53 gene do?
Triggers cell cycle arrest or apoptosis after DNA damage.
380
What is recombinant DNA?
DNA composed of sequences from different sources.
381
What is a restriction enzyme?
Bacterial enzyme that cuts DNA at specific sites.
382
What is PCR?
Polymerase chain reaction; amplifies DNA segments.
383
What do DNA microarrays measure?
Expression levels of thousands of genes at once.
384
What is proteomics?
Study of the entire complement of proteins (the proteome).
385
What is metabolomics?
Study of all small molecules (metabolites) in a cell/tissue.
386
What is the action of gibberellins?
Promote stem elongation, seed germination.
387
What is the action of auxins?
Promote cell elongation, root initiation, phototropism, apical dominance.
388
How do plants acclimate to drought?
Upregulate drought genes, increase root growth, close stomata.
389
What is the source of plant hormones?
Synthesized in various tissues; act locally or systemically.
390
What is the function of ethylene?
Promotes fruit ripening, leaf/flower abscission.
391
What is the role of cytokinins?
Promote cell division and growth, delay aging in plant tissues.
392
What is a phytohormone?
Hormone affecting plant growth/development.
393
What is auxin’s role in phototropism?
Redistributed to shaded side, stimulates cell elongation (bend toward light).
394
What does ABA do during seed dormancy?
Maintains dormancy/prevents germination.
395
What is genetic drift?
Random changes in allele frequency, especially in small populations.
396
What is artificial selection?
Humans select desirable traits for breeding (domestication).
397
Why are seed banks important?
Preserve genetic diversity, allow crop improvement, recovery after disasters.
398
What is nutriepigenomics?
Study of how diet/nutrients modify the epigenome and gene expression.
399
How are brown and white fat different?
Brown: heat generation, rich in mitochondria; White: energy storage.
400
What principle underlies all life science inquiry?
Use of experimentation, observation, and hypothesis testing (the scientific method).
