BIOLOGY REVIEWER (DOST)

When the chromosomes line up in mitosis this is known as which phase?

Metaphase

Cellulose is a tough carbohydrate fiber that provides support to the plant body. Which of the following organelles contain this substance?

Cell wall

Which statement is part of the cell theory?

All cells com from preexisting cells

Which of the following plant cell types function for food storage and photosynthesis in cell plants?

Parenchyma cell

Which part of the following blood cells is important in the immune system?

Leukocytes

What happens to red blood cells if we place them in distilled water?

They swell up and burst

A compound is made of carbon, hydrogen, and oxygen in 1:2:1 ratio and is commonly used for quick energy in cells. Which biomolecule is most consistent with this description?

Carbohydrate

A molecule stores long-term energy and consists mainly of long hydrocarbon chains with few oxygen atoms. Which classification best fits this molecule?

Lipid

A laboratory heats an enzyme solution until the protein unfolds and loses its shape. What is the most likely immediate effect on the enzyme’s function?

The active site changes shape, reducing catalytic activity

A protein’s primary structure remains intact, but its alpha-helices and beta-sheets are disrupted after exposure to extreme pH. Which level of structure is most likely directly affected?

Secondary structure

Two enzymes act on different substrates even though the substrates differ by only one functional group. Which mechanism best explains this specificity?

The active site has a shape and chemical environment that fits only certain substrates

An enzyme-catalyzed reaction is measured as temperature increases from 10C to 80C. The reaction rate rises, reaches a peak, then rapidly decreases. Which explanation best accounts for the decrease at high temperature?

The enzyme denatures and loses its functional shape

In an enzyme reaction, increasing substrate concentration restores the original maximum rate in the presence of inhibitor X. Which type of inhibition is most consistent with inhibitor X?

Competitive inhibition

An enzyme’s reaction rate is measured at different substrate concentrations. Substrate (mM): 1 2 4 8 16 Rate (units): 10 18 30 38 40 which conclusion is best supported by data?

The enzyme approaches a maximum rate as substrate concentration increases

A cell increases the concentration of a substrate for an enzyme far beyond normal levels. Which outcome is most likely if the enzyme amount remains constant?

The reaction rate rises then levels off at a maximum

Which pathway produces the greatest number of ATP molecules per glucose molecule under aerobic conditions?

Oxidative phosphorylation

A toxin blocks electron transfer in the mitochondrial electron transport chain. Which change is expected first?

Decreased ATP production from oxidative phosphorylation

During aerobic respiration, NADH is primarily important because it:

Provides high-energy electrons to the electron transport chain

A scientist measure oxygen consumption in cultured cells. After adding a compound, oxygen consumption rapidly decreases while glucose uptake remains high. Which interpretation best fits the results?

The compound inhibits the electron transport chain

Under which condition is ATP production mainly dependent on substrate-level phosphorylation?

Anaerobic conditions with fermentation pathways active

An aquatic plant shows higher oxygen production under blue light than under green light. Which explanation best accounts for this pattern?

Chlorophyll absorbs blue light more effectively than green light

A leaf disk flotation test is performed under different light colors. Light Red Green Dark Float time: Fast Fast Slow None Which conclusion is best supported?

Red and blue light support higher photosynthesis than green light

In hot, dry conditions, some plants lose carbon because Rubisco binds oxygen more often. Which statement best explains why photorespiration reduces sugar production?

Photorespiration consumes oxygen and releases carbon dioxide without making sugar

A chemical uncouples the electron transport chain from ATP synthesis by allowing protons to cross the inner mitochondrial membrane without ATP synthase. What is the most direct effect?

ATP production decreases even though electron transport can continue

An enzyme is tested under different conditions. Condition: Normal +inhibitor +More substrate +High pH Relative rate: 100 60 60 20 Which interpretation best fits the pattern?

The inhibitor effect is not overcome by substrate, suggesting noncompetitive inhibition

A mutation reduces the ability of the inner mitochondrial membrane to maintain a proton gradient. What is the most likely outcome for ATP production?

ATP synthesis via ATP synthase decreases due to reduced proton motive force

Muscle cells experience low oxygen during intense exercise. Which metabolic shift is most likely to maintain ATP production?

Increased reliance on fermentation to regenerate NAD+

A student claims, "Ifa cell consumes more oxygen, it must always produce more ATP." Which critique best evaluates this conclusion?

Oxygen consumption can rise without more ATP if respiration is uncoupled or inefficient

In a metabolic pathway, increasing substrate concentration does not increase the overall product formation rate. Which explanation best fits this observation?

The pathway is controlled bya rate-limiting enzyme step

A cell treated with a reversible ATP synthase inhibitor continues to consume oxygen briefly but produces far less ATP. Which explanation best accounts for both observations?

Electron transport can proceed while ATP synthase is blocked, reducing ATP yield

Glucose moves into a cell down its concentration gradient using a membrane protein. Which process best describes this transport?

Facilitated diffusion

A red blood cell is placed in a solution with higher solute concentration than its cytoplasm. What will most likely happen?

The cell shrinks as water leaves the cell

A cell pumps sodium ions out of the cytoplasm against their concentration gradient. Which feature is required?

A source of energy such as ATP

A mutation disables a membrane carrier that normally imports an amino acid. Which effect is most direct?

The amino acid concentration inside the cell decreases

Which organelle is most directly responsible for modifying. sorting, and packaging proteins for secretion?

Golgi apparatus

A secreted protein is synthesized by ribosomes attached to a membrane. Which organelle is most directly associated with this early step of targeting?

Rough endoplasmic reticulum

A drug prevents microtubules from forming. Which cellular process is most directly impaired?

Chromosome separation during cell division

A hormone triggers secretion of a protein trom a gland cell. Which sequence best describes the path of a newly made secreted protein?

Rough ER+ Golgi apparatus * secretory vesicle → plasma membrane

Which checkpoint most directly determines whether a cell proceeds from G1 into DNA synthesis?

G1 checkpoint

A cell has a mutation that prevents proper DNA damage detection. Which outcome is most likely?

The cell may proceed through division with mutations, increasing cancer risk

Compared with mitosis, meiosis produces daughter cells that are:

Genetically varied and haploid

A population of cels is analyzed for DNA content. Observation: A large fraction has double the DNA content of G1 cells. Which phase is most consistent with this observation?

G2/M phase

A signaling molecule diffuses through the plasma membrane and binds an intracellular receptor. Which type of molecule most likely acts this way?

Steroid hormone

A cell's surface receptor binds its ligand normally, but the cell shows no internal response. Which defect is most likely?

A mutation in an intracellular signaling protein downstream of the receptor

In a signaling pathway, a small molecule rapidly increases inside the cell and activates multiple enzymes, amplifying the signal. What is this molecule best described as?

A second messenger

A receptor activates a G protein, which then activates adenytyl cyclase. Condition: Normal +Adenylyl cyclase inhibitor Response: High cAMP production Low cAMP production Which conclusion is best supported?

CAMP is produced downstream of adenylyl cyclase activity

A cell is repeatedly exposed to the same hormone at high levels, but its response decreases over time. What is the most likely explanation?

The cell downregulates receptors or signaling components, reducing sensitivity

A researcher tests whether a drug blocksa signaling pathway after receptor binding. Which result best supports that the drug acts downstream of the receptor?

The ligand binds normally, but second messenger levels fail to rise after stimulation

A mutation causes many proteins to fold incorrectly inside the cell. Which response is most likely to increase first?

Increased synthesis of chaperone proteins to assist folding

A signaling molecule triggers opening of ion channels and also activates gene transcription in the same cell. Which integration best explains how both effects occur?

The cell uses distinct branches of the signaling pathway to produce rapid and long-term responses

A cell is exposed to a stimulus and two measurements are recorded. Measurement: Normal +Kinase inhibitor lon channel opening: High Low Gene transcription: High Low Which conclusion is best supported?

The kinase is required for both responses to the stimulus

A patient's cells show normal receptor binding but abnormally high cell division rates. Which explanation best fits this phenotype?

A mutation in a checkpoint regulator that allows division despite signals to stop

Two hypotheses are proposed to explain reduced secretion of a protein: (1) the protein is not synthesized, (2) the protein is synthesized but not trafficked properly. Which test best distinguishes between these hypotheses?

Use a labeled amino acid to track whether the protein is made and where it accumulates

A cell has normal membrane receptors, normal ATP levels, and normal gene transcription, yet it fails to respond to a signal requiring rapid ion movement. Which defect is most consistent?

A nonfunctional ion channel protein in the membrane

In a pea plant, the allele for tall stems (T) is dominant to short stems (). A plant is tall but its genotype is unknown. Which genotype is possible?

Tt or T

A heterozygous tall plant (T) is crossed with a short plant (tt). What proportion of the offspring is expected to be tall?

50%

A student flips a coin and draws one marble froma bag. The probability of heads is 1/2, and the probability of drawing a red marble is 1/3. If these events are independent, what is the probability of getting heads and drawinga red marble?

1/6

A plant shows a recessive phenotype for a trait. Which cross best tests whether a dominant-phenotype plant is homozygous or heterozygous?

Cross the dominant plant with a homozygous recessive plant

In snapdragons, a red-flowered plant crossed witha white-flowered plant produces pink-flowered offspring. Which inheritance pattern best explains this result?

Incomplete dominance

In a cross, two genes interact so that one gene masks the expression of the other, producinga 9:3:4 phenotypic ratio. Which conclusion best fits this pattern?

The genes assort independently with complete dominance only

A trait occurs more frequently in males than in females, and affected sons often have mothers who show no symptoms. Which pattern is most consistent with this trait?

X-linked recessive inheritance

In a pedigree, an unaffected couple has an affected son, and the trait appears mostly in males. Which inference is most supported?

The mother is likely a carrier of an X-linked recessive allele

A trait appears in every generation and affects males and females equally. Which pattern is most consistent?

Autosomal dominant

A pedigree shows an affected female whose father is affected and whose mother shows no symptoms. Several affected males appear in later generations. Which interpretation best fits the data?

The trait is X-linked recessive and the affected female is homozygous recessive due to a carrier mother and affected father

DNA polymerase adds nucleotides to a growing strand primarily in which direction?

5' to 3'

A mutation reduces the proofreading ability of DNA polymerase. Which outcome is most likely?

More mutations due to increased base-pairing errors

A gene has the sequence shown below. Coding strand: 5-ATG GAA TTT-3' Template strand:3-TAC CTT AAA-5' Which sequence matches the mRNA produced (5' to 3)?

5-AUG GAA UUU-3

A singte nucleotide is inserted near the beginning of a coding sequence. Which consequence is most likely for the protein produced?

The reading frame shifts, altering many downstream aminoids

A DNA change converts the codon GAA to GAG, and both codons specify the same amino acid. Which mutation type best describes this change?

Silent mutation

A point mutation changes a codon from UAU to UAA in an mRNA. What is the most ikely effect on the resulting protein?

A shorter protein due to premature termination

Which DNA region is most directly required for RNA polymerase to begin transcription of a gene?

Promoter

Increased DNA methylation near a gene's promoter is most likely to cause:

Decreased transcription by reducing access to DNA

Gene expression is measured under four conditions. Condition: No hormone +Hormone +Hormone+Drug X Drug X only mRNA level: Low High Low Low Which conclusion is best supported?

Drug X prevents the hormone-induced increase in transcription

A bacterial gene is transcribed only when lactose is present. A mutation prevents the repressor from binding the operator. What is the most ikely result?

The gene is transcribed continuously, even without lactose

A karyotype shows a person with three copies of chromosome 21. Which interpretation is most consistent?

A nondisjunction event produced trisomy 21

During meiosis, homologous chromosomes fail to separate in anaphase I. Which outcome is most likely in the gametes produced?

Some gametes have an extra chromosome and some lack that chromosome

Which change best describes a chromosomal translocation compared with a deletion?

Transtocation exchanges segments between chromosomes, deletion

A DNA sample is run on a gel after restriction enzyme digestion. Lane 1: Sample A shows two bands Lane 2: Sample B shows three bands Lane 3: Sample C shows one band Which conclusion is best supported?

Sample B likely has more restriction cut sites than Sample A

A lab performs PCR on a DNA region expected to be 500 base pairs long. After 30 cycles, a strong 500 bp band appears on the gel. Which inference is most supported?

The DNA region was amplified through repeated primer extension

A researcher claims a gene is required for resistance to a virus because cells lacking the gene become infected more often. Which critique best evaluates this claim?

The claim is incomplete without controling for other differences between the cell lines

Two children have a recessive genetic disorder, but both parents show normal phenotype. Which explanation best fits this pattern?

Both parents are likely carriers of the recessive allele

Two hypotheses explain a disease: (1) a point mutation disrupts an enzyme active site, (2) reduced gene expression lowers enzyme amount. Which test best distinguishes between them?

Measure the enzyme's catalytic activity per molecule and the enzyme quantity

A mutation prevents a transcription factor from binding its enhancer. What is the most likely effect?

Decreased transcription because activation is reduced

Two genes influence a trait. Gene A affects pigment production, and Gene B affects pigment transport. Gene A is normal, but Gene B is nonfunctional. The organism lacks pigment in its skin cells. Which conclusion is best supported?

Pigment is produced but cannot be transported to where it is needed

A mutation prevents mRNA splicing so that introns remain in the final mRNA. Which effect is most direct?

The protein sequence is likely altered due to disrupted coding information

A scientist compares evidence for two explanations of a phenotype: (1) altered protein function due to mutation, (2) altered gene expression due to methylation. Which evidence best strengthens explanation (2)?

The DNA sequence is unchanged but the gene's mRNA level is reduced

A transcription factor activates multiple genes involved in glucose metabolism. Which statement best describes this regulatory role?

It binds specific DNA sequences to increase transcription of target genes

A mutation destroys the start codon of a gene. What is the most likely immediate effect?

Translation initiation is disrupted, greatly reducing protein production

A bacterial cell is grown in the presence of a compound that blocks ribosome function. Which process is most directly affected?

Translation

A researcher observes that a protein level is low despite normal mRNA levels. Which explanation is most consistent?

Rapid protein degradation or reduced translation

A mutation eliminates a stop codon but leaves the reading frame unchanged. Which outcome is most likely?

Translation continues beyond the normal stop, producing a longer protein

A gene produces two different proteins in different tissues from the same DNA sequence. Which mechanism best explains this?

Alternative splicing of the pre-mRNA

Body temperature increases during infection, and sweating increases as the temperature returns toward normal. This response best illustrates:

Negative feedback

A hormone is released into the blood and causes the liver to increase blood glucose by breaking down glycogen. Which hormone most directly fits this effect?

Glucagon

A person produces very little insulin. Which outcome is most likely?

Higher blood glucose due to reduced cellular uptake

Which comparison best distinguishes endocrine signaling from nervous signaling?

Endocrine signals travel through the blood and act more slowly than nerve impulses

During dehydration, ADH increases and helps conserve water. When hydration is restored, ADH levels decrease. Which interpretation best explains this pattern?

It is negative feedback because the response reduces the initial change

A hormone is lipid-soluble and diffuses into target cells to bind an intracellular receptor. Which target effect is most likely?

Activation of gene transcription after receptor binding

Which nephron segment is most directly responsible for most water reabsorption under normal conditions?

Proximal tubule

A person secretes high levels of ADH. Which change is most likely observed?

Decreased urine volume with increased urine concentration