Mixed Deck — All Biology Test Topics Flashcards

What is the purpose of the ubiquitin-proteasome pathway?

Answer: Tagging and degrading damaged or misfolded proteins

Ubiquitin molecules are attached to proteins marked for destruction, directing them to the proteasome where they are degraded into peptides.

Which term describes organisms that live suspended or swimming in open water, unable to overcome currents?

Answer: Plankton

Plankton are organisms that drift with ocean currents and include both phytoplankton (photosynthetic) and zooplankton (heterotrophic).

How does a testcross help determine whether an organism showing a dominant phenotype is homozygous or heterozygous?

Answer: Cross it with a homozygous recessive organism and observe offspring

Crossing with a homozygous recessive (aa) reveals the unknown genotype: if any offspring show the recessive phenotype, the parent is heterozygous.

A patient develops symptoms 48–72 hours after exposure to an antigen. Which type of hypersensitivity is most likely?

Answer: Type IV (delayed-type)

Type IV hypersensitivity is T cell-mediated and takes 48–72 hours to develop, as seen in contact dermatitis and the tuberculin skin test.

Which type of RNA carries amino acids to the ribosome during translation?

Answer: tRNA

Transfer RNA (tRNA) carries specific amino acids to the ribosome, matching anticodons to mRNA codons.

What is the primary function of chloroplasts in plant cells?

Answer: To carry out photosynthesis

Chloroplasts are the organelles responsible for photosynthesis, converting light energy into chemical energy (glucose) using carbon dioxide and water.

What is the primary function of the smooth endoplasmic reticulum (SER)?

Answer: Lipid synthesis and detoxification

The SER synthesizes lipids, phospholipids, and steroids, and detoxifies drugs and harmful substances.

Which process describes the movement of water across a selectively permeable membrane from low to high solute concentration?

Answer: Osmosis

Osmosis is the passive movement of water molecules through a semipermeable membrane toward the region of higher solute concentration.

What distinguishes K-selected species from r-selected species?

Answer: K-selected species produce few offspring with high parental investment

K-selected species invest heavily in fewer offspring, providing extensive parental care, and are adapted to stable environments near carrying capacity.

What is the functional unit of the kidney?

Answer: Nephron

Each nephron, consisting of a renal corpuscle and renal tubule, performs the complete process of filtration, reabsorption, and secretion.

Which organ is the control center of the nervous system?

Answer: Brain

The brain serves as the central control organ of the nervous system, coordinating all voluntary and involuntary actions. It processes sensory information, regulates body functions, and is responsible for thought, emotion, and memory. Its complex network of neurons enables communication throughout the entire body.

What is totipotency in the context of cell development?

Answer: The capacity of a single cell to give rise to every cell type in the organism, including both embryonic tissues and extraembryonic structures such as the placenta

Totipotency is the highest level of developmental potential; a totipotent cell can form a complete organism including all extraembryonic tissues—only the zygote and the earliest blastomeres (up to the 4-cell stage in mammals) are truly totipotent.

Which structure allows bacteria to survive extreme environmental conditions?

Answer: Endospore

Endospores are highly resistant dormant structures formed by certain bacteria (e.g., Bacillus) that survive heat, desiccation, and chemicals.

Which lobe of the liver produces bile that is stored in the gallbladder?

Answer: All hepatocytes throughout the liver produce bile

Bile is continuously produced by hepatocytes throughout the entire liver and flows into bile canaliculi toward the gallbladder.

What is a frameshift mutation?

Answer: An insertion or deletion that alters the reading frame

Frameshift mutations result from insertions or deletions of nucleotides that are not multiples of three, disrupting the reading frame.

Peroxisomes differ from lysosomes in that peroxisomes:

Answer: Use hydrogen peroxide as an oxidative tool to detoxify substances

Peroxisomes use oxidative reactions (often generating and then neutralizing H₂O₂) to break down fatty acids and detoxify alcohol, while lysosomes use acid hydrolases.

A newborn is found to lack both T and B lymphocytes. Which condition does this most likely represent?

Answer: Severe combined immunodeficiency (SCID)

SCID is characterized by the absence of functional T and B lymphocytes, often due to mutations in genes like IL-2Rγ (γc chain) or ADA (adenosine deaminase).

Which complement pathway is activated by mannose-binding lectin (MBL)?

Answer: Lectin pathway

The lectin pathway is activated when mannose-binding lectin recognizes mannose residues on microbial surfaces.

Which process allows a cell to break down its own damaged organelles by sequestering them in a double membrane and fusing with lysosomes?

Answer: Autophagy

Autophagy involves the formation of autophagosomes (double-membrane vesicles) that engulf damaged organelles or proteins, then fuse with lysosomes for enzymatic degradation.

What is photoperiodism in plants?

Answer: Response to the relative lengths of day and night

Photoperiodism is a plant's physiological response to the relative duration of light and dark periods, which controls flowering, dormancy, and other seasonal processes.