BIO 101 — Introduction to Cell Biology

Question 1: Which organelle is responsible for producing the majority of a cell's ATP?

•          Mitochondrion

•          Golgi apparatus

•          Lysosome

•          Peroxisome

Explanation: The mitochondrion is often called the "powerhouse of the cell" because it carries out oxidative phosphorylation, generating the bulk of a cell's ATP through the electron transport chain and chemiosmosis.

Question 2: Which structure regulates what enters and exits a cell?

•          Cell wall

•          Plasma membrane

•          Nuclear envelope

•          Cytoskeleton

Explanation: The plasma membrane is selectively permeable, controlling the movement of ions, nutrients, and waste products into and out of the cell through channels, pumps, and passive diffusion.

Question 3: Ribosomes are the site of which cellular process?

•          DNA replication

•          Protein synthesis

•          Lipid digestion

•          ATP hydrolysis only

Explanation: Ribosomes translate messenger RNA into polypeptide chains, assembling amino acids in the sequence specified by the mRNA codons during protein synthesis.

Question 4: The plasma membrane is composed primarily of a phospholipid bilayer.

•          True

•          False

Explanation: The fluid mosaic model describes the plasma membrane as a bilayer of phospholipids with embedded proteins, cholesterol, and carbohydrates that together regulate membrane fluidity and function.

Question 5: Which process allows water to move across a membrane from an area of low solute concentration to high solute concentration?

•          Active transport

•          Facilitated diffusion

•          Osmosis

•          Endocytosis

Explanation: Osmosis is the passive movement of water across a semipermeable membrane toward the side with higher solute concentration, working to equalize concentration on both sides.

Question 6: What distinguishes prokaryotic cells from eukaryotic cells?

•          Prokaryotes lack a membrane-bound nucleus

•          Prokaryotes have mitochondria

•          Prokaryotes contain a nuclear envelope

•          Prokaryotes have linear chromosomes

Explanation: Prokaryotic cells, such as bacteria, lack a membrane-bound nucleus and other membrane-bound organelles, with their genetic material located in a region called the nucleoid.

Question 7: Which phase of the cell cycle involves the separation of sister chromatids?

•          Prophase

•          Metaphase

•          Anaphase

•          Telophase

Explanation: During anaphase, the centromeres split and spindle fibers pull the sister chromatids apart toward opposite poles of the cell, ensuring each daughter cell receives a complete set of chromosomes.

Question 8: The endoplasmic reticulum studded with ribosomes is called smooth ER.

•          True

•          False

Explanation: Endoplasmic reticulum studded with ribosomes is called rough ER, which is involved in synthesizing and modifying proteins. Smooth ER lacks ribosomes and functions in lipid synthesis and detoxification.

Question 9: Which macromolecule stores genetic instructions in most living cells?

•          RNA

•          DNA

•          Protein

•          Carbohydrate

Explanation: DNA (deoxyribonucleic acid) stores hereditary information in the sequence of its nucleotide bases and is transcribed into RNA, which then directs protein synthesis.

Question 10: What is the primary function of the Golgi apparatus?

•          Energy production

•          Modifying, sorting, and packaging proteins

•          DNA replication

•          Photosynthesis

Explanation: The Golgi apparatus receives proteins from the endoplasmic reticulum, further modifies them, and packages them into vesicles for transport to their final cellular or extracellular destination.

Question 11: Cellular respiration is an anabolic process that builds larger molecules.

•          True

•          False

Explanation: Cellular respiration is a catabolic process; it breaks down glucose and other organic molecules to release energy stored in their chemical bonds, ultimately producing ATP.

Question 12: Which type of transport requires energy to move substances against their concentration gradient?

•          Simple diffusion

•          Facilitated diffusion

•          Active transport

•          Osmosis

Explanation: Active transport uses cellular energy, typically from ATP hydrolysis, to move molecules or ions across a membrane against their concentration gradient, as seen with the sodium-potassium pump.

Question 13: Which of the following best describes the function of lysosomes?

•          Storing genetic material

•          Breaking down waste materials and cellular debris

•          Synthesizing lipids

•          Producing ribosomal RNA

Explanation: Lysosomes contain hydrolytic enzymes that break down worn-out organelles, food particles, and foreign material engulfed by the cell, functioning as the cell's recycling and waste-disposal center.

Question 14: Turgor pressure in plant cells results from water entering the central vacuole.

•          True

•          False

Explanation: As water enters the central vacuole by osmosis, it pushes the cell membrane against the rigid cell wall, generating turgor pressure that keeps plant cells firm and supports non-woody plant structures.

Question 15: Which junction type allows direct communication between the cytoplasm of adjacent animal cells?

•          Tight junction

•          Desmosome

•          Gap junction

•          Plasmodesma

Explanation: Gap junctions are channel-forming proteins that connect the cytoplasm of neighboring cells, allowing ions and small molecules to pass directly between them for coordinated cellular activity.

Question 16: What is the role of the nucleolus within the nucleus?

•          DNA repair

•          Ribosomal RNA synthesis and ribosome assembly

•          Protein degradation

•          Lipid storage

Explanation: The nucleolus is a dense region within the nucleus where ribosomal RNA is transcribed and combined with proteins to begin assembling the subunits that will become ribosomes.

Question 17: Facilitated diffusion requires the use of transport proteins but not ATP.

•          True

•          False

Explanation: Facilitated diffusion moves substances down their concentration gradient through channel or carrier proteins; because it follows the gradient, it does not require the cell to expend ATP.

Question 18: Which stage of mitosis is characterized by chromosomes aligning at the cell's equator?

•          Prophase

•          Metaphase

•          Anaphase

•          Telophase

Explanation: During metaphase, spindle fibers align the chromosomes along the metaphase plate at the center of the cell, ensuring accurate separation of chromatids in the following phase.

Question 19: Which of the following is NOT a function of the cytoskeleton?

•          Providing structural support

•          Enabling cell movement

•          Facilitating intracellular transport

•          Synthesizing ATP

Explanation: The cytoskeleton, composed of microfilaments, microtubules, and intermediate filaments, provides shape, support, and enables movement and transport, but ATP synthesis is carried out primarily by mitochondria.

Question 20: Chloroplasts and mitochondria both contain their own DNA, supporting the endosymbiotic theory.

•          True

•          False

Explanation: The endosymbiotic theory proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells; both organelles retain their own circular DNA and can replicate independently within the cell.