Cell Theory, Structure, and Function – Comprehensive Review

A set of 100 question-and-answer flashcards covering cell theory, organelles, cellular processes, microscopy, cell types, tissues, cell modifications, and the cell cycle for exam review.

What are the three main tenets of the Cell Theory?

1) All organisms are composed of one or more cells. 2) The cell is the basic structural and functional unit of life. 3) Cells arise only by division from pre-existing cells.

Which scientist coined the term “cell” after observing cork under a microscope?

Robert Hooke.

Who first observed red blood cells, sperm cells, and single-celled pond organisms?

Anton van Leeuwenhoek.

Which botanist concluded that plant embryos arise from single cells and that plants are made of cells?

Matthias Schleiden.

Which zoologist concluded that animal tissues are composed of cells similar to those of plants?

Theodor Schwann.

Who provided strong evidence that cells arise only from pre-existing cells through division?

Rudolf Virchow.

What is an organelle?

A specialized subcellular structure that performs a specific task within a cell.

What is the primary function of the plasma membrane?

It selectively controls what enters and leaves the cell, maintaining homeostasis.

Which cell structure houses the cell’s genetic material and acts as the control center?

The nucleus.

What semitransparent fluid suspends organelles inside the cell?

Cytosol (the fluid portion of cytoplasm).

What rigid outer layer found in plant cells provides structural support and filtration?

The cell wall.

Which organelle is studded with ribosomes and transports proteins to the Golgi apparatus?

Rough endoplasmic reticulum (Rough ER).

What is the main role of the smooth endoplasmic reticulum?

Synthesizing and transporting lipids to the Golgi apparatus.

Which organelle is known as the “powerhouse of the cell” because it produces ATP?

Mitochondria.

What tiny structures are the actual sites of protein synthesis?

Ribosomes.

Which sub-nuclear body assembles ribosomal subunits?

The nucleolus.

Which plant organelle captures sunlight energy to produce food?

Chloroplast.

What name is given to the DNA-protein complex that forms chromosomes in the nucleus?

Chromatin.

Which organelles contain digestive enzymes that break down waste and damaged parts?

Lysosomes.

What is the major function of the Golgi body?

To modify, package, and distribute proteins and other molecules.

Which organelle stores water, food, and wastes?

Vacuoles.

What cylindrical structures help organize the mitotic spindle in animal cells but are usually absent in plant cells?

Centrioles.

What are microfilaments primarily composed of, and what is their role?

Actin; they provide cellular movement and structural support.

What is the function of microtubules?

They form tracks for organelle movement, make up the mitotic spindle, and support cell shape.

What is a vesicle?

A small membrane-bound sac that transports or stores materials within a cell.

What double membrane surrounds the nucleus?

The nuclear envelope.

What term describes the gel-like material inside the nucleus?

Nucleoplasm.

Which organelle contains enzymes that break down hydrogen peroxide and detoxify substances?

Peroxisome.

What are plasmodesmata?

Channels through plant cell walls that allow cytoplasmic exchange between adjacent cells.

Which type of microscopy allows observation of living processes in real time?

Live-cell imaging.

What imaging technique uses differences in refractive index to produce high-contrast images without staining?

Differential interference contrast (DIC) microscopy.

Which microscope uses visible light and lenses to magnify specimens up to about 1000×?

Light microscope.

Which microscope uses electron beams for high-resolution imaging of cellular ultrastructure?

Electron microscope.

In amoebae, where are ingested algae broken down?

In food vacuoles.

What process ejects secretory products from the cell by vesicle fusion with the plasma membrane?

Exocytosis.

What class of proteins catalyzes biochemical reactions in the cell?

Enzymes.

What energy molecule do mitochondria generate to power cellular activities?

Adenosine triphosphate (ATP).

What molecule serves as the genetic blueprint for building proteins and entire organisms?

DNA (deoxyribonucleic acid).

What type of organism has cells without a nucleus and lacks membrane-bound organelles?

Prokaryote.

What type of organism is composed of cells with a true nucleus and membrane-bound organelles?

Eukaryote.

Name three basic structures shared by all cells.

Plasma membrane, cytoplasm, and DNA (along with ribosomes for protein synthesis).

Where is the DNA located in a prokaryotic cell?

In the nucleoid region as a circular chromosome.

What is the primary role of ribosomes?

Synthesizing proteins by linking amino acids.

What plant tissue transports water and minerals from roots to shoots?

Xylem cells.

Which plant tissue transports sugars and nutrients produced by photosynthesis?

Phloem cells.

What are parenchyma cells mainly responsible for in plants?

Synthesis and storage of food such as starch.

Which plant cell type provides flexible support with thickened primary walls?

Collenchyma cells.

What plant cells possess thick secondary walls for support and protection?

Sclerenchyma cells.

What animal cells are specialized for contraction and movement?

Muscle cells.

Which animal cells transmit electrical signals in the nervous system?

Nerve cells (neurons).

What is the role of red blood cells?

Transporting oxygen to body tissues.

Which cells defend the body against infection?

White blood cells.

What is the main function of epithelial cells?

Forming protective linings and regulating exchange such as gas, fluids, and macromolecules.

What do adipose (fat) cells primarily do?

Store energy as fat and secrete hormones affecting metabolism.

What unique ability do stem cells possess?

They can differentiate into specialized cells for growth, repair, and therapy.

What are sex cells and what is their function?

Gametes (sperm and egg) that unite during fertilization for reproduction.

Define tissue in biological terms.

A group of similar cells that work together to perform a specific function.

What side of an epithelial cell rests on the basement membrane?

The basal surface.

What are cell junctions?

Specialized structures that connect cells or cells to the extracellular matrix, contributing to tissue integrity and communication.

What structure consists of six connexin proteins forming a channel between cells?

Connexon (part of a gap junction).

Which epithelial tissue type consists of cube-shaped cells specialized for secretion?

Simple cuboidal epithelium.

Which epithelial tissue is composed of brick-shaped cells specialized for secretion and active absorption?

Simple columnar epithelium.

What epithelial tissue is made of a single layer of plate-like cells for rapid diffusion?

Simple squamous epithelium.

Which epithelial tissue type is multilayered and rapidly regenerates to protect underlying tissues?

Stratified squamous epithelium.

What epithelial tissue appears multilayered but is actually one layer of varying heights, often ciliated in the respiratory tract?

Pseudo-stratified columnar epithelium.

What defines connective tissue compared to other tissue types?

Cells widely spaced within an abundant extracellular matrix.

What are the three formed elements in blood besides plasma?

Erythrocytes, leukocytes, and platelets.

What type of connective tissue stores fat for energy and insulation?

Adipose tissue.

Which connective tissue has collagen fibers embedded in chondroitin sulfate acting as a cushion between bones?

Cartilage.

What mineralized connective tissue formed by osteoblasts provides the body’s framework?

Bone.

What two main cell types compose nervous tissue?

Neurons and glial cells.

What part of the neuron receives incoming signals?

Dendrite.

Through which part of a neuron is an impulse transmitted to other cells?

Axon.

What muscle tissue is striated and under voluntary control?

Skeletal muscle.

Which muscle tissue is striated, contains intercalated discs, and contracts involuntarily?

Cardiac muscle.

What muscle tissue lacks striations and is responsible for involuntary movements in organs?

Smooth muscle.

What are cell modifications?

Structural changes in cells that enable specialized functions.

Which apical modification greatly increases surface area for absorption?

Microvilli.

What hair-like apical structures move fluids or particles across cell surfaces?

Cilia.

What long, whip-like structure propels certain cells, such as sperm?

Flagellum.

What temporary extensions of the cell membrane aid in movement and engulfing particles?

Pseudopods.

Which basal modification anchors epithelial cells to the basement membrane?

Hemidesmosomes.

What type of lateral junction forms a watertight seal between adjacent cells?

Tight junction.

Which anchoring junction provides strong mechanical adhesion between cells?

Desmosome.

Which lateral junction forms channels that allow ions and small molecules to pass between cells?

Gap junction.

What is the cell cycle?

The ordered sequence of events a cell undergoes to grow and divide.

During which interphase sub-phase does DNA replication occur?

S phase.

What happens during G1 phase of interphase?

The cell grows, increases organelles, and prepares for DNA replication.

What key event characterizes G2 phase?

Completion of DNA replication and error checking before mitosis.

What two processes make up the mitotic (M) phase?

Mitosis and cytokinesis.

What is mitosis?

Nuclear division producing two genetically identical daughter nuclei.

In which cells does mitosis occur?

Somatic (non-reproductive) cells.

How many daughter cells are produced by one round of mitosis, and what is their ploidy?

Two diploid cells.

During which stage of mitosis do chromosomes align on the metaphase plate?

Metaphase.

What event marks anaphase?

Sister chromatids are separated and pulled toward opposite poles.

Which mitotic stage involves re-formation of nuclear envelopes around chromosome sets?

Telophase.

What is cytokinesis?

Division of the cytoplasm resulting in two separate daughter cells.

What structure organizes spindle fibers in animal cells and duplicates during prophase?

Centrosome/centriole pair.

Why is mitosis essential for multicellular organisms?

It enables growth, development, and replacement of damaged or lost cells.

What Greek word is the term “mitosis” derived from, and what does it mean?

"Mitos," meaning "thread."