Cell Structure and Function — Practice Quiz
A Biology cheat sheet for Cell Structure and Function — every key formula with its symbols defined — plus a medium-level practice quiz to test recall.
Formulas & key concepts
The biological concept that states that all organisms are composed of one or more cells, the cell is the basic unit of life, and new cells arise from existing cells.
| Feature | Prokaryotes | Eukaryotes |
|---|---|---|
| Nucleus | No | Yes |
| Size | 0.1–5.0 µm | 10–100 µm |
| Organelles | None | Membrane-bound |
| Examples | Bacteria, Archaea | Animals, Plants, Fungi |
| Component | Function | Animal Cell | Plant Cell |
|---|---|---|---|
| Plasma Membrane | Separates cell from external environment; controls passage of materials | Yes | Yes |
| Cytoplasm | Provides structure; site of metabolic reactions | Yes | Yes |
| Nucleus | Houses DNA; directs synthesis of ribosomes and proteins | Yes | Yes |
| Ribosomes | Protein synthesis | Yes | Yes |
| Mitochondria | ATP production / cellular respiration | Yes | Yes |
| Peroxisomes | Oxidizes fatty acids/amino acids; detoxifies poisons | Yes | Yes |
| Vesicles & Vacuoles | Storage and transport; digestive function in plants | Yes | Yes |
| Centrosome | Role in cell division; organizing center of microtubules | Yes | No |
| Lysosomes | Digestion of macromolecules; recycling of organelles | Yes | No |
| Cell Wall | Protection, structural support, maintenance of shape | No | Yes (Cellulose) |
| Chloroplasts | Photosynthesis | No | Yes |
| Endoplasmic Reticulum | Modifies proteins and synthesizes lipids | Yes | Yes |
| Golgi Apparatus | Modifies, sorts, tags, packages, and distributes lipids/proteins | Yes | Yes |
| Cytoskeleton | Maintains shape; secures organelles; movement | Yes | Yes |
| Flagella | Cellular locomotion | Some | No (except some sperm) |
| Cilia | Locomotion; movement of particles; filtration | Some | No |
A phospholipid bilayer with embedded (integral) or attached (peripheral) proteins that separates the internal contents of the cell from its surrounding environment.
The entire region between the plasma membrane and the nuclear envelope, consisting of organelles suspended in the gel-like cytosol, the cytoskeleton, and various chemicals.
The gel-like material of the cytoplasm in which cell structures are suspended.
The cell organelle that houses the cell’s DNA and directs the synthesis of ribosomes and proteins.
The double-membrane structure that constitutes the outermost portion of the nucleus.
The darkly staining body within the nucleus that is responsible for assembling ribosomal subunits.
Chromosome: Structure within the nucleus that comprises chromatin that contains DNA, the hereditary material.
A cellular structure that carries out protein synthesis.
The cellular organelles responsible for carrying out cellular respiration, resulting in the production of ATP, the cell’s main energy-carrying molecule.
A small, round organelle that contains hydrogen peroxide, oxidizes fatty acids and amino acids, and detoxifies many poisons.
A plant cell organelle that carries out photosynthesis.
A series of interconnected membranous structures within eukaryotic cells that collectively modify proteins and synthesize lipids.
Smooth ER: Few or no ribosomes; synthesizes carbohydrates, lipids, and steroid hormones; detoxifies chemicals; stores calcium.
A eukaryotic organelle made up of a series of stacked membranes that sorts, tags, and packages lipids and proteins for distribution.
An organelle in an animal cell that functions as the cell’s digestive component; it breaks down proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles.
A membrane-bound sac, somewhat larger than a vesicle, that functions in cellular storage and transport.
A large plant cell organelle that acts as a storage compartment, water reservoir, and site of macromolecule degradation.
A small, membrane-bound sac that functions in cellular storage and transport; its membrane is capable of fusing with the plasma membrane and other membrane systems.
The network of protein fibers that collectively maintains the shape of the cell, secures some organelles in specific positions, allows cytoplasm and vesicles to move within the cell, and enables unicellular organisms to move.
Flagella: Long, hair-like structures used to move the cell.
A rigid cell covering made of cellulose in plants, peptidoglycan in bacteria, non-peptidoglycan compounds in Archaea, and chitin in fungi that protects the cell, provides structural support, and gives shape to the cell.
The material, primarily collagen, glycoproteins, and proteoglycans, secreted from animal cells that holds cells together as a tissue, allows cells to communicate, and provides mechanical protection.
Tight Junctions: Firm seals between animal cells.
Desmosomes: Linkages between epithelial cells.
Gap Junctions: Channels between animal cells for communication.
A model of the structure of the plasma membrane as a mosaic of components, including phospholipids, cholesterol, proteins, and glycolipids, resulting in a fluid rather than static character.
The characteristic of a membrane that allows some substances through but not others.
A method of transporting material that does not require energy. Includes diffusion, osmosis, and facilitated transport.
A passive process of transport of low-molecular weight material down its concentration gradient.
A process by which material moves down a concentration gradient (from high to low concentration) using integral membrane proteins.
The transport of water through a semipermeable membrane from an area of high water concentration to an area of low water concentration across a membrane.
Water channel proteins that allow water to pass right through cell membranes.
The pressure that must be applied to prevent osmotic movement across a selectively permeable membrane.
Hypotonic: Extracellular fluid has lower osmolarity than the cell (water moves in).
Isotonic: Extracellular fluid has the same osmolarity as the cell.
The method of transporting material that requires energy. Moves substances against their concentration gradient.
A gradient produced by the combined forces of the electrical gradient and the chemical gradient.
A type of active transport that moves substances, including fluids and particles, into a cell. Includes <b>Phagocytosis</b> (cell eating) and <b>Pinocytosis</b> (cell drinking).
A process of passing material out of a cell.
Relatively constant internal physical and chemical conditions that organisms maintain.
On or in a cell, a specific protein to whose shape fits that of a specific molecular messenger, such as a hormone.
Practice quiz
Which of the following statements is NOT a tenet of the Unified Cell Theory?
- All organisms are composed of one or more cells.
- The cell is the basic unit of life.
- All cells contain a nucleus that houses genetic material.
- New cells arise from existing cells.
Answer: All cells contain a nucleus that houses genetic material.
A newly discovered single-celled organism is observed to lack a membrane-bound nucleus and other membrane-bound organelles. Based on this information, what is its most likely approximate size?
- $0.5 \text{ \mu m}$
- $50 \text{ \mu m}$
- $150 \text{ \mu m}$
- $10 \text{ nm}$
Answer: $0.5 \text{ \mu m}$
Which organelle is characteristic of animal cells but is typically absent in plant cells?
- Mitochondria
- Ribosomes
- Lysosomes
- Plasma membrane
Answer: Lysosomes
A eukaryotic cell is observed to have a rigid outer layer and contains organelles responsible for converting light energy into chemical energy. This cell most likely possesses which two structures?
- Cell wall and chloroplasts
- Centrosome and mitochondria
- Lysosomes and a small vacuole
- Flagella and a nucleus
Answer: Cell wall and chloroplasts
The plasma membrane's ability to allow certain substances to pass through while blocking others is described by which term?
- Fluid mosaic model
- Active transport
- Selectively permeable
- Electrochemical gradient
Answer: Selectively permeable
Within a eukaryotic cell, the assembly of ribosomal subunits primarily occurs in which specific region?
- Cytosol
- Rough Endoplasmic Reticulum
- Nucleolus
- Golgi Apparatus
Answer: Nucleolus
Which pair of organelles is directly involved in the primary energy conversion processes of eukaryotic cells, specifically ATP production and photosynthesis?
- Ribosomes and Peroxisomes
- Mitochondria and Chloroplasts
- Endoplasmic Reticulum and Golgi Apparatus
- Lysosomes and Vacuoles
Answer: Mitochondria and Chloroplasts
A cell that specializes in synthesizing and secreting large quantities of protein hormones would likely have an extensive network of which two organelles?
- Smooth ER and Peroxisomes
- Mitochondria and Lysosomes
- Rough ER and Golgi Apparatus
- Cytoskeleton and Central Vacuole
Answer: Rough ER and Golgi Apparatus
If a plant cell is placed in a solution with a higher solute concentration than its cytoplasm, what will be the most likely immediate effect on the cell?
- Water will move into the cell, causing it to swell.
- Water will move out of the cell, causing the plasma membrane to pull away from the cell wall.
- Solutes will move into the cell, increasing its turgor pressure.
- The cell will remain unchanged due to the cell wall.
Answer: Water will move out of the cell, causing the plasma membrane to pull away from the cell wall.
Which type of intercellular junction in animal cells is characterized by channels that allow for the direct passage of ions and small molecules between adjacent cells, facilitating rapid communication?
- Tight Junctions
- Desmosomes
- Plasmodesmata
- Gap Junctions
Answer: Gap Junctions
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