Cell Structure and Transport: Key Concepts for Biology

A1. What are the three main structural areas of a cell?

The nucleus, cytoplasm, and plasma membrane.

A2. Where is the nucleus located and what does it contain?

The nucleus is usually located near the center of the cell and contains DNA, which holds the cell's genetic instructions. It is surrounded by a nuclear envelope.

A3. What are the functions of the plasma membrane?

The plasma membrane surrounds and protects the cell, controls what enters and leaves the cell, helps maintain homeostasis, and allows cells to communicate with their environment.

A4. The plasma membrane of the cell is made of a ______ bilayer with various types of _____.

A phospholipid bilayer with various types of proteins.

A5. Where is the cytoplasm located and what are its three structural components?

The cytoplasm is everything between the plasma membrane and nucleus. Its three components are cytosol, organelles, and inclusions.

A6. What is the function of ribosomes and where are they typically found?

Ribosomes make proteins. They are found either free in the cytoplasm or attached to the rough endoplasmic reticulum.

A7. What is the difference between rough and smooth endoplasmic reticulum?

Rough ER has ribosomes attached to its surface and makes/processes proteins. Smooth ER lacks ribosomes and is involved in lipid production, detoxification, and calcium storage.

A8. Where is the Golgi apparatus located and what are its function and structure?

The Golgi apparatus is located in the cytoplasm, usually near the ER and nucleus. It consists of flattened membrane sacs and modifies, sorts, packages, and ships proteins and lipids.

A9. What is the role of lysosomes?

Lysosomes contain digestive enzymes that break down damaged organelles, waste materials, and substances taken into the cell.

A10. What is the role of peroxisomes?

Peroxisomes contain enzymes that break down fatty acids and detoxify harmful substances. They also break down hydrogen peroxide.

A11. What is the function of mitochondria?

Mitochondria produce ATP, the cell's main usable form of energy, through cellular respiration.

A12. What are the three cytoskeleton filaments?

Microfilaments, intermediate filaments, and microtubules.

A13. What are the general functions of cytoskeletal filaments?

They maintain cell shape, support and organize the cell, allow cell movement, and help move materials and organelles within the cell.

A14. What are the three types of cell junctions?

Tight junctions, desmosomes, and gap junctions.

A15. What is the function of tight junctions?

Tight junctions seal neighboring cells together and prevent substances from leaking between the cells.

A16. What is the function of desmosomes?

Desmosomes anchor neighboring cells together and provide strength, especially in tissues exposed to stretching.

A17. What is the function of gap junctions?

Gap junctions form channels between neighboring cells that allow ions and small molecules to pass directly from cell to cell for communication.

A18. What are the three common plasma membrane projections?

Microvilli, cilia, and flagella.

A19. What are microvilli and what is their function?

Microvilli are small, nonmoving projections that increase the cell's surface area for absorption.

A20. What are cilia and what is their function?

Cilia are short, numerous, moving projections that move substances across the cell surface.

A21. What are flagella and what is their function?

Flagella are long, usually single projections that move the entire cell. The human sperm cell has a flagellum.

A22. What cytoskeletal filament do cilia and flagella contain?

Microtubules.

A23. What cytoskeletal filament do microvilli contain?

Microfilaments, specifically actin filaments.

B1. What are the two basic methods of transport for solutes across the plasma membrane?

Passive transport and active transport.

B2. What two components make up a solution?

A solution consists of a solvent and solutes. The solvent is the dissolving medium, while solutes are substances dissolved in the solvent.

B3. What are the two areas where a solution exists relative to a cell?

The extracellular fluid is outside the cell, and the intracellular fluid is inside the cell.

B4. What does selectively permeable mean?

It means the cell membrane allows some substances to cross while preventing or limiting other substances from crossing.

B5. Which molecules easily diffuse across the plasma membrane without membrane proteins?

Small, nonpolar, hydrophobic molecules such as oxygen and carbon dioxide can easily diffuse through the phospholipid bilayer.

B6. Which molecules require membrane proteins to diffuse across the plasma membrane?

Polar molecules, ions, and larger molecules generally require membrane proteins because they cannot easily pass through the hydrophobic interior of the phospholipid bilayer.

B7. What is tonicity?

Tonicity is the ability of a solution to cause a cell to gain or lose water.

B8. What is a hypotonic solution?

A hypotonic solution has a lower solute concentration outside the cell than inside the cell, causing water to move into the cell. The cell swells.

B9. What is a hypertonic solution?

A hypertonic solution has a higher solute concentration outside the cell than inside the cell, causing water to move out of the cell. The cell shrinks.

B10. What is an isotonic solution?

An isotonic solution has approximately the same solute concentration inside and outside the cell, so there is no net movement of water and the cell remains about the same size.

B11. In diffusion, molecules move from an area of ______ to an area of ______.

High concentration to low concentration.

B12. Simple diffusion, osmosis, facilitated diffusion, and filtration are all forms of what type of transport?

Passive transport.

B13. What is simple diffusion?

Simple diffusion is the movement of small, nonpolar molecules from an area of high concentration to an area of low concentration directly through the phospholipid bilayer without ATP or membrane proteins.

B14. What is osmosis?

Osmosis is the diffusion of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration.

B15. What is facilitated diffusion?

Facilitated diffusion is the movement of substances from high concentration to low concentration through membrane proteins without using ATP.

B16. What is filtration?

Filtration is the movement of water and small solutes across a membrane because of a pressure gradient.

B17. What is the difference between passive and active transport?

Passive transport does not require ATP and moves substances down their concentration or pressure gradient. Active transport requires energy and moves substances against their concentration gradient.

B18. All forms of ______ transport do not require ATP but require energy stored in the ______ gradient.

Passive transport; concentration gradient.

B19. What does active transport require and how does it move molecules?

Active transport requires ATP and moves molecules against their concentration gradient, from low concentration to high concentration.

B20. What type of membrane protein assists active transport?

Transport proteins, especially protein pumps, assist active transport.

B21. What types of molecules are typically transported by active transport?

Ions and other substances that cannot easily cross the phospholipid bilayer are commonly transported by active transport.

B22. What is the sodium-potassium pump and what provides its energy?

The sodium-potassium pump is a membrane protein powered by ATP. It pumps sodium ions (Na+) out of the cell and potassium ions (K+) into the cell against their concentration gradients.

B23. As a result of the sodium-potassium pump, what ions are more concentrated outside and inside the cell?

Sodium (Na+) is more concentrated outside the cell, while potassium (K+) is more concentrated inside the cell.

B24. What is the purpose of vesicular transport?

Vesicular transport moves large particles, fluids, and large molecules into or out of the cell using membrane-bound vesicles.

B25. Is vesicular transport active or passive transport?

Vesicular transport is a form of active transport because it requires energy, usually ATP.

B26. What are the two types of vesicular transport?

Endocytosis brings materials into the cell, while exocytosis moves materials out of the cell.

B27. What is phagocytosis?

Phagocytosis is a type of endocytosis in which the cell engulfs large particles or other cells. It is sometimes called "cell eating."

B28. What is pinocytosis?

Pinocytosis is a type of endocytosis in which the cell takes in extracellular fluid and dissolved substances. It is sometimes called "cell drinking."

B29. What is the difference between phagocytosis and pinocytosis?

Phagocytosis takes in large particles or cells, while pinocytosis takes in extracellular fluid and dissolved substances.

B30. All body cells except sex cells divide by what process?

Mitosis.

B31. What is the genetic instruction of the cell and where is it found?

DNA is the genetic instruction of the cell and is found primarily in the nucleus.

B32. What four nucleotides are found in a DNA sequence?

Adenine (A), thymine (T), cytosine (C), and guanine (G).

B33. What are the two major phases of the cell cycle?

Interphase and the mitotic phase (cell division).

B34. What major activities occur during interphase?

The cell grows, performs its normal functions, duplicates its DNA, and prepares for cell division.

B35. During which phase is DNA duplicated?

DNA is duplicated during the S phase of interphase, not during mitosis.

B36. What happens during prophase?

Chromatin condenses into visible chromosomes, the nuclear envelope begins to break down, the mitotic spindle forms, and centrosomes move toward opposite sides of the cell.

B37. What happens during metaphase?

Chromosomes line up along the middle of the cell.

B38. What happens during anaphase?

Sister chromatids separate and move toward opposite poles of the cell.

B39. What happens during telophase?

Chromosomes reach opposite poles, new nuclear envelopes form around them, and the chromosomes begin to uncoil.

B40. What is mitosis?

Mitosis is the division of the nucleus that produces two genetically identical nuclei.

B41. What is cytokinesis?

Cytokinesis is the division of the cytoplasm, producing two separate daughter cells. It begins during late anaphase and continues through telophase.

B42. Protein synthesis means the production of what?

Protein synthesis means the production of proteins.

B43. What is a gene?

A gene is a segment of DNA that contains the instructions for making a specific protein or functional RNA.

B44. A gene is a small segment of which molecule, DNA or RNA?

DNA.

B45. What molecule contains several blueprints for building many proteins?

DNA, located primarily in the nucleus, contains many genes that provide instructions for making proteins.

B46. What happens during protein synthesis?

A specific segment of DNA called a gene is transcribed into messenger RNA (mRNA). The mRNA is then translated into a protein.

B47. What is transcription?

Transcription is the process of copying the information in a gene's DNA into mRNA.

B48. What is translation?

Translation is the process of using the information in mRNA to build a protein.

B49. Where does transcription occur?

Transcription occurs in the nucleus.

B50. Where does translation occur?

Translation occurs at ribosomes in the cytoplasm, including ribosomes attached to the rough ER.

C1. What are the four tissue types found in the body?

Epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

C2. What is the general function of epithelial tissue?

Epithelial tissue covers body surfaces, lines body cavities and organs, protects underlying tissues, absorbs substances, secretes substances, and allows sensation.

C3. What is the general function of connective tissue?

Connective tissue supports, connects, protects, insulates, and transports materials throughout the body.

C4. What is the general function of muscle tissue?

Muscle tissue contracts to produce movement, maintain posture, and generate heat.

C5. What is the general function of nervous tissue?

Nervous tissue detects stimuli and communicates information through electrical signals.

C6. Where are the four tissue types generally found?

Epithelial tissue covers surfaces and lines cavities and organs; connective tissue is found throughout the body; muscle tissue is found in muscles and organs; nervous tissue is found in the brain, spinal cord, and peripheral nerves.

C7. What is simple squamous epithelium?

Simple squamous epithelium consists of one layer of thin, flat cells. It allows rapid diffusion and filtration. It is found in areas such as alveoli, blood vessels, and the lining of body cavities.

C8. What is simple cuboidal epithelium?

Simple cuboidal epithelium consists of one layer of cube-shaped cells. It is involved in secretion and absorption and is found in kidney tubules and many glands.

C9. What is simple columnar epithelium?

Simple columnar epithelium consists of one layer of tall, rectangular cells. It is involved in absorption and secretion and is commonly found lining much of the digestive tract.

C10. What is stratified squamous epithelium?

Stratified squamous epithelium has multiple layers with flat cells at the surface. It provides protection against abrasion and is found in areas such as the skin, mouth, esophagus, and vagina.

C11. What is stratified cuboidal epithelium?

Stratified cuboidal epithelium usually has two or more layers of cube-shaped cells. It provides protection and is involved in secretion and is found in ducts of some glands.

C12. What is stratified columnar epithelium?

Stratified columnar epithelium has multiple layers with column-shaped cells at the surface. It provides protection and secretion and is found in limited areas such as parts of the male urethra and large ducts of some glands.

C13. What does "simple" mean when describing epithelial tissue?

Simple means the epithelium has one layer of cells.

C14. What does "stratified" mean when describing epithelial tissue?

Stratified means the epithelium has two or more layers of cells.

C15. What does "squamous" mean?

Squamous means the cells are thin and flat.

C16. What does "cuboidal" mean?

Cuboidal means the cells are approximately cube-shaped.

C17. What does "columnar" mean?

Columnar means the cells are taller than they are wide and have a column-like shape.

C18. How are epithelial tissues classified?

Epithelial tissues are classified by the number of cell layers and the shape of the cells at the apical surface.