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Anatomy & Physiology: Cells and Cellular Functions

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  • What is the cell theory?

    Cell theory states that a cell is the structural and functional unit of life, all cells arise from preexisting cells, and the organism's function depends on the activities of its cells.

  • What are the three basic parts of a generalized human cell?

    The three basic parts are the plasma membrane (flexible outer boundary), cytoplasm (intracellular fluid with organelles), and nucleus (DNA-containing control center).

  • What are extracellular materials and their classes?

    Extracellular materials are substances outside cells, including extracellular fluids (interstitial fluid, blood plasma, cerebrospinal fluid), cellular secretions (saliva, mucus), and extracellular matrix (glue holding cells together).

  • Describe the plasma membrane structure and its role.

    The plasma membrane is a phospholipid bilayer with embedded proteins forming a fluid mosaic. It acts as a selective barrier controlling entry and exit of substances and supports cell communication and adhesion.

  • What are the components of the membrane lipid bilayer?

    The bilayer consists of 75% phospholipids (polar hydrophilic heads and nonpolar hydrophobic tails), 5% glycolipids (lipids with sugar groups), and 20% cholesterol (increases membrane stability).

  • Differentiate between integral and peripheral membrane proteins.

    Integral proteins span the membrane and function as transporters, enzymes, or receptors. Peripheral proteins are loosely attached, support membrane structure, and function in enzymes, motor proteins, and cell connections.

  • What is the glycocalyx and its function?

    The glycocalyx is a sugar coating on the cell surface made of glycolipids and glycoproteins. It acts as a biological marker for cell recognition and helps the immune system distinguish self from nonself.

  • Name and describe the three types of cell junctions.

    Tight junctions form impermeable seals preventing fluid passage. Desmosomes are anchoring junctions that resist tearing. Gap junctions are channels allowing small molecules and ions to pass between cells.

  • What is the function of tight junctions?

    Tight junctions fuse integral proteins of adjacent cells to form an impermeable barrier that prevents fluids and molecules from passing between cells.

  • How do desmosomes contribute to tissue integrity?

    Desmosomes use linker proteins (cadherins) and keratin filaments to anchor cells together, allowing flexibility and reducing tearing under tension.

  • What role do gap junctions play in cells?

    Gap junctions form tunnels (connexons) that allow ions and small molecules to pass quickly between cells, facilitating electrical signal transmission in cardiac and smooth muscle.

  • What are the two main types of plasma membrane transport?

    Passive transport requires no energy and moves substances down their concentration gradient. Active transport requires ATP to move substances against their gradient.

  • What are the components of cytoplasm?

    Cytoplasm includes cytosol (gel-like fluid), inclusions (insoluble molecules like glycogen or pigments), and organelles (specialized structures, membranous or nonmembranous).

  • List the membranous and nonmembranous organelles.

    Membranous organelles: mitochondria, endoplasmic reticulum, Golgi apparatus, peroxisomes, lysosomes. Nonmembranous organelles: ribosomes, cytoskeleton, centrioles.

  • What is the function of mitochondria?

    Mitochondria produce most of the cell's ATP via aerobic respiration. They have double membranes with folds called cristae and contain their own DNA and ribosomes.

  • Describe the two types of ribosomes and their roles.

    Free ribosomes float in cytosol and synthesize proteins for use inside the cell. Membrane-bound ribosomes attach to rough ER and synthesize proteins for membranes, lysosomes, or export.

  • What are the differences between rough and smooth endoplasmic reticulum (ER)?

    Rough ER has ribosomes and synthesizes proteins for secretion or membranes. Smooth ER lacks ribosomes and functions in lipid metabolism, detoxification, glycogen breakdown, and calcium storage.

  • What is the role of the Golgi apparatus?

    The Golgi apparatus modifies, sorts, and packages proteins and lipids from the rough ER into vesicles for transport inside or outside the cell.

  • What are peroxisomes and their function?

    Peroxisomes contain enzymes that detoxify harmful substances like free radicals by converting them to hydrogen peroxide and then to water. They also metabolize fatty acids.

  • What are lysosomes and their functions?

    Lysosomes are membranous sacs with digestive enzymes that break down bacteria, viruses, toxins, and damaged organelles, and participate in intracellular digestion and autolysis.

  • What is the cytoskeleton and its components?

    The cytoskeleton is a network of protein rods providing structural support and movement. It includes microfilaments (actin), intermediate filaments (rope-like fibers), and microtubules (hollow tubes).

  • Describe the structure and function of microfilaments.

    Microfilaments are the thinnest cytoskeletal elements made of actin. They strengthen the cell surface, resist compression, and are involved in cell motility and shape changes.

  • What are intermediate filaments and their role?

    Intermediate filaments are tough, ropelike fibers that provide tensile strength, help resist pulling forces, and anchor desmosomes. Examples include keratin in epithelial cells.

  • What is the function of microtubules?

    Microtubules are the largest cytoskeletal elements made of tubulin. They determine cell shape, organize organelles, and serve as tracks for motor proteins moving substances within the cell.

  • What are the main structures of the nucleus?

    The nucleus contains the nuclear envelope (double membrane with pores), nucleoli (ribosomal RNA synthesis sites), and chromatin (DNA and proteins).

  • What is the nuclear envelope and its function?

    The nuclear envelope is a double membrane surrounding the nucleus, continuous with rough ER, with pores that regulate transport of molecules in and out of the nucleus.

  • What is chromatin and how is it organized?

    Chromatin consists of DNA, histone proteins, and RNA arranged in nucleosomes (DNA wrapped around histones). It condenses into chromosomes during cell division.

  • What are the phases of the cell cycle?

    The cell cycle has two major periods: interphase (cell growth and DNA replication) and mitotic phase (cell division including mitosis and cytokinesis).

  • What occurs during interphase?

    Interphase includes G1 (growth and metabolism), S (DNA replication), and G2 (preparation for division). Cells not dividing enter G0 phase.

  • What are the four stages of mitosis?

    Mitosis stages are prophase (chromatin condenses, spindle forms), metaphase (chromosomes align at equator), anaphase (chromatids separate), and telophase (nuclei reform).

  • What is the role of RNA in protein synthesis?

    RNA acts as a messenger and translator: mRNA carries DNA code, rRNA forms ribosomes, and tRNA brings amino acids to ribosomes for protein assembly.

  • What are the two main steps of protein synthesis?

    Protein synthesis occurs in transcription (DNA code copied to mRNA) and translation (mRNA decoded to assemble polypeptides).

  • What happens during transcription?

    Transcription transfers DNA base sequence to complementary mRNA by RNA polymerase, involving initiation, elongation, and termination phases.

  • How does translation occur?

    Translation decodes mRNA at ribosomes with tRNA bringing amino acids. It has initiation, elongation (codon recognition, peptide bond formation, translocation), and termination phases.

  • how many different types of cells are in the human body

    250

    • differ in size, shape, and subcellular components, these differences lead to differences in functions

  • Plasma membrane

    flexible outer layer