Chapter 3 Flashcards
Define cell
A cell is the basic structural and functional unit of living organisms.
List the three major regions of a generalized cell and their functions
Plasma membrane: outer boundary
Cytoplasm: intracellular fluid packed with organelles
Nucleus: organelle that controls cellular activities
Describe the chemical composition of the plasma membrane and relate it to membrane functions
Fluid mosaic model: phospholipid bilayer of with protein molecules dispersed in it
Proteins allow communication and transport; Bilayer moves freely, but protects
Compare the structure and function of tight junctions, desmosomes, and gap junctions
Tight: impermeable, prevent molecules from passing through
Desmosomes: anchor cells together forming an internal tension-reducing network of fibers (molecular Velcro)
Gap: communicating junctions allow ions and small molecules to pass through
Relate plasma membrane structure to active and passive transport processes
Selectively permeable: allows some substances to pass while excluding others; Passive processes cross the membrane without energy input; Active processes requires energy to move substances across the membrane
Compare and contrast simple diffusion, facilitated diffusion, and osmosis relative to substances transported, direction, and mechanism
Simple diffusion: nonpolar and lipid-soluble substances diffuse directly though the lipid bilayer (oxygen, carbon dioxide), down concentration gradient
Facilitated diffusion: transported substance either binds to protein carriers or moved through water-filled protein channels (glucose, amino acids, ions), down concentration gradient
Osmosis: diffusion of a solvent (water) through a selectively permeable membrane, down concentration gradient
Differentiate between primary and secondary active transport
Primary: the energy to do work comes directly from hydrolysis of ATP
Secondary: driven indirectly by energy stored in ionic gradients created by primary active transport pumps
Compare and contrast endocytosis and exocytosis in terms of function and direction
Endocytosis: vesicular transport moves substances into the cell
Exocytosis: vesicular transport processes that eject substances from the cell interior into the extracelluar fluid; hormone secretion, mucus secretion, etc.
Compare and contrast pinocytosis, phagocytosis, and receptor mediated endocytosis
Pinocytosis: “cell drinking”; infolding plasma membrane surrounds a small volume of extracellular fluid containing dissolved molecules, uses ATP
Phagocytosis: “cell eating”; the cell engulfs some relatively large or solid material, uses ATP
Receptor-mediated endocytosis: the main mechanism for specific endocytosis, uses ATP
Define membrane potential and explain how the resting potential is established and maintained
Membrane potential: an electrical potential energy resulting from the separation of ions by the plasma membrane
Resting potential is established when diffusion causes ionic imbalances that polarize the membrane, active transport processes maintain it
Describe the role of glycocalyx when cells interact with their environment
- Anchor themselves to molecules and to each other (molecular “Velcro”)
- The “arms” that migrating cells use to haul themselves past one another
- SOS signals for white blood cells
- Mechanical sensors that respond to changes
- Transmitters of intracelluar signals
List several roles of membrane receptors and that of voltage-gated membrane channel proteins
Membrane receptors: Serve as binding sites; Contact signaling, chemical signaling
Voltage gated: Electrical signaling
Describe the composition of the cytosol
The fluid in which other cytoplasmic elements are suspended; made up of water, proteins, salts, sugars, and other solutes
Discuss the structure and function of the mitochondria
A double membraned, lozenge-shaped, organelle with inner membrane folds called cristae; provide the cell with most of its ATP
Discuss the structure and function of ribosomes, the endoplasmic reticulum, and the Golgi apparatus, including functional interrelationships among these organelles
Ribosomes: small, dark-staining granules composed of proteins and ribosomal RNAs; sites of protein synthesis
ER: system of interconnected tubes and parallel membranes enclosing fluid-filled cavities called cisterns; Rough contains ribosomes and assembles proteins; Smooth does not, but work with metabolism, synthesis, and detoxification
Golgi apparatus: stacked and flattened membranous vesicles that modify, concentrate, and package proteins and lipids from the Rough ER
Compare the functions of lysosomes and peroxisomes
Peroxisomes: detoxify harmful substances and neutralize free radicals
Lysosomes: contain enzymes that dispose of invading bacteria and cell debris
Name and describe the structure and function of cytoskeletal elements
Microfilaments: the thinnest elements of the cytoskeleton, semi-flexible strands of the protein actin; terminal web strengthens, resists compression, and transmits force
Intermediate filaments: tough, insoluble protein fibers that resemble woven ropes, most stable and permanent; attach desmosomes, act as guy-wires (resist pulling forces)
Microtubules: hollow tubules made of spherical protein subunits called tubulins; move organelles with help of motor proteins
Describe the role of centrioles in cell division and in formation of cilia and flagella
Generate microtubules and organize mitotic spindle in cell division; Form the bases of cilia and flagella
Describe how the two main types of cell extensions, cilia and microvilli, differ in structure and function
Cilia: whip-like, motile cellular extensions that move substances in one direction across cell surfaces
Microvilli: minute, fingerlike extensions of the plasma membrane that project from an exposed cell surface, increase surface area
Outline the structure and function of the nuclear envelope, nucleolus, and chromatin
Nuclear envelope: double membrane barrier separated by fluid-filled space; semipermeable for transport into and out of the cell
Nucleolus: dark-staining spherical bodies found within the nucleus where ribosomal subunits are assembled
Chromatin: system of bumpy threads weaving though the nucleoplasm, composed of DNA and histone proteins (nucleosomes); DNA constitutes the genes
List the phases of the cell cycle and describe key events of each stage
Interphase: G1, S, G2
Mitotic phase: Mitosis (Prophase, Metaphase, Anaphase, Telophase), Cytokinesis
Describe the process of DNA replication
- DNA helix is uncoiled and hydrogen bonds are broken
- Each strand acts as a template for the complementary strand
- DNA polymerases work in only one direction, so the strands are synthesized in opposite directions
- Each DNA molecule consists of one old and one new strand
Define gene and genetic code and explain the function of genes
Gene: a segment of a DNA molecule that carries instructions for creating one polypeptide chain
Genetic code: the rules by which the base sequence of a gene is translated into an amino acid sequence
Name the two phases of protein synthesis and describe the roles of DNA, mRNA, tRNA, and rRNA in each phase
- Transcription: DNA’s information is encoded in mRNA
- Translation: information carried by mRNA is decoded and used to assemble polypeptides using tRNA, to bind the amino acid and mRNA,and rRNA
Contrast triplets, codons, and anticodons
Triplets: a sequence of 3 DNA bases
Codon: corresponding 3 base sequence on mRNA
Anticodon: a 3 base sequence complementary to the mRNA codon calling for the amino acid carried by that particular tRNA
Define autophagy and indicate its major cellular function
Autophagy: “self eating”; sweeps up bits of cytoplasm and excess organelles into double-membrane vesicles called autophagosomes, which are sent to the lysosomes to be digested
Describe the importance of ubiquitin-dependent degradation of soluble proteins
Ubiquitins mark proteins that are to be hydrolyzed to small peptides by proteasomes, which provides amino acids for synthesis of new and needed proteins during starvation
Discuss some theories of cell differentiation and aging
-Wear and tear theory: little chemical insults and formation of free radicals
-Mitochondrial theory of aging: free radicals
-Immune system: autoimmune responses and weakening of immune response
-Inflammation
Genetic theory: cessation of mitosis and cell aging are programmed into our genes; telomere clock
Indicate the value of apoptosis to the body
Apoptosis eliminates excess cells that are stressed, no longer needed, injured, or aged.
- Carves out fingers and toes
- Develops nervous system
