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Cytology
“And nothing of theirs was lacking, either small or great” 1Sam 30:19
Cells
• units of structure and function of living things
• cytology/cell biology: study of cells; began in 1665
• cell theory: all living things composed of living units called cells; all cells come from
preexisting cells
• size of an organism determined by number of cells, not the size of cells
• cell variety [Fig. 22.2 p. 471]
Cell Design
• [Fig. 22.10 p.478]
• nucleus: spherical body often located near center of cell which contains genetic code
of cell (DNA: deoxyribonucleic acid) and serves as master control center
• separated from rest of cell by nuclear envelope - two separate layers with narrow
water-filled space between
• nuclear pores serve as gates regulating molecule transport
• DNA thought to be threaded through scaffold/nuclear matrix
• nucleolus: ribosome assembly (protein factories)
• cytoplasm: fluid medium for organelles
• cytoskeleton: internal skeleton composed of microtubules made of tubulin protein
arranged in complex lattice
• centrioles: cylindrical tubulin structures located in centrosome; microtubule-organizing
center (not found in plant cells)
• mitochondria: “power plants” of cells that oxidizes carbs and fats and uses the energy
to produce ATP (adenosine triphospate); smooth outer membrane; inner membrane
highly folded due to transport proteins, ion pumps, and large ATP generators; more
active cells need more mitochondria (cardiac muscle cells v. fat cells)
• chloroplasts: plant cells only; contain chlorophyll necessary for photosynthesis
• ribosomes: protein factories; assemble amino acids into complex protein chains;
smallest and most numerous of organelles
• endoplasmic reticulum (ER): network of interconnected sacs and tubules connected to
nuclear envelope and extending throughout cell
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ribosome attaches to ER and injects protein into internal cavity (lumen)
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1) rough ER: near cell's nucleus; rough appearance from ribosomes
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2) smooth ER: contains enzymes for fat production, breakdown of drugs and
waste products; abundant in cells involved in lipid metabolism (liver)
• golgi complex/apparatus: “shipping centers” of cell; stack of flattened membraneenclosed compartments; receives proteins manufactured in rough ER, modifies if
necessary, packages them in vesicles and ships to final destinations within or outside
of cell via microtubules
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lysosome: proteins destined for recycling dumped into lysosome to be broken down
by acidic interior and enzymes; also used to destroy bacteria that invades body cells
vacuoles: storage space which allow cells to regulate size and water pressure by
swelling or shrinking; more numerous and smaller in plants than animals
cell membrane [Fig. 22.12 p. 481]
-outer boundary later that separates cell from environment and controls what
enters/leaves cell
-made of phospholipids/lipid bilayer; membrane proteins function in bilayer
-membrane skeleton made of spectrin, reinforcing membrane; some attached
to actin
filaments enabling constriction of membrane
-ion pumps - membrane proteins that allow cell to pump (Na, K, Ca, H) to
preserve ion balance
-receptors - proteins that inform cell about outside environment; some detect
hormones
cell wall: only present in plants; stiffens cell, offers protection again pathogens;
composed of cellulose threads; lignin provides further strengthening in wood; xylem
cells designed to die when mature, leaving empty box to transport materials
Cell Life
cells must keep working to maintain homeostasis for self and organism
osmotic pressure: related to [solutes] in cell; water diffusing through semipermeable
membrane dependent on dissolved salts in cytoplasm
proper pH: maintain relative concentration of acids and bases; shift in pH
compensated by ion pumps
temperature: regulated by sweat, goose bumps
regulate food and waste in cytoplasm
proteins remove and replace old proteins; repair damaged DNA
Energy
• plants: photosynthesis transforms solar energy into chemical energy; occurs in
chloroplasts; 6CO₂ + 6H₂O + sunlight --> C₆H₁₂O₆ + 6O₂
• cellular respiration:
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ATP: adenine triphosphate serves as energy carrier; energy from carbs (glucose), fats,
proteins
1) in cytoplasm: breakdown of glucose; 2ATP produced; anerobic
2) in mitochondria: oxidation - 34ATP produced; waste products water, carbon
dioxide
Active Transport
• passive transport: diffusion [high] --> [low]
• active transport: [low] --> [high] with expenditure of energy
• endocytosis: taking in large substances [Fig. 22.16 p.485]
• phagocytosis: surround solid particles with cell membrane and engulf them (bacteria)
• pinocytosis: cell membrane allows liquid to enter then pinches off to entrap liquid
• exocytosis: secretion-containing vesicles move to the surface of the cell and open,
spilling contents to exterior
Cell Movement
• flagella: whiplike tail
• cilia: hairlike projections that extend from cell membrane
• bundled microtubules and motor proteins encased in flexible membrane; pull of
motor proteins slides microtubules past each other, causing bend
Cell Cycle and Mitosis
• cell cycle: reproductive process in which duplicate cell components constructed then
divided into two separate cells; cell cycle divided into:
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G1 (gap 1)/S (synthesis)/G2 (gap 2)/M (mitosis)
• G1/S/G2 - gap interphase; stage between cell division
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S - DNA replication
• Mitosis [Fig. 22.19 p. 488]
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chromatin organized into chromosomes (46 human)
• 1) prophase - cell packages DNA into chromosomes (paired, two stranded); single
chromatid
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nucleolus dismantled, nuclear membrane dismantled
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additional centrioles produced; new set moves to opposite end of cell
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spindle apparatus forms
• 2) metaphase - chromosomes attach to spindle apparatus and line up along “equator”
• chromatids separate
• 3)anaphase - chromatids dragged to opposite ends of cell
• 4) telophase - nuclear membrane reappears, new nucleus at each end of dividing cell;
chromosomes uncoil
• cytokinesis: cell membrane pinches in half (human/animal), cell wall forms (plant)
Homework
Section 22.1 #1-3
Section 22.2 #1-6
Section 22.3 #1-5
Finish mitosis lab