CYTOLOGY Biology 221 Cellular Physiology

CELLULAR ACTIVITIES Transport systems – Movement within cells or across cell membranes The Cell Cycle –Activities of cells from formation to death or division Protein Synthesis – using DNA & RNA to make proteins

TRANSPORT SYSTEMS Passive Transport (does not require energy) Active transport (does require energy; ATP most common form)

PASSIVE TRANSPORT SYSTEMS Diffusion Facilitated diffusion Filtration Osmosis

DIFFUSION (Passive) Molecules in constant motion Solute molecules move from [high] to [low] Continues until Equilibrium (no more net movement)

Equilibrium

Diffusion Across Membrane

FACILITATED DIFFUSION Channel proteins or carrier proteins Allow diffusion of larger molecules & lipid insoluble molecules (e.g. Glucose)

Filtration (Passive) Small molecules forced across membrane Depends on pressure e.g. kidney filtration

OSMOSIS Diffusion of water across plasma membrane Water moves from [low solute] to [high solute]

Tonicity Concentration of solutes in a solution (relative to the concentration inside the cell) Isotonic = concentration is the same Hypotonic = lower concentration of solutes Hypertonic = higher concentration of solutes

Osmosis & Tonicity During osmosis, water moves into the more concentrated solution The net movement is from the hypotonic solution into the hypertonic solution

Osmosis in RBCs

ACTIVE TRANSPORT SYSTEMS Facilitated active transport Vesicular transport -Endocytosis -Exocytosis

FACILITATED ACTIVE TRANSPORT Molecules are moved against a concentration gradient Molecules move from [low] to [high] Proteins act as Carrier Molecules Sodium and potassium pump moves Na + out of cell and K + into cell; energy is required

Active Transport

ENDOCYTOSIS Materials accumulate at surface of plasma membrane Membrane evaginates or invaginates, pinches off Brings material into cell

Types of Endocytosis Phagocytosis - engulfment of large solids (e.g. WBCs & bacteria/viruses) Pinocytosis - engulfment of extracellular fluid

EXOCYTOSIS Secretory vesicles fuse to cell membrane Releases substances outside cell -Cellular products (e.g. secretion) -Cellular wastes

CELL CYCLE Interphase Cell Division -Mitosis (nuclear division) -Cytokinesis (division of the cytoplasm)

CELL CYCLE: INTERPHASE *High metabolic activity *Protein synthesis *DNA replication (46  92 )

CELL CYCLE: MITOSIS Growth & Repair 4 phases: -Prophase -Metaphase -Anaphase -Telophase

MITOSIS: PROPHASE  Chromatin condenses into chromosomes  Centrioles organize spindle  Spindle microtubules attach to chromosomes  Nuclear membrane disassembles

MITOSIS: METAPHASE  Spindle aligns chromosomes  Alignment is around “equator”  Alignment is random

MITOSIS: ANAPHASE  “Daughter” chromosomes separate  Chromosomes are moved toward poles  Cytoplasm elongates & cytokinesis begins

MITOSIS: TELOPHASE  “Reverse” of prophase  Chromosomes relax into chromatin  Nuclear membrane reassembles  Spindle breaks up

Cytokinesis Division of the cytoplasm & organelles Begins during Anaphase Completed at end of Telophase

Mitosis

CYTOLOGY PROTEIN SYNTHESIS

DNA codes for proteins The sequence of bases (nucleotides) carries the information Gene = a segment of DNA that codes for one polypeptide (simple protein) A single gene has between 300 – 3000 base pairs

DNA & RNA in Protein Synthesis DNA’s Bases: T, A, C, G Each strand of DNA is complementary to the other RNA’s Bases: U, A, C, G Messenger RNA is complementary to DNA & carries instructions from DNA to ribosomes

RIBONUCLEIC ACID (RNA) Messenger RNA (mRNA) -polynucleotide strand that is complementary to DNA -carries instructions from DNA to ribosomes Transfer RNA (tRNA) -transports specific amino acids to ribosomes Ribosomal RNA (rRNA) -part of ribosomes -site of protein synthesis

PHASES OF PROTEIN SYNTHESIS Transcription -Complementary mRNA is made from a DNA gene (sequence coding for a polypeptide) -Occurs in Nucleus Translation -mRNA’s information is used to assemble proteins with the help of tRNA & rRNA -Each 3-base sequence specifies one amino acid -Occurs in Cytoplasm

Overview of Protein Synthesis

Codon Table