Chapters 3 & 4

Cells, DNA, Mitosis & RNA

Cells

• vary in size• vary in shape• measured in micrometers

A Composite Cell

• hypothetical cell• major parts

• nucleus• cytoplasm• cell membrane

Cell Membrane

• outer limit of cell

• selectively permeable – controls what moves in and out of the cell

•phospholipid bilayer • hydrophilic water-soluble “heads” form surfaces• hydrophobic water-insoluble “tails” form interior

Cytoplasmic OrganellesEndoplasmic Reticulum

• transportation system• Rough ER

• studded with ribosomes• protein and lipid synthesis

• Smooth ER• lipid synthesis• break down of drugs

Ribosomes• free floating or connected to ER• site of protein synthesis

Cytoplasmic Organelles

Golgi apparatus• group of flattened, membranous sacs (pancakes)• packages and modifies proteins then ships• “Fed Ex”

Mitochondria• powerhouse of the cell (energy) ATP• looks like a jellybean with squiggles

Cytoplasmic Organelles

Lysosomes• digest worn out cell parts or unwanted substances via enzymes•Like “Lysol” they kill unwanted things

Peroxisomes• break down organic molecules

Centrosome• two rod-like centrioles• distributes chromosomes during cell division

Cytoplasmic Organelles

Cilia• short hair-like projections• propel substances on cell surface

Flagellum• long tail-like whip• provides motility to sperm

Vesicles• membranous sacs• store substances •GA and ER packs things into vesicles!

Microfilaments and microtubules• thin rods and tubules• give cytoplasm strength• allows for movement of organelles

Cytoplasmic Organelles

Cell Nucleus

• control center of cell

• nuclear envelope• porous double membrane• separates nucleoplasm from cytoplasm

• nucleolus• dense collection of RNA and proteins• site of ribosome production

• chromatin• fibers of DNA and proteins• stores information for synthesis of proteins

Structure of DNA

Pages 115-117•Double helix•Sugar and phosphates on the sides•Bases pairs as the rungs

• Adenine and Thymine (2)•Cytosine and Guanine (3)

• DNA wrapped about histones forms chromosomes

DNA Replication

1. Unwind2. Unzip3. Complementary base

pairs (AT, CG)A. In orderB. Okazaki

fragments4. Proofreading enzyme5. Winds back up again

Simple Diffusion

• movement of substances from regions of higher concentration to regions of lower concentration• requires no energy, happens naturally

Facilitated Diffusion

• diffusion across a membrane with the help of a channel or carrier molecule•Still requires no energy

Osmosis• movement of water through a selectively permeable membrane from regions of higher concentration to regions of lower concentration• Diffusion of water• Still no energy needed

How osmosis affects the body, especially RBCs

• Isotonic solution- same inside and out, no net change

• Hypertonic solution- solution outside is stronger so water leaves the cell to dilute the outside; cell shrivels

• Hypotonic solution- solution outside is weaker so water goes into the cell to dilute the cell; cell swells and may burst

Filtration

• smaller molecules are forced through porous membranes• Ex: molecules leaving blood capillaries• Still requires no energy

Movements Into and Out of the Cell

Passive Transport• NO cellular energy• simple diffusion• facilitated diffusion• osmosis• filtration

Active Transport• carrier molecules transport substances across a membrane from regions of lower concentration to regions of higher concentration• “going against the flow”• REQUIRES ENERGY

Endocytosis• cell engulfs a substance by forming a vesicle around the substance•REQUIRES ENERGY

Pinocytosis- cell drinking Phagocytosis- cell eating

Exocytosis• reverse of endocytosis• substances in a vesicle fuse with cell membrane• contents released outside the cell• REQUIRES ENERGY

Transcytosis

• endocytosis followed by exocytosis• transports a substance rapidly through a cell• Ex: HIV crossing a cell layer

Movements Into and Out of the Cell

Passive (Physical) Processes• NO cellular energy• simple diffusion• facilitated diffusion• osmosis• filtration

Active (Physiological) Processes• REQUIRE cellular energy• active transport• endocytosis• exocytosis• transcytosis

The Cell Cycle

• 4 major stages • interphase• mitosis• cytokinesis•differentiation

Interphase

• very active period• cell grows• cell maintains routine functions

•Divided into 3 phases• G1 phase – cell grows and synthesizes organelles• S phase – DNA replication• G2 phase - more cell growth until mitosis occurs

Mitosis

• produces two daughter cells from an original cell• Stages (PMAT)

• Prophase – chromosomes become visible; nuclear envelope disappears; centrioles move to opposite sides

• Metaphase – chromosomes line up down the middle

• Anaphase – chromosomes move apart to opposite sides

• Telophase – chromosomes uncoil; nuclear envelope forms (opposite of prophase)

Mitosis

Cytokinesis

• begins during anaphase• continues through telophase• contractile ring pinches cytoplasm in half

Differentiation

Tumors

Two types of tumors• benign – usually remains localized• malignant – invasive and can metastasize; cancerous

Genes that cause cancer• oncogenes – activate other genes that increase cell division• tumor suppressor gene – normally regulate mitosis; if inactivated they will not regulate mitosis

RNA Molecules

Messenger RNA (mRNA) -• delivers genetic information from nucleus to the cytoplasm

• single polynucleotide chain

• formed beside a strand of DNA

• RNA nucleotides are complementary to DNA nucleotides (exception – no thymine in RNA; replaced with uracil)

• making of mRNA is transcription

RNA Molecules

Transfer RNA (tRNA) -• carries amino acids to mRNA• carries anticodon to mRNA• translates a codon of mRNA into an amino acid

Ribosomal RNA (rRNA) –• provides structure and enzyme activity for ribosomes

Protein Synthesis

Protein Synthesis