 All cells have a plasma membrane. ◦ Controls what gets in and out. ◦ Made of phospholipid molecules  All cells have cytoplasm ◦ Gel-like substance  All cells have genetic material ◦ Either DNA or RNA  All cells have ribosomes ◦ For making proteins

 Prokaryotic cells ◦ Smallest cells ◦ No nucleus or membrane-bound organelles ◦ Examples: Bacteria  Eukaryotic cells ◦ Complex cells ◦ Have a nucleus and membrane-bound organelles ◦ Examples: Plant cells and Animal Cells

 Most cells reproduce by dividing in two.  Before they can do this, they must copy all their genetic information, so that each new daughter cell has a full set of genetic material  The genetic material in eukaryotic cells is in the form of chromosomes.

 Humans have 46 chromosomes in the nucleus of every cell ◦ Two are the sex chromosomes (X and Y)  XX = female  XY = male ◦ The other 44 are called autosomes ◦ They occur in matching pairs  Called homologous chromosome pairs  One chromosome in each pair comes from mom and the other comes from dad

 Cells grow and reproduce just like every other living thing.  The cell cycle represents the life cycle of a typical eukaryotic cell.

 G1 phase: Cell grows  S phase: (synthesis) Cell copies its DNA  G2 phase: Cell continues to grow and get ready to divide  Mitosis: The cell divides the content of the nucleus  Cytokinesis: The cell divides its cytoplasm

 The G1, S, and G2 phase make up a stage called interphase. The cell spends most of its time in interphase.  The cell grows and copies DNA during interphase.

 Mitosis is when the cell divides the contents of the nucleus  Mitosis occurs in stages: ◦ Prophase ◦ Metaphase ◦ Anaphase ◦ Telophase

 Cytokinesis occurs when the rest of the cell divides. ◦ For animal cells---the cell membrane pinches in and the cell splits in two. ◦ For plant cells---an new cell plate forms to create a cell wall between the dividing cells.

 Prokaryotes (bacteria cells) reproduce by a process known as Binary Fission. ◦ DNA is circular (no chromosomes) ◦ DNA copies itself ◦ Cell divides…simple

 The reproductive cells divide by a different method….Meiosis.  The cell divides twice.  The result is four gamete cells (sperm and egg cells) with half the number of chromosomes.

 Fertilization—union of sperm and egg cell.  Sexual reproduction, involving the production of sperm and egg cells by meiosis followed by fertilization, ensures genetic variation in all offspring