Transcript Cells
Cells The Basic Unit of Life Organelles • Special structures that perform specific functions in cells • Cell Animations Nucleus • Has a double-layered porous (with pores - very tiny holes) membrane • Contains DNA (deoxyribonucleic acid), DNA forms chromatin (long strands) and has instructions to assemble the necessary substances for building the cell and making it work • Has a nucleolus, a dark structure that manufactures ribosomes Cytoplasm • The area outside the nucleus and inside the cell membrane. The cell membrane separates the cell contents from its surroundings. • Jelly-like material • Supports nucleus and other organelles Ribosomes • Structures that make protein • Protein is used to make enzymes, muscle tissue, and other important structures Endoplasmic Reticulum • Series of canals • Canals are used to transport materials to different parts of the cells • Rough Endoplasmic reticulum has ribosomes attached Mitochondria • Transform energy for the cell Golgi Bodies • Package useful materials and secrete them to the outside of the cell for use elsewhere Vacuoles • Fluid-filled storehouses that contain water, food, wastes and other materials Lysosomes • Break down food and digest wastes and worn out cell parts The Cell Cycle • Cell division allows organisms to grow and develop • When cells divide, they must have a complete nucleus, so all the instructions in the DNA are reproduced • The process that makes this happen is MITOSIS Before Mitosis • Cells copy the chromatin so there are two sets of DNA • The chromatin coils up to form doublestranded chromosomes, joined by a centromere • Copy Figure 1.9 on page 17 Phases of Mitosis • • • • Remember PMAT Four major phases Results in two complete sets of DNA Prophase, Metaphase, Anaphase, Telophase Prophase • Chromosomes visible with a microscope • Nuclear membrane disappears • Spindle fibres form and stretch across the cell • Spindle fibres attach to centromeres Metaphase • Spindle fibres pull chromosomes into a line across the middle of the cell Anaphase • Spindle fibres shorten • Centromeres are pulled apart • Chromosomes move to the opposite (ends) poles of the cell Telophase • Final phase of mitosis • Spindle fibres disappear • Nuclear membrane forms around each set of chromosomes • Nucleolus appears • Single stranded chromosomes uncoil into strands of chromatin • The cell is ready to divide-cytokinesis Cell Division • After telophase • Animal cells - the membrane pinches together and the cell divides • Plant cells - a cell plate develops across the centre of the cell forming a new cell wall • Two new cells- daughter cells • Number of chromosmes in the nucleus of each cell is identical to the number in the original cell Interphase • • • • • • • • Inter- between Cell growth, replication of DNA Prepares for mitosis Refer to the cell cycle pie graph on page 23 Mitosis is ____ h Rapid growth is ____ h Growth and DNA replication is ____h Growth and preparation for division is ____ h