4.1 The Function of the Nucleus within the Cell Chapter 4 Notes

Survey of Animal and Plant Cells Cell membrane – controls the flow of material into and out of the cell Cell wall (plants) – tough, rigid structure that provides support Cytoplasm – jelly like substance that contains organelles (specialized cell parts that carries out specific functions) Mitochondria – provide energy for cells by changing sugar (glucose) into usable energy Chloroplasts (plants) – traps the Sun’s energy to make glucose Ribosomes – either attached to the endoplasmic reticulum or floats in the cytoplasm and produces proteins (essential materials for survival)

Survey cont. Endoplasmic reticulum – membrane covered channels that act as a transport system for materials made in the cell Vesicles – sacs formed on the ends of the ER that transport new proteins to the Golgi body Golgi bodies – sorts and packages proteins for transport Vacuoles – storage containers within cells Nucleus – controls all the activities of the cell and is surrounded by a nuclear membrane that protects it Nucleolus – inside the nucleus and makes ribosomes Nuclear pores – holes in the nuclear membrane that allows material into and out of the nucleus

Animal cell

Plant cell

Nucleus functions Deoxyribonucleic acid (DNA) Carries all the instructions Two stranded double helix (twisted ladder) sides of the ladder are phosphate and sugar “steps” are 4 nitrogen bases adenine (A) always joins thymine (T) guanine (G) always joins cytosine (C) How the bases are ordered gives us the codes for everything in our bodies

Dna diagram Exists as chromatin (DNA is uncoiled) most of the time   When a cell is ready to divide, each chromatin strand coils into a compact X-shaped chromosome Found in pairs; 23 in humans In males, the last pair is XY and XX in females

Dna cont. Genes are small segments of DNA located at specific places on a chromosome Only specific genes are “read’ in each cell to produce specific proteins (specialized) Specialized proteins called enzymes speed up chemical reactions Specialized proteins called hormones act as chemical messengers

Protein synthesis 1. The nucleus receives a chemical signal to make a specific protein 2. The DNA message for a specific protein is copied into a small molecules called ribonucleic acid (RNA) 3. RNA leaves through a nuclear pore 4. The RNA message is delivered to the ribosome and the ribosome makes the protein (like a factory) 5. The manufactured protein enters the endoplasmic reticulum

Protein synthesis cont. 6. A vesicle forms off the end of the ER and carries the protein to the Golgi body 7. The Golgi body repackages the protein for transport out of the cell 8. A vesicle forms off the end of the Golgi body to carry the protein to the cell membrane 9. The vesicle attaches to the cell membrane and its protein contents are released out of the cell

Protein synthesis pic