Cell Structure and Functions Chapter 2

1. Cell Structure and FunctionsChapter 2

2. Cell Organelles

3. Nucleus • The largest organelle in animals • Contains the organism’s genetic material in the form of DNA • Controls cell function by regulating gene expression (protein synthesis) • Controls DNA replication during the cell cycle • Located towards the center of the cell for protection

4. Nucleus continued… • Nuclear envelope (membrane) – surrounds the nucleus to separate it from the cytoplasm • Contains pores to allow RNA and proteins to enter and leave the nucleus • DNA within the nucleus is in the form of chromatin

5. Nucleolus • Found within the nucleus • Function is to create rRNA and form ribosomes for gene expression • Ribosomes pass through the nuclear pores into the cytoplasm

6. Ribosomes • Consists of rRNA and proteins • Used during translation of gene expression by linking amino acids together to form proteins • Exist all through out the cell

7. Endoplasmic Reticulum • Two types: Rough and Smooth

8. Rough ER • Bumpy appearance due to ribosomes that cover the outside membrane • Synthesizes and packs proteins • Transports the proteins that are made from the ribosomes • Forms vesicles around the proteins and pinches off

9. Smooth ER • Smooth appearance because it lacks ribosomes • Acts as storage for ions and steroids for when the cell may need them. • Creates steroids and lipids • Breaks down toxic substances.

10. Vesicle • Small, membrane-bound spheres whose contents are isolated from the surrounding cytoplasm • Transport materials into and out of the cell using endocytosis and exocytosis

11. Endocytosis • Endocytosis: Movement of a substance into the cell • Cell membrane forms a pouch around a substance, then pinches off from the membrane to form a vesicle with the substance inside. • Vesicle is fused with a lysosome, which breaks down the membrane to release the food

12. Endocytosis continued… • Three types: Pinocytosis, phagocytosis, and receptor-mediated endocytosis • Pinocytosis: “cell drinking”. Cell is taking in a liquid substance such as extracellular fluid or dissolved particles. • Phagocytosis: “cell eating”. Cell is taking in a solid substance such as bacteria, debris, or other large objects

13. Phagocytosis Pinocytosis

14. Endocytosis: Receptor-mediated • Receptor proteins on the cell membrane recognize specific molecules that the cell needs • After ligand binds to receptor, a message is sent through the membrane to the nucleus

15. Endocytosis: Receptor-mediated • A protein coat forms when enough receptors are bound • Vesicle forms with the protein coat surrounding it • Vesicle will fuse with a lysosome to release the contents

16. Exocytosis • Movement of a substance by a vesicle to the outside of a cell. • Vesicle fuses with the membrane and releases contents, such as proteins.

17. Golgi Complex • Vesicles with newly made proteins are transported from the ER to the Golgi Complex. • A set of flattened, membrane-bound sacs that pack and distribute proteins • Enzymes within Golgi modify proteins and create new vesicles

18. Lysosomes • Vesicles with newly made proteins may stay in the cell and become lysosomes while some are released outside of the cell via exocytosis • Holds digestive enzymes • Breaks down the cell when it dies, damaged organelles, or foreign materials

19. Nucleolus creates ribosomes Ribosomes move to rough ER Ribosomes on rough ER create proteins Rough ER transports the proteins to the Golgi complex using vesicles The vesicles fuse with the Golgi complex The Golgi complex modifies the proteins using enzymes and creates another vesicle The new vesicle travels to the cell membrane to be released or stays within the cell to become a lysosome Overview…

20. Mitochondria • Harvests energy from organic compounds to make ATP • Some cells have much more mitochondria than others, such as muscle cells. • Contains two membranes – smooth outer membrane and a folded inner membrane with large surface area.

21. Mitochondria continued… • Also contains its own DNA and ribosomes • Where cellular respiration occurs

22. Cellular Respiration • Process of creating cell energy • The cell uses oxygen to break down glucose (sugar), which creates energy C6H12O6+ 6O2⇒ 6CO2+ 6H2O + energy Sugar + Oxygen ⇒ Carbon Dioxide + water + energy

23. Chloroplast • Only in plant cells • Contains chlorophyll – gives the plant a green color • Contains a double outer membrane. • Stroma - an area inside of the chloroplast where reactions occur and sugars are created

24. Chloroplast Continued… • Carry out photosynthesis by capturing light and creating energy • Energy is in the form of ATP: Adenosine Tri-Phosphate • Uses the sun to convert water and CO2 into oxygen and sugar 6CO2 + 6H2O⇒ C6H12O6 + 6O2 Carbon Dioxide + Water ⇒ Sugar + Oxygen

25. Cell Wall • Only found in plant cells • NOT the same as the cell membrane • Composed of proteins and carbohydrates (cellulose) • For support and shape of the cell – Rigid shape • Protects cell from damage – Strong structure • Connects with adjacent cells

26. Photosynthesis vs. Cellular Respiration

27. Vacuole • Are in both plant and animals cells, but much larger in plant cells. • Stores food, waste, and water • In plants, it stores a lot of water and takes up more than ½ of the cell’s volume. • Gives a plant cell support and structure

28. Animal vs. Plant Vacuoles