Chapter 3

2. Cells and Tissues Chapter 3

3. Preview • Cells: Carry out all the chemical activities needed to sustain life. • Tissues: provide for a division of labor among body cells.

4. Cells • Robert Hooke, “cells” in monastery • Cube- like structures observed in cork. • Smallest unit, or the building block, of all living things. • Contain all the parts necessary to survive in a changing world. • Trillions in the body

5. Basics of Life • Primarily made of 4 Elements • Carbon, Oxygen, Hydrogen, Nitrogen • Trace Elements are also very important • Calcium- blood clotting • Iron- hemoglobin • Iodine- thyroid hormone • Calcium, Sodium, Potassium- electrical charge (ionic form) • Sodium and Potassium- Nerve impulses

6. Basics of Life • Cells are 60% water • Interstitial fluid • Dilute saltwater solution • All exchanges between cells and blood • Cells range widely in shape and size • 2 micrometers-1 meter • Vast difference in function and roles

7. Generalized Cell Anatomy • Although cell types vary, all cells do have the same basic parts and certain functions common to all cells. • Nucleus • Cytoplasm • Plasma membrane

8. The Nucleus • “headquarters” or the “control center” • Gene-containing • Genetic material, deoxyribonucleic acid (DNA) • Instructions for building proteins • Necessary for cell reproduction

9. Nuclear Envelope (membrane) • A double membrane barrier that bounds the nucleus. • Between the two membranes is a fluid-filled space • Two layers fuse and Nuclear Pores penetrate through • Nucleoplasm • Jellylike fluid inside the nuclear membrane • Place where other nuclear elements are suspended

10. Nucleoli • Usually 1 or more dark round stained bodies in the nucleus • Sites where ribosomes are assembled • Eventually migrate into the cytoplasm and serve as actual site of protein synthesis

11. Chromatin • When the cell is not dividing, its DNA combines with protein forming a loose network of bumpy threads that are scattered throughout the nucleus. • When the cell divides, the chromatin threads coil and condense to form dense, rod-like bodies - chromosomes

12. Plasma Membrane • Fragile, transparent barrier that contains the cell contents and separates them from the surrounding environment. • Phospholipids • Cholesterol • Hydrophobic • Hydrophilic • Microvilli • Greatly increase cell’s surface area for absorbtion

13. Plasma Membrane • Tight Junctions • Impermeable junctions the bind cells together into leakproof sheets • Desmosomes • Anchoring junctions that prevent cells subjected to mechanical stress from being pulled apart (skin cells) • Gap Junctions • Allow communication, chemicals can pass directly from one cell to another ( heart and between embryonic cells)

14. Cytoplasm • Material outside the nucleus and inside the plasma membrane. • Cite of most cellular activities • Cytosol- semitransparent fluid that suspends the other elements • Organelles • Metabolic machinery of the cell • Inclusions • Not functioning units, chemical substances that may/may not be present depending on specific cell type. • Most are stored nutrients or cell products (lipid droplets)

15. Cytoplasmic Organelles • “little organs” are specialized cellular compartments, each performing their own job to maintain the life of the cell. • Many bound by a membrane • Allows them to maintain an internal environment apart from surrounding cytosol

16. Mitochondria • Tiny threadlike organelle, they squirm,lengthen, and change shape almost continuously • Wall is a double membrane=2 plasma membranes • Outer is smooth • Inner protrusions called Cristae • Enzymes dissolved in mitochondria membrane form cristae membranes • Carry out reactions where oxygen is used to break down foods.

17. ATP in Mitochondria • When foods are broken down, energy is released- as heat and ATP molecules. • Provides energy for all cellular processes to take place • All living cells require a constant supply • “powerhouse” • The more metabolic a cell is the more mitochondria they have and more ATP they use. (liver and muscle cells)

18. Ribosomes • Bilobed, dark bodies made of proteins and ribosomal RNA. • The actual site of protein synthesis • Some free-float in the cytoplasm and manufacture proteins that function in cytoplasm. • Others attach to membranes, combination of ribosome and membrane is the rough endoplasmic reticulum.

19. Endoplasmic Reticulum • “network within the cytoplasm” • A system of fluid-filled cisterns that coil and twist through the cytoplasm • Mini-circulatory system for the cell; provides a network of channels for carrying substances (primary proteins) from one part of cell to another. • 2 forms, not all cells have both • Rough and Smooth Endoplasmic Reticulum

20. Rough Endoplasmic Reticulum • Studded with Ribosomes • All of the building materials of the cellular membranes are formed either in or on the ER. • “cells membrane factory” • The proteins made on the RER fold into the tubules and are dispersed to other areas of the cell in the Transport vesicles.

21. Smooth Endoplasmic Reticulum • Plays no role in protein synthesis • Lipid metabolism • Cholesterol • Fat synthesis and breakdown • Detoxification of drugs and pesticides • Liver cells and body cells that produce steroid-based hormones – have a large amount of Smooth ER.

22. Golgi Apparatus • “Traffic director” for cellular proteins • Stack of flattened membranous sacs usually found close to the nucleus • Modify and package proteins sent to it by the Rough ER via transport vesicles. • Proteins that are ready for transport accumulate, the sacs swell. • Sacs pinch off and form secretory vesicles. • FIGURE 3.6 PAGE 69

23. Lysosomes • “breakdown bodies”; cells demolition site • Membranous pouches containing powerful digestive enzymes. • Capable of digesting worn-out or non-usable cell structures and most foreign substances that enter the cell. • Enzymes they contain are formed by ribosomes in the Golgi Apparatus • Very abundant in the White Blood Cells.

24. Peroxisomes • Membranous sacs containing powerful oxidase enzymes that use molecular oxygen (O2) to detox a harmful or poisonous substances. • Alcohol • Formaldehyde • Most important role is to “disarm” Free Radicals. (numerous in Liver and Kidney) • Highly reactive chemicals with unpaired electrons that can scramble the structure of proteins and nucleic acids. • Convert free radicals to hydrogen peroxide (H2O2) which is then turned into water

25. Cytoskeleton • Elaborate network of protein structures extends throughout the cytoplasm. • Acts as the cells “bones and muscles” • Made up of the following: • Intermediate filaments- stable ropelike help form desmosomes and provide internal guy wires to resist pulling forces on the cell. • Microfilaments- (actin and myosin) involved in cell motility and in producing changes in cell shape • Microtubules- determine the overall shape of a cell and the distribution of organelles.

26. Centrioles • Lying close to the nucleus, they are rod-shaped bodies that lie at right angles to each other • Internally made up of fine microtubules • Cila- whip-like cellular extensions that move substances along the cell surface. • Ciliated cells in respiratory system • Flagella- projections formed by centrioles and substantially longer (tail-like) • sperm