Chapter 3 Part 1: Cellular processes

1. Chapter 3Part 1: Cellular processes Anatomy and Physiology

2. Introduction • An adult human body consists of about 75 trillion cells. • There are at least 260 varieties of cells. • Cells differentiate considerably in size, shape, and function. • Cells have different, distinctive shapes that make possible their functions.

3. History • Late 1600’s, Robert Hooke was looking through a primitive microscope at some plant tissue (cork). • Saw cube-like structure that reminded him of monk’s rooms (cells) so he named the structure cells.

4. Overview of the Cellular Basis of Life • Cells are made up of 4 elements primarily: Carbon, Oxygen, Hydrogen, and Nitrogen. • The other elements are important for cell functions: • Calcium- blood clotting and other things. • Iron- necessary to make hemoglobin (carries oxygen in the blood. • Iodine is required to make the thyroid hormone that controls metabolism. • Calcium, potassium, and sodium- carry electrical impulse. Electrolytes. • Sodium and Potassium: nerve impulse and muscle contractions.

5. Overview of the cellular basis of life • Cells are about 60% water. • Interstitial fluid- all the cells of the body are constantly bathed in a dilute saltwater solution. • Comes from the blood. • All exchanges between cells and blood are made through this fluid. • Cell size: • 2micrometers (1/12000th of an inch) to over 1 meter (3 feet) • Long cells are nerve cells to your feet.

6. Overview of the cellular basis of life • Cell structure reflects the job. • Disk shaped - red blood cells • Threadlike extensions - nerves • Toothpick shaped - smooth muscle cells • Cube-like - epithelial cells • White blood cells - wander freely through the body tissue. And protect the body by destroying bacteria and other foreign substances.

7. Anatomy of a Generalized Cell • All cells have three main regions: nucleus, cytoplasm, and plasma membrane. • Nucleus- usually located near the center of the cell • Cytoplasm- semifluid in the cell • Plasma membrane- forms the outer cell boundary.

8. Nucleus • DNA- contains the blueprint that contains all the instructions needed for building the whole body • Instructions for building proteins. • If a cell ejects its nucleus it is programmed to die. • Nucleus usually forms to the cell shape so not always round. • Nucleus has three distinct regions: • Nuclear envelope • Nucleoli • Chromatin

9. Nuclear Envelope • Double membrane barrier • Between the two layers is fluid-filled moat. • At various points the two layers of the nuclear envelope approach each other and fuse- nuclear pores penetrate through the fused regions • Selectively permeable but much freer than else where because of large pores. • Encloses a jellylike fluid called nucleoplasm in which nucleoli and chromatin are suspended.

10. Nucleoli • One or more small, dark staining, essentially round bodies. • Ribosomes are assembled here • Then the ribosomes are released into the cytoplasm. • Ribosomes do protein synthesis.

11. Chromatin • Loose network of bumpy threads • When a cell is dividing to form two daughter cells the chormatin threads coil and condense to form dense, rodlike bodies called chromosomes

13. Plasma Membrane • Fragile transparent barrier that contains the cell contents and separates them from the surrounding environment. • Consists of 2 lipid layers arranged “tail to tail” in which protein molecules float. • Most of the lipid portion is phospholipids with a substantial amount of cholesterol. • The heads are polar (hydrophilic) • The tails are nonpolar (hydrophobic). These tails make the cell relatively impermeable to most water-soluble molecules.

14. Cell Membrane

15. Plasma Membrane • Some proteins are enzymes • Many proteins mounted on the cell exterior are receptors for hormones or other chemical messengers. • Most proteins are for transport functions. • Glycoproteins- are a sugar protein. The cell surface is a fuzzy, sticky area. • Determine your blood type • Changes in glycoproteins occur in cells that are being transformed into cancer cells

17. Specializations of the Plasma Membrane • Microvilli- tiny fingerlike projections that greatly increase the cell’s surface area for absorption so that the process occurs more quickly. • Membrane junctions- vary structurally depending on their roles. • Tight junctions- impermeable junctions that bind cells together into leakproof sheets that prevent substances from passing through the extracellular space between cells • Keep digestive enzymes from seeping into the blood stream.

18. Specializations of the Plasma Membrane • Membrane junctions • Desmosomes- anchoring junctions that prevent cells subjected to mechanical stress (skin cells) from being pulled apart. • Gap junctions- commonly seen in the heart and between embryonic cells, function mainly to allow communication. • Connexons- connected to neighboring cells.

20. Cytoplasm • The cellular material outside the nucleus and inside the plasma membrane. • Site of most cellular activity. Factory area • 3 major elements: cytosol, organelles, and inclusions. • Cytosol is semitransparent fluid that suspends the other elements. • Organelles are the metabolic machinery of the cell. • Inclusions are not functioning units but are chemical substances that may or may not be present • Include fat droplets, glycogen granules, pigments such as melanin, mucus and other secretory products and various crystals.

22. Cytoplasmic Organelles • Mitochondria- sausage-shaped organelles • Squirm, lengthen and change shape almost continuously. • Outer membrane is smooth but inner membrane has shelves called cristae. • Carry out reactions in which oxygen is used to break down foods. • Captured and used to form ATP molecules • Powerhouse of the cell • Liver cells and muscle cells have lots of mitochondria • Unfertilized egg has few mitochondria

23. Cytoplasmic organelles • Ribosomes- tiny round, dark bodies made of proteins and one variety of RNA called ribosomal RNA. • Protein synthesis • Some float free in the cytoplasm and others attach to membranes. • Rough endoplasmic reticulum has ribosomes attached to it.

24. Cytoplasmic organelles • Endoplasmic Reticulum- is a system of fluid-filled cisterns that coil and twist through the cytoplasm. • Mini circulatory system for the cell • Carries substances - mostly proteins • Rough ER has ribosomes (export proteins) • Smooth ER continuation of the rough variety. Does not do protein synthesis. It does cholesterol synthesis and breakdown (fat and detoxification of drugs) found in the liver and testes

25. Cytoplasmic organelles • Golgi Apparatus- appears as a stack of flattened membranous sacs, associated with swarms of tiny vesicles. • Traffic director of the cell • Modify and package proteins • Sends proteins out of the cell. • Secretory vesicles pinch off and go to the cell membrane and fuse with the membrane. The membrane then ruptures to the outside of the cell. • Mucus and digestive enzymes are packaged this way.

26. Cytoplasmic organelles • Lysosomes- breakdown bodies, appear in different sizes and are membrane bags containing powerful digestive enzymes. • Eat nonusable or worn-out cell structures and foreign substances that enter the cell. • Demolition site. • Abundant in white blood cells • Homeostatic Imbalance: • If the lysosomal membrane becomes fragile when a cell is injured or deprived of oxygen and when excessive amounts of vitamin A are present the cell self digests.

27. Cytoplasmic organelles • Peroxisomes- membranous sacs containing powerful oxidase enzymes that use molecular oxygen (O2) to detoxify a number of harmful or poisonous substances (alcohol and formaldehyde) • Disarm dangerous free radicals: highly reactive chemicals with unpaired electrons that can scramble the structure of proteins and nucleic acids. • Convert free radicals into hydrogen peroxide • Catalase converts excess hydrogen peroxide into water. • Liver and kidney cells which both are very active in detoxification

28. Cytoplasmic organelles • Cytoskeleton- elaborate network of protein structures extends throughout the cytoplasm. • Act as cell’s bones and muscles • Determines cell shape • Intermediate filaments- help form desmosomes - provide internal guy wires to resist pulling forces • Microfilaments- cell motility and in producing changes in cell shape • Microtubles- tubelike, distribution of organelles and are very important during cell division

29. Cytoplasmic organelles • Centrioles- paired lie close to the nucleus • Rod-shaped bodies that lie at right angles to each other • Made up of fine microtubules • Mitotic spindle

30. Cytoplasmic organelles • Cilia- whip-like cellular extensions that move substances along the cell surface. • Flagella- sperm tail that helps with movement.

31. Cell Physiology • Membrane Transport- • Solution- homogeneous mixture of 2 or more components. • Solvent- dissolving medium (body has water) • Solutes- substances that are present in smaller amounts. • Intracellular fluid- solution containing small amounts of gases (oxygen and carbon dioxide) nutrients, and salts, dissolved in water. • Interstitial fluid- continuously bathes the exterior of our cells • Selective permeability- means that a barrier allows some substances to pass through it while excluding others.

32. Passive Transport Processes: Diffusion and Filtration • Diffusion- the process by which molecules tend to scatter themselves throughout the available space. • The speed of diffusion is affected by the size of the molecules (the smaller the faster and the warmer the faster). • Molecules move passively through the membrane if: • They are small enough to pass through its pores • They can dissolve in the fatty portion of the membrane. • Simple diffusion- unassisted diffusion of solutes through the plasma membrane. • Lipid-soluble or small enough to pass through the membrane pores. • Osmosis- diffusion of water through a selectively permeable membrane • Facilitated diffusion- means for certain needed substances (glucose) to enter the cell.

34. Filtration • The process by which water and solutes are forced through a membrane by fluid. • Pushes a fluid from a high pressure to a low pressure. • Kidneys • Not selective process

35. Active Transport Processes • Solute pumping- similar to facilitated diffusion • Uses ATP to energize its protein carriers instead of kinetic energy. • Solute pumps pump the ATP to the molecules • Amino acids and some sugars and most ions • Nerve cell transmissions

36. Active Transport Processes • Bulk Transport- • Exocytosis- out of the cell • Secretes hormones, mucus, and other cell products • Packaged before released into a vesicle • Endocytosis- into the cell • Released into the cytoplasm. • Phagocytosis • Bulk-phase endocytosis- the cell forms a tiny pit and then its edges fuse around the droplet of extracellular fluid unlike phagocytes this is routine activity for a cell.

38. Cell division • 2 major periods: interphase and cell division • Interphase is really metabolic phase not resting phase. • Events of cell division: • Mitosis: 1st is division of nucleus and 2nd cytokinesis is division of the cytoplasm (happens when mitosis is nearly completed)

39. Cytokinesis • Occurs during late anaphase and completes during telophase. • At the end two daughter cells exist. • Genetically identical to the mother cell • Carry out normal cell activity until it is their turn to divide. • Sometimes the cytoplasm does not divide. This leads to binucleate or multinucleate cells. • Fairly common in the liver. • Mitosis gone wild is the basis for tumors and cancers.

41. Metabolism and T3 and T4 hormones • The sum total of the chemical reactions that occur in the body • T3 and T4 are thyroid hormones that are required for normal development of brain tissue. Also normal metabolism of the body. • Too little you have lack of concentration and focus • Can also cause infertility. • Too much leads to anxiety disorders. • Iodine required for normal thyroid activity.