Cellular Level of Organization

1. Cellular Level of Organization

2. Cells • There are approximately 200 different types of cells that make up the basic structures of the human body. • Cell division creates new cells. A “parent” cell divides into two new “daughter” cells. • Different types of cells carry out different functions in the body.

3. Parts of a Cell • Plasma membrane • Cytoplasm • Cytosol • Organelles • Nucleus • Chromosomes • Genes

4. 3 main parts of a cell • Plasma membrane – the cells flexible outer surface. • Cytoplasm – all the cellular contents between the plasma membrane and the nucleus. • Nucleus – a large organelle that houses most of the cell’s DNA. Chromosomes and genes are contained here.

5. Typical Structures

6. Plasma Membrane • A flexible, yet sturdy barrier that surrounds and contains the cytoplasm of a cell. • Fluid mosaic model. • Lipid Bilayer • Membrane proteins • Membrane Permeability – Selective

7. Plasma Membrane continued… • Gradients • Concentration • Electrochemical • Osmosis • Diffusion • Active Transport

8. Lipid Bilayer • Phospholipids – 2 layers • Amphipathic – polar and nonpolar • Hydrophilic • Hydrophobic

10. Membrane Proteins • Integral Proteins – extend into or through the lipid bilayer. • Transmembrane proteins • Peripheral Proteins – attached to either the inside or outside of the membrane.

11. Functions of Membrane Proteins • Ion channel • Transporter • Receptor • Enzyme • Cell Identity Marker • Linker

13. Membrane Permeability • Selectively Permeable • Permeable to nonpolar, uncharged molecules, such as oxygen, carbon dioxide, & steroids. • Impermeable to ions and charged or polar molecules, such as glucose. • Slightly permeable to water and urea.

14. Gradients • Concentration Gradient – A difference in the concentration of a chemical from one place to another. • Electrochemical Gradient – The combination of the effects of the concentration gradient and the membrane potential.

16. Transport Across the Membrane • Passive Transport – does not require cellular energy. • Substances move down their concentration or electrochemical gradients using only their own kinetic energy. • Active Transport – requires cellular energy in the form of ATP.

17. 3 Types of Passive Transport • Diffusion through the lipid bilayer. • Diffusion through membrane channels. • Facilitated diffusion.

18. Endocytosis • Material enters the cell in vesicles.

20. Exocytosis • Material leaves the cell in vesicles.

21. Diffusion • Materials diffuse from areas of high concentration to areas of low concentration. They move down their concentration gradient. • Equilibrium – molecules are mixed uniformly throughout the solution.

23. Factors Influencing Diffusion • Steepness of the concentration gradient. • Temperature. • Mass of the diffusing substance. • Surface Area. • Diffusion distance.

24. Osmosis • The net movement of a solvent (water) across a selectively permeable membrane. • Water moves from an area of higher water concentration to an area of lower water concentration.

25. Osmotic Pressure • A solution containing solute particles that cannot cross the membrane exerts a force called osmotic pressure. • The greater the number of solute particles the greater the pressure.

27. Tonicity • A solution’s tonicity measures the solution’s ability to change the volume of cells by altering their water content. • Isotonic – cell maintains shape • Hypotonic – cell swells and bursts • Hypertonic – cell shrinks - crenation

29. Cytoplasm • 2 components • Cytosol – fluid portion that surrounds organelles. • 55% of total cell volume • Water with dissolved and suspended components • Ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, and waste products. • Organelles – specialized structures • Specific shapes • Specific functions

30. Cytoskeleton • Network of protein filaments. • Structural framework for the cell. • 3 Types of filaments • Microvilli – small – increase surface area • Intermediate filaments • Microtubules – largest – in cilia and flagella – participate in cell division.

31. Centrosome • Located near the nucleus • Plays a critical role in cell division

32. Cilia and Flagella • Comprised of microtubules. • Cilia – short, hairlike projections that extend from the surface of the cell. • Line respiratory tract • Movement is paralyzed by nicotine • Flagella – longer than cilia • Usually move an entire cell • Sperm’s tail

34. Ribosomes • Sites of protein synthesis • Free Ribosomes – located in cytosol • Attached to nuclear membrane and ER • In mitochondria

38. Endoplasmic Reticulum ER • Plasmic = cytoplasm; reticulum = network • Network of folded membranes • Transports substances throughout cell • Rough ER – ribosomes attached – synthesizes proteins • Smooth ER – synthesizes fatty acids and steroids

41. Rough ER

42. Smooth ER

43. Golgi Complex • Consists of 3 – 20 golgi cisternae (membranous sacs) • Modifies, sorts, and packages proteins for distribution • Proteins leave through secretory vesicles, membrane vesicles, or transport vesicles.

44. Lysosomes • Lyso = dissolving; somes = bodies • Contain powerful digestive enzymes and hydrolytic enzymes • Lysosomal enzymes can destroy their own cell – autolysis (due to pathology)

46. Lysosome

47. Mitochondria • Generate ATP – “powerhouses” of the cell

48. Mitochondrian with Matrix

49. Mitochondria

50. Nucleus • Spherical or oval shaped • Most prominent feature in the cell • Most structures have a single nucleus, although mature RBCs have none • Contain genes arranged in chromosomes • Genome – total genetic information for an organism