Cell Biology Insights: The A&P of the Cell

1. The A&P of the Cell

2. The cell • The smallest living unit. • Your body consists of billions and billions of cell that are all working together to keep you alive.

3. Refresher: *The cell theory* • 1. A cell is the simplest living unit. • 2. The activity of an organism depends on both the individual and collective activities of its cell. • 3. The biochemical activities of cells are dictated by the relative number of their specific subcellular structures. • 4. Continuity of life from one generation to another has a cellular basis.

4. The composite/generalized cell • All cells generally have three main structures: • Cytoplasm • A plasma membrane • Genetic material

6. Cell Structures: The plasma membrane • The plasma membrane is the defining point of a cell. It separates the inside of the cell from the outside. • Another name for the plasma membrane is the phospholipid bilayer.

7. The phospholipid bilayer • Let’s break down the phrase phospholipid bilayer. • Bilayer= • Bi=two • Bilayer= two layers • Phospho=phosphate • Lipid=fat

8. Has a “head” that contains the choline, a nutrient necessary for building a cell membrane, and phosphate that causes a change in polarity on the cell surface. The head is called “hydrophyllic” because it is designed to touch water.

9. Has a “tail” that is a chain of fatty acids that are insoluble in water. They are called hydrophobic because the fatty acids avoid water at all costs.

10. Phospholipid bilayer- a two layer lining of phospholipids that have hydrophyllic “heads” that touch the inside and outside of the cell, and a hydrophobic “tail” that creates a barrier that defines what stays inside and what stays outside the cell.

11. Fluid Mosaic model • Fluid- movable • Mosaic- Structure made up of many different parts. • Fluid Mosaic Model- a multitude of different proteins float in the fluid bilayer.

12. Membrane lipids • Glycolipids-lipids with carbohydrate sugars attached. Also act as a cell surface marker.

13. Transmembrane proteins: Proteins that are in or on the lipid bilayer. Allows the transport of substances and information across the membrane. • Interior protein network: provides structural support and helps give membrane its shape. • Cell surface marker: “self”-recognition. Creates glycoproteins and glycolipids that give the cell its own identity.

14. Transporters: selective; only lets certain substances through. • Enzymes: carries out chemical reactions inside the cell membrane. • Cell surface receptors: Picks up chemical messages outside of the cell. • Glycocalyx: Gives the cell its own “ID” tag. • Cell adhesion proteins: allows cells to stick together…literally. • Cytoskeletal attachments: surface proteins that interact with other cells are often anchored by the cytoskeleton by linking proteins.

15. Cholesterol • Cholesterol is a steroid found in the cell membrane of all animalcells. • Cholesterol is needed to maintain the cell membrane, and can be produced in our bodies, and retrieved in the food we eat.

16. Membrane Transport • Although there is constantly information and materials moving back and forth to and from the cell by the access of a transmembrane protein, there are certain selective means by which these materials can enter the cell.

17. Methods of getting material through a membrane • Passive Processes • Diffusion • Osmosis • Filtration • Active Processes • Active Transport • Vesicular trafficking • Endocytosis • Exocytosis • Phagocytosis

18. Passive Processes • Diffusion- the tendency of molecules and ions to move from areas of high concentration to areas of low concentration.

19. Simple diffusion • Nonpolar and lipid soluble substances diffuse directly through the lipid bilayer. Includes oxygen, carbon dioxide, and fat soluble vitamins. • Example: oxygen in blood cells

20. Facilitated diffusion • Some molecules are way too large to fit through a membrane. These molecules, like glucose, need to either be ferried across by a carrier molecule, or it needs to be dissolved in a solution, like water and brought through a channel.

21. Facilitated diffusion

22. Osmosis • The diffusion of water through a semipermeable membrane is called osmosis. • Water can freely move in and out of the cell through specialized channels called aquaporins.

23. It is all about homeostasis:Tonicity • If two solutions have different concentrations of solutes, then the one with the higher concentration of solutes is called hypertonic. • The solution with the lower amount of solutes is called hypotonic. • If the two solutions are equal in solutes, it is called isotonic.

24. Tonicity: Animal Cell

25. Tonicity: Plant cell

26. Active Transport • Primary Active Transport- Sometimes, when we must maintain a certain concentration gradient of solutes regardless of the outside environment, we can expend ATP and use solute “pumps” to push a certain amount of solutes against a concentration gradient to maintain a particular level. • Example: sodium-potassium pumps

27. Primary active transport

28. Secondary active transport • As ions are built up inside a cell membrane, the ions that will eventually leak out can be used to facilitate transport. As these ions are leaking back down a concentration gradient, they can do work by taking other solutes with them.

30. Vesicular trafficking • Movement of large particles through the cell membrane through sacs called vesicles. • Exocytosis-shipping materials out of the cell. • Endocytosis- bringing materials from outside of the cell to inside the cell.

32. phagocytosis • Also known as “cell eating” • Phagocytosis is a type of endocytosis that brings in a large particle for digestion. These vesicles are usually brought to and combined with a lysosome that will release enzyme to break down the larger particle into smaller particles. Indigestible materials are then kicked out of the cell through exocytosis.

34. The plasma membrane’s interaction with the environment • The glycocalyx is a major player in the cell’s interaction with the outside. • Cell membrane can react with biochemicals and other hormones outside of the cell that may cause the cell to act or react to the outside environment differently.

35. Cell organelles Primary focus is on eukaryotes, as they have many membrane bound organelles.

36. Cytoplasm • Cellular material between the plasma membrane and the nucleus. Contains three major pieces: • Cytosol • Cytoplasmic organelles • Inclusions

37. Cytosol • A viscous semitransparent fluid that suspends other cytoplasmic elements. (i.e. organelles, solutes, etc.)

38. Inclusions • Chemicals that may or may not be present depending on cell type. (Melanin, glycogen granules)

39. Cytoplasmic organelles • Metabolic machinery of the cell. Each organelle has its own function.

40. Mitochondria • Structure: • Rodlike, double-membrane structures; inner membrane folded into projections called cristae. • Function: • Site of ATP synthesis; powerhouse of the cell.

41. Ribosome • Structure: • Dense particles consisting of two subunits, each comprised of rRNA and protein. Free or attached to rough endoplasmic reticulum. • Function: • The site of protein synthesis

42. Rough Endoplasmic reticulum • Structure: • Membrane system enclosing a cavity, the cisterna, and coiling through the cytoplasm. Externally studded with ribosomes. • Function: • Sugar groups are attached to proteins within the cisternae. Proteins are bound in vesicles for transport to the Golgi apparatus and other sites. External face synthesizes phospholipids.

44. Smooth ER • Structure: • Membranous system of sacs and tubules; free of ribosomes. • Function: • Site of lipid and steroids (cholesterol) synthesis, lipid metabolism, and drug detoxification.

45. Golgi body • Structure: • A sack of smooth membrane sacs and associated vesicle close to the nucleus. • Function: • Packages, modifies and segregates proteins for secretions from the cell, inclusion in lysosomes, and incorporation into the plasma membrane.

46. Lysosomes • Structure: • Membranous sac containing acid hydrolases. • Function: • Site of intracellular digestion.

47. Peroxisomes • Membranous sacs of oxidase enzymes. • The enzymes detoxify a number of toxic substances. The most important enzyme catalase, breaks down hydrogen peroxide.

48. Cilia • Structure: • Short cell-surface projections; each cilium is composed of nine pairs of microtubules surrounding a central pair. • Function: • Coordinated movement creates a unidirectional current that propels substances across cell surfaces.

49. Flagella • Structure: • Like cilium. But longer. • Example: sperm cells in humans. • Function: • Propels the cell.

50. Microvilli • Structure: • Tubular extensions of the plasma membrane; a bundle of actin filaments. • Function: • Increase surface area for absorption.