1. Chapter 3 Cell Structure and Function

2. What does the cell theory tell us? A cell is the basic unit of life All living things are made up of cells New cells arise from preexisting cells 3.1 What is a cell?

3. Cellular Organization Cell = smallest living unit Performs all life functions

4. Why are most cells small? Consider the cell surface-area-to-volume ratio: –Small cells have a larger amount of surface area compared to the volume –An increase in surface area allows for more nutrients to pass into the cell and wastes to exit the cell more efficiently –There is a limit to how large a cell can be and be an efficient and metabolically active cell 3.1 What is a cell?

5. Thinking about surface area to volume in a cell 3.1 What is a cell?

6. What are some common microscopes used to view cells? Compound light microscope –Lower magnification –Uses light beams to view images –Can view live specimens Transmission electron microscope –2-D image –Uses electrons to view internal structure –High magnification, no live specimens Scanning electron microscope –3-D image –Uses electrons to view surface structures –High magnification, no live specimens 3.1 What is a cell?

7. What are the two major types of cells in all living organisms? Prokaryotic cells –Thought to be the first cells to evolve –Lack a nucleus –Represented by bacteria and archaea Eukaryotic cells –Have a nucleus that houses DNA –Many membrane-bound organelles 3.2 How cells are organized

8. What do prokaryotic and eukaryotic cell have in common? A plasma membrane that surrounds and delineates the cell A cytoplasm that is the semi-fluid (cytosol) portion inside the cell that contains organelles DNA 3.2 How cells are organized

9. Where did eukaryotic cells come from? 3.2 How cells are organized

10. Eukaryotic Cell

11. Two Categories of Cells Sex cells (germ cells): –reproductive cells –male sperm –female oocytes (eggs) Somatic cells (soma = body): –all body cells except sex cells

12. Organelle Functions

14. The structures and functions of the cell membrane.

15. Plasma Membrane: Components Phospholipid bilayer Cholesterol: resist osmotic lysis Carbohydrates Proteins

16. Functions of Plasma (Cell) Membrane Physical barrier: –Maintain homeostasis: Separates intracellular fluid from extracellular fluid, different conditions in each Regulates exchange with environment: –ions and nutrients enter –waste and cellular products released Monitors the environment: –extracellular fluid composition –Cell communication and signaling Structural support: –anchors cells and tissues

17. Plasma Membrane: Components 1. Phospholipid Bilayer: –hydrophilic heads—toward watery environment, both sides –hydrophobic fatty-acid tails—inside membrane –barrier to ions and water soluble compounds 2. Cholesterol: resist osmotic lysis

18. 3. Carbohydrates: -linked to other molecules as proteoglycans, glycoproteins, and glycolipids -Functions -lubrication & protection -anchoring & locomotion -binding specificity *(acts as receptor) -self recognition Plasma Membrane: Components

19. 4. Protein: –½ mass of membrane –Integral proteins: span width of membrane within the membrane –Peripheral proteins: Adhere to inner or outer surface of the membrane

20. 6 Functions of Membrane Proteins 1.Anchoring proteins (stabilizers): – attach to inside or outside structures 2.Recognition proteins (identifiers): – Self identification by immune system – Label cells normal or abnormal 3.Enzymes: –catalyze reactions in cytosol in extra cellular fluid 4.Receptor proteins: – bind and respond to ligands (ions, hormones) or signaling, or import/export 5.Carrier proteins: – transport specific solutes through membrane 6.Channels: –regulate water flow and solutes through membrane

21. How things get in and out of cells.

22. Overcoming the Cell Barrier The cell membrane is a barrier, but: –nutrients must get in –products and wastes must get out Permeability determines what moves in and out of a cell: A membrane that: –lets nothing in or out is impermeable –lets anything pass is freely permeable –restricts movement is selectively permeable

23. Selective Permeability Cell membrane is selectively permeable: –allows some materials to move freely –restricts other materials Restricts materials based on: –size –electrical charge –molecular shape –lipid solubility

24. Selectively Permeable 3.3 The plasma membrane and how substances cross it

25. How do things move across the plasma membrane? 1. Diffusion 2. Osmosis 3. Facilitated transport 4. Active transport 5. Endocytosis and exocytosis 3.3 The plasma membrane and how substances cross it

26. Solutions All molecules are constantly in motion Molecules in solution move randomly Random motion causes mixing

27. Concentration Gradient Concentration is the amount of solute (glucose) in a solvent (e.g. H20) Concentration gradient: –more solute in 1 part of a solvent than another Function = Diffusion –molecules mix randomly –solute spreads through solvent –eliminates concentration gradient –Solutes move down a concentration gradient From high concentration to low concentration

28. What are diffusion and osmosis? 1. Diffusion is the random movement of molecules from a higher concentration to a lower concentration 2. Osmosis is the diffusion of water molecules 3.3 The plasma membrane and how substances cross it

29. How does tonicity change a cell? Hypertonic solutions have more solute than the inside of the cell and lead to lysis (bursting) Hypotonic solutions have less solute than the inside of the cell and lead to crenation (shriveling) Isotonic solutions have equal amounts of solute inside and outside the cell and thus does not affect the cell 3.3 The plasma membrane and how substances cross it

30. What are facilitated diffusion and active transport? 3. Facilitated transport is the transport of molecules across the plasma membrane from higher concentration to lower concentration via a protein carrier 4. Active transport is the movement of molecules from a lower to higher concentration using ATP as energy; requires a protein carrier 3.3 The plasma membrane and how substances cross it

31. Transport Vesicles 5. Endocytosis transports molecules or cells into the cell via invagination of the plasma membrane to form a vesicle 6. Exocytosis transports molecules outside the cell via fusion of a vesicle with the plasma membrane 3.3 The plasma membrane and how substances cross it

32. Receptor-Mediated Endocytosis Figure 3–21

33. Figure 3–22a Pinocytosis Pinocytosis (cell drinking) Endosomes “drink” extracellular fluid and enclose it in membranous vesicles at the cell surface –Similar to the steps in receptor-mediated endocytosis, except that ligand binding is not the trigger

34. Phagocytosis Phagocytosis (cell eating) –pseudopodia (psuedo = false, podia = feet) –engulf large objects in phagosomes Figure 3–22b

35. Cytoskeleton A series of proteins that maintain cell shape as well as anchors and/or moves organelles in the cell Made of 4 fibers: –Large microtubules Forms the foundation of the cytoskeleton Allows the cell to change shape and assists in mobility –Thin actin filaments provide additional strength by attaching the membrane to the cytoplasm Attach integral proteins to cytoskeleton Pairs with thick filaments of myosin for muscle movement –Medium-sized intermediate filaments strengthen cell and maintain shape stabilize position of organelles

36. Cilia and Flagella Made of microtubules Cilia are about 20x shorter than flagella Cilia: Short, numerous –Function: sweep substances over cell surface Flagella: Long, singular –Function: propel cell through environment 3.5 The cytoskeleton and cell movement

37. Structures involved in protein production Nucleus Ribosomes Endomembrane system 3.4 The nucleus and the production of proteins

38. The structure and function of the nucleus 3.4 The nucleus and the production of proteins Nucleus: –largest organelle Nuclear envelope: –double membrane around the nucleus, connected to ER Nuclear pores with regulator proteins: –Control exchange of materials between cytoplasm and nucleus

39. Within the Nucleus Nucleoplasm: –fluid containing ions, proteins (enzymes), DNA, RNA, and nucleoli Nucleoli: Dark areas –site of rRNA synthesis and packaging into ribosomal subunits In non-dividing cells DNA is loose  Called chromatin During Nuclear Division –Chromatin is tightly coiled into visible chromosomes (23 pairs in humans) Chromosomes –tightly coiled DNA (cells dividing)

40. The structure and function of ribosomes Organelles made of RNA and protein Found bound to the endoplasmic reticulum and free floating in the cell Site of protein synthesis 3.4 The nucleus and the production of proteins

41. The Endomembrane System A series of membranes in which molecules are transported in the cell It consists of the nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes and vesicles 3.4 The nucleus and the production of proteins

42. How does the endomembrane system function and appear? 3.4 The nucleus and the production of proteins

43. The parts of the endomembrane system Rough endoplasmic reticulum – studded with ribosomes used to make proteins Smooth endoplasmic reticulum – lacks ribosomes but aids in making carbohydrates and lipids Golgi apparatus – flattened stacks that process, package and deliver proteins and lipids from the ER –Phosphate, carbohydrates, or lipids are attached Lysosomes – membranous vesicles made by the Golgi that contain digestive enzymes Vesicles – small membranous sacs used for transport

44. Mitochondria A highly folded organelle in eukaryotic cells Produces energy in the form of ATP They are thought to be derived from an engulfed prokaryotic cell 3.6 Mitochondria and cellular metabolism

45. Mitochondrial Function: Power House of the Cell Aerobic respiration occurs on surface of cristae –takes chemical energy from food (glucose) –With the use of oxygen, Glucose is catabolized creating CO2 waste to convert ADP into ATP Mitochondria supply most of cell’s energy Have their own DNA (maternal) Can replicate independent of the cell Figure 3–9b glucose + oxygen + ADP carbon dioxide + water + ATP

46. Carbohydrate Catabolism (Metabolism) Carbohydrates are the primary source of cellular energy for most organisms Glucose is the most commonly used carbohydrate and will always be used first Generates ATP and other high-energy compounds by breaking down carbohydrates: glucose + oxygen  carbon dioxide + water 

47. Carbohydrate Catabolism (Metabolism) Two methods for ATP productions via catabolism of glucose 1.Cellular Respiration  Aerobic reactions: -Requires oxygen to serve as the final electron acceptor -Generate ATP in ETC -Most efficient method of ATP production -1 glucose generates 36 ATP -Involves reaction performed inside the mitochondria 2.Fermentation  Anaerobic reactions -Requires an organic molecule (carbon based) to serve as the final electron acceptor -Can be done in the absence of oxygen -ATP is synthesized using glycolysis -Less efficient, 1 glucose generates 2 ATP -In humans, results in lactic acid

48. Enzymes are important for cellular respiration and many activities in the cell Most enzymes are proteins Enzymes are often named for the molecule that they work on or substrates Enzymes are specific to what substrate they work on Enzymes have active sites where a substrate binds Enzymes are not used up in a reaction but instead are recycled Some enzymes are aided by non-protein molecules called coenzymes 3.6 Mitochondria and cellular metabolism

49. How do enzymes work? 3.6 Mitochondria and cellular metabolism

50. What is cellular respiration? Production of ATP in a cell Includes: 1.Glycolysis 2.Citric acid cycle 3. Electron transport chain 3.6 Mitochondria and cellular metabolism

51. What happens in glycolysis – step 1 of cellular respiration? Glycolysis –Occurs in the cytoplasm –Breaks glucose into 2 pyruvate –NADH and 2 ATP molecules are made –Does not require oxygen 3.6 Mitochondria and cellular metabolism

52. What happens in glycolysis – step 2 of cellular respiration? Citric acid cycle –A cyclical pathway that occurs in the mitochondria –Produces NADH and 2 ATP –Requires oxygen 3.6 Mitochondria and cellular metabolism

53. What happens in glycolysis – step 3 of cellular respiration? Electron transport chain –Series of molecules embedded in the mitochondrial membrane –NADH made in steps 1 and 2 carry electrons here –32-34 ATP are made depending on the cell –Requires oxygen as the final electron acceptor in the chain 3.6 Mitochondria and cellular metabolism

54. Oxygen is needed as the Final Electron acceptor in the ETC - At the end of the chain the electrons are accepted by oxygen creating an anion (O - ) inside, which has a strong affinity for the cations (H + ) outside. -Chemiosmosis generates ATP: - H + from the outside moves toward O - on the inside through special membrane channels that are coupled to ATP synthase - High-energy diffusion of H + drives the reaction ADP + P  ATP. - H+ combines with O - inside the mitochondria creating water (H 2 O)

55. Oxidative Phosphorylation Figure 25–5b Occurs on a membrane, the mitochondrial cristae, to generate most of the ATP produced from glucose

56. What other molecules besides glucose can be used in cellular respiration? Other carbohydrates Proteins Lipids Nucleic Acids 3.6 Mitochondria and cellular metabolism

57. Lipolysis – Lipid Catabolism Hydrolyzes triglycerides (fat storage)  glycerol and three fatty acids Glycerol: –Glycerol  pyruvic acids in the cytoplasm –Pyruvic acid catabolized through TCA in mitochondria Fatty Acids: –Fatty acids are catabolized –Enter the TCA as two-carbon fragments –For each two-carbon fragment of fatty acid produced by beta-oxidation, the cell can generate 17 molecules of ATP This is 1.5 times the energy production as with glucose Generates more energy but requires more oxygen –Occurs much more slowly than equal carbohydrate metabolism

58. Protein and Amino Acid Catabolism 1. Protein  amino acids 2. Amino group (-NH 2 ) is removed from amino acid in process called deamination –Requires vitamin B 6 3. Amino group is removed with conjunction with a hydrogen creating ammonia (NH 3 ) –Toxic 4. Liver converts the NH 3  urea –Harmless and excreted by the kidney 5. Remaining amino acid carbon chains are used at various stages in the Citric Acid Cycle to generate ATP –Amount of ATP produced varies

59. Amino Acid Catabolism Figure 25–10 (Navigator)

60. Protein and Amino Acid Catabolism Not a Practical Source of Quick Energy Typically only used in starvation situations Harder to break apart than carbohydrates or lipids Proteins are structural and functional parts of every cell –Thus tend to only be used when no other energy source is available Amino acids are simply recycled by hydrolysis of peptide bonds in one protein, to be reassembled by dehydration synthesis into the next.

61. Nucleic Acid Catabolism DNA is never catabolized for energy RNA can be broken down into: –Simple sugars –Nitrogenous bases Sugars: –Metabolized in glycolysis but only the pyrimidine bases (uracil and cytosine) can be processed in the TCA cycle Purines (adenine and guanine) are deaminated and excreted as uric acid making RNA metabolism very inefficient Typically nucleotides are simply recycled into new nucleic acid molecules and are not used for energy production