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Outcomes A and G Chapters 3, 4, and parts of 7

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1 Outcomes A and G Chapters 3, 4, and parts of 7
Unit 2: Cell Biology Outcomes A and G Chapters 3, 4, and parts of 7 Prepared by: Wendy Vermillion Columbus State Community College Reformatted for use at G.P. Vanier by Ilene Yeomans

2 A. Cellular Level of Organization
1. Cells are the smallest unit of life Exhibit all characteristics of life Are highly organized Many become specialized for complex functions 2. Cell theory All living things are composed of cells Cells are the functional and structural units of organisms All cells are derived from previously existing cells 3. Discovery of cells a) Antonie van Leeuwenhoek- invented the light microscope b) Robert Hooke- first observed cells in cork (actually saw the cell walls of dead cells) c) Schleiden and Schwann-proposed cell theory

3 Cellular level of organization, cont’d.
4. Cell size Most cells are smaller than 1 mm in diameter Surface area/volume ratio determines cell size:

4 Cell Size, cont’d. determining surface area to volume ratios
Cell Dimensions Surface Area Volume SA/Vol SA:Vol 1 cm x 1 cm 2 cm X 2 cm 6 cm x 6 cm Let L be the length of one side = L x L x 6 = L x L x L :1 :1 :1

5 Cell Size continued As the cell size increases, the volume increases faster than the surface area does Therefore small cells have a greater surface area to volume ratio than larger cells Nutrients from the environment must cross the surface of the cell to enter Cells must be small in order for the surface area to be adequate to supply nutrients This is one reason why we are made up of lots of cells instead of just one big one

6 Cellular level of organization, cont’d.

7 B. Eukaryotic cells Eukaryotic cells have a membrane-bound nucleus
Cell Membrane (or Plasma Membrane)

8 Eukaryotic cells, cont’d.
Organelles Subcellular structures which perform specific life functions for the cell Many organelles are found in both animal and plant cells Some are found exclusively in plants or animals Plants chloroplasts, large central vacuole, cell wall Animals centrioles

9 Animal cell anatomy Fig. 3.2

10 Eukaryotic Cells cont’d
Nucleus Contains the genetic material (DNA) Nucleoplasm -semifluid within nucleus Chromatin -threadlike DNA which has a grainy appearance Nucleoli (Nucleolus) -dark regions of chromatin These produce rRNA which makes up the two subunits of ribosomes when combined with protein Nuclear membrane - double layered, surrounds nucleus and has large pores

11 The Nucleus and Nuclear Envelope
Fig 3.4

12 C. Animal Cell Organelles
1. Ribosomes- Site of protein assembly (“Protein Synthesis”) Composed of rRNA and protein subunits Exist either as free ribosomes (in groups called polysomes) or bound to endoplasmic reticulum (ER) Polysomes produce multiple copies of the same protein for use inside the cell Proteins produced at the ER’s ribosomes are destined for export from the cell

13 2. Rough endoplasmic reticulum (RER)
Organelles, cont’d. 2. Rough endoplasmic reticulum (RER) Complex system of sacs and channels Has attached ribosomes Serves as site of assembly of proteins for export Assembled proteins enter channels for processing e.g. addition of sugar chains to form glycoproteins Released in vesicles 3. Smooth endoplasmic reticulum (SER) No ribosomes Synthesizes lipid products such as phospholipids and steroids AND is used to detoxify Product released in vesicles

14 The Endoplasmic Reticulum
Fig 3.5

15 4. Golgi Apparatus (or Golgi Body)
Organelles, cont’d. 4. Golgi Apparatus (or Golgi Body) Packaging and processing center for cell products Receives the vesicles from ER Vesicles fuse with Golgi and products are released inside Further modification of proteins occurs Products are packaged into secretory vesicles and released to travel to the cell membrane Golgi also produces lysosomes Easier to remember the functions with MRS Golgi = M (modify), R (repackage), S (sort)

16 The Endomembrane System
Smooth ER Rough ER Fig 3.6

17 5. Lysosomes Contain hydrolytic enzymes (very powerful enzymes)
Organelles, cont’d. 5. Lysosomes Contain hydrolytic enzymes (very powerful enzymes) Three functions of lysosomes: Intracellular Digestion lysosome fuses with a vesicle and digests its contents Autodigestion lysosomes fuse with worn out organelles or cell components and digest them (e.g. mitochondria) Autolysis lysosomes sometimes called “suicide sacs” because they release their enzymes into the cell causing cell death

18 The Endomembrane System
Fig 3.6

19 6. Mitochondria Site of aerobic cellular respiration
Organelles, cont’d. 6. Mitochondria Site of aerobic cellular respiration = production of ATP (energy) Uses oxygen we breathe and food that we eat to produce energy for every action in and of our body Up to 38 ATP are made per glucose molecule 6 O2 + C6H12O6  6 CO2 + 6 H2O

20 Mitochondrion Structure
Fig. 3.9

21 7. Peroxisomes Specialized vesicles Smaller than lysosomes
Organelles, cont’d…. 7. Peroxisomes Specialized vesicles Smaller than lysosomes Contain powerful oxidative enzymes Use oxygen to strip H’s from certain molecules Produce peroxide (H2O2), hence the name Role is detoxification Found in large numbers in liver cells

22 8. Vaults Serve as cellular transport vehicles (we think)
Organelles, continued 8. Vaults Serve as cellular transport vehicles (we think) Discovered in the early 1990s (do not show up with normal staining techniques) Shaped like octagonal barrels, hollow, 3X size of ribosomes Intriguingly, vaults are the same size and shape as nuclear pores Research supports vaults’ role in transport from the nucleus to the cytoplasm Unknown cargo, BUT are the right size to accommodate the two ribosomal subunits!

23 D. Cytoskeleton The Cytoskeleton Maintains cell shape
Allows cells to move or allows organelles to move within cells Made of protein Components include microfilaments and microtubules: Microfilaments are slender fibers that often occur in bundles e.g. ACTIN which works to contract muscles Microtubules protrude from the centrosome and form centrioles, cilia, and flagella

24 Eukaryotic cells, cont’d.
Centrioles see p60 Short tubules with 9+0 pattern of microtubule triplets In animal cells, centrosome is composed of 2 centrioles Believed to be involved in microtubule formation including mitotic spindle Basal Bodies Found at the bases of both cilia and flagella Organize the microtubules in the cilium or flagellum Have a 9+0 arrangement of microtubules.

25 Centrioles Fig. 3.14

26 E. Cellular Movement Cilia and Flagella
Cilia are generally multiple and hair-like Move mucus (phlegm) up the trachea Move the egg (or zygote) along the oviduct Flagella occur single or double and are whip-like Propel the sperm BOTH have a 9+2 pattern of microtubules

27 Structure of Cilia and Flagella
Fig. 3.15

28 The Cell Membrane

29 F. Cell (Plasma) Membrane
1. Membrane Structure Fluid-Mosaic Membrane Model (FMMM) Phospholipid bilayer Hydrophilic heads face surfaces Hydrophobic tails face inward Proteins Integral proteins- embedded Peripheral proteins- surface Glycoproteins and Glycolipids Cell markers (antigens) Cholesterol Changes fluidity of the membrane

30 Fluid-Mosaic Model of Membrane Structure
Fig. 4.1

31 Functions of the Cell Membrane
Cell Membrane cont’d Functions of the Cell Membrane Functions as a barrier between the cell and its environment Regulates what enters or exits the cell (Regulates transport of substances into and out of the cell) Contains receptors that determine how a cell will respond to stimuli in the environment Contains proteins that are important in immune responses It is a very dynamic, fluid structure

32 membrane protein diversity
Fig 4.2

33 G. Permeability of Cell Membrane
Cell membrane is selectively permeable Some substances pass through the membrane freely while others do not Crossing depends on factors like: size and shape of molecule, molecule’s chemical nature (e.g. lipid soluble?) temperature number of passages (channel proteins, carrier proteins, etc.) Rate depends on: concentration gradient of substance permeability of membrane to substance surface area of membrane molecular weight of substance distance travelled (thickness of membrane)

34 H. Passive Movement Passive Mechanisms (of crossing the cell membrane)
= no cellular energy required Kinetic energy drives passive mechanisms Movement is always from high concentration to low concentration ( = DOWN a concentration gradient)

35 Diffusion For instance:
Passive mechanisms…. For instance: Diffusion The movement of substances from an area of high concentration to an area of low concentration Drink crystals in water Perfume in a room The movement of lipid-soluble substances directly through the phospholipid bilayer from an area of high concentration to an area of low concentration Gases (oxygen and carbon dioxide) Alcohol

36 Process of Diffusion Fig. 4.4

37 2. Facilitated Transport
Passive mechanisms…. 2. Facilitated Transport The movement of small, lipid-insoluble substances such as simple sugars and amino acids across a cell membrane Uses a carrier protein Movement is down a concentration gradient High Low

38 Facilitated Transport
Fig. 4.8

39 Movement of Molecules Across Cell Membranes
Table 4.1

40 Passive Mechanisms Cont’d
3. Osmosis- A special case of diffusion = movement of WATER from an area of low solute concentration to an area of high solute concentration. The water moves to an area of high ‘saltiness’ in order to dilute the area Water moves through protein-lined pores (“aquaporins”) in the cell membrane. Osmotic pressure- force that causes water to move in a direction

41 Tonicity Isotonic solutions-no change
Hypotonic solutions-cause cells to swell and burst Hypertonic solutions-cause cells to shrink, or crenate

42 Osmosis demonstration
Fig. 4.6

43 Osmosis in animal and plant cells
Fig 4.7

44 Permeability of plasma membrane, cont’d.
I. Active Mechanisms = require ATP Active Transport Uses ATP Requires a carrier protein Transports molecules from an area of low concentration to an area of high concentration = (UP or AGAINST a concentration gradient) Example: sodium/potassium pump in nerve cells Iodine accumulation in the thyroid gland Low High

45 Active Transport Fig. 4.9

46 The Sodium-Potassium Pump
Fig 4.10

47 Active Mechanisms, cont’d.
2. Exocytosis Requires ATP Vesicle used Transports cell products and wastes (big stuff) out of the cell by vesicle formation Vesicles fuse with plasma membrane Products are released Vesicle membrane becomes part of the plasma membrane

48 Exocytosis Fig 4.11

49 Active Mechanisms, cont’d
3. Endocytosis Requires ATP Vesicle used Transports substances (big stuff) into the cell by vesicle formation membrane invaginates and surrounds a substance, then pinches off to form a vesicle

50 Pinocytosis-”cell drinking” material is liquid or small
Endocytosis, cont’d Pinocytosis-”cell drinking” material is liquid or small Receptor-mediated endocytosis is a specific type of pinocytosis which occurs in response to receptor stimulation b) Phagocytosis-”cell eating” material taken in is large like bacteria or cell debris

51 Endocytosis Fig 4.12

52 POINTS TO PONDER 1. The stomach has two different types of secretory cells. The chief cells secrete pepsinogen (the inactive form of the enzyme pepsin), while the parietal cells secrete hydrochloric acid. Both of these cell types have lots of mitochondria to make ATP. The chief cells use ATP to make pepsinogen. Parietal cells use ATP to actively transport H+ and Cl- from the blood into the cells. Only one of these cell types also has extensive RER and Golgi. Which one and why?

53 POINTS TO PONDER 2. One type of the affliction epidermolysis bullosa is caused by a genetic defect that results in production of abnormally weak keratin. Based on your knowledge of the role of keratin, what part of the body do you think would be affected by this condition?

54 POINTS TO PONDER 3. Colostrum, the first milk a mother produces, contains an abundance of antibodies (infection-fighting proteins). By what means would you suggest these Ab’s are transported across the cells of a newborn’s digestive tract into his or her bloodstream?

55 Clinical-1 Kevin J and his wife have been trying to have a baby for the past three years. On seeking the help of a fertility specialist, Kevin learned that he has a hereditary form of male sterility involving non-motile sperm. His condition can be traced to defects in the cytoskeletal components of the sperm’s flagella. Based on this finding, the physician suspected that Kevin also has a long history of recurrent respiratory tract disease. Kevin confirmed that he has had colds, bronchitis and influenza more frequently than his friends. Why would the physician suspect this?

56 Clinical-2 When William H was helping victims in an earthquake-ravaged region, he developed severe diarrhea. He was diagnosed as having cholera, a disease transmitted through unsanitary water supplies that is spread by fecal contamination. The toxin produced by the cholera bacteria leads to the opening of Cl- channels in the lining of the intestine. Cl- then floods into the intestine. How does this account for the diarrhea that is severe enough to kill many who have cholera?

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