Exploring Cells: The Fundamental Units of Life

1. Unit 2 (Part 1) Cells

2. The Cell • Carry out all chemical activities needed to sustain life • Cells are considered the building blocks of all living things • Size can range from 2 micrometers to over a meter (nerve cells that cause you to wiggle toes) • Cells have different shapes, depending on function

3. Parts of the Cell • All cells share general structures, but do have specialized parts depending on the type of cell! • Cells are organized into three main regions: • Nucleus • Cytoplasm • Plasma Membrane • A special type of cell membrane!

4. The Nucleus • Function: contains DNA which codes for building your body and building proteins • Structure: 3 main parts - the nuclear envelope, nucleoli, and chromatin • Also: empty space filled with karyoplasm fluid

5. Parts of the Nucleus • Nuclear Envelope (Membrane): holds in the fluid, contains pores • Nucleoli: sites where ribosomes are assembled • Chromatin: bumpy threads formed from DNA coiling with proteins; will tighten into “chromosomes” during cell division

7. Plasma Membrane • Function: barrier that contains the cell contents and separates them from the environment • Structure: Double phospholipid layer • Hydrophilic (likes water) heads, made of phosphate • Hydrophobic (dislikes water) tails, made of 2 fatty acid chains

10. Plasma Membrane • Also: • Contains proteins, glycoproteins, cholesterol, and carbohydrates • Proteins serve as binding sites for hormones, and carriers to move substances through membrane

11. Cytoplasm • Function: site of most cellular activities • Structure: any material outside the nucleus and inside the plasma membrane • Cytosol: fluid that suspends elements • Organelles: metabolic machinery of the cell • Inclusions: other chemical substances, including fats & pigments (melanin = skin)

13. Cytoplasmic Organelles • Mitochondria – “Powerhouse of Cell” • Function: carry out reactions where oxygen is used to break down food, provides ATP (energy) for cellular processes • Structure: Sausage-shaped, double membrane (inner folds = cristae), actually has its own DNA

15. Cytoplasmic Organelles • Ribosomes – “Assembly” • Function: Site of protein synthesis (from amino acids) • Structure: made of proteins and ribosomal RNA, has a large & small unit • Also: Can be found free in the cytoplasm or attached to rough endoplasmic reticulum; assembled in the nucleoli

16. Cytoplasmic Organelles • Endoplasmic Reticulum – “Conveyor Belt” • Function: carries proteins (and other substances) from one part of the cell to another • Structure: fluid filled canals, two types • Rough ER: dotted with ribosomes, site where building materials of cellular membrane are formed • Smooth ER: cholesterol synthesis & breakdown, fat metabolism

18. Cytoplasmic Organelles • Golgi Apparatus – “Post Office” • Function: modifies and packages proteins (from the Rough ER) based on their final destination • Structure: stacks of flattened membrane sacs • Also: will fill up with proteins, and pinch off to form vesicles – which are then released into the cytoplasm to stay in the cell, or to be released through the plasma membrane

20. Cytoplasmic Organelles • Lysosomes – “Breakdown Bodies” • Function: digest worn-out cell structures or harmful substances (present in large number in White Blood Cells!) • Structure: sacs containing powerful digestive enzyme proteins (which were formed by ribosomes & packaged by golgi apparatus) http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__lysosomes.html

21. Cytoplasmic Organelles • Peroxisomes • Function: change dangerous free radicals (reactive chemicals with unpaired electrons) into hydrogen peroxide, then into water • Structure: sacs with enzymes

22. Cytoplasmic Organelles • Cytoskeleton – “Bones & Muscles of Cell” • Function: forms framework to determine cell shape, support organelles, and aid in movement • Structure: protein structures, 3 types • Microfilaments: cell motility & cell shape change (thinnest) • Intermediate Filaments: resist pulling forces • Microtubules: overall shape and distribution of organelles (thickest)

23. Cellular Projections • Not found in all cells • Two types… • Cilia: whip-like extensions, propel other substances along cell surface • Flagella: long extensions that move the cell itself, “tail” (ex: sperm)

24. Cell Diversity • So far, we have looked at an “average” human cell • However, cells vary greatly in size, shape, and function!

25. Types of Cells • Cells that connect body parts • Examples… • Fibroblasts have Rough ER & Golgi to make fiber proteins • Erythrocytes need room for pigment, so no organelles

26. Types of Cells • Cells that cover and line body organs • Ex: Epithelial Cells • Shape allows packing together

27. Types of Cells • Cells that move organs and body parts • EX: Skeletal Muscle & Smooth Muscle • Elongated so they can contract

28. Types of Cells • Cells that store nutrients • EX: Fat cell • Cells that fight disease • EX: Macrophage cell • Has “false feet” to move to infection sites, lysosomes to digest harmful substances

29. Types of Cells • Cells that gather information & control body functions • EX: Nerve cell • Long processes for sending & receiving messages

30. Types of Cells • Cells of Reproduction • EX: Oocyte (female egg) • Many copies of organelles for distribution to daughter cells • EX: sperm (male) • Flagellum used in movement

31. Membrane Transport • Membrane Transport: movement of substances in and out of the cell to maintain homeostasis • Transport is by two basic methods • Passive Transport • No energy is required • Active Transport • Cell must provide metabolic energy (ATP) • The membrane doesn’t let everything through – selective permeability

32. Passive Transport Processes • Diffusion • Particles distribute evenly through solution • Movement is from high concentration to low concentration

33. Passive Transport Processes • Types include: • Simple diffusion: solutes pass directly through plasma membrane • Osmosis: diffusion of water (solvent) from an area with little solute (high concentration of water) to an area with high solute (low concentration of water) • Facilitated diffusion: need a protein carrier to move through

34. Extracellular fluid Lipid- soluble solutes Water molecules Lipid-insoluble solutes Lipid bilayer Cytoplasm (b) Carrier-mediated facilitated diffusion via protein carrier specific for one chemical; binding of substrate causes shape change in transport protein (d) Osmosis, diffusion through a specific channel protein (aquaporin) or through the lipid bilayer (a) Simple diffusion directly through the phospholipid bilayer http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

35. Passive Transport Processes • Filtration • Water & solutes forced through a membrane by pressure • Pushed from area of high pressure to low pressure

36. Active Transport Processes • Transport substances that are unable to by diffusion • Reasons include: • Too large • Not able to dissolve in fatty acid core of membrane • Need to move against concentration (from low to high)

37. Active Transport Processes • Solute pumping • Amino acids, some sugars, and ions transported this way • ATP energizes protein carriers to move substances against concentration • Ex: sodium-potassium pump http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

38. Active Transport Processes • Bulk Transport (2 Types) • Exocytosis • Moves materials out of cell in a membranous vesicle

39. Active Transport Processes • Endocytosis • Moves materials into a cell in a membranous vescicle • Includes Phagocytosis (cell eating) and Pinocytosis (cell drinking)

41. Cell Division • Cell Life Cycle has two major periods • Interphase • Cell Grows • Cell carries on metabolic processes • At the very end, DNA replicates itself (in preparation for cell division) • Most of cell life is here • Cell division • Cell replicates itself • Produces more cells for growth and repair • Has two sections

43. Events of Cell Division • Mitosis • Nucleus Divides • Results in 2 daughter nuclei • Includes: Prophase, Metaphase, Anaphase, and Telophase steps • Cytokinesis • Cytoplasm divides • Results in 2 daughter cells http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

46. Prophase • The nuclear membrane is mostly gone. • Chromosomes have paired up according to homologous pairs (identical pairs). • Centrioles are at opposite ends of the cell.

47. Late Prophase Figure 3.32.3

48. Metaphase • Chromosomes are attached to spindle fibers by centromeres. • Chromosomes are lined up along the middle of the cell on spindle fibers.

49. Metaphase Figure 3.32.4

50. Anaphase • Chromosomes are pulled to opposite ends of the cell by spindle fibers. • Centromeres are pulled apart.