Chapter 6 Introduction to Cells

1. Chapter 6Introduction to Cells

2. COMMON CELL TRAITS • A cell is the smallest unit that is capable of performing life functions. • All organisms are made of cells

3. COMPARING CELLS • The size & shape of a cell relates to its function. (job it does)

4. TYPES OF CELLS • Every organism is one of TWO TYPES of cells • PROKARYOTIC (Pro- before) (Karyon- Kernel) In Prokaryotic cells, the DNA is concentrated in a region called the NUCLEOID with no membrane separating it from the rest of the cell

5. TYPES of CELLS • EUKARYOTIC (Eu- true) (Karyon -Kernel) Has a true NUCLEUS, bounded by a membranous nuclear envelope

6. SIZE Prokaryotic cells are smaller than Eukaryotic • Mycoplasmas (bacteria) = smallest cells between 0.1 and 1.0 Micrometers in diameter • Most bacteria are 1-10 Micrometers Eukaryotic cells are 10-100 Micrometers in diameter

7. Found in all cells • All cells have several basic features in common: • They are all bounded by a PLASMA MEMBRANE (thin skin). This membrane is a selective barrier that allows sufficient passage of Oxygen, Nutrients, and waste. • Within the membrane, is a semi-fluid substance called CYTOSOL (jelly-like)

8. Found in all cells • ALL cells contain CHROMOSOMES- carrying genes in the form of DNA • All cells have RIBOSOMES- Tiny organelles that make proteins • The interior of the cell- from the Plasma membrane to the Nucleus (Nucleoid) is called the CYTOPLASM

9. Prokaryotic Cells(proh KAYR ee yah tihk) • cells without membrane-bound structures • EX: bacteria pond scum Only the DOMAINS Bacteria and Archaea consist of Prokaryotic cells

10. Eukaryotic Cells(yew KAYR ee yah tihk) • cells with membrane-bound structures • EX: animals, plants, fungi and protists

11. NUCLEUS • Directs all cell activities • Contains instructions for everything the cell does • These instructions are found on a hereditary material called DNA • Usually the largest organelle

12. DNA & Chromosomes • In the nucleus, DNA is organized into discrete units called CHROMOSOMES- that carry genetic material • Each CHROMOSOME is made up of CHROMATID- a complex of proteins and DNA

13. NUCLEAR ENVELOPE • separates nucleus from cytoplasm • controls movement of materials in & out of nucleus • Is a DOUBLE membrane- each a lipid bilayer with associated proteins

14. NUCLEOLUS • Aka “little nucleus” • Found in the nucleus • Ribosomal RNA (rRNA) is synthesized from instructions in the DNA • Some Proteins are assembled by rRNA in the Nucleolus

15. RIBOSOMES-Protein Factories • Made up of Ribosomal RNA (rRNA) and Protein • Carry about Protein Synthesis (make Proteins) • Build Proteins in two locations..

16. RIBOSOMES * FREE RIBOSOMES are found floating in the CYTOSOL- proteins made here function within the cytosol * BOUND RIBOSOMES are found on the outside of the Endoplasmic Reticulum (ER)

17. Carries out a variety of tasks in the cell such as: Synthesis of proteins and their transportation Metabolism and movement of lipids Detoxification of poisons Includes: Nuclear Envelope Endoplasmic Reticulum (ER) Golgi Apparatus Lysosomes Vacuoles Plasma Membrane Chapter 6.4 Endomembrane System

18. Endoplasmic Reticulum: Biosynthetic Factory • Endoplasmic =“within the cytoplasm” • Reticulum = “Little Net” • A network of membranous tubules and sacs called Cisternae • Smooth and Rough ER

19. Functions of Smooth E.R.Smooth= Lacks Ribosomes • Smooth= Lacks Ribsomes • Enzymes of the smooth E.R. are important to: • Synthesis of Lipids (oils, phospholipids, Steroids) • Sex Hormones of Invertebrates • Detoxify drugs and poisons • Stores Calcium Ions

20. Functions of Rough E.R.Rough= Contains Ribosomes • Many types of specialized cells secrete proteins produced by Ribosomes attached to the rough E.R. • GLYCOPROTEINS- Proteins that have Carbohydrates covalently bonded are attached to the protein in the E.R. by specialized molecules built into the ER membrane

21. Transport Vesicles

22. Golgi Apparatus- Shipping and Receiving Center • After leaving the ER, many transport vesicles travel to the Golgi Apparatus • Golgi is a center for manufacturing, warehousing, sorting and shipping • In the Golgi, products of the ER are modified and stored and then sent to other destinations

23. Golgi Apparatus • Consists of flattened membranous sacs - CISTERNAE • The membrane of each cisterna in a stack separates its internal space from the Cytosol

24. Golgi Apparatus • Products of the ER are usually modified during their transit in the Golgi Apparatus • In addition to modifying products, the Golgi Apparatus manufactures certain macromolecules by itself • Macromolecules such as: Polysaccharides, including Pectins

25. Lysosomes • A membranous sac of hydrolytic enzymes that an animal cell uses to digest all kinds of macromolecules • Contain acidic enzyme to break down wastes • Excessive leakage from a large number of lysosomes can destroy a cell by autodigestion

26. Lysosomes • Hydrolytic enzymes and Lysosomal membrane are made by rough ER and then transferred to the Golgi apparatus for further processing • Lysosomes carry out intracellular digestion in a variety of circumstances

27. Phagocytosis (Phagein- to eat) (Kytos-Vessel) • Amoebas and other protists eat by engulfing smaller organisms by phagocytosis • The food vacuole formed this way then fuses with a lysosome, whose enzymes digest the food • Digestion products, including simple sugars, pass into the cytosol and become nutrients for the cell

28. Autophagy • Lysosomes use their hydrolytic enzymes to recycle the cell’s own genetic material- AUTOPHAGY • During Autophagy, a damaged organelle or small amount of cytosol becomes surrounded by a membrane and a lysosome fuses with this vesicle • With the help of Lysosomes, the cell continuously renews itself

29. Tay-Sachs Disease • Example of Lysosomal storage disease: • A lipid-digesting enzyme is missing or inactive, and the brain becomes impaired by an accumulation of lipids in the cells.

30. Vacuoles- Diverse Maintenance Compartments • In plant or fungal cells- similar to Lysosomes in animal cells • Food Vacuoles- formed by Phagocytosis • Contractile Vacuoles- pump excess water out of the cell, maintaining the appropriate concentration of salts and other molecules

31. Central Vacuole • Enclosed by a membrane called the TONOPLAST- selective in transporting solutes • Central Vacuole- holds reserves of important organic compounds such as proteins • Plant’s cell main repository of inorganic ions, such as potassium and chloride • Disposal sites for metabolic by-products • Some contain pigments or poisons

32. Chapter 6.5- Mitochondria and Chloroplasts • In Eukaryotic Cells, Mitochondria and Chloroplasts are the organelles that convert energy to forms that cells can use for work • MITOCHONDRIA- are the sites of cellular respiration, the metabolic process that generates ATP by extracting energy from sugars, fats and other fuels with the help of oxygen.

33. Mitochondria • Enclosed by two membranes- a phospholipid bilayer with embedded proteins • Outer membrane-smooth • Inner membrane is convoluted- with infoldings called CRISTAE • ATP is made in inner membrane • Highly folded- for large surface area for more protein contact

34. Chloroplasts • Found only in plants and algae, are the sites of PHOTOSYNTHESIS • They convert solar energy to chemical energy by absorbing sunlight and using it to drive the synthesis of organic compounds such as sugars from Carbon Dioxide and Water

35. Chloroplasts- Capture of Light Energy • Amyloplasts- colorless plastids that store starch • Chromoplasts- have pigments that give fruits and flowers their color • Chloroplasts- contain CHLOROPHYLL- for photosynthesis

36. Chloroplasts • Contain- THYLAKOIDS are stacked like poker chips • Each stack is called a GRANUM • The fluid outside of the Thylakoids- is the STROMA • Stroma contains the chloroplast DNA and Ribosomes as well as many enzymes

37. Peroxisomes- Oxidation • Contain enzymes that transfer hydrogen from various substrates to Oxygen, producing Hydrogen Peroxide as a by-product • These reactions have different functions- may break down fatty acids, may detoxify alcohol and other harmful compounds by transferring Hydrogen from the poisons to Oxygen

38. Chapter 6.6- CYTOSKELETON • A network of fibers extending throughout the cytoplasm- plays a major role in organizing the structure and activities of the cell • Gives structure and is also involved in several types of cell motility

39. CELL WALL • protects the cell • gives shape • is made of cellulose • A cell wall is found in plants, algae, fungi, & most bacteria.

40. CELL MEMBRANE • Outer covering, protective layer around ALL cells • For cells with cell walls,the cell membrane is inside the cell wall • Allows food, oxygen, & water into the cell & waste products out of the cell.

41. CYTOPLASM • gelatin-like inside cell membrane • constantly flows • aka protoplasm

42. CYTOSKELETON • scaffolding-like structure in cytoplasm • helps the cell maintain or change its shape • made of protein

43. CHROMATIN • contains genetic code that controls cell • made of DNA & proteins