1. A Tour of the Cell Chapter 4 Cell Organelles Wakefield 2015

2. Cells Made primarily of H, O, C, & N Though it also needs trace elements Contains about 60% water Extracellular and Interstitial Main solid consists mainly of proteins Macromolecule Structure Carbohydrate – C, H, O Protein – C, H, O, N Lipid – C, H, O, P Nucleic Acids – C, H, O, N Water – H, O

3. Cells Cells are very diverse Vary in length 2 micrometers to more than 3 feet Structure defines its function which are also very diverse

4. Microscopy Resolution A measurement of the clarity of the image The minimum distance between 2 points Magnification A ratio of an object’s image size to its real size Contrast The difference in brightness between the light and dark areas of an image

5. Cells Robert Hooke discovered the cell in the late 1600’s The smallest part of any living organism Contains all parts necessary to survive in changing environments

6. Microscopy Light Microscope (LM) Visible light passes through the specimen then magnified by glass lenses Uses prepared slides Wet mount Dry mount

7. Microscopy Transmission Electron Microscope (TEM) Used to study the internal structure of the cell Aims an electron beam through a very thin section of a specimen which has been stained with heavy metals to enhance the structure Uses magnets as lenses rather than glass Focuses on a monitor for viewing Disadvantage – specimen must be dead

8. Microscopy Scanning electron Microscope (SEM) Used to study detailed topographical images of a specimen Uses electromagnetic lenses to scan the surface of the sample – Usually coated with fine film of gold Disadvantage – specimen must be dead

9. Cytology – the study of the cell

10. Prokaryotic Cells vs. Eukaryotic Cells All cells have generalized features: Cytosol – semi-liquid fluid in which organelles are suspended – found in both pro & eukaryotic cells Organelles – small organs of cell – most found only eukaryotic cells Plasma Membrane – double layer of phospholipids which surrounds cell – found in both pro & eukaryotic cells Inclusions – Non-functioning parts of cell

12. NUCLEUS – CONTROL CENTER Located near the center of the cell Found in both plants & animals Found only in eukaryotic cells Contains the organism’s genetic material The cell (and organism’s) “blueprint” DNA – Deoxyribonucleic Acid Chromatin Genes Chromosomes

13. NUCLEOLUS – 1 OR MORE SMALL BODIES IN CENTRAL AREA OF NUCLEUS Located near the center of nucleus Found in both plants & animals Found only in eukaryotic cells Site for ribosome production which will migrate to cytoplasm

14. NUCLEAR ENVELOPE – (aka) NUCLEAR MEMBRANE Located surrounding the nucleus Found in both plants & animals Found only in eukaryotic cells Consists of a double-layer selectively permeable membrane with relatively large pores (nuclear pores) Serves to protect the nucleus and determines what enters & leaves nucleus

15. CHROMATIN– DNA (when it is not dividing) Located inside the nucleus Found in both plants & animals Found only in both prokaryotic and eukaryotic cells – just not within a membrane bound nucleus Consists of DNA (Genetic Material) Appears as loose bumpy granular material scattered throughout the nucleus

16. CHROMOSOME – DNA (when it is dividing) Located inside the nucleus Found in both plants & animals Found only in both prokaryotic & eukaryotic cells Consists of DNA (Genetic Material) Appears as shortened thick structures resembling X’s or curved lines – condensed chromatin material

17. CHROMASOME – CONDENSED CHROMATIN / DNA

18. PLASMA MEMBRANE – (aka) CELL MEMBRANE Surrounds the outside of the cell’s cytoplasm Found in both plants & animals Found only in eukaryotic cells & prokaryotic cells Consists of phospholipid bi-layer With a hydrophobic & hydrophilic side Functions to determine what enters and leaves the cell – is selectively permeable – selects which materials can pass across the membrane

19. PLASMA MEMBRANE – (aka) CELL MEMBRANE Specializations – Microvilli – tiny fingerlike projections that greatly increase the cell’s surface area Enhances cell’s absorption ability Small intestines

20. PLASMA MEMBRANE – (aka) CELL MEMBRANE Specializations – Membrane Junctions – varies structurally Tight Junctions Impermeable Bind cells together like a zipper Desmosomes Anchoring junctions which prevent cells from tearing apart (i.e. – skin to skin or skin to muscle)

21. PLASMA MEMBRANE – (aka) CELL MEMBRANE Specializations – Membrane Junctions – varies structurally Gap Junctions Connects adjacent cells with tubular connexons which look like hollow cylinders Found in the heart, embryonic cells Functions mainly in cell to cell communication

22. CYTOPLASM – Located outside the nucleus and inside the plasma membrane Found in both plants & animals Found in prokaryotic & eukaryotic cells Consists of 3 major elements Cytosol Organelles inclusions

23. Plasmodesmata Channels (in plants) which function to connect the cytoplasms of adjacent plants Similar to the desmosomes and gap junctions in animals

24. CYTOPLASM – 3 major elements of cytoplasm Cytosol – semitransparent fluid which suspends the organelles Organelles – “little organs” of cell where all cell functioning occurs Inclusions – non-functioning units of the cell such as lipid droplets,, melanin (color pigment), etc.

25. MITOCHONDRIA – (aka) POWERHOUSE OF CELL In the cell’s cytoplasm Found in both plants & animals Found only in eukaryotic cells only Consists of a double layer membrane surrounding “sausage-like” structures which can move and wriggle about Functions to carry out the reactions which use O 2 to break down food into cellular energy (ATP) Found most in metabolically busy cells such as the liver & muscle cells

26. RIBOSOME – cell’s protein factories In the cell’s cytoplasm – tiny dark bilobed bodies of protein Ribosomal RNA – (rRNA) Some float free but most are attached to the Rough Endoplasmic Reticulum Found in both plants & animals Found in eukaryotic cells as well as prokaryotic cells Not membrane bound in prokaryotic cells Functions synthesize proteins for cell

27. ENDOPLASMIC RETICULUM – (aka) ER In the cell’s cytoplasm Found in both plants & animals Found only in eukaryotic cells ONLY A “network” of tubules or “cisterns” Accounts for about ½ of cell’s membranes Location for ribosomes protein systhesis Functions to carry substances (primarily proteins) from 1 part of cell to another part of cell 2 forms – Rough ER & Smooth ER

28. ROUGH ENDOPLASMIC RETICULUM – (aka) ROUGH ER Rough ER Studded with ribosomes Site of ribosomsal protein synthesis Abundant in cells that export protein products Pancreas – insulin & other digestive fluids

29. SMOOTH ENDOPLASMIC RETICULUM – (aka) SMOOTH ER Smooth ER Plays no actual role in protein synthesis – Communicates with the Rough ER & functions in lipid metabolism Synthesis of lipids & steroid hormones Metabolism of carbs Detoxifies drugs & pesticides; Storage of Ca ions Abundant in: Liver Testes – to produce testosterone

30. GOLGI APPARATUS – (aka) GOLGI BODY Located in the cytoplasm of cell Found in both plant & animal cells Found in Eukaryotic cells only Functions to modify, package and transport prot eins 2 types – Transport Vesicles – modifies & packages proteins Secretory Vesicles – transports proteins from Golgi Apparatus to plasma mem brane

31. LYSOSOME – (aka) cell’s demolition sites Located in the cytoplasm of cell Found in animal cells Found in Eukaryotic cells only Functions to breakdown other materials Contain powerful “digestive” enzymes “digest worn-out or non-usable” cells or cell parts Exocytosis – transporting materials out of cell Abundant in white blood cells “digest” bacteria & other foreign substances

32. Cellular Digestive & Excretory Processes Endocytosis – cells taking materials INTO the cell Phagocytosis – taking in solid molecules Pinocytosis – taking in liquid molecules Exocytosis – cells passing materials OUT of the cell

33. PEROXISOME – Located in the cytoplasm of cell Found in both plant & animal cells – Eukaryotic only Contains powerful oxidase enzymes that use molecular O 2 to detoxify harmful substances Functions to disarm free radicals – highly reactive chemicals Can also convert H 2 O 2 to H 2 O Look like small lysosomes Abundant in the liver & kidneys

34. CYTOSKELETON – Located in the cytoplasm of cell Found in both plant & animal cells Functions to provide form & structure to cells Found in Eukaryotic cells only Made of protein components

35. CYTOSKELETON – Consists of 3 types of protein filaments Intermediate filaments – help form desmosomes to provide internal guy wires to resist pulling forces Microfilaments – such as actin & myosin – involved in cell motility and changes in cell shape (muscle cells) Microtubules – determine the overall shape of the cell and the distribution of organelles Important during cell division

36. CENTRIOLES – Located in the cytoplasm of cell – usually near the nucleus Found in both plant & animal cells Found in Eukaryotic cells only Rod-shaped bodies that lie at right angles to each other Made up of fine microtubules and form the mitotic spindle during cell division Some have cilia and/or flagella

38. Cilia & Flagella – Cilia - Microtubules used to move materials around outside of cell Usually many of these small projections surrounding the cell or at least the exterior surface of a cell Flagella – responsible for motility of the cell as a whole Usually only one or a few and are long whip-like structures

39. Vacuole Predominantly found in eukaryotic / plants Functions to Storage of water & other nutrients Breakdown wastes to be disposed of Hydrolysis of macromolecules Enlargement of vacuole is major mechanism in plant growth Can act as a pump to rid the plant of excess water Contractile Vacuoles

40. Chloroplasts Predominantly found in eukaryotic / plants Sit of photosynthesis – in leaf 7 other green organ of plants Contain the green pigment – chlorophyll Membranous system Thylakoid Granum Stroma a type of plastid Other examples are Amyloplast Chromoplast