Cell organelles

1. Cell organelles

3. Nucleus • Largest organelle in eukaryotic cells • Control center of the cell • Contains DNA scattered throughout as Chromatin • Consists of:

4. 1. 2 membranes surrounding the nucleus: each a phospholipid bilayer • Outer bilayer continues into the endoplasmic reticulum • Inner bilayer defines the nucleus • NUCLEAR PORES are found on the membrane • regulates movements of material between nucleus and cytosol

5. 2. Nucleolus • Condensed area of chromatin in the nucleus • Synthesizes: • Ribosomal RNA (rRNA) • Ribosomal Protein/subunits • **These travel through the nuclear pores into the cytosol.

7. Chromosomes: • Linear structures composed of DNA molecules • Found in nuclei of eukaryotic cells • Total DNA in the chromosomes of an organism is referred to as its genome

8. DNA is wound around Proteins called histones. Histones help keep the DNA organized. • A series of histones and DNA is called a nucleosomes. • A Chromosome is composed of many nucleosomes.

9. Each chromosome consists of 2 identical sister Chromatids (Each consisting of one double-stranded DNA molecule) • Chromatids are attached at a specific region called a centromere.

10. Note: When cell division is not happening, chromosomes are uncoiled and may be called chromatin.

13. Cytoplasm: • Gel-like material • Found between the nucleus and cell membrane • Consists: • Mostly of water • Many organelles • Protein-rich • Enzymes • Creates the chemical environment in which the other cell structures function

16. Ribosomes: • Location: • Free ribosomes in the cytoplasm are attached to cytoskeletal filaments • Ribosomes can also be attached to the endoplasmic reticulum making it ‘Rough’ Endoplasmic reticulum.

17. Structure: • 2 Subunits • 1 large subunit (50S) • 1 small subunit (30S) Total of 80S **In prokaryotes, ribosomes contain 2 subunits but only add up to 70S • Both composed of • Ribosomal RNA and • Protein

18. Function: • Translate RNA (coming from the nucleus) into protein. (Protein synthesis) • Ribosomes attached to the Endoplasmic Reticulum (ER) produce proteins that move into the ER.

21. Endoplasmic Reticulum (ER) • Membrane bound network of interconnected vesicles • Enzymes are found embedded on the surface of the ER. • Materials synthesized here include: • Membrane phospholipids and cellular lipids • Sex hormones (testosterone and estrogen) (In Specialized cells ex. testicular cells produce testosterone) • Production of Insulin (ex. liver) Other functions at this site include: • Storage of calcium ions until they are needed in muscle contractions. • Transporation of lipids to different parts of the cell. • The ER keeps these materials from the rest of the cell. If not, they may have harmful effects to the cell.

22. There are 2 types: • 1. Rough Endoplasmic Reticulum (RER) • Ribosomes are attached to the ER – ‘Rough’ These ribosomes synthesize: • Proteins • Digestive Enzymes • As they are synthesized they move into the ER to become modified

23. 2. Smooth ER • Synthesis of : • Membrane lipids (fatty acids and phospholilpids) • Membrane Proteins

25. Once synthesized and modified in the ER, the materials are carried to the golgi complex through vesicles • Vesicles are formed from portions of membrane from the ER budding off to form a small membrane bound transport ‘vehicle’.

27. Golgi Apparatus or Golgi Complex • Location and structure: • Series of flattened saucer shaped sacs • Located near the nucleus

28. Function: • Vesicles transfers macromolecules from the ER to one golgi complex sac. (The Cis side) • Golgi complex completes the processing of these molecules making them ‘functional’.

29. They also get sorted, packaged and transported out of the complex by a second set of transport vesicles. (On the opposite side called the Trans side) • Vesicles then travel to the cell membrane and secrete their contents into the extracellular fluid

32. Lysosomes: • Structure: • Special vesicle formed from the golgi complex Function: • Transports cellular digestive enzymes safely through the cytoplasm • Degrades: • Worn out cellular components • Foreign molecules

33. I.e. • Contains enzymes such as: • 1. Nuclease: Degrades RNA & DNA into nucleotides • 2. Proteases: Degrades Proteins and peptides • 3. Phosphatases: Remove phosphate groups from nucleotides, phospholipids

34. Tay-Sachs Disease • Commonly found in the Jewish Population • Non-Jewish people are 100 times less likely to have the Tay-Sachs gene • Children Born with Tay-sachs: • Appear normal at birth • Central nervous system begins to deteriorate rapidly • Motor development slows down • Most children that have Tay Sachs die by the age of 2 or 3 years.

35. How does it occur? • A recessive gene is inherited from both parents • Lacks the gene to produce a lysosomal enzyme that breaks down a certain glycolipid called gangliosides found in nerve cells • Nerve cells are therefore, greatly enlarged with swollen lipid-filled lysosomes • Nerve cells are eventually destroyed

36. Cell Organelles Continued

38. Mitochondria FYI: • Evidence shows, mitochondria evolved from bacteria that were endocytosed into ancestral cells containing a eukaryotic nucleus. • Over time, • Some Genetic Material transferred to the nucleus and some stayed in the mitochondria ***Ribosomes found here are of the 70S

39. Function: • Responsible for producing energy for the cell • Transforming energy from macromolecules into ATP (Adenosine triphosphate) • ‘Power Plant’ of the cell • They replicate themselves by dividing down the middle to create 2 daughter mitochondria

40. Structure: • Contains: • 1. Two membranes:  • Outer Membrane • Composed of lipid and protein • Permeable, allowing molecules to pass through • Separates the chemical reactions occurring here from the rest of the cytoplasm 

41. Inner membrane • Composed of lipid and protein • Less permeable • The inner membrane folds many times to create CRISTAE • Cristae increases the surface area for enzymes to produce ATP THEREFORE, • Larger surface area = more chemical Reaction (ATP production)

42. 2. Their own set of Ribosomes • 3. Circular DNA • DID YOU KNOW?

43. White Fat Tissue • Stores fat • Few mitochondria • More commonly found in adult humans

44. Brown Fat Tissue • Colour is due to presence of many mitochondria • Specialized for the generation of heat (Thermogenesis) • The inner-membrane protein thermogenin is responsible for converting energy into heat

45. Seen commonly in : • Cold adapted animals (ie. Rats, snakes) • Hibernating mammals (i.e. Bear) • Human infants (Thermogenesis is vital for newborns to survive)

47. Chloroplast: • Has the same evolutionary line as mitochondria • Location: • Characteristic organelles in plants and green algae

48. Structure and Function: • Contains its own ribosomes and DNA • Surrounded by 2 membranes: (outer and inner membrane) • Internal system of membrane bound sacs called Thylakoids • Thylakoids are flattened to form disks • Contains the pigment chlorophyll (gives green colour and absorbs solar energy to carry out photosynthesis)

49. Thylakoids are: • Grouped in stacks called Grana • These stacks (or Grana) are embedded in the matrix called the Stroma

50. Intermediate Filaments