1. CELL STRUCTURE & DIFFERENTIATION
H.A. MWAKYOMA, MD

2. Cell Structures and Their Functions
H.A. MWAKYOMA, MD

3. Cell Structure Highly Organized
. Specialized structures called organelles in a jelly like substance called cytoplasm
Amount and type of organelles is related to function

4. Cytoplasm- home of the organelles
Thick, gel-like fluid enclosed by cell membrane
Contains organelles, which carry out specific jobs

5. Entering an Animal cell
vacuole
cytoplasm
Cell Membrane: controls what goes into and out of the cell
No Cell Wall
nucleus
mitochondrion
cell membrane

6. Functions of the Cell
Basic Unit of Life -smallest part that still retains characteristics of life
Protection And Support – cells secrete substances that provide
Movement- occurs because of molecules that are located in specific cells e.g. muscle cells

7. Functions of the Cell--- CONT---
Communication-cells receive information that allow them to communicate with each other eg nerves cell tells muscle cells to contract
Cell metabolism and energy release- all the chemical reactions that occur within the cell
Inheritance – each cell contains a copy of the genetic information of the individual

8. The Organelles The Nucleus Nucleoli and Ribosomes
Rough and Smooth Endoplasmic Reticulum
The Golgi Apparatus
Secretory Vesicles
Lysosomes and Peroxiisomes
Mitochondria
Cytoskeleton
Centrioles
Cilia, Flagella and Microvilli
The Cell Membrane

9. Cell Membrane Phospholipid Bilayer Protection and Transport
Types of Transport
Active ( requires ATP)
Passive

10. Two types of cells

11. Eukaryotes (you are)/ take the tour Eukaryotic Cell Tour

12. Nucleus- the brain Nucleus Control Center Directs all of the
cell’s activities
Bound by a nuclear envelope
video

13. Structure of Eukaryote (plant and animal cells )
The nucleus containerizes the DNA.
Double membrane
This double membrane is apparently derived from or closely associated with the rough endoplasmic reticulum (r.e.r).

14. Nucleus Contains the genetic material of cell (DNA)
Located near the center of the cell
Some cells lose their nucleus as they mature, some have more than one nucleus - bone cells
Nuclear envelop (outer and inner membranes and nuclear pores)
Contains loosely coiled fibers called chromatin consisting of DNA
When a cell divides the chromatin becomes more tightly coiled to form the 23 pairs of chromosomes

15. Nucleus
The job of the nucleus is to protect the DNA which in turn had the ability to make proteins.
Remember this dogma:
DNA --- RNA ---- Protein

16. EM nucleus

17. 'Nuclear pores'
  Some ions and some other small molecules can not diffuse in easily. Nuclei also have osmotic properties suggesting a semipermeable membrane.
Electron microscopy shows structural and well ordered structures in the pores called the nuclear pore complex

18. Inside nucleus is chromatin
Chromatin is threadlike material that coils into chromosomes before cell division

19. EM chromatin

20. Chromosomes
Rod like structures formed when chromatin is coiled or folded prior to cell division

21. Nucleoli
Dark stained spherical bodies, sites where rRNA joins proteins to form ribosomes. In this case the nucleus has two nucleoli

22. Nucleoli and Ribosomes
Nucleoli- are rounded dense well defined nuclear bodies with no surrounding membranes
Ribosome's- are the organelles where proteins are produced
- may be free OR attached to the endoplasmic reticulum (RER)
-made in the nucleus

23. Ribosomes are the sites of Protein Synthesis
Ribosome of eukaryotic cells are 20nm by 30nm
Composed of large and small units
Each subunit has mix of own rRNA and protein
coordinate assembly of amino acids into proteins
Some attached to ER (called rough ER)

24. Protein Synthesis DNA in nucleolus is Transcribed to MRNA
MRNA is translated at the level of the ribosomal subunits where the codons are read and translated into amino acids
The amino acids form peptide bonds to create one larger protein

25. Smooth and Rough Endoplasmic Reticulum
The ER is a series of membranes forming sacs and tubules that extends from the outer nuclear membrane into the cytoplasm
Rough ER – has ribosomes attached indicting that it is synthesizing large amounts of protein for export from the cell

26. Smooth & Rough Endoplasmic Reticulum (ER)- Passageways
Smooth ER- no ribosomes
Rough ER- has ribosomes
Carry material throughout the cell
Ribosomes Form Proteins

27. RER
Rough Endoplasmic reticulum is studded with ribosomes on cytoplasm side of nucleus.
Polypeptides are process and modified.

28. RER

29. Polyribosomes
Polyribosomes are several ribosomes synthesizing same protein, may be attached or ER or free floating
Polyribosomes

30. SER
Smooth ER is continuous with RER but lacks ribosomes. Used as detox and storage center.. Forms transport vesicles for disposal
Found in large numbers in the liver.

31. The Golgi Apparatus
Golgi Apparatus- closely packed stacks of curved membrane –bound sacs.
Its function is to collect, modify , package and distribute proteins and lipids manufactured by the Endoplasmic Reticulum
May also chemically modify the proteins by attaching carbohydrates or lipids to them
Found in great number in cells that make a great deal of protein e.g. pancreas, liver

32. Golgi Apparatus Part of the system for exocytosis and endocytosis
Vesicle Budding and Fusing
Exocytosis = move out
Endocytosis = move in

33. Golgi Apparatus Golgi consists of a stack of 3-20 slightly curved sacs
Golgi receives protein filled vesicles that bud from ER
Has cis and tran sides

34. Golgi Bodies- the post office
Flattened Sacs and Tubes
Receives Proteins and other material from ER
Packages and Distributes Materials

36. Secretory Vesicles
a vesicle is a small membrane bound sac that transports or stores materials within cells
Secretory vesicles – pinch off from the golgi apparatus and move to the surface of the cell . Their membranes fuse with the cell membrane and release contents to the exterior of the cell

37. Lysosome- Clean Up Crew
Small, round structures containing chemicals
Breaks down large food particles and old cell parts

38. Lysosomes
Membrane bound vesicles produced by Golgi apparatus and contain digestive enzymes.
Macromolecules enter a cell by vesicle formation, lysosomes fuse with vesicle and digest . (as seen in next slide)
Lysosomes are membrane bound vesicles formed from the golgi apparatus .
They contain a variety of enzymes that functions as intracellular digestive systems

39. Peroxisomes Peroxisomes break down fatty acids and amino acids.
These reactions produce hydrogen peroxide which could harm cells if it were allowed to persist.
An enzyme (catalase) breaks down the hydrogen peroxide to water and oxygen, both of which can be used by the cell. Peroxisomes also breakdown alcohol.

40. Peroxisomes
Peroxisomes small membrane bound vesicles containing enzymes that break down fatty acids , amino acids and hydrogen peroxide.

41. Mitochondria
Mitochondria- small bean shaped, long threadlike organelles
that has inner and outer membranes separated by a space.
The outer membranes have a smooth core but the inner membrane has numerous folds called cristae
Site of ATP production within the cells and carry out aerobic respiration in cells

42. Mitochondria Teachers' Domain: The Powerhouse of the Cell
The site for cellular respiration .
Have a double membrane.
Inner membrane folds called cristae
The matrix contains rnzymes
Has own DNA and ribosomes

43. Mitochondria- the powerhouse/the engine
Rod-shaped
Converts energy in food into energy that the cell can use
video

44. Looks like…

45. Centrioles
Centosome- a specialized zone of cytoplasm close to the nucleus that is the center of microtubule formation.
It contains the centrioles normally oriented perpendicular to each other
Shaped like a cylinder and has nine triplets , each consisting of three parallel microtubules joined together.

46. Vacuole- Public Storage
Water-filled Sac
Plants-large, central vacuoles
Animals- small storage areas
Stores food, waste, and other materials

47. Vacuoles
Large membranous sac, vesicles are smaller than vacuoles

48. Cytoskeleton
A network of connected filaments and tubules extends from nucleus to plasma membrane.
Maintains cell shape and allows for movement of other organelles

49. Cytoskeleton Cytoskeleton- consists of proteins that;
support the cell ,
hold organelles in place and
enable the cell to change shape.

50. Microtubules, Microfilaments and Intermediate filaments

51. DNA and RNA
DNA has 4 nitrogenous bases : adenine, guanine, cytosine and thiamine plus the sugar deoxyribose
RNA has 4 nitrogenous bases : adenine, guanine, cytosine and uracil plus the sugar ribose.
Remember there are 64 sets of codons (a codon is 3 base pairs) that encode for only 20 amino acids

52. Fate of the Cell Divides ( Mitosis and Meiosis) Differentiates
Apoptosis
Tumor ( Benign or Malignant)
Ages
Death

53. Cell Division Mitosis all cells except sex cell(meiosis) Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

54. Differentiation
We learned that through mitosis all cells in an individuals body contain the same amount and type of DNA
So, even though the genetic material is the same , why is it that cells do not look and function the same way, example of diverse cells in text
The process by which a cell develop special structure and functions is called DIFFERENTIATION.

55. Cell Differentiation
The variety of structure in cells reflects differences in cell function

56. What happens during differentiation?
DNA is either active or inactive pending in the cell type via the selective activation of certain portions of the DNA
As they mature and differentiate the rate eventually slows and stops

57. Differentiation Differential gene expression leads to differentiation
All Adult cells have the genes necessary to become another type of cell
Cell fate is a four-step process:
pattern formation,
morphogenesis,
determination, and
differentiation.
Morphogenesis is the process by which cells become assembled into recognizable tissues and organs

58. Differentiation
Determination indicates a cell’s irreversible commitment to becoming a particular cell type
Differentiation involves turning on/off certain genes to transform a cell

60. Put it all together

61. Different kinds of animal cells
white blood cell
red blood cell
cheek cells
sperm
nerve cell
muscle cell
Amoeba
Paramecium

62. Review Levels of Organization
Cells
Tissues
Organs
Organ Systems
Organism

63. Cells
Cells are grouped together and work as a whole to perform special functions

64. Tissue A group of similar cells to perform a particular function
Animals : brain tissue, muscular tissue, heart tissue
Plants : vascular tissue, mesophyll tissue

65. Organs
Different tissues group together to carry out specialized functions
Heart : consists of muscles, nervous tissue and blood vessels
Leaf : consists of epidermis, mesophyll and vascular tissue

66. System
Several organs and tissues work together to carry out a particular set of functions in a coordinated way
Human : digestive, respiratory, excretory, circulatory and reproductive systems
Plant : root and shoot systems

67. Levels of Organization
CELLS (muscle cells,nerve cells)
TISSUES (muscle, brain)
ORGANS (heart, lungs, brain)
SYSTEMS (circulatory system)
ORGANISM (human)

68. Apoptosis
Programmed cell death is a normal process by which cell numbers within various tissues are adjusted and controlled . During development any extra tissue s removed, such as the webs between the toes and the fingers.

69. It’s You!