3. Discovery of Cells
• Robert Hooke (mid-1600s)
– Observed bark of oak tree
– Saw “row of empty boxes”
– Coined the term cell
4. Cell theory
• (1839)Theodor Schwann & Matthias Schleiden
“ all living things are made of cells”
• (50 yrs. later) Rudolf Virchow
“all cells come from cells”
5. Principles of Cell Theory
• All living things are made of cells
• Smallest living unit of structure and
function of all organisms is the cell
• All cells arise from preexisting cells
6. The origin and evolution of cells
• On the basis of presence of nucleus cells are divided
into two groups:
– Prokaryotic cells: lack a nuclear envelope
– Eukaryotic cells: have a nucleus in which the genetic material
is separated from the cytoplasm.
• Prokaryotic cells are generally smaller and simpler than
eukaryotic cells; their genomes are less complex and
they do not contain cytoplasmic organelles.
7. Eukaryotic Cells
• Eukaryotes, animals, plants, fungi have a membrane-
enclosed nucleus in each of their cells.
• Eukaryotic cells:
– tend to be larger than prokaryotic cells.
– have a variety of membrane-enclosed compartments called
organelles.
– have a protein scaffolding called the cytoskeleton.
8. Eukaryotic Cells
• Compartmentalization is the key to eukaryotic cell function.
• Each organelle has a specific role defined by chemical processes.
• Membranes surrounding these organelles keep away
inappropriate molecules and also act as traffic regulators for raw
materials into and out of the organelle.
11. Plasma Membrane
• Every cell is surrounded by a plasma membrane, a continuous membrane composed of a
lipid bilayer with proteins floating within it and protruding from it.
• The current model of how membranes are constructed is known as Fluid-Mosaic Model.
• Proposes that various molecules of membrane are able to flow and move about.
13. Proteins
• Can be found on the surface of the membrane or within
the membrane among phospholipids.
14. • Roles of the plasma membrane:
– Acts as a selectively permeable barrier.
– Is an interface for cells where information is received
from adjacent cells and extracellular signals.
– Allows cells to maintain a constant internal
environment.
– Has molecules that are responsible for binding and
adhering to adjacent cells.
16. Nucleus
• Known as the “ control centre of the Cell”
• a membrane-bound sac evolved to store the cell’s
chromosomes(DNA)
• stores the genetic material of the cell in the form of multiple,
linear chromosomes
• To control the activity of cell by regulating gene expression
17. • Nuclear membrane:
• separates the nucleoplasm, liquid material in the
nucleus, from the cytoplasm.
• Nuclear pores:
• Exchange of materials
• allows thousands of large molecules such as RNA to
pass into and out of the nucleus each minute.
19. Endoplasmic Reticulum
• Is a set of folded membranes and tubes
throughout the system.
• The general structure :membranous network
of cisternae.
• Two types: rough endoplasmic reticulum
smooth endoplasmic reticulum
20.
21. Functions
• Provides a large surface area on which chemical
reactions can take place.
• It synthesizes lipids, phospholipids .
• It also carries out the metabolism of carbohydrates,
drug detoxification.
• RER involved in protein synthesis
22. Golgi Bodies
• The Golgi is composed of stacks of membrane-bound structures
known as cisternae.
• The cisternae stack has two main functional regions: the cis-
Golgi network and trans-Golgi network.
• Vesicles from the endoplasmic reticulum fuse with the network
and subsequently progress through the stack to the trans Golgi
network, where they are packaged and sent to their destination
23. Mitochondria
• Have their own DNA- semiautonomous
Structure :
1. the outer mitochondrial membrane
2. the intermembrane space
3. the inner mitochondrial membrane
4. the cristae space
5. the matrix
24. Mitochondria
• Break down fuel molecules (cellular respiration)
– Glucose
– Fatty acids
• Release energy
– ATP
Mitochondria found in both plants and animals are called the power
houses of the cell. They convert the energy in the bonds of glucose and
oxygen to readily available energy in the form of ATP. This process is
called aerobic respiration.
25. 25
Chloroplasts
Chloroplasts
-organelles present in cells of plants and some other
eukaryotes
-contain chlorophyll for photosynthesis
-surrounded by 2 membranes
-thylakoids are membranous sacs within the inner
membrane
-grana are stacks of thylakoids
26.
27. Functions
• Site of synthesis and packaging of molecules
produced in cells.
• Involved in transportation of molecules s/a
carbohydrates, proteins, insulin outside the cell.
28. Lysosomes
• Lysosomes are cellular organelles that contain
hydrolase enzymes that break down waste
materials and cellular debris.
29. Functions
• Cell damaged- membranes of Lysosomes break-
enzymes release- components of cells broken-
available for surrounding cells.
• Used in destruction of engulfed harmful microbes
30. Peroxisomes
• Peroxisomes are small membrane bound
vesicles.
• In human cells, peroxisomes produce hydrogen
peroxides that is used to destroy invading
microbes.
• They contain enzymes responsible for
breakdown of fatty acids and cholesterol
synthesis.
32. Ribosomes
• A ribosome is made from complexes of RNAs and
proteins -ribonucleoprotein.
• Each ribosome is divided into two subunits: the
smaller subunit and the larger subunit
33. 33
Cytoskeleton
Cytoskeleton
-network of protein fibers found in all
eukaryotic cells
-supports the shape of the cell
-keeps organelles in fixed locations
-helps move materials within the cell
34. 34
Cytoskeleton
Cytoskeleton fibers include
- microfilaments – responsible for cellular
contractions, crawling, “pinching”
-microtubules – provide organization to the
cell and move materials within the cell
-intermediate filaments – provide structural
stability
36. • both cilia and flagella are constructed from microtubules
• both provide either locomotion for the cell or move fluid pass the cell
Cilia and flagella
