Chapter 7. A TOUR OF THE CELL. Robert Hooke, 1665. Coined the term “Cell” after viewing cork tissue under a simple microscope. Cell Theory Schleiden and Schwann , 1838. The cell is the basic unit of life All living organisms are either cells or made up of cells
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A TOUR OF THE CELL
Coined the term “Cell” after viewing cork tissue under a simple microscope.
- Brightfield (Used for stained or unstained specimen)
- Phase – Contrast
- Differential-interference – contrast
- Scanning Electron Microscopes
- Transmission Electron Microscopes
The beam of electrons scans the surface of the specimen
Used for detailed study of external surfaces of the specimen – which could be a cell, an organelle or a whole organism
Beam of electrons passes through a thinly prepared specimen
Used to view internal structures of the specimen – a cell, an organelle or a structure like a flagellum
An unfertilized ostrich egg is the largest single cell on the planet, weighing in at a whopping 3 lbs!
Prokaryotic and Eukaryotic
“Karyon” = nucleus
“Pro” = before
“Eu” = true
The Fluid mosaic model
Phospholipid bi-layer embedded with
Cholesterol, amphipathic proteins and glycoproteins
Keeps cell contents and precious nutrients inside
Allows certain atoms and molecules in and out (selectively permeable)
Cytoplasm: The cytosol-containing area outside the nucleus
Nucleoplasm: The cytosol-containing area inside the nucleus
Free ribosomes synthesize proteins that are to remain and be
used in the cytosol.
Bound ribosomes synthesize proteins:
Detoxification involves adding OH groups to the drug, so it becomes soluble and can be washed out of the system. Drugs like Phenobarbital (used for epilepsy) are removed from the liver in this manner
Alcoholics and drug abusers have highly proliferated smooth ERs
Proteins that have sugar added to them are called glycoproteins.
Flattened sac-like structures
Has a “cis-face” that faces the ER and is the “receiving” side
Has a “trans-face” that is the “shipping” side
Receives material from the ER and further processes it (like adding sugar molecules to proteins), stores it and ships it to its final destination in transport vesicles.
These transport vesicles have proteins tags that help them “dock” with specific organelles or plasma membrane
Membrane-bound sacs of various hydrolytic enzymes. They can digest fat, proteins, carbohydrates or nucleic acids.
Their primary role is digestion
They can digest:
Hydrolysis is the opposite of dehydration synthesis
Central VacuoleVacuoles – cont’d.
Plants have a “central vacuole” surrounded by a membrane called the tonoplast.
The central vacuole stores water and nutrients for the plant cell, for release into the cytosol as and when needed. It helps the cell elongate by filling itself up and creating “turgor pressure”
The “Powerhouse” of the cell
Uses the energy (e-) stored in the chemical bonds of food molecules such as Glucose, to produce ATP, the energy currency of the cell
All our mitochondria came from our mothers
Belong to a family of organelles called Plastids. Amyloplasts are colorless and store starch (amylose). Chromoplasts such as chloroplasts store various pigments such as chlorophyll
Found in plant cell and cells of protists that photosynthesize
Belong to the Plastid family, which consists of amyloplasts and chromoplasts. Amyloplasts store starch, in roots and tubers, while chromoplasts contain pigments of various types. Chloroplasts are a type of chromoplast.
Inner and Outer membrane enclose a jelly-like matrix called Stroma (Matrix in mitochondrion)
Stacks of disc-shaped Thylakoids actually contain the pigment chlorophyll, making the organelle look green
Chloroplasts also contain their own circular DNA, and they can replicate on their own
The thylakoid membrane and the stroma are the sites of Photosynthesis
Mitochondria and chloroplasts have their own DNA and ribosomes
Their ribosomes are smaller than those in the cytosol (normal eukaryotic)
They divide on their own – whether or not the cell is dividing
They have double membranes – a clear indication of “phogocytosis”
Centrioles are the animal cell’s microtubule organizing centers. They can elongate the microtubule by adding tubulin dimers or shorten it by removing them. Plant cells lack centrioles.
Cytoplasmic streaming is promoted by actin filaments and allows plant cells to circulate the nutrients in their cytoplasm
Many cells have additional boundaries over their plasma membrane for extra protection, communication or interaction with neighboring cells or recognition.
Cell walls (Bacteria, plants and fungi)
Glycocalyx (Bacteria, Animal cells)
Intercellular junctions (multicellular organisms)
Help integrate cells into higher levels of structure and function