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A journey into the cell

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by

Nyma Siddiqui

on 20 August 2013

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Transcript of A journey into the cell

A JOURNEY INTO THE CELL
Introduction
The life of a cell
All cells must do the following things to stay alive:
Process matter- synthesize, acquire and digest molecules
Process energy-energy must be provided
mainly from food and mitochondria
Process information-DNA and RNA
Most cells also :
1)Reproduce
2)Communicate

Inside the cell
The Cytoskeleton
Structure
Structural proteins that extend throughout the cytoplasm
Function
Support
Shape
Organelle Anchorage
Movement of chromosomes during cell division
Cillia&
Flagella
Structure
Extensions of cytoskeleton's protein
Function
The movement of cell through space
Centrosome
Structure
Present only in animal cells and is a region present near the nucleus and is a"microtubule organizing center
Function
Origin of all microtubule cells and plays a major role in cell division.
At the boundary
The Cell Membrane
Structure
The "Fluid Mosaic Model"
It contains a phospholipid bi-layer with associated proteins
Functions
1)Boundary of a cell
2)Transport in and out of materials (includes carbon and nitrogen)
3)Communication between cell and environment
Membrane Proteins
Structure:
Various depending on the role they play:
Integral proteins: penetrate one or both layers of the bi-layer.
Peripheral proteins: associated with the membrane, but don't penetrate the bi-layer.
The polarity of different regions of a membrane protein vary according to the role of the protein

membrane proteins are mobile in the cell membrane
Functions
A lot and more. Here is a summary
Case Study: Membrane Receptors
Structure:
Integral proteins that span the bi-layer regions ("domains") that extend extra and intra- cellularly.
Function:
Signal Transduction: The receipt of chemical messages from the environment and the relay (transduction") of those messages into the cell for response.
Membrane receptors are exploited by viruses (how?)
Spotlight: Glycoproteins
Structure
Integral proteins that span the bi-layer with short polysaccharide residues projecting extra-cellularly into the environment
Function:
Cell-Cell Recognition: Glycoproteins serve as an identifying marker in cellular populations (like your body).
Membrane Phospholipids
Structure:
lipids with a phosphate attached to glycerol in place of a fatty acid tail.
polar (hydrophilic) phosphate "head", nonpolar (hydrophobic) fatty acid tails. This type of polar/non-polar molecule is called "amphipathic"
Spontaneously organizes in the presence of water to form a bi-layer
fluid: phospholipids are constantly moving
Function:
Makes a "selectively permeable" membrane. Only small, non-polar molecules can easily move through the phosopholipid bi-layer
Cholesterol:
Structure:
Function:
acts as a "temperature buffer" to help maintain membrane fluidity over a range of temperatures

Outside the cell
Between Cells
Cell Wall
Structure
A cross-linked network of structural polysaccharides.
Cellulose
Plant like cell
Chitin
Fungal cells
Peptidoglycan
:
Bacterial Cells
Function:
Structural support only! Cell walls are non-living
Structural support only! Cell walls are non-living
No Cells Walls in animal cells. Why?

ECM
(extracellular matrix)
Structure
A network of connective proteins and "proteoglycan" molecules outside of the cell membrane of animal cells
Function:
Only animal cells have Extracellular matrix
Intercellular Junctions
Structure
Proteins that connect cells to other cells
Depending on the junction, a channel between them may exist
Function
Anchorage & Transport open junctions only
"Open" Junctions
Plants
"Closed" Junctions
Animals
Desmosomes:
Cellular "rivets" that anchor cells to basement membranes in tissues
Tight Junctions:
Cell-cell connections that make a water-proof seals
Prokaryotic cells:
cells that lack nucleus
Eukaryotic cells:
cells with nucleus
Credits
Cambell Reece Biology 9E Picture
Youtube.com -video introduction of the cell
Provided under the terms of a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. By David Knuffke.
A cytoskeleton contributes to the cell function by:
The various functions demonstrate that
1. Carbon moves from the environment to organisms where it is used to build carbohydrates, proteins, lipids or nucleic acids. Carbon is used in storage compounds and cell formation in all organisms.
2. Nitrogen moves from the environment to organisms where it is used in building proteins and nucleic acids. Phosphorus moves from the environment to organisms where it is used in nucleic acids and certain lipids.
This would be further demonstrated in the cell membrane section.

Thus, the cell membrane allows carbon and nitrogen both move from the environment to organism to build carbon and phosphorus which are a component of phospholipid.
Hydro= water philic= love
phobic= fear
Phospholipid bilayers have a hydrophilic head region and a hydrophobic tail.
As the name suggests the hydrophilic regions are attracted aqueous water. On the other hand,hydrophobic repells water.
This shows that living systems depend on properties of water that result from its polarity and hydrogen bonding.
Water molecules stay together by hydrogen bonds. The phenomenon of hydrogen bonding linked together is called cohesion.
Cohesion due to hydrogen bonding contributes to the transport of water and dissolved nutrients against gravity in plants. Also, cohesion helps to the hold the column of water within the cells. Thus, it shows that living systems depend on properties of water that result from its polarity and hydrogen bonding.
Many of the eukaryotic cells belong to the endomembrane system which includes the nuclear envelope, the endoplasmic reticulum, the golgi aparatus, lysosomes and other vesicles and vacuoles. The system aids in carrying out various tasks which include synthesis of proteins, transport of protein into membranes and organelles or out of the cell, metabolism and movement of lipids, and detoxification of poisons.
Thus, this proves that
a. Internal membranes facilitate cellular processes by minimizing competing
interactions and by increasing surface area where reactions can occur.
b. Membranes and membrane-bound organelles in eukaryotic cells localize (compartmentalize) intracellular metabolic processes and specific enzymatic reactions.

Back to inside the cell
Full transcript