CELL
- This most basic and living unit of any organism.
- Cell organelles perform various functions in the cell, as organs and organ systems do in our body.
CELL MEMBRANE
- Cell membranes are semi permeable.
- These membranes are composed of proteins and phospholipids.
- FUNCTIONS
1- Separates cell organelles from external environment.
2- Control the exchange of gases and solutes.
3- At times functions as a site for photosynthesis and etc.
4- It carries receptors to which various hormones, antibiotics and other chemicals may attach and invite a variety of reaction
MEMBRANE PROTEINS
- Different types of proteins occur in different membranes.
- Usually hydrophobic portions of the proteins interact with lipids while hydrophilic aqueous contents of the membrane.
- Other membrane proteins may function as receptors for ligands, electrons carrier.
- Some membrane proteins are glycosylated for cell to cell adhesions.
- They play important rule in the immune response.
- The structure of a membrane can be explained with a fluid mosaic model.
NUCLEUS
- It is found in all eukaryotic cells.
- It is largest of all cell organelles.
- Nuclear membrane contains pores to allow exchange of substances between nucleus and cytoplasm.
- Nucleus contains one or more nucleoli, chromatin and gel like nucleoplasm.
- Chromatin is composed of DNA which is compliced with basic proteins called histons.
- DNA and histons are organised into bead like structure called NUCLEOSOMES.
-The loosely coiled chromatins that stain less are called euchromatin and the tightly coiled are called heterochromatin
CYTOPLASM
- This is the aqueous substance inside the cell.
- The solute part of cytoplasm is called cytosol.
- Cytosol is 90% of water in which ions, salts, sugars, amino acids, fatty acids, nucleotides and gases are dissolved.
- The nucleus and cytoplasm constitute the protoplasm.
- Cytoplasm is also the site of many other metabolic pathways.
ENDOPLASMIC RETICULUM ( ER )
- It is complex network of membranes running through the cytoplasm of the eukaryotic cells.
- It consists of flattened membranes called CISTERNAE.
TYPES:-
1. Rough endoplasmic reticulum (RER)
§ It has ribosomes embedded on the surface of cisternae , making it look rough.
§ It helps in protein synthesis.
§ ER sacs covered with ribosomes are called microsomes.
2. Smooth endoplasmic reticulum (SER)
§ It does not have ribosomes embedded on it.
§ This helps in lipid synthesis.
§ It is also the site of glycosylation.
- This is found in plant animal and bacterial cells.
- Found throughout the cytoplasm in large numbers.
- This is the site of protein synthesis.
- Each ribosome consists of two subunits a smaller unit and a larger unit.
- It consists of equal amount of RNA and protein.
- RNA found here is called ribosomal RNA (rRNA).
- TYPES:-
1. 70S
§ This type is found only in prokaryotes.
§ It has two subunits 50S and 30S.
§ S stands for Svedberg (unit of sedimentation rate).
2. 80S
§ Found only in eukaryotic cells.
§ The two subunits are 60S and 40S.
- Found in all eukaryotes.
- Consists of flattened membrane bound sacs called cisterane.
- Cisterane is formed by the fusion of vesicles, which bud off from the ER.
- Site of glycosylation.
- It synthesizes lysosomes.
- Packing and moving of organelles in and out if the cell.
LYSOSOMES
- These are single membrane organelles.
- Contains hydrolytic enzymes like protease, nuclease and lipase.
MITOCHONDRIA
- These are elongated organelles bounded by two membranes,
- Inner membrane is folded and called cristae.
- Its matrix contains few ribosomes, DNA and phosphate granules.
- Its matrix site for kerbs cycle.
- Its site for respiration and ATP synthesis.
- Cristae is the site for oxidative phosphorylation.
- It is known as power house of the cell.
PLASTIDS
- These are found only in plant cells and bounded by two membranes.
- Types
1) Chloroplast - contains chlorophyll and green in clour and carries out photosynthesis.
2) Chromopast – these are non photosynthetic colored plastids containing red, orange and yellow pigments.
3) Leucoplasts - Colorless plastids and lack pigments. These are modified into food storage sites.
CYTOSKELETON
-These are fibrous protein structure which exsists in all eukaryatic cells giving them their shape.
-Types
1) Microtubules
- Un-branched, hollow cylindrical organelles and consists of protein called tubulin.
- These are responsible for the movement of chromosomes and other organelles such as golgi vesicle.
2) Micro filaments
- These are fine protein filaments.
- Made of actin.
- Occur in sheets or bundles just below the all membrane.
- Involved in endocytosis and exocytosis.
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