Biological Molecules

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Structure                                                                              (

-Largest organelle.                                    


-Dark Patches = chromatin.

-Surrounded by nuclear envelope.

-Composed of 2 fluid filled membranes.

-Has nuclear pores - allows large molecules through (mRNA).

-Nucleolus inside


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-Contains genetic material.

-Chromatin consists of DNA and proteins.

-Contains instructions for making proteins.

-When cells divide, chromatin condenses into visible chromosomes.

-Nucleolus makes RNA and ribosomes.

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2 Types of Cells

Eukaryotic (Multicellular) & Prokaryotic (Single Celled):


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-Very small organelles in the cytoplasm and bound to rough ER (Endoplasmic Reticulum).

-Consists of 2 subunits.


-Site of Protein Synthesis which acts as an assembly line using mRNA as code to assemble proteins.                                       

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Cell Organelles (Membrane bound compartments)


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Endoplasmic Reticulum


-Consists of flattened membrane bound sacs called cisternae.

-Cisternae = they are continuous with the outer nuclear membrane.

-Rough ER - Ribosomes.

-Smooth ER - No Ribosomes.


-Rough ER - Transports proteins made on attached ribosomes.

-Smooth ER - Involved in making lipids.

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Endoplasmic Reticulum Diagram


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-Small spherical sacs surrounded by a single plasma membrane.


-Vacuoles: contain mostly water to control the correct water potential in cells.


-Transport vesicles: move molecules between locations in the cell.

-Secretory vesicles: contain substances to be moved to the plasma membrane to be excreted from cells.

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Vesicles Diagram


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Golgi Apparatus


-Stack of membrane-bound, flattened sacs called cisternae.


-Recieves protein from the ER.

-Modifies the protein e.g adds sugar.

-Packages proteins into vesicles to be transported inside the cell or to the outside.

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-Contain digestive enzymes which break down materials. e.g acrosome in the head of the sperm cells helps it penetrate the egg.


-Spherical sacs surrounded by a single membrane.


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- 2 membranes sperated by a fluid filled space.

- Inner membrane is folded to form cristae.

- Central part is the matrix.


-Site where ATP is produced during respiration.

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Mitochondria Diagram


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- 2 membranes seperated by a fulid filled space.

- Inner membrane is continuous with a network of thylakoids.

- A stack of thylakoids is called a granum.

- Chlorophyll molecules are present on these membranes.


- Site of photosynthesis.

- Light energy is used to derive carbohydrate molecules from carbon dioxide.

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Chloroplasts Diagram

chloroplast diagram labeled (

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-Small protein tubes of microtubules.


-Form fibres in cell division knows as spindles which separate chromosomes. (

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-Gram Stain technique: sperate bacteria into two groups. Gram negative and Gram positive. 

                      Gram positive: Blue or Violet

                      Gram negative: Have thinner cell walls so they loose the stain.

The bacteria is then stained with a counterstain (Safranin dye) - bacteria will then turn red.

-Acid-fast technique: used to differentiate mycobacterium from other bacteria.

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Magnification: how many times larger the image is than the actual size of the object being viewed.

Resolution: the ability to see individual objects as seperate enteties. (

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Electron Microscopy

-Electron microscopy: a beam of electrons with a wavelength of less than 1 nm is used to illuminate the specimen.

-More detail can be seen because the electrons have a smaller wavelength than light waves.

-Can produce images of up to x500,000.


-Very expensive.

-Can only be used inside a carefully controlled environment

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Protein Production

1. Proteins are synthesised on the ribosomes bound to the endoplasmic reticulum.

2. Proteins then pass into cisternae and repackages into transport vesicles.

3. Vesicles containing the newly synthesised proteins move towards the golgi apparatus via the cytoskeleton.

4. The vesicles fuse with the cis face and the proteins enter.

5. The proteins are structually modified before leaving the Golgi Apparatus from the trans face.

6. Secretory vesicles carry proteins that are to be released from the cell, the vesicles move towards the cell membrane releasing their content by exocytosis.

7. Some vesicles form lysosmes.

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