Organelles - Structure and Function

A set of revision cards to help you learn the structures and functions of various organelles for AS Biology F211 - find someone to test you on them 

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THE NUCLEUS

Structure:

-Largest organelle.

-Shows darkened patches (chromatin) when stained.

-Surrounded by nuclear envelope - which is made of 2 membranes with fluid between them. This contains nuclear pores -  holes large enough for relatively large molecules to pass through.

-Contains a nucleolus. 

Function:

- Houses nearly all of cell's genetic material.

-The chromatin consists of DNA and proteins. When cells divide, chromatin condenses into visible chromosomes.

-Nucleolus makes RNA and ribosomes

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ENDOPLASMIC RETICULUM

Structure:

-Consists of a series of flatterned, membrane-bound sacs called cristernae

-ROUGH ER: studded with ribosomes

-SMOOTH ER: No ribosomes 

Function:

-ROUGH ER: transports proteins made on attached ribosomes

-SMOOTH ER: Lipid synthesis 

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GOLGI APPARATUS

Structure: 

-Stack of membrane-bound, flattened discs 

Function:

-Receives proteins from ER and modifies them - may add sugar molecules to them. 

-Packages the modified proteins into vesicles that can be transported

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MITOCHONDRIA

Structure:

-Have 2 membranes separated by a fluid-filled space.

-Inner membrane folded to form cristae

-Central part of mitochondrion is called the matrix

Function:

-Site where ATP is produced during respiration

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CHLOROPLASTS

Structure:

-Found only in plant cells and the cells of some protoctists

-Have 2 membranes separated by a fluid-filled space

-Inner membrane is continuous, with a network of flattened membrane sacs called thylakoids (a stack of these is called a granum)

-Cholorophyll molecules are present on the thylakoid membranes and in the intergranal membranes

Function:

-Site of photosynthesis in plant cells. Light energy is used to drive the reactions of photosynthesis, in which carbohydrate molecules are made from carbon dioxide and water

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LYSOSOMES

Structure:

-Spherical sacs surrounded by single membrane

Function:

-Contain digestive enzymes which break down materials e.g. white blood cell lysosomes help break down invading microorganisms

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RIBOSOMES

Structure:

-Tiny organelles

-Some found in cytoplasm and some are bound to ER

-Each ribosome consists of 2 subunits

-No membrane surrounding them

Function:

-Site of protein synthesis. 

-They act as an assembly line where coded information (mRNA) from nucleus is used to assemble proteins from amino acids

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CENTRIOLES

Structure:

-Small tubes of protein fibres (microtubules).

-There is a pair of them next to the nucleus in animal cells and in the cells of some protoctists

Function:

-Take part in cell division. They form fibres (spindle fibres) which move the chromosomes during nuclear division

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