Organelles: Structure and Function Recognise cell structures under the electron microscope Outline the function of the different cell organelles

CELL ORGANELLES 1 Surrounded by membranes 2 Without membranes Nucleus Endoplastic reticulum Golgi apparatus Mitochondria Chloroplasts (plants only) Lysosomes 2 Without membranes Ribosomes Centrioles Cytoskeleton

THE NUCLEUS Structure Largest organelle Spherical Dark patches=chromatin Surrounded by nuclear envelope – double membrane Has nuclear pore - allows large molecules through Nucleolus inside Function 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. THE NUCLEUS

ENDOPLASMIC RETICULUM Structure: Consists of flattened membrane-bound sacs - cisternae which are continuous with the outer nuclear membrane. RER- Ribosomes Smooth ER- no Ribosomes ENDOPLASMIC RETICULUM Function: Smooth ER- Involved in making Lipids RER- Transports proteins made on attached ribosomes

GOLGI APPARATUS Structure: Stack of membrane-bound, flattened sacs Function: Receives proteins from the ER Modifies them, adding other chemicals Packages proteins into vesicles to be transported inside cytoplasm or to the outside

MITOCHONDRIA Function Structure: 2 membranes separated by a fluid filled space Inner membrane is folded to form cristae Central part is the matrix. Function Site where ATP is produced during cell respiration

CHLOROPLASTS Structure: 2 membranes separated by fluid filled space Inner membrane surrounds a network of thylakoids A stack of thylakoids is called a granum Chlorophyll molecules are present on these membranes. CHLOROPLASTS Function: Site of photosynthesis Light energy is used to make carbohydrate molecules from carbon dioxide and water

Function: Contain digestive enzymes which break down materials e.g. specialised lysosome (acrosome) in head of sperm cells helps it penetrate the egg. Structure: Spherical sacs surrounded by a single membrane

Organelles NOT surrounded by membranes Ribosomes Centrioles

RIBOSOMES Structure Very small organelles. Free in the cytoplasm, or bound to rough ER, or in mitochondria and chloroplasts. Consist of 2 subunits. Function: Where the instructions (mRNA) from the nucleus are turned into proteins – protein synthesis

CENTRIOLES Structure Small microtubules made of protein. Mother and daughter centrioles with a very characteristic design. Function: Form fibres in cell division known as spindles which separate chromosomes.

CYTOSKELETON Structure Microtubules and microfibrils in the cytoplasm, made of protein. Function: Give cells shape and structure Help cells move or change shape