FUNCTION OF CELL ORGANELLES

FUNCTION OF CELL ORGANELLES : 

FUNCTION OF CELL ORGANELLES

Objectives: 

Objectives At the end of the lecture You should be able to describe the function of organelles in eukaryotic cells

Organelles: 

Organelles Nucleus Mitochondria Golgi complex Endoplasmic reticulum Ribosome Lysosomes Peroxisomes

NUCLEUS : 

NUCLEUS Brain of the animal cell The largest organelle Found only in eukaryotic cells Present in all cells except mature RBC Most cells contain single nucleus Muscle cells and some liver cells are multinucleate Is composed of three main parts

1-Nuclear envilope: 

1-Nuclear envilope Contains pores through which molecules move in and out of the nucleus

Slide 6: 

2-CHROMATIN Consist of 15%DNA+10%RNA+75% protein Main repository of cellular DNA Human DNA is organized into chromosomes & is usually associated with basic proteins called histones Individual chromosomes become visible only during cell division

3-THE NUCLEOLUS: 

3-THE NUCLEOLUS Nucleus may contain one or more nucleoli (Rich in RNA) Is the site where ribosomal RNA ( rRNA ) is synthesized and temporarily stored before it is assembled into ribosomal precursors and transferred out of the nucleus

ENDOPLASMIC RETICULUM: 

ENDOPLASMIC RETICULUM

ENDOPLASMIC RETICULUM(ER) : 

ENDOPLASMIC RETICULUM(ER) A series of flattened membranous sacs and tubes extending throughout the cytoplasm Two types of ER Rough ER (RER)- have attached ribosomes Smooth ER (SER)- free of ribosomes

FUNCTIONS OF RER: 

FUNCTIONS OF RER Synthesis of proteins Proteins synthesized are sent via small vesicles to golgi complex before secretion or directly inserted membranes

FUNCTION OF SER: 

FUNCTION OF SER Packaging & delivering proteins into golgi Major site for lipid biosynthesis (steroids, triacyiglycerois , PL’s). Desaturation & elongation of F.A’s (Enzymes + cytochrome ) Detoxification of drugs & other toxic compounds (Enzymes + cytochrome P450 )

RIBOSOMES: 

RIBOSOMES

FUNCTIONS: 

FUNCTIONS Sites of protein synthesis, where RNA is translated into protein

GOLGI COMPLEX: 

GOLGI COMPLEX

THE GOLGI COMPLEX (GOLGI APPARATUS): 

THE GOLGI COMPLEX (GOLGI APPARATUS) A series of flat, single membraned vesicle ( cisternae ) that a often stacked. Functions To receive proteins & lipids from ER & distribute them to plasma membrane, lysosomes and secretory vesicles. Before undergoing packaging & distribution, proteins undergo modifications (e.g. addition of lipids, phosphorylations , followed by terminal sugars to form glycoprotein). –Post translational modifications.

MITOCHONDRIA: 

MITOCHONDRIA

MITOCHONDRIA: 

MITOCHONDRIA Double- membraned organelles. Each mitochondria has four components Central matrix Inner mitochondria Membrane (IMM) Cristae (folds of IMM that increase surface area of membrane) Outer mitochondria membrane

CENTRAL MATRIX: 

CENTRAL MATRIX Contains enzymes & other components participating in Oxidation of carbohydrates, lipids & proteins. Synthesis is haem & urea. Contains mitochondria DNA and other components for synthesis of mitochondria proteins

INNER MITOCHONDRIA MEMBRANE: 

INNER MITOCHONDRIA MEMBRANE Cristae contain small spherical particles (with proteins involved in ATP synthesis) attached by short stalks. ATP synthase Impermeable to sucrose & most metabolites. Contain several transport systems to move substances into & out of the matrix

OUTER MITOCHONDRIAL MEMBRANES : 

OUTER MITOCHONDRIAL MEMBRANES Separates mitochondria from cytoplasm. Permeable to many substances Synthesis of mitochondria proteins Contains own DNA (mt.DNA), Ribosome & RNA Mt.DNA lacks histones & not organized into chromosomes. DNA is circular & double stranded like in bacteria.

SUMMERY OF FUNCTIONS : 

SUMMERY OF FUNCTIONS Power house of the cell-Major site of cellular respiration & energy production. Components of electron transport chain & oxidative phosphorylation are located in IMM Site of complete oxidation of carbohydrates , lipids & proteins, and haem & urea synthesis. Enzymes for oxidation are found in matrix (except succinate dehydrogenase that is found associated with the IMM).

LYSOSOME: 

LYSOSOME Function Digestion of: Materials brought into the cell by phagocytosis or pinocytosis Cell components after death

PEROXISOME: 

PEROXISOME Catalase/ D-Amino acid/ oxidase etc…. Functions Catalase detoxifies H 2 O 2 Oxidation of long chain fatty acids (>C 18 ) Help in biosynthesis of bile acids Help in synthesis of plasmalogens and glycolipids