Cell Architecture

CELL THEORY Mathias Schleiden and Theodore Schwann Prokaryotic cell Eukaryotic cell – plant cell and animal cell Figure 9-1

Animal cell substructures

Single and Double Membrane Substructures Single Membrane Structures – Plasma Membrane – Endoplasmic Reticulum – Golgi Apparatus – Lysosome – Peroxisome – Endosome Double membrane structures – Nucleus and Mitochondria

Plant Cell Substructures

Single and Double Membrane Substructures Single Membrane Structures – Plasma Membrane – Endoplasmic Reticulum – Golgi Apparatus – Lysosome – Peroxisome – Endosome Double membrane structures – Nucleus and Chloroplast

Plasma Membrane Chapter10 Fig.10-1

EM OF A THIN ERYTHROCYTE MEMBRANE

How do endosomes work?

Lysosomes Internal compartment is very different form the cytosol –more acidic pH Degrades substances that are obsolete Phagocytosis and Endocytosis All lysosmal enzymes are acid hydrolases Tays Sach’s disease – defect in enzyme catalyzing a step in the lysosomal breakdown of gangliosides.

Autophagy

Plant Vacuoles Similar to lysosomes – degradative enzymes Concentration of solutes is larger inside the vacuole than outside Stores small molecules and is permeable to water Elongation of the plant is related to water uptake by the vacuole

EM OF A PLANT CELL

Peroxisomes micrometer in diameter Oxidases Catalase 2H₂O₂ -----> 2H₂O + O₂ Main site of fatty acid peroxidation Various toxic molecules that enter the body are degraded here

Mitochondrial vs. Peroxisomal Oxidation Fig

Endoplasmic Reticulum Smooth ER: – Synthesis of Fatty Acids and Lipids – Metabolism of Carbohydrates – Detoxify Drugs and Poisons Rough ER: – Synthesis of Secretory Proteins, Membrane and Organelle Proteins

ROUGH ER IS MADE OF RIBOSOMES

RIBOSOMES Composed of rRNA and protein Site of protein synthesis Proteins are marked for different organelles or for secretion Ribosomes are assembled in the nucleolus Free Ribosomes

PROTEIN MODIFICATION IN THE ER SECRETED PROTIENS – GLYCOSYLATION – DISULFIDE BOND FORMATION

HORMONE SECRETING CELL FROM RAT PITUITARY

Golgi Apparatus

Golgi - Function Flattened membrane vesicles or sacs Cis, medial and trans -Golgi Proteins targeted for different points in the cell are modified differently Secretory proteins Plasma membrane proteins Membrane or soluble proteins to other organelles

HOW SECRETORY PROTEINS ARE TRANSPORTED?

ORGANELLES WITH DOUBLE MEMBRANES MITOCHONDRIA – Power house of the cell – Site of cellular respiration – Organic molecules are used fro ATP synthesis NUCLEUS contains chromosomes, DNA and RNA CHLOROPLAST Site of Photosynthesis

EM OF A MITOCHONDRION

STRUCTURE OF A MITOCHONDRION

OUTER MEMBRANE AND INNER MEMBRANE OUTER MEMBRANE – 50% lipid and 50% protein – Porin proteins (MW of 10,000) INNER MEMBRANE - CRISTAE

POWER HOUSE OF THE CELL

Nucleus Inner membrane and outer membrane Outer membrane is continuous with rough ER The intermembrane space is continuous with the lumen of the ER Nuclear pores and nucleoporins Heterochromatin Ribosomal RNA assembly

HETEROCHROMATIN

CHLOROPLAST Double membraned organelle Length is 10µm and thickness of µm Sacs - Thylakoids Stacks are grana Matrix space called Stroma Photosynthesis

MITOCHONDRIA AND CHLOROPLAST ATP production Move around in the cell Contain their own DNA Some of their proteins are encoded in the nucleus

EM OF A PLANT CHLOROPLAST