Cell Architecture CELL THEORY Mathias Schleiden and Theodore

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 Chapter 10 Fig. 10 -1

EM OF A THIN ERYTHROCYTE MEMBRANE

How do endosomes work?

Lysosomes • Internal compartment is very different form the cytosol –more acidic p. H • 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 • 0. 2 -1. 0 micrometer in diameter • Oxidases • Catalase 2 H₂O₂ -----> 2 H₂O + O₂ • Main site of fatty acid peroxidation • Various toxic molecules that enter the body are degraded here

Mitochondrial vs. Peroxisomal Oxidation Fig. 12 -12

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 r. RNA 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 0. 5 -2 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