Lecture for Chapter 4 DNA organization Endomembrane System

Outside of cell Inside of cell 0.1  m (a) TEM of a plasma membrane Hydrophilic region Hydrophobic region Hydrophilic region Carbohydrate side chains Proteins Phospholipid (b) Structure of the plasma membrane

Outside of cell Inside of cell 0.1  m (a) TEM of a plasma membrane

ENDOPLASMIC RETICULUM (ER) Rough ER Smooth ER Nuclear envelope Nucleolus Chromatin Plasma membrane Ribosomes Golgi apparatus Lysosome Mitochondrion Peroxisome Microvilli Microtubules Intermediate filaments Microfilaments Centrosome CYTOSKELETON: Flagellum NUCLEUS

Nuclear envelope Nucleolus Chromatin Golgi apparatus Mitochondrion Peroxisome Plasma membrane Cell wall Wall of adjacent cell Plasmodesmata Chloroplast Microtubules Intermediate filaments Microfilaments CYTOSKELETON Central vacuole Ribosomes Smooth endoplasmic reticulum Rough endoplasmic reticulum

The eukaryotic cell’s genetic instructions are housed in the nucleus and carried out by the ribosomes The nucleus contains most of the DNA in a eukaryotic cell Ribosomes use the information from the DNA to make proteins © 2011 Pearson Education, Inc.

The Nucleus: Information Central The nucleus contains most of the cell’s genes and is usually the most conspicuous organelle The nuclear envelope encloses the nucleus, separating it from the cytoplasm The nuclear membrane is a double membrane; each membrane consists of a lipid bilayer © 2011 Pearson Education, Inc.

Nucleus Rough ER Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Ribosome Pore complex Close-up of nuclear envelope Surface of nuclear envelope Pore complexes (TEM) 0.25  m 1  m Nuclear lamina (TEM) Chromatin 1  m

Nucleus Rough ER Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Chromatin Ribosome Pore complex Close-up of nuclear envelope

Nuclear envelope: Inner membrane Outer membrane Nuclear pore Surface of nuclear envelope 1  m

Pore complexes (TEM) 0.25  m

Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER Large subunit Small subunit Diagram of a ribosome TEM showing ER and ribosomes

The endomembrane system regulates protein traffic and performs metabolic functions in the cell Components of the endomembrane system – Nuclear envelope – Endoplasmic reticulum – Golgi apparatus – Lysosomes – Vacuoles – Plasma membrane These components are either continuous or connected via transfer by vesicles © 2011 Pearson Education, Inc.

The Endoplasmic Reticulum: Biosynthetic Factory The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells The ER membrane is continuous with the nuclear envelope There are two distinct regions of ER – Smooth ER, which lacks ribosomes – Rough ER, surface is studded with ribosomes © 2011 Pearson Education, Inc.

Smooth ER Rough ER ER lumen Cisternae Ribosomes Smooth ER Transport vesicle Transitional ER Rough ER 200 nm Nuclear envelope

Smooth ER Rough ER Cisternae Ribosomes Transport vesicle Transitional ER Nuclear envelope ER lumen

Functions of Smooth ER The smooth ER – Synthesizes lipids – Metabolizes carbohydrates – Detoxifies drugs and poisons – Stores calcium ions © 2011 Pearson Education, Inc.

Functions of Rough ER The rough ER – Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) – Distributes transport vesicles, proteins surrounded by membranes – Is a membrane factory for the cell © 2011 Pearson Education, Inc.

The Golgi apparatus consists of flattened membranous sacs called cisternae Functions of the Golgi apparatus – Modifies products of the ER – Manufactures certain macromolecules – Sorts and packages materials into transport vesicles The Golgi Apparatus: Shipping and Receiving Center © 2011 Pearson Education, Inc.

cis face (“receiving” side of Golgi apparatus) trans face (“shipping” side of Golgi apparatus) 0.1  m TEM of Golgi apparatus Cisternae

TEM of Golgi apparatus 0.1  m

Compartmentalization! A way to protect yourself from yourself

Lysosomes: Digestive Compartments A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Lysosomal enzymes work best in the acidic environment inside the lysosome © 2011 Pearson Education, Inc.

Some types of cell can engulf another cell by phagocytosis; this forms a food vacuole A lysosome fuses with the food vacuole and digests the molecules Lysosomes also use enzymes to recycle the cell’s own organelles and macromolecules, a process called autophagy Play cartoon! © 2011 Pearson Education, Inc.

Figure 6.13 Nucleus Lysosome 1  m Digestive enzymes Digestion Food vacuole Lysosome Plasma membrane (a) Phagocytosis Vesicle containing two damaged organelles 1  m Mitochondrion fragment Peroxisome fragment (b) Autophagy Peroxisome Vesicle Mitochondrion Lysosome Digestion

Figure 6.13a Nucleus Lysosome 1  m Digestive enzymes Digestion Food vacuole Lysosome Plasma membrane (a) Phagocytosis

Figure 6.13b Vesicle containing two damaged organelles 1  m Mitochondrion fragment Peroxisome fragment Peroxisome Vesicle Mitochondrion Lysosome Digestion (b) Autophagy

Vacuoles: Diverse Maintenance Compartments A plant cell or fungal cell may have one or several vacuoles, derived from endoplasmic reticulum and Golgi apparatus © 2011 Pearson Education, Inc.

Food vacuoles are formed by phagocytosis Contractile vacuoles, found in many freshwater protists, pump excess water out of cells Central vacuoles, found in many mature plant cells, hold organic compounds and water © 2011 Pearson Education, Inc.

Central vacuole Cytosol Nucleus Cell wall Chloroplast Central vacuole 5  m

Smooth ER Nucleus Rough ER Plasma membrane

Figure Smooth ER Nucleus Rough ER Plasma membrane cis Golgi trans Golgi

Figure Smooth ER Nucleus Rough ER Plasma membrane cis Golgi trans Golgi

Mitochondria and chloroplasts change energy from one form to another Mitochondria are the sites of cellular respiration, a metabolic process that uses oxygen to generate ATP Chloroplasts, found in plants and algae, are the sites of photosynthesis Peroxisomes are oxidative organelles © 2011 Pearson Education, Inc.

Mitochondria and chloroplasts have similarities with bacteria – Enveloped by a double membrane – Contain free ribosomes and circular DNA molecules – Grow and reproduce somewhat independently in cells © 2011 Pearson Education, Inc. The Evolutionary Origins of Mitochondria and Chloroplasts

Mitochondria: Chemical Energy Conversion Mitochondria are in nearly all eukaryotic cells They have a smooth outer membrane and an inner membrane folded into cristae The inner membrane creates two compartments: intermembrane space and mitochondrial matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesize ATP © 2011 Pearson Education, Inc.

Intermembrane space Outer membrane DNA Inner membrane Cristae Matrix Free ribosomes in the mitochondrial matrix (a) Diagram and TEM of mitochondrion (b) Network of mitochondria in a protist cell (LM) 0.1  m Mitochondrial DNA Nuclear DNA Mitochondria 10  m

Intermembrane space Outer DNA Inner membrane Cristae Matrix Free ribosomes in the mitochondrial matrix (a) Diagram and TEM of mitochondrion 0.1  m membrane

Chloroplast structure includes – Thylakoids, membranous sacs, stacked to form a granum – Stroma, the internal fluid The chloroplast is one of a group of plant organelles, called plastids © 2011 Pearson Education, Inc.

Ribosomes Stroma Inner and outer membranes Granum 1  m Intermembrane space Thylakoid (a) Diagram and TEM of chloroplast (b) Chloroplasts in an algal cell Chloroplasts (red) 50  m DNA

Peroxisomes: Oxidation Peroxisomes are specialized metabolic compartments bounded by a single membrane Peroxisomes produce hydrogen peroxide and convert it to water Peroxisomes perform reactions with many different functions How peroxisomes are related (evolutionarily) to other organelles is still unknown © 2011 Pearson Education, Inc.

The cytoskeleton is a network of fibers that organizes structures and activities in the cell The cytoskeleton is a network of fibers extending throughout the cytoplasm It organizes the cell’s structures and activities, anchoring many organelles It is composed of three types of molecular structures – Microtubules – Microfilaments – Intermediate filaments © 2011 Pearson Education, Inc.

Make an Endomembrane system Go to back where there are craft supplies Make a cell (use the whole paper) Draw in the organelles included in the endomembrane system. Map out the production and delivery of a membrane protein. What kind of proteins are in the membrane? Think function (there are several)