What is the primary functions of the nucleus? Concept 4.3: The nucleus What is the primary functions of the nucleus? It houses the cell’s genetic material and produces rRNA (ribosomal RNA) Most conspicuous of the organelles (~5um) Directs protein synthesis by synthesizing mRNA © 2014 Pearson Education, Inc. 1

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 © 2014 Pearson Education, Inc. 2

Pores regulate the entry and exit of molecules from the nucleus The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein © 2014 Pearson Education, Inc. 3

Close-up of nuclear envelope Chromatin Nucleus Nucleolus Chromatin Figure 4.8a Nucleus Nucleolus Chromatin Nuclear envelope: Inner membrane Outer membrane Nuclear pore Rough ER Pore complex Figure 4.8a The nucleus and its envelope (part 1: detail of art) Ribosome Close-up of nuclear envelope Chromatin 4

Surface of nuclear envelope Figure 4.8b 1 m Nuclear envelope: Inner membrane Outer membrane Nuclear pore Figure 4.8b The nucleus and its envelope (part 2: nuclear envelope, TEM) Surface of nuclear envelope 5

Pore complexes (TEM) 0.25 m Figure 4.8c Figure 4.8c The nucleus and its envelope (part 3: pore complexes, TEM) 6

Nuclear lamina (TEM) 0.5 m Figure 4.8d Figure 4.8d The nucleus and its envelope (part 4: nuclear lamina, TEM) 7

Each chromosome is one long DNA molecule associated with proteins In the nucleus, DNA is organized into discrete units called chromosomes Each chromosome is one long DNA molecule associated with proteins The DNA and proteins of chromosomes are together called chromatin Chromatin condenses to form discrete chromosomes as a cell prepares to divide © 2014 Pearson Education, Inc. 8

Ribosomes: Protein Factories The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis Ribosomes are complexes of ribosomal RNA and protein Ribosomes carry out protein synthesis in two locations In the cytosol (free ribosomes) On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes) © 2014 Pearson Education, Inc. 9

Free ribosomes in cytosol Figure 4.9 0.25 m Ribosomes ER Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER Large subunit Small subunit Figure 4.9 Ribosomes TEM showing ER and ribosomes Diagram of a ribosome 10

Free ribosomes in cytosol Figure 4.9a 0.25 m Free ribosomes in cytosol Endoplasmic reticulum (ER) Ribosomes bound to ER Figure 4.9a Ribosomes (TEM) TEM showing ER and ribosomes 11

Components of the endomembrane system Concept 4.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell Components of the endomembrane system Nuclear envelope Endoplasmic reticulum (smooth and rough) Golgi apparatus Lysosomes Vacuoles Plasma membrane These components are either continuous or connected through transfer by vesicles © 2014 Pearson Education, Inc. 12

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: lacks ribosomes Rough ER: surface is studded with ribosomes Video: Endoplasmic Reticulum Video: ER and Mitochondria © 2014 Pearson Education, Inc. 13

0.2 m Smooth ER Rough ER Smooth ER Rough Nuclear ER envelope ER lumen Figure 4.10 0.2 m Smooth ER Rough ER Smooth ER Rough ER Nuclear envelope Figure 4.10 Endoplasmic reticulum (ER) ER lumen Cisternae Transitional ER Ribosomes Transport vesicle 14

The smooth ER Functions of Smooth ER Synthesizes lipids—such as hormones Detoxifies drugs and poisons—by adding hydroxyl, making molecule more soluble. Stores calcium ions—drives muscle cell contraction © 2014 Pearson Education, Inc. 15

The rough ER Functions of Rough ER Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates) Distributes transport vesicles, proteins surrounded by membranes Most proteins synthesized in rough ER are bound for membranes or excretion from cell Is a membrane factory for the cell © 2014 Pearson Education, Inc. 16

The Golgi Apparatus: Shipping and Receiving Center 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 Video: ER to Golgi Traffic Video: Golgi 3-D Video: Golgi Secretion © 2014 Pearson Education, Inc. 17

Golgi apparatus 0.1 m cis face (“receiving” side of Golgi apparatus) Figure 4.11 Golgi apparatus 0.1 m cis face (“receiving” side of Golgi apparatus) Cisternae Figure 4.11 The Golgi apparatus trans face (“shipping” side of Golgi apparatus) TEM of Golgi apparatus 18

Lysosomes: Digestive Compartments A lysosome is a membranous sac of hydrolytic enzymes that can digest macromolecules Breaks down macromolecules, providing more basic monomers for cell energy Lysosomal enzymes can hydrolyze proteins, fats, polysaccharides, and nucleic acids Lysosomal enzymes work best in the acidic environment inside the lysosome © 2014 Pearson Education, Inc. 19

A lysosome fuses with the food vacuole and digests the molecules 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 Animation: Lysosome Formation Video: Phagocytosis Video: Paramecium Vacuole © 2014 Pearson Education, Inc. 20

Lysosomes: Phagocytosis Figure 4.12 Nucleus 1 m Lysosome Digestive enzymes Figure 4.12 Lysosomes: phagocytosis Lysosome Plasma membrane Digestion Food vacuole Lysosomes: Phagocytosis 21

Lysosomes: Phagocytosis Figure 4.12a Digestive enzymes Lysosome Plasma membrane Digestion Food vacuole Figure 4.12a Lysosomes: phagocytosis (part 1: detail of art) Lysosomes: Phagocytosis 22

Vesicle containing two damaged organelles 1 m Figure 4.13 Vesicle containing two damaged organelles 1 m Mitochondrion fragment Peroxisome fragment Lysosome Figure 4.13 Lysosomes: autophagy Peroxisome Mitochondrion Digestion Vesicle Lysosomes: Autophagy 23

Lysosome Peroxisome Mitochondrion Digestion Vesicle Figure 4.13a Lysosome Peroxisome Mitochondrion Digestion Vesicle Figure 4.13a Lysosomes: autophagy (part 1: detail of art) Lysosomes: Autophagy 24

Vesicle containing two damaged organelles 1 m Figure 4.13b Vesicle containing two damaged organelles 1 m Mitochondrion fragment Peroxisome fragment Figure 4.13b Lysosomes: autophagy (part 2: TEM) 25

Vacuoles: Diverse Maintenance Compartments Vacuoles are large vesicles derived from the endoplasmic reticulum and Golgi apparatus © 2014 Pearson Education, Inc. 26

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 Certain vacuoles in plants and fungi carry out enzymatic hydrolysis like lysosomes © 2014 Pearson Education, Inc. 27

Central vacuole Cytosol Central vacuole Nucleus Cell wall Chloroplast Figure 4.14 Central vacuole Cytosol Central vacuole Nucleus Figure 4.14 The plant cell vacuole Cell wall Chloroplast Plant cell vacuole 5 m 28

Period 1 stopped

Cytosol Central vacuole Nucleus Cell wall Chloroplast 5 m Figure 4.14a Cytosol Central vacuole Nucleus Cell wall Figure 4.14a The plant cell vacuole (TEM) Chloroplast 5 m Plant cell vacuole 30

Concept 4.5: 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 © 2014 Pearson Education, Inc. 31

The Evolutionary Origins of Mitochondria and Chloroplasts 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 © 2014 Pearson Education, Inc. 32

The endosymbiont theory An early ancestor of eukaryotic cells engulfed a nonphotosynthetic prokaryotic cell, which formed an endosymbiont relationship with its host The host cell and endosymbiont merged into a single organism, a eukaryotic cell with a mitochondrion At least one of these cells may have taken up a photosynthetic prokaryote, becoming the ancestor of cells that contain chloroplasts Video: ER and Mitochondria Video: Mitochondria 3-D © 2014 Pearson Education, Inc. 33

using nonphotosynthetic prokaryote, which becomes a mitochondrion Figure 4.16 Endoplasmic reticulum Nucleus Engulfing of oxygen- using nonphotosynthetic prokaryote, which becomes a mitochondrion Nuclear envelope Ancestor of eukaryotic cells (host cell) Mitochondrion Engulfing of photosynthetic prokaryote At least one cell Figure 4.16 The endosymbiont theory of the origin of mitochondria and chloroplasts in eukaryotic cells Chloroplast Nonphotosynthetic eukaryote Mitochondrion Photosynthetic eukaryote 34

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 © 2014 Pearson Education, Inc. 35

Outer membrane Inner membrane Figure 4.17 Mitochondrion Intermembrane space Outer membrane DNA Inner membrane Free ribosomes in the mitochondrial matrix Figure 4.17 The mitochondrion, site of cellular respiration Cristae Matrix 0.1 m 36

Outer membrane Inner membrane Figure 4.17a Outer membrane Inner membrane Figure 4.17a The mitochondrion, site of cellular respiration (TEM) Cristae Matrix 0.1 m 37

Chloroplasts: Capture of Light Energy Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae © 2014 Pearson Education, Inc. 38

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 © 2014 Pearson Education, Inc. 39

Inner and outer membranes Figure 4.18a Ribosomes Stroma Inner and outer membranes Granum DNA Figure 4.18a The chloroplast, site of photosynthesis (part 1: detail) Thylakoid Intermembrane space 1 m (a) Diagram and TEM of chloroplast 40