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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.

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Presentation on theme: "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."— Presentation transcript:

1 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.

2 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.

3 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.

4 Figure 4.8a Ribosome Chromatin Rough ER Nucleus Nucleolus Chromatin Nuclear envelope: Nuclear pore Inner membrane Outer membrane Pore complex Close-up of nuclear envelope

5 Figure 4.8b 1  m Nuclear envelope: Nuclear pore Inner membrane Outer membrane Surface of nuclear envelope

6 Figure 4.8c 0.25  m Pore complexes (TEM)

7 Figure 4.8d 0.5  m Nuclear lamina (TEM)

8 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.

9 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.

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

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

12 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.

13 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 © 2014 Pearson Education, Inc. Video: Endoplasmic Reticulum Video: ER and Mitochondria

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

15 Functions of Smooth ER The 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.

16 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 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.

17 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 © 2014 Pearson Education, Inc. Video: Golgi 3-D Video: Golgi Secretion Video: ER to Golgi Traffic

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

19 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.

20 Animation: Lysosome Formation Video: Phagocytosis 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 © 2014 Pearson Education, Inc. Video: Paramecium Vacuole

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

22 Figure 4.12a Lysosome Digestive enzymes Plasma membrane Food vacuole Lysosomes: Phagocytosis Digestion

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

24 Figure 4.13a Lysosome Lysosomes: Autophagy Peroxisome Mitochondrion Vesicle Digestion

25 Figure 4.13b Mitochondrion fragment Peroxisome fragment Vesicle containing two damaged organelles 1  m

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

27 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.

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

29 Period 1 stopped

30 Figure 4.14a Central vacuole Chloroplast Cytosol Cell wall Nucleus Plant cell vacuole 5  m

31 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.

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

33 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 © 2014 Pearson Education, Inc. Video: ER and Mitochondria Video: Mitochondria 3-D

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

35 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.

36 Figure 4.17 Free ribosomes in the mitochondrial matrix Mitochondrion Intermembrane space Matrix Cristae DNA Outer membrane Inner membrane 0.1  m

37 Figure 4.17a Matrix Cristae Outer membrane Inner membrane 0.1  m

38 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.

39 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.

40 Figure 4.18a Intermembrane space Ribosomes Inner and outer membranes 1  m Stroma Granum DNA Thylakoid (a) Diagram and TEM of chloroplast


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