1. 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
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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
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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
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4. 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

5. 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

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

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

8. 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
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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)
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10. 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

11. 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

12. 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
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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
Video: Endoplasmic Reticulum
Video: ER and Mitochondria
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14. 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

15. 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
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16. 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
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17. 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
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18. 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

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
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20. 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
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21. 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

22. 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

23. 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

24. 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

25. 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

26. Vacuoles: Diverse Maintenance Compartments
Vacuoles are large vesicles derived from the endoplasmic reticulum and Golgi apparatus
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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
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28. 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

29. Period 1 stopped

30. 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

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
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32. 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
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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
Video: ER and Mitochondria
Video: Mitochondria 3-D
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34. 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

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
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36. 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

37. 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

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
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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
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40. 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