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Cell Structure and Function






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Cell Structure and Function. Chapter 4 Part 2. 4.7 Visual Summary of Eukaryotic Cells. CENTRAL VACUOLE Increases cell surface area; stores metabolic wastes. CELL WALL Protects, structurally supports cell. CHLOROPLAST Specializes in photosynthesis. NUCLEUS. nuclear envelope.
Cell Structure and Function

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Slide 1

Cell Structure and Function

Chapter 4 Part 2

Slide 2

4.7 Visual Summary of Eukaryotic Cells

Slide 3

CENTRAL VACUOLE Increases cell surface area; stores metabolic wastes

CELL WALL

Protects, structurally supports cell

CHLOROPLAST Specializes in photosynthesis

NUCLEUS

nuclear envelope

Keeps DNA separated from cytoplasm; makes ribosome subunits; controls access to DNA

nucleolus

DNA in nucleoplasm

CYTOSKELETON

microtubules

Structurally supports, imparts shape to cell; moves cell and its components

microfilaments

RIBOSOMES

intermediate filaments (not shown)

(attached to rough ER and free in cytoplasm) Sites of protein synthesis

ROUGH ER

MITOCHONDRION

Modifies proteins made by ribosomes attached to it

Energy powerhouse; produces many ATP

by aerobic respiration

SMOOTH ER

Makes lipids, breaks down carbohydrates and fats, inactivates toxins

PLASMODESMA

Communication junction between adjoining cells

GOLGI BODY

Finishes, sorts, ships lipids, enzymes, and membrane and secreted proteins

PLASMA MEMBRANE

Selectively controls the kinds and amounts of substances moving into and out of cell; helps maintain cytoplasmic volume, composition

LYSOSOME-LIKE VESICLE

Digests, recycles materials

a Typical plant cell components.

Fig. 4-15a, p. 63

Slide 4

4.7 Visual Summary of Eukaryotic Cells

Slide 5

NUCLEUS

Keeps DNA separated from cytoplasm; makes ribosome subunits; controls access to DNA

nuclear envelope

nucleolus

CYTOSKELETON

DNA in nucleoplasm

Structurally supports, imparts shape

to cell; moves cell and its components

microtubules

microfilaments

RIBOSOMES

(attached to rough ER and free in cytoplasm) Sites of protein synthesis

intermediate filaments

MITOCHONDRION

Energy powerhouse; produces many ATP by aerobic respiration

ROUGH ER Modifies proteins made by ribosomes attached to it

CENTRIOLES

SMOOTH ER

Makes lipids, breaks down carbohydrates and fats, inactivates toxins

Special centers that produce and organize microtubules

GOLGI BODY

PLASMA MEMBRANE

Selectively controls the kinds and amounts of substances moving into and out of cell; helps maintain cytoplasmic volume, composition

Finishes, sorts, ships lipids, enzymes, and membrane and secreted proteins

LYSOSOME

Digests, recycles materials

Fig. 4-15b, p. 63

Slide 6

4.8 The Nucleus

  • The nucleus keeps eukaryotic DNA away from potentially damaging reactions in the cytoplasm

  • The nuclear envelope controls when DNA is accessed

Slide 7

The Nuclear Envelope

  • Nuclear envelope

    • Two lipid bilayers pressed together as a single membrane surrounding the nucleus

    • Outer bilayer is continuous with the ER

    • Nuclear pores allow certain substances to pass through the membrane

Slide 8

The Nucleoplasm and Nucleolus

  • Nucleoplasm

    • Viscous fluid inside the nuclear envelope, similar to cytoplasm

  • Nucleolus

    • A dense region in the nucleus where subunits of ribosomes are assembled from proteins and RNA

Slide 9

The Chromosomes

  • Chromatin

    • All DNA and its associated proteins in the nucleus

  • Chromosome

    • A single DNA molecule with its attached proteins

    • During cell division, chromosomes condense and become visible in micrographs

    • Human body cells have 46 chromosomes

Slide 10

Chromosome Condensation

Slide 11

one chromosome (one unduplicated DNA molecule)

one chromosome (one duplicated DNA molecule, partially condensed)

one chromosome (one duplicated DNA molecule, completely condensed)

p. 65

Slide 12

4.9 The Endomembrane System

  • Endomembrane system

    • A series of interacting organelles between the nucleus and the plasma membrane

    • Makes lipids, enzymes, and proteins for secretion or insertion into cell membranes

    • Other specialized cell functions

Slide 13

The Endoplasmic Reticulum

  • Endoplasmic reticulum (ER)

    • An extension of the nuclear envelope that forms a continuous, folded compartment

  • Two kinds of endoplasmic reticulum

    • Rough ER (with ribosomes) folds polypeptides into their tertiary form

    • Smooth ER (no ribosomes) makes lipids, breaks down carbohydrates and lipids, detoxifies poisons

Slide 14

Vesicles

  • Vesicles

    • Small, membrane-enclosed saclike organelles that store or transport substances

  • Peroxisomes

    • Vesicles containing enzymes that break down hydrogen peroxide, alcohol, and other toxins

  • Vacuoles

    • Vesicles for waste disposal

Slide 15

Golgi Bodies and Lysosomes

  • Golgi body

    • A folded membrane containing enzymes that finish polypeptides and lipids delivered by the ER

    • Packages finished products in vesicles that carry them to the plasma membrane or to lysosomes

  • Lysosomes

    • Vesicles containing enzymes that fuse with vacuoles and digest waste materials

Slide 16

The Endomembrane System

Slide 17

The Endomembrane System

Slide 18

The Endomembrane System

Slide 19

nucleus

rough ER

smooth ER

Golgi body

vesicles

Fig. 4-18a, p. 66

Slide 20

A Nucleus

Inside the nucleus, DNA instructions

for making proteins are transcribed

into RNA, which moves through

nuclear pores into the cytoplasm.

protein

RNA

C Vesicles

Vesicles that bud from the rough ER carry some of the new proteins to Golgi bodies. Other proteins migrate through the interior of the rough ER, and end up in thesmooth ER.

B Rough ER

Some of the RNA in the cytoplasm is translated into polypeptide chains

by ribosomes attached to the rough ER. The chains enter the rough ER, where they are modified into final form.

ribosome attached to ER

vesicle budding from ER

Fig. 4-18b, p. 66

Slide 21

F Plasma membrane

Golgi vesicles fuse with the plasma membrane. Lipids and proteins of a vesicle’s membrane fuse with the plasma membrane, and the vesicle’s contents are released to the exterior of the cell.

D Smooth ER

Some proteins

from the rough

ER are packaged into new vesicles and shipped to

the Golgi. Others become enzymes

of the ER, which assemble lipids or inactivate toxins.

E Golgi body Proteins arriving in vesicles from the ER are modified into final form and sorted. New vesicles carry them to the plasma membrane

or to lysosomes.

protein in smooth ER

Fig. 4-18c, p. 67

Slide 22

4.10 Lysosome Malfunction

  • When lysosomes do not work properly, some cellular materials are not properly recycled, which can have devastating results

  • Different kinds of molecules are broken down by different lysosomal enzymes

    • One lysosomal enzyme breaks down gangliosides, a kind of lipid

Slide 23

Tay Sachs Disease

  • In Tay Sachs disease, a genetic mutation alters the lysosomal enzyme that breaks down gangliosides, which accumulate in nerve cells

    • Affected children usually die by age five

Slide 24

4.11 Other Organelles

  • Eukaryotic cells make most of their ATP in mitochondria

  • Plastids function in storage and photosynthesis in plants and some types of algae

Slide 25

Mitochondria

  • Mitochondrion

    • Eukaryotic organelle that makes the energy molecule ATP through aerobic respiration

    • Contains two membranes, forming inner and outer compartments; buildup of hydrogen ions in the outer compartment drives ATP synthesis

    • Has its own DNA and ribosomes

    • Resembles bacteria; may have evolved through endosymbiosis

Slide 26

Mitochondrion

Slide 27

outer membrane

outer compartment

inner compartment

inner membrane

0.5 µm

Fig. 4-20, p. 69

Slide 28

Plastids

  • Plastids

    • Organelles that function in photosynthesis or storage in plants and algae; includes chromoplasts, amyloplasts, and chloroplasts

  • Chloroplasts

    • Plastids specialized for photosynthesis

    • Resemble photosynthetic bacteria; may have evolved by endosymbiosis

Slide 29

The Chloroplast

Slide 30

two outer membranes

stroma

thylakoids

(inner membrane system folded into flattened disks)

Fig. 4-21, p. 69

Slide 31

The Central Vacuole

  • Central vacuole

    • A plant organelle that occupies 50 to 90 percent of a cell’s interior

    • Stores amino acids, sugars, ions, wastes, toxins

    • Fluid pressure keeps plant cells firm

Slide 32

4.12 Cell Surface Specializations

  • A wall or other protective covering often intervenes between a cell’s plasma membrane and the surroundings

Slide 33

Eukaryotic Cell Walls

  • Animal cells do not have walls, but plant cells and many protist and fungal cells do

  • Primary cell wall

    • A thin, pliable wall formed by secretion of cellulose into the coating around young plant cells

  • Secondary cell wall

    • A strong wall composed of lignin, formed in some plant stems and roots after maturity

Slide 34

Plant Cell Walls

Slide 35

Fig. 4-22a, p. 70

Slide 36

middle lamella

plasma membrane

cytoplasm

A Plant cell secretions form the middle lamella,

a layer that cements adjoining cells together.

primary

cell wall

Fig. 4-22a, p. 70

Slide 37

Fig. 4-22b, p. 70

Slide 38

B In many plant tissues, cells also secrete materials that are deposited in layers on the inner surface of their primary wall. These layers strengthen the

wall and maintain its shape. They remain after the

cells die, and become

part of pipelines

that carry water

through the

plant.

secondary cell wall (added in layers)

primary

cell wall

pipeline

made of

abutting

cell walls

Fig. 4-22b, p. 70

Slide 39

Fig. 4-22c, p. 70

Slide 40

middle lamella

C Plasmodesmata are channels across the cell walls and the plasma membranes of living cells that are pressed against one another in tissues.

plasmodesma

middle lamella

Fig. 4-22c, p. 70

Slide 41

A Plant cell secretions form the middle lamella, a layer that cements adjoining cells together.

middle lamella

plasma membrane

cytoplasm

B In many plant tissues, cells also secrete materials that are deposited in layers on the inner surface of their primary wall. These layers strengthen the wall and maintain its shape. They remain after the cells die, and become part of pipelines that carry water through the

plant.

middle lamella

C Plasmodesmata are channels across the cell walls and the plasma membranes of living cells that are pressed against one another in tissues.

primary

cell wall

secondary cell wall (added in layers)

plasmodesma

primary

cell wall

middle lamella

pipeline

made of

abutting

cell walls

Stepped Art

Fig. 4-22, p. 70

Slide 42

Plant Cuticle

  • Cuticle

    • A waxy covering that protects exposed surfaces and limits water loss

Slide 43

thick, waxy cuticle at leaf surface

cell of leaf epidermis

photosynthetic cell inside leaf

Fig. 4-23, p. 71

Slide 44

Matrixes Between Animal Cells

  • Extracellular matrix (ECM)

    • A nonliving, complex mixture of fibrous proteins and polysaccharides secreted by and surrounding cells; structure and function varies with the type of tissue

    • Example: Bone is mostly ECM, composed of collagen (fibrous protein) and hardened by mineral deposits

Slide 45

ECM

  • A bone cell surrounded by extracellular matrix

Slide 46

Cell Junctions

  • Cell junctions allow cells to interact with each other and the environment

  • In plants, plasmodesmata extend through cell walls to connect the cytoplasm of two cells

  • Animals have three types of cell junctions: tight junctions, adhering junctions, gap junctions

Slide 47

Cell Junctions in Animal Tissues

Slide 48

free surface of epithelial tissue

different kinds of tight junctions

gap junction

basement membrane (extracellular matrix)

adhering junction

Fig. 4-25, p. 71

Slide 49

4.6-4.12 Key Concepts:Eukaryotic Cells

  • Cells of protists, plants, fungi, and animals are eukaryotic; they have a nucleus and other membrane-enclosed compartments

  • They differ in internal parts and surface specializations

Slide 50

4.13 The Dynamic Cytoskeleton

  • Eukaryotic cells have an extensive and dynamic internal framework called a cytoskeleton

  • Cytoskeleton

    • An interconnected system of many protein filaments – some permanent, some temporary

    • Parts of the cytoskeleton reinforce, organize, and move cell structures, or even a whole cell

Slide 51

Components of the Cytoskeleton

  • Microtubules

    • Long, hollow cylinders made of tubulin

    • Form dynamic scaffolding for cell processes

  • Microfilaments

    • Consist mainly of the globular protein actin

    • Make up the cell cortex

  • Intermediate filaments

    • Maintain cell and tissue structures

Slide 52

Components of the Cytoskeleton

Slide 53

Fig. 4-26 (a-c), p. 72

Slide 54

Fig. 4-26a, p. 72

Slide 55

tubulin subunit

25 nm

Microtubule

Fig. 4-26a, p. 72

Slide 56

Fig. 4-26b, p. 72

Slide 57

actin subunit

6–7 nm

Microfilament

Fig. 4-26b, p. 72

Slide 58

one

polypeptide chain

Intermediate filament

Fig. 4-26c, p. 72

Slide 59

actin subunit

one

polypeptide chain

tubulin subunit

Intermediate filament

25 nm

6–7 nm

Microtubule

Microfilament

Stepped Art

Fig. 4-26, p. 72

Slide 60

Motor Proteins

  • Motor proteins

    • Accessory proteins that move molecules through cells on tracks of microtubules and microfilaments

    • Energized by ATP

    • Example: kinesins

Slide 61

Motor Proteins: Kinesin

Slide 62

Cilia, Flagella, and False Feet

  • Eukaryotic flagella and cilia

    • Whiplike structures formed from microtubules organized into 9 + 2 arrays

    • Grow from a centriole which remains in the cytoplasm as a basal body

  • Psueudopods

    • “False feet” used by amoebas and other eukaryotic cells to move or engulf prey

Slide 63

Moving Cells

  • Flagellum of the human sperm, and pseudopods of a predatory amoeba

Slide 64

Fig. 4-28a, p. 73

Slide 65

Fig. 4-28b, p. 73

Slide 66

Eukaryotic Flagella and Cilia

Slide 67

Fig. 4-29a, p. 73

Slide 68

protein spokes

pair of microtubules in a central sheath

pair of microtubules

plasma membrane

A Sketch and micrograph of one eukaryotic flagellum, cross-section. Like a cilium, it contains a 9+2 array: a ring of nine pairs of microtubules plus one pair at its core. Stabilizing spokes and linking elements that connect to the microtubules keep them aligned in this radial pattern.

dynein arms

Fig. 4-29a, p. 73

Slide 69

Fig. 4-29b, p. 73

Slide 70

B Projecting from each pair of microtubules in the outer ring are “arms” of dynein, a motor protein that has ATPase activity. Phosphate-group transfers from ATP cause the dynein arms to repeatedly bind the adjacent pair of microtubules, bend, and then disengage. The dynein arms “walk” along the microtubules. Their motion causes adjacent microtubule pairs to slide past one another

basal body, a microtubule organizing center that gives rise to the 9+2 array and then remains beneath it, inside the cytoplasm

Fig. 4-29b, p. 73

Slide 71

Fig. 4-29c, p. 73

Slide 72

C Short, sliding strokes occur in a coordinated sequence around the ring, down the length of each microtubule pair. The flagellum bends as the array inside bends:

Fig. 4-29c, p. 73

Slide 73

4.13 Key Concepts:A Look at the Cytoskeleton

  • Diverse protein filaments reinforce a cell’s shape and keep its parts organized

  • As some filaments lengthen and shorten, they move cell structures or the whole cell

Slide 74

Summary: Components of Prokaryotic and Eukaryotic Cells


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