A Tour of the Cell

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8

The chloroplast is a member of a family of organelles called plastids

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

Slide 62

Chloroplast structure includes:

Thylakoids, membranous sacs, stacked to form a granum

Stroma, the internal fluid

Slide 63

Fig. 6-18

Ribosomes

Thylakoid

Stroma

Granum

Inner and outer membranes

1 µm

Slide 64

Peroxisomes: Oxidation

Peroxisomes are specialized metabolic compartments bounded by a single membrane

Peroxisomes produce hydrogen peroxide and convert it to water

Oxygen is used to break down different types of molecules

Slide 65

Fig. 6-19

1 µm

Chloroplast

Peroxisome

Mitochondrion

Slide 66

Concept 6.6: 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

Slide 67

Fig. 6-20

Microtubule

Microfilaments

0.25 µm

Slide 68

Roles of the Cytoskeleton: Support, Motility, and Regulation

The cytoskeleton helps to support the cell and maintain its shape

It interacts with motor proteins to produce motility

Inside the cell, vesicles can travel along “monorails” provided by the cytoskeleton

Recent evidence suggests that the cytoskeleton may help regulate biochemical activities

Slide 69

Fig. 6-21

Vesicle

ATP

Receptor for motor protein

Microtubule

of cytoskeleton

Motor protein (ATP powered)

(a)

Microtubule

Vesicles

(b)

0.25 µm

Slide 70

Components of the Cytoskeleton

Three main types of fibers make up the cytoskeleton:

Microtubules are the thickest of the three components of the cytoskeleton

Microfilaments, also called actin filaments, are the thinnest components