Chapter 7A Tour of the Cell -- Part 1

TOPICS: How to study cells

Eukaryotic vs Prokaryotic

Nucleus and Ribosomes

Endomembrane system

Other membranous organelles

How do we study cells?How do we study cells?

Know the different microscopes and their purposes: Light microscope (what we have at TPHS) Electron microscope SEM (scanning)—surface “scanning”, the outside (see

fig. 7.2, 7.9, or 7.23 b in the book) TEM (transmission)—”transmits” through the specimen

to see inside. (see fig. 7.2, 7.13 b, or 7.18 in the book)

Figure 7.1: size range in cells

Figure 7.3Figure 7.3cell fractionation, centrifugecell fractionation, centrifuge

What are the largest organelles/parts of a cell that fraction off into the pellet first? What are the smallest? (last)

Why are most cells Why are most cells so small?so small?

THIS IS REVIEW: Prokaryotic (“before”, “kernel” aka: nucleus) Archaea and Bacteria, no nucleus, no membrane-bound

organelles, usually much smaller, figure 7.4, they have: cytoplasm, cytosol, 1 circular chromosome, plasma membrane, cell wall, ribosomes, nucleiod.

Eukaryotic (“true”, “kernel”) Membrane-bound nucleus and other organelles,

compartmentalized cells, animals, plants, fungi, protists. These cells are larger due to compartmentalization.

Figures on pages 108 – 109.Figures on pages 108 – 109.

Know the names, identify the structures and know the functions of all of the organelles listed on these diagrams.

Know major differences between the typical animal and typical plant cells.

Animals: centrioles, Plants: (plastids) chloroplasts, cell wall,

large central vacuole, tonoplast

The Nucleus and Ribosomes

Nucleus: contains most of the genes that control a Eukaryotic cell.

Nuclear envelope/nuclear lamina: porous (why?) and double membrane

Chromatin (46)/ tightly coiled chromosomes (46), genes Nucleolus, synthesizes ribosomes, in the nucleus Ribosomes: site of protein synthesis Free ribosomes=for the production of proteins to be used in

the cytosol and attached ribosomes =on the ER for the production of proteins which are packaged or exported via the ER system.

Pores Lamina Outer and

inner mem-branes

Nucleolus Ribosomes Attachment

site of ER

Free and bound ribosomes, ER

Endomembrane system

Definition: all of these structures have interchangeable membranes, they are all made of a phospholipid bilayer and are fusible with one another.

Includes: nuclear envelope (lamina)ERGolgi apparatuslysosomesvacuolesplasma membrane

See Figures 7.14, 7.16, 8.7

Why aren’t mitochondria and chloroplasts in this

group?

The endomembrane system’s interconnectedness. All membranes are the same bilayer.

Endoplasmic ReticulumEndoplasmic Reticulum

“Network” of membranes “within the cytoplasm” (compartmentalization: cisternal space) Rough ER: network attached to the nucleus.

Example proteins which are made from the attached ribosomes and then “shipped” via the ER: insulin, glycoproteins, transport vesicles.

Smooth ER: conducts diverse processes: synthesizes Lipids, detoxifies drugs, metabolizes carbos.: ex: glycogen hydrolysis (breakdown) in the liver.

Golgi Apparatus / BodiesGolgi Apparatus / Bodies

Modification and sorting of products from the ER.

Secretion organelle Flattened sacs (cisternae), cis and trans faces,

(“receiving” and “shipping/transport” sides of the golgi apparatus)

Fusion of membranes (fig 7.14, 7.16, & 8.7) is possible since the ER and the Golgi are both of the endomembrane system.

Some vesicles have external “identification” molecules *see fig. 8.7

Fig. 7.14 Notice how the vesicle from the ER fuses with the cis side of the golgi and then the trans side of the golgi fuses with a food vacuole to deliver digestive enzymes.

Lysosomes Fig. 7.14Lysosomes Fig. 7.14

Contains hydrolytic enzymes which digest macromolecules and recycle materials from the cell. (see fig 7.14)

Usually maintains pH of 5 (acid)

VacuolesVacuoles

Many types: Food vacuoles (in all cells) Contractile vacuoles, in protists

like the paramecium (*fig 8.12) for osmoregulation (water regulation).

Plants: large central vacuole (tonoplast)

MitochondriaMitochondria

Energy transformation (from glucose to ATP)

Cellular respiration and ATP generation Contain a small amount of their own DNA

(semiautonomous) (Ch. 28), not of the endomembrane system.

Double phospholipid bilayer. Cristae, large surface area. Inner membrane and Matrix.

* More to come… stay tuned for Chapters 9-10 *

Know the parts…

Chloroplasts Chloroplasts (a type of plastid)(a type of plastid)

Energy transformations (sun energy to ATP) Photosynthesis (CO2 and H2O to Glucose) Synthesize organic molecules from carbon

dioxide and water. Contain a small amount of their own DNA

(semiautonomous) (Ch 28) Double membrane, thylakoids, grana,

stroma fluid

Know the parts:Stroma = fluidthylakoid membranes = are chlorophyll rich

grana = stacks of many thylakoids, site of light reactions (because of chlorophyll.)

Peroxisomes Peroxisomes

Consume deadly free oxygen within the cell, transport it to mitochondria.

Enzymes transfer hydrogen to oxygen, producing hydrogen peroxide (H2O2)

H2O2 is also toxic to a cell, and an enzyme made by the peroxisome can break down H2O2

Fig. 7.19