Midterm Review #4:

Enzyme Activity;

Cellular Structures and Functions

White Blood Cells

Prokaryotes and Eukaryotes are Different

But the following may be said of all cells (Prokaryotes and Eukaryotes)

ALL are surrounded, protected, and separated from the abiotic world by a PLASMA MEMBRANE.

EITHER group may also have a CELL WALL (tough, strong outer covering to protect and contain pressure)

Prokaryotes and Eukaryotes

Prokaryotes and Eukaryotes

Both have a NUCLEUS or NUCLEOID containing GENETIC MATERIAL

(Eukaryotes have a NUCLEAR ENVELOPE that surrounds and protects this material.)

Prokaryotes and Eukaryotes

BOTH complete COMPLEXMETABOLIC PROCESSES(chemical reactions that assemble or disassemble polymers, often storing and releasing chemical energy).

ENZYMES• Are a special class of polymers (mostly proteins)

that catalyze chemical reactions in cells.• EVERY metabolic reaction is helped by one or

more enzymes.• In the graphic at

right, an enzymeis doing this by reducing the acti-vation energy needed to com-plete a reaction.

Enzyme Structure and FunctionThis figure shows an enzyme, its substrates (reactants) and products in a catalyzed reaction. Where is the “active site?” how does it work? What does the

enzyme do to the substratesand how?

How much is the rate of thisreaction sped up?

How this is Affected by Surrounding Factors

Every enzyme operates in an aqueous (watery) environment (such as plasma or cytoplasm).

Enzymes have “optimal” (ideal) surrounding conditions, including: Temperature pH (concen-

tration of H+

vs. OH- ions).

Cell Research PioneersName Dates of

ResearchSummary of Findings/Conclusions

Robert Hooke 1635-1703 Physicist, astronomer, architect, physician. Using a basic compound microscope, he observed that cork is divided into units (“cells”) impossible to see with the naked eye.

Anton Van Leeuwenhoek

1632-1723 Carpet merchant; amateur physicist. Using a simple microscope, observed unicellular creatures moving in pond water, the human mouth, and various other locations.

Matthias Schleiden 1804-1881 Botanist and plant physiologist. Determined that all plants are entirely made of individual, specialized cells, including reproductive cells.

Theodor Schwann 1810-1882 Animal physiologist (contemporary of Pasteur). Learned that animals are also entirely made of individual, specialized cells. Those cells only come from pre-existing cells.

Rudolph Virchow 1821-1902 Learned that disease originates in individual cells, and may be spread through contamination of food and water combined with reproduction of disease organisms.

Lynn Margulis  1935-2011 Professor of cellular physiology. Based upon their separate DNA and their ability to reproduce within eukaryotic cells, inferred that mitochondria may have once been free-living prokaryotes that enter and co-evolved with eukaryotic symbionts. (This hypothesis is called “symbiogenesis.”)

Modern Cell Viewing TechnologiesLight Microscope Electron MicroscopeProjects light through a thinly-sliced specimen. Magnifies the image using ground, polished optical lenses.

Projects a beam of electrons at the specimen. Steers and focuses the beam using electromagnets. Once the beam strikes the specimen, it may reflect (producing a magnified surface image) or it may cast a “shadow” of the cells’ internal structures.

How it Works

Relatively inexpensive; easily used and maintained; may be used to see live cells at magnifications up to about 1000X

May be used to see specimens at magnification approaching 2 million X. May be used to see structures less than 1 micron in diameter.

Advantages

Limited magnification; limited ability to see objects that are not transparent.

Instrument may cost several hundred thousand dollars and is difficult to maintain. Objects must be observed in a vacuum chamber. Cells cannot survive electron beam, vacuum, or metal plating used to see surface features.

Disadvantages

Eukaryotic Cell Structure

Comparing Eukaryotes to Prokaryotes

Prokaryotes are smaller (less complexity, no nucleus or organelles)

All metabolic activity in a prokaryote must take place in the cytoplasm or on/across the plasma membrane. (Example: ribosomes are all “free floating”)

Prokaryotes have 1, circular chromosome (rather than several)

Prokaryotes reproduce by a simpler process called “binary fission”

Cytoplasm (cytosol & contents)All contents of the cell between its nuclear envelope & cell membrane (water, salts, enzymes, filaments, tubules, organelles, etc.)

Aqueous environment in which metabolism may occur.

Microfilaments

Narrow protein structures offering tensile (“stretching”) structure to the cell & used to transport substances through it (part of the cytoskeleton)

Microtubules

Contractile or supportive filaments—capable of being reduced or extended in length

Offer compressive structure, change of shape, and amoeboid movement

Can be polymerized or broken down as necessary to change length

Centrioles

Small, protein bundles used during cell division

Attach to the chromosomes after copying, pulling them toward the ends of the dividing cell before cytokinesis

Nuclear Envelope

Separates cytoplasm from nucleoplasm; along with other organelles,only found in eukaryotes

NucleusLatin for “center.”

Once regarded as the cell’s “boss” or center of control and coordination. This is now regarded as over-simplification.

Cytoplasm & nucleus are now regarded as an “interactive pair”

Chromatin (DNA & associated proteins)

Genetic material: used to control protein synthesis and cell reproduction;

DNA helix is “super-coiled”—wound tightly & bound with “smart” proteins called histones

Only visible immediately before & during cell division

Nucleolus

Dense section of DNA used for formation of ribosomal RNA

rRNA made here leaves nucleus only as needed to form proteins on rough endoplasmic reticulum and in cytoplasm

(DNA only leaves nucleus during cell reproduction)

Vacuole

Membrane-bound storage center.

Generally small in animal cells, but occupies most of a plant or algal cell.

Used to maintain turgor (internal water pressure).

Vesicles / Lysosomes / Peroxisomes

• Generally, small spaces surrounded by membrane and used for shipping and storage.

• Lysosomes & peroxisomes are used to store and move digestive enzymes (used to break down polymers)

Mitochondrion(a)

Often called the “powerhouses” of eukaryotic cells

Chief site of ATP production (using glucose to do so; oxygen must also be available in plentiful supply)

Chloroplasts

Found only in photo-autotrophs

Generate glucose (and other carbohydrates) from CO2 and water

Oxygen (needed by all eukaryotes) is released as a byproduct

Endoplasmic Reticulum & Ribosomes

Complex system of interconnected passageways.

Used for protein synthesis, trans-port, cell detoxification, and packaging

Golgi Apparatus

• “Pancake- shaped”

• Lipid synthesis and finishing of proteins exported from cell

• “UPS” (Packaging & transport of many chemicals)

Midterm Review #4:

Enzyme Activity;

Cellular Structures and Functions

White Blood Cells