CHAPTER 6

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A TOUR OF THE CELL
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biology 201
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1

Light Microscope (LM)

visible light passes through a specimen and then through glass lenses, which magnify the image

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The quality of an image depends on

Magnification, Resolution and Contrast

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Magnification:

the ratio of an object’s image size to its real size

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Resolution:

the measure of the clarity of the image, or the minimum distance of two distinguishable points
1 star in sky may really be two using a telescope

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Contrast:

visible differences in parts of the sample

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Electron microscope (EM)

Most cell structures “organelles"

Can even view small molecules

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Scanning electron microscopes (SEMs)

focus a beam of electrons onto the surface of a specimen, providing images that look 3-D

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Transmission electron microscopes (TEMs)

focus a beam of electrons through a specimen
TEMs are used mainly to study the internal structure of cells

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The basic structural and functional unit of every organism is one of two types of cells

prokaryotic or eukaryotic

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prokaryotic cells

Only organisms of the domains Bacteria and Archaea

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eukaryotic cells

Protists, fungi, animals, and plants

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Basic features of ALL cells:

Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
Ribosomes (make proteins)

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phospholipids

a lipid containing a phosphate group in its molecule

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Lipids

any of a class of organic compounds that are fatty acids or their derivatives and are insoluble in water but soluble in organic solvents. They include many natural oils, waxes, and steroids.

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Plasma Membrane protected by

A selective barrier made of a double layer of phospholipids

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The nucleus

contains most of the cell’s genes
DNA also in mitochondria and chloroplasts

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The nuclear envelope

encloses the nucleus, separating it from the cytoplasm

a double membrane; each membrane consists of a lipid bilayer

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Pores

regulate the entry and exit of molecules from the nucleus

Inner and outer envelope are connected

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nuclear lamina

The shape of the nucleus is maintained, which is composed of protein
A matrix for support

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Ribosomes

are particles made of ribosomal RNA and protein

Ribosomes carry out protein synthesis in two locations

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The endomembrane system

Regulates protein and lipid traffic, detoxifies poisons and performs metabolic functions in the cell