Cell Biology Chapter One

Intermolecular interactions

the chemical personality of a molecule determines how it will interact with other molecules

Intramolecular interactions

determine the structure and activity within the molecule

Eubacteria

Kingdom of unicellular prokaryotes whose cell walls are made up of peptidoglycan

Green alga

A member of a group of photosynthetic protists that includes chlorophytes and charophyceans, the closest living relatives of land plants. Green algae include unicellular, colonial, and multicellular species.

Epithelial sheet

thin layer of simple squamous epithelium

Archaebacteria

kingdom of unicellular prokaryotes whose cell walls do not contain peptidoglycan

Purkinje neuron

Cell with a type of dendritic branching that looks like a tree

Robert Hook

Built the first microscope and coined the term "cellula" (cell).

How did Robert Hooke discover cells?

With his microscope, he examined thin slices of cork cut with a penknife. He saw tiny box-life compartments that looked like honeycomb which he called "cells"

Antoine van Leeuwenhoek

Developed superior lenses for the rudimentary microscope created by Robert Hook. These lenses could magnify lenses almost 300 times their size. He thus was the first to observe living cells

What was the resolution of Hooke's microscope

Only 30x

What were the two factors that restricted further understanding of the nature of cells

Limited resolution and the descriptive nature of seventeenth-century biology

Seventeenth-century biology observation

It was basically an age of observation, with little thought given to explaining the intriguing architectural details of biological materials that were beginning to yield the probing lens of the microscope

What was the time period in the 18th and 19th century that was deemed unproductive in the field of cell biology

1700 AD to 1825 AD

What happened in cell biology in 1830

Improved lenses with better magnification were invented thus resulting in an improvement in magnification. Microscopes could now resolve structures, micrometers in size

Robert Brown

coined the term "nucleus".

Why was it so easy to distinguish plant cells and why it was thought that animal and plants cells did not resemble each other

every plant cell Robert Brown looked at contained a rounded structure which he called a nucleus. German cytologist Theodor Schwann came to the same conclusion as Matthias Schleiden did by noticing that animal tissues were also composed of cells hence laying to rest earlier speculations that plants and animals might not resemble each other structurally

What important conclusion did German colleague of Robert Brown, Matthias Schleiden, come to when studying plant cells

all plant tissues are composed of cells and that an embryonic plant always arises from a single cell

Theodor Schwann

concluded that all animals are made of cells and that their tissues were comprised up of cells in the same way that plant tissues were

The Cell Thoery

1. All living things are composed of one or more cells

2. Cells are basic unit of structure and function in an organism

3. Cells only come from pre-existing cells

What are cells seen as in all organisms?

The basic unit of structure AND reproduction for all organisms

ORGERRE

Cells have the characteristics of life being: Order, Regulation (internal), Growth and Development, Energy Utilization, Response to Environment, Reproduction, and Evolution

O of the characteristics of life

order

R of the characteristics of life

Regulation (internal)

G of the characteristics of life

Growth and development

E of the characteristics of life

Energy utlization

R (2) of the characteristics of life

Response to the environment

R (3) of the characteristics of life

Reproduction

E (2/final) of the characteristics of life

Evolution

By 1855, what did German physiologist Rudolf Virchow conclude about cells

That cells arose only by the division of other, preexisting cells. He encapsulated this conclusion in the now-famous Latin phrase omnis cellula e cellula which translates to "All cells arise only from preexisting cells"

Omnis cellula e cellula

every cell originates from another cell

Micrometer

millionth of a meter. It is the most useful unit for expressing the size of cells and larger organelles.

What is a micrometer sometimes called

a micron

Bacteria and plant and animal cell relative sizes

Bacterial cells are a few micrometers in diameter, and the cells of plants and animals are 10 to 20 times larger in any single dimension

Organelles and bacteria relative size

Organelles such as mitochondria and chloroplasts tend to have diameters or lengths of a few micrometers and are thus comparable in size to whole bacterial cells

Nanometer

one billionth of a meter. The unit of choice for molecules and subcellular structures that are too small or too thin to be seen with the light microscope.

Structures that can be measured conveniently in nanometers

ribosomes, microtubules, microfilaments, membranes, and DNA molecules

Angstrom

10^-10. Equals that of 0.1 nanometers and is about the size of a hydrogen atom

The first strand of cell biology to emerge

cytology

Cytology

concerned primarily with cellular structure. It had its origins more than three centuries ago and depended heavily on the light microscope

Biochemistry

chemistry dealing with chemical compounds and processes in living plants and animals. It represents our understanding of cellular function.

When did most of the developments in the field of biochemistry occur

Over the past 75 years though the roots go back much further

What techniques of biochemistry have been developed?

ultracentrifugation, chromatography, electrophoresis, and mass spectrometry for separating and identifying cellular components and molecules

Genetics

The scientific study of heredity

When did genetics have its beginning as a science?

150 years ago with Austrian monk and biologist Gregor Mendel

Gregor Mendel

Father of genetics.

What is a recent accomplishment of genetics

The sequencing of the entire genomes (all of the DNA) of humans and other species as well as the cloning (production of genetically identical organisms) of mammals including sheep, cattle, and cats

What does the cytological strand of cell biology deal with

Cellular structure

The importance of the light microscope in cytology

The earliest tool of the cytologists which continues to play an important role in our elucidation of cellular structure.

What did light microscopes allow cytologists to identify?

Membrane bounded structures such as nuclei, mitochondria, and chloroplasts

What are organelles

any of a number of organized or specialized structures within a living cell.

When was the microtome developed

in the mid-1800s

Microtome

an instrument for slicing very thin sections of biological samples, usually after they have been dehydrated and embedded in paraffin or plastic

Why are biological samples typically dehydrated and embedded in paraffin or plastic

This technique enables rapid and efficient preparation of thin tissue slices of uniform thickness

Limit of resolution

refers to how far apart adjacent objects must be in order to be distinguished as separate entities.

resolving power

A measure of the clarity of an image; the ability of an optical instrument to show two objects as separate.

brightfield microscopy

white light is passed directly through a specimen that is either stained or unstained and the background is illuminated

What is a limitation of brightfield microscopy?

Specimens often must be fixed (preserved), dehydrated, and embedded in paraffin or plastic

What happens to fixed specimens

the process of fixing a specimen renders them dead which raises the possibility that features observed by this method could be artifacts or distortions caused by the fixation, dehydration, and embedding processes.

How to overcome the disadvantage of fixing specimens using brightfield microscopy

a variety of special optical techniques have been developed that make it possible to observe living cells directly.

The kinds of microscopy that makes it possible to observe living cells directly

phase-contrast microscopy, differential interference contrast microscopy, fluorescence microscopy, and confocal microscopy

electron microtome

can cut samples in slices to look at the sample at any angle neccessary

Electron microscope

a microscope that forms an image by focusing beams of electrons onto a specimen. The beam of electrons is deflected and then focused by using an electromagnetic field.

How does electron microscopy work?

electrons replace light as the illuminating beam; wavelength of electron beam is much shorter than light, resulting in higher resolution!

Different electron microscope staining techniques

negative staining, gold shadowing, freeze fracturing, and freeze itching

What is light microscopy limited by?

It's limit of resolution

What are the two types of electron microscopes?

transmission electron microscope and scanning electron microscope

Scanning Electron Microscope (SEM)

What are the two types of microscopy that make it possible to see living cells?

Phase-contrast and differential interference contrast microscopy by enhancing and amplifying slight changes in the phase of transmitted light as it passes through a structure having a different refractive index than the surrounding medium

How What are most modern light microscopes equipped with

phase-contrast and differential interference contrast as well as simple light transmission

fluorescence microscopy

a powerful method that enables researchers to detect specific proteins, DNA sequences, or particular molecules that are made fluorescent by coupling them to a fluorescent dye or binding them to a fluorescently labeled antibody. By simultaneously using two more such dyes or antibodies, each emitting light of a different color, researchers can follow the distributions of different kinds of molecules in the same cell

Green Fluorescent Protein (GFP)

a protein that exhibits bright green fluorescence when exposed to blue light

How Green Fluorescent Protein is used

When the protein of interest is fused with GFP its synthesis and movement can be followed in living cells in real time

What is a limitation of fluorescence microscopy

The viewer can focus on only a single plane of the specimen at a time, yet fluorescent light is emitted throughout, blurring the image

How to overcome limitations with fluorescent light microscopy

confocal scanning

confocal scanning

uses a laser beam to illuminate just one plane of the specimen at a time.

What happens when confocal scanning is used for a thick specimen as opposed to whole cells

it gives much better resolution than traditional fluorescent microscopy does

Brightfield (unstained specimen)

passes light directly through specimen; unless cell is naturally pigmented or artificially stained, image has little contrast

Brightfield (stained specimen)

staining with various dyes enhances contrast, but most staining procedures require that cells be fixed (preserved)

Fluorescence

shows the locations of specific molecules in the cell. Fluorescent substances absorb ultraviolet radiation and emit visible light. The fluorescing molecules may occur naturally in the specimen but more often are made by tagging the molecules of interest with fluorescent dyes or antibodies

Phase contrast

enhances contrast in unstained cells by amplifying variations in density within specimen; especially useful for examining living, unpigmented cells

Differential Interference Contrast Microscopy

Accentuates diffraction of the light that passes through a specimen; uses two beams of light. It uses optical modifications to exaggerate difference in refractive index

digital video microscopy

recent development in light microscopy. uses video cameras to collect digital images for computer storage

deconvolution microscopy

yields high-resolution optical sections that can be reconstructed into one three-dimensional image

Friedrich Wohler

attempted to make an "inorganic" salt, ammonium cyanite, by mixing solns of ammonium ions(NH4+) and cyanate ions (CNO-) but instead made urea, an organic compound present in the urine of animals

What branch of biology did Fredrich Wohler help start

Biochemistry

Louis Pasteur

linked the activity of living organisms to specific processes by showing that living yeast cells were responsible for the fermentation of sugar into alcohol

Eduard and Hans Buchner

found that fermentation could also take place with extracts from yeast cells- that is, the intact cells themselves were not required. Initially, such extracts were called "ferments" but gradually it became clear that the active agents in the extracts were specific biological catalysts that have sine come to become called enzy,es

enzymes

Catalysts for chemical reactions in living things

Embden-Meyerhof pathway

another name for glycolysis

Krebs Cycle (Citric Acid Cycle)

second stage of cellular respiration, in which pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions

Melvin Calvin

Used radioactive tracers to identify the steps of the dark phase (of the Calvin cycle)

centrifugation

Separates components by density using high speed spinning

subcellular fractionation

A procedure to separate cell components; often includes ultracentrifugation.

Ultracentrifuge

A machine that spins mashed tissue so quickly that it separates the homogenate into separate pellets of different organelles.

differential centrifugation

Procedure for separating cellular components according to their size and density by spinning a cell homogenate in a series of centrifuge runs. After each run, the supernatant is removed from the deposited material (pellet) and spun again at progressively higher speeds.

density gradient centrifugation

A method of separating particles by centrifugation through a gradient of a dense substance, such as sucrose or cesium chloride.

Chromatography

A technique that is used to separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material.

Electrophoresis

method of separating serum proteins by electrical charge

mass spectrometry

a technique that separates particles according to their mass