Cell Theory 2.1 U2 Flashcards
What does a light microscope do?
Uses lenses to magnify the image of an object by focusing light after it passes through the specimen
What are the pros of a light microscope?
Great for viewing living organismsEasy to use, common in schoolsCheaper, smaller, and simpler than other types of microscopesNo need for other special machinery or techniques (ie. vacuum, radiation) to operateObject being viewed retains its natural/authentic color
What are the cons of a light microscope?
Components may not be visible (most cells are transparent) unless using special stains (usually kills the cell)Lower resolution than other types A microscope can only show an image of something that is smaller than the wavelength of light used. Since visible light has a (relatively) long wavelength, and the light is diffracted/scattered as it passes through the matter and lenses, this makes the image blurry at higher magnifications.Maximum useful magnification - 1000xOnly shows a 2D image at higher magnifications
What are the two types of light microscopes?
Compound MicroscopeDissecting (or Stereo) Microscope
What is a compound microscope?
Typically 40x-400x, can view individual cells, 2-D image
What is a dissecting(stereo) microscope?
Typically 7-20x, can only view larger objects, 3-D image
What does an electron microscope do?
Uses a beam of electrons, instead of light, which are focused using magnetic fields
What are the pros of an electron microscope?
Higher resolution images (due to shorter wavelength of electrons vs. visible light)Good for viewing whole cells or individual components Can be used at higher magnifications, up to 1,000,000x
What are the cons of an electron microscope?
Requires sample to go through a special chemical fixation process and then viewed in a vacuumCannot view living cellsMuch more expensive, complicated, larger, and difficult to operate Requires a lot of specialized equipment to work properly and is very sensitive/easy to damage
What are the two types of electron microscopes?
Transmission Electron Microscopy (TEM)Scanning Electron Microscopy (SEM)
What is a TEM microscope?
Transmission Electron Microscopy (TEM)Beams pass through thin samples, creates flat/2D imagesGood for viewing cellular structures and larger proteins
What is a SEM microscope?
Scanning Electron Microscopy (SEM)Beam scans the surface, producing high resolution 3D imagesGood for viewing surfaces of cells
What main thing did Robert Hooke discover?
He described the cork as having box-shaped, pore-like structures, which he called “cells” In 1665, Robert Hooke published observations he made using a microscope, in the book Micrographia.
What did Antonie van Leeuwenhoek discover?
He developed hundreds of simple single lens microscopes with an increased magnification! This allowed him to view organisms in more detailObserved many biological specimens using his single lens microscopes, and sent his findings to the Royal SocietySaw tiny creatures he called them animalcules(Micromolecules)
What did theodor schwann and schleiden discover?
Studied cells along with Matthias Schleiden, compared their studies of animal and plant cellsIn 1839, proposed classical cell theory:All living organisms are made of cellsCells are the basic unit of lifeBoth Schwann and Schleiden were mistaken about the origins of those cells, though, which was correctly identified by another scientist…
What did Rudolf Virchow add to the cell theory?
In 1855, he added a third conclusion to classical cell theory:All cells come from preexisting cells
What is the classical cell theory and what does the modern cell theory add to that?
Classical Cell Theory:- All living things are made up of cells- Cells are the basic units of structure and function in living things- All cells are produced from existing cellsModern Cell Theory adds:- DNA contains hereditary information that is passed from cell to cell during division- All cells are basically the same in chemical composition and metabolic activities- Energy flow occurs within cells
What do all cells(most) have?
Contain DNA (molecule that carries genetic information)Are surrounded by a cell membrane (plasma membrane)Have cytoplasmHave ribosomesOn average range from 5 to 50 micrometers in diameter
What are traits of prokaryotes?
NO nucleusNO membrane-bound organellesThey are simple & unicellular
What are the two types of prokaryotes?
Bacteria vs. Archaea
What is bacteria?
Domain of prokaryotes that contain peptidoglycan in their cell wallsLive almost everywhere (fresh/salt water, land, within and on human bodies, etc)Some a “good” some are “bad” (ie. some “help” other organisms and some cause disease, etc)
What is archaea?
Domain of prokaryotes without peptidoglycan in their cell wallsMost live in extremely harsh environments (acidic, hot, salty, etc.)
What is peptidoglycan?
Polymer of sugars and amino acids that can surround the cell membrane
How do prokaryotes reproduce?
Binary fission
What is Binary fission?
type of asexual reproduction in which an organism replicates its DNA and divides in half, producing 2 identical daughter cells.
What is Conjugation?
Process in which some prokaryotes exchange genetic information by moving a cell through a hollow bridge from one cell to another
How do favorable conditions affect asexual reproduction?
In favorable conditions, can grow and divide quickly! As fast as once every 20 minutes!In unfavorable conditions, many form an endospore (a thick internal wall that encloses DNA and a portion of the cytoplasm) that can remain dormant for months or years!
What is an endospore?
a thick internal wall that encloses DNA and a portion of the cytoplasm
What are prokaryotes two categories of their modes of nutrition?
AutotrophsHeterotrophs
How can you further split up auto trophs and heterotrophs?
Photo-AutotrophChemo-AutotrophPhoto-HeterotrophChemo-Heterotroph
What does a Photo-Autotroph do?
-Light as energy source-CO2 as C source
What does a Chemo-Autotroph do?
-Chemicals as energy source-CO2 as C source
What does a Photo-Heterotroph do?
-Light as energy source-Organic compounds as C source
What does a Chemo-Heterotroph do?
-Chemicals as energy source-Organic compounds as C source
Explain good prokaryotes?
Essential in maintaining ecological balance of the living world!Decomposers, Producers, Nitrogen fixers, Human uses
Explain bad prokaryotes?
Bacteria can be pathogensCan damage host tissues and cells, or cause tissue damage when they provoke an immune response (ex. tuberculosis)Can release toxins that act as poison, interfering or killing the host (ex. diptheria)
What are decomposers?
break down dead organisms, supply raw materials
What are producers?
conduct photosynthesis
What are nitrogen fixers?
provide 90% of nitrogen used by other organisms
What are Human uses?
used in wide variety of foods and other commercial products
What are Pathogens?
agents that cause diseases (bacteria and virus can be pathogenic, there are currently no known pathogenic archaea)
What are characteristics of eukaryotes?
Generally larger and more complex than prokaryotes, can be unicellular or multicellularDNA found in nucleus, have dozens of internal structures (organelles)Includes Animals, Plants, Protists, and Fungi
What is the Endosymbiotic theory?
The endosymbiotic theory states that some of the organelles in today’s eukaryotic cells were once prokaryotic microbes
What is some evidence for the endosymbiotic theory?
Mitochondria and chloroplasts are both similar in size to bacteria and contain their own DNA, ribosomes, and double membrane. This single stranded DNA is found exclusively in prokaryotes.Chloroplast membranes closely resemble the membranes of photosynthetic prokaryotesSome cells today contain bacteria and algae living in an endosymbiotic relationship
What is Asexual Reproduction?
a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes.
What is Mitosis?
Eukaryotes reproduce asexually in the process of mitosis.A part of the cell cycle in which replicated chromosomes are seperated into two new nuclei.
What is the microscope term resolution?
Shortest distance btwn two places on one specimen that can be identified as different
What is the microscope term field of view?
what you can see through the microscope lens
What is the microscope term Depth of field?
the range in which the object can still be clearly seen
What is the microscope term magnification?
when a microscope creates an image a differnt size to the actual object it is looking at.
