Cell Structure Flashcards
What is the basis structural unit of all living organisms?
Cells are the basic structural unit of all living organisms
What is the cell theory?
-All organisms are made of cells.
-All existing cells come from pre-existing cells.
-The cell is the most basic unit of life.
What are the exceptions to the theory?
- Striated muscle fibres
-Aseptate fungal hyphae
Giant algae.
Why are optical light microscopes an invaluable tool?
Optical (light) microscopes are an invaluable tool for scientists as they allow for tissues, cells and organelles to be seen and studied
How do optical light microscopes work?
-Light is directed through the thin layer of biological material that is supported on a glass slide
-This light is focused through several lenses so that an image is visible through the eyepiece
-The magnifying power of the microscope can be increased by rotating the higher power objective lens into place
What are the key components of an optical light microscope?
The eyepiece lens
The objective lenses
The stage
The light source
The coarse and fine focus
What is the formula for magnification?
magnification: image/drawing size : actual size.
What are the common unifying features of ALL cells?
-DNA as genetic material
-cytoplasm
-Plasma membrane
How does the DNA differ between eukaryotes and prokaryotes?
All living cells contain some sort of DNA, this varies between eukaryotic cells and prokaryotic cells
What does the presence of DNA mean in a cell?
The presence of DNA means that a new cell can be formed from an old cell, as genetic material is able to be stored and transferred
What else does DNA control in the cell?
DNA also controls the production of enzymes and other vital proteins within the cell
What is the cytoplasm composed of?
It is composed of mainly water with dissolved substances, such as ions
The fluid is known as cytosol
What occurs in the cytoplasm?
Important chemical reactions occur in the cytoplasm.
Where is the cytoplasm found?
Cytoplasm is found within the boundary of a cell.
It is enclosed by a plasma membrane composed of lipids.
Where is the plasma membrane found in a cell?
The plasma membrane surrounds the cell and encloses all the cell contents.
How is the plasma membrane composed?
In all cell types, the plasma membrane has two layers and this is called a bilayer
What does the bilayer consist of?
The bilayer consists of lipids; these vary depending on the type of organism
What is the membrane responsible for?
For controlling the interactions of the cell’s interior with the exterior
-Needed materials are transported into the cell interior
-Waste substances are exported out of the cell to the surrounding environment
What functions do the proteins have that are studded on the membrane?
Cell recognition
Cell communication
Transport into and out of the cell
What are prokaryotes?
Prokaryotes have the simplest cell structure, being the first organisms to evolve on Earth and have been classified into two domains.
What structure do prokaryotes not have?
Prokaryotes do not have a nucleus.
What does the structure of a prokaryote lack?
Prokaryotes have a simple cell structure and lack compartmentalisation (not divided into compartments). it lacks membrane-bound organelles
What structures are common to prokaryotes?
70S ribosomes
DNA in a loop
Cytoplasm
Plasma membrane
Cell wall
What is the difference between the ribosomes in prokaryotes and eukaryotes?
Ribosomes in prokaryotes are 70S because they are much smaller. Ribosomes in eukaryotes are much larger and knows as 80S.
What two domains have prokaryotes been classified in:
-Bacteria includes commonly known bacteria such as E.coli and Helicobacter.
-Archaebacteria or Archaea - typically found in extreme environments such as high temperatures and salt concentrations and include methanogens (organisms that exist in anaerobic conditions and produce methane gas)
What is the function of prokaryotic ribosomes (70S)?
The binding and reading of MRNA during translation to produce proteins.
Where is the genetic material of a prokaryote located?
Although prokaryotes do not have a nucleus, they do have genetic material in the form of a singular circular DNA molecule located in the nucleoid and in smaller loops called plasmids.
What are plasmids in prokaryotes?
Plasmids are small loops of DNA that are separate from the main circular DNA molecule.
What do plasmids in prokaryotes contain?
Plasmids contain genes that can be passed between prokaryotes.
What is found in the cytoplasm of a prokaryote?
The cytoplasm is the site where the 70S ribosomes are found in a prokaryote.
What occurs in the cytoplasm of a prokaryote?
It is the site of many cellular reactions.
What is a major component of the cytoplasm of a prokaryote?
A major component is a gel-like cytosol, a water-based solution that contains ions, small molecules and macromolecules.
What is the cell membrane of prokaryotes composed of?
A lipid bilayer.
What do a group of prokaryotes (archaea) have their plasma membrane formed as?
An archaea have their plasma membrane formed as a monolayer as opposed to a bilayer.
What is the role of the plasma membrane?
To control substances entering and exiting the cell.
What does the cell wall of most prokaryotes contain?
a cell wall containing murein/ peptidoglycan (glycoprotein).
What does the cell wall do in a prokaryote?
It acts as protection, maintaining the shape of the cell and preventing it from bursting.
How does the cell wall of prokaryotes (bacteria) allow us to classify them?
-ability to retain a dye called crystal violet classifies a group of bacteria as gran positive, they appear blue/violet after exposure to the dye.
-bacteria that does not react with the dye are Gran negative bacteria.
What are examples of gran positive bacteria?
Examples of gram positive bacteria are Bacillus and Staphylococcus.
What are the structures that only some prokaryotic cells have that differentiate the species and act as a selective advantage?
-Plasmids
-Capsules
-Flagellum
-Pili
What is a capsule?
Some prokaryotes are surrounded by a final outer later known as a capsule.
-Helps to protect bacteria from drying out and from attack by cells of the immune system fo the host organism.
What is a flagellum?
Long, tail-like structures that rotate, enabling the prokaryote to move.
What are pili?
Shorter and thinner structures than flagella.
They assist with movement, avoidance of attack by white blood cells, conjugation and are commonly used to allow bacteria to adhere to surfaces.
