Cell structure

Cell structure
Chapter 2
Microbiology for the Surgical Technologist
Eukaryotic and Prokaryotic Cells
Prokaryotes
Simple cell structure such as bacteria
Eukaryotes
Complex cells
Include protozoa, fungi, algae, some plant and all animal cell, including human cells
Eukaryotic Cells
Range in size from 10-100 μm
Have a true nucleus that is enclosed within a membrane
Contain organelles
Plasma Membrane
Also called the cell membrane
Hold internal structures of the cell in place
Encloses cytoplasm and forms outer boundary of the cell
Composed of large molecules of phosphate-containing fat lipids called phospholipids and protein
Also contains cholesterol, another lipid, that stabilizes and fortifies the other phospholipids
Plasma Membrane - continued
The protein adds structural support and protection
The membrane functions to create selective permeability
Only certain substances are allowed to enter and leave the cell
Responsible for managing the inflow and outflow of nutrients, waste, and other types of cell secretions
Plasma Membrane
Plasma Membrane - continued
Two ways that materials cross the plasma membrane
Passive
Substances move through the membrane from an area of high concentration to an area of low concentration without the cell using any ATP.
ATP is the cells store of energy
Active
The cell uses ATP to move substances from a low area of concentration to a high area
Osmosis
Passive process
Three types of osmotic solutions
Isotonic
Hyoptonic
Hypertonic
Isotonic solution
The concentration of the solution outside the cell equal the solution inside the cell
Hypotonic solution
The concentration of the solution outside the cell is lower that the solution inside the cell
Hypertonic solution
The concentration of the solution outside the cell is higher than the solution inside the cell
Nucleus
A small spherical structure in the center of the cell
Is the control center for all cell activity
Surrounded by a nuclear membrane that encloses the neoplasm
Neoplasm
Contains two important structures
The nucleolus
The chromatin granules
Nucleolus
Designs and oversees the construction of ribosomes
The ribosomes then migrate out of the nuclear membrane into the cytoplasm and are responsible for the production of protein
Chromatin granules
Made of protein and DNA
Deoxyribonucleic acid
Double stranded
Contains genetic information
Cytoplasm
Semifluid nutrient solution within the cell membrane
Organelles are contained in it
The portion of the cell where the most work is performed
Organelles
Endoplasmic Reticulum (ER)
A system of membranes that form a series of tubules that twist through the cytoplasm
Responsible for the transport of nutrients to the nucleus
The majority is rough ER
It appears rough because ribosomes are attached to it
Smooth ER
Has no ribosomes
Responsible for the manufacture of fats, carohydrates, and proteins that make up the cell membrane
Golgi complex
Connects and communicates with the ER
Look like small flattened sacs stacked on top of each other like pancakes
Process protein from the ER into vesicles (small sacs) that are sent to the cell membrane where they attach then open and release their contents into the interstitial fluid of the membrane
Lysosomes
Small vesicles created by the Golgi complex
Contain the enzyme lysozyme
That lyses or destroys foreign substances ingested by the cell
Uses the process of phagocytosis with a particular leukocyte called a phagocyte
If the enzymes escape from the lysosomes into the cytoplasm, they can destroy the cell itself

Mitochondria
Are the power plant of the cell, create the energy
Produces ATP (adenosine triphosphate) by way of cellular respiration
Energy is released from glucose molecules by enzymes utilizing oxygen to provide energy for the other cellular functions
Centrioles
Form spindle fibers to aid in cell division
Eukaryotic cell division is called mitosis
The cell divides and the resulting daughter cell has the same number of chromosomes as the parent
May also me responsible for the manufacture of Eukaryotic flagella and cilia, because their protein composition is the same
Flagella and Cilia
Eukaryotic flagella are more complex than those of prokaryotic cells
Consist of microtubules
Move back and forth in a wavelike motion
Prokaryotic Cells
Range in size from 0.2 to 2.0 μm
Have no true nucleus
Not enclosed in a membrane
Cell walls are chemically complex
All bacteria are prokaryotes
Reproduce by binary fission
Cell Wall
Rigid and gives shape to the cell
Main component is peptidoglycan
Thickness varies in Gram-positive and Gram-negative
Gram-positive have thicker walls
Gram-negative have thin walls
Cytoplasmic (Cell) Membrane
Surrounds cytoplasm just inside cell wall
Protects cell from external substances
Functions in the synthesis and secretion of bacterial toxins
Used for flagellar propulsion
Contains mesosomes
Embedded in membrane and produce ATP for cell function
Capsules
Some bacteria have capsule on the outside of the cell wall
Called the slime layer if loosely attached
Provide the cell the ability to move on solid surfaces
Allow cells to anchor to the surface of teeth and mucous membranes so they cannot be washed away
Cytoplasmic Particles
The cytoplasm is gelatinous
Contains particles
Majority are ribosomes that perform the same protein synthesis as in eukaryotic cells, only smaller
Chromosomes
No nuclear membrane
Not stable shape
Contain a single strand of DNA
To control the function of the cell only
Guides the process of binary fission
Flagella
Mostly found on Gram-negative bacillus
Extend from the cytoplasmic membrane
Classification can be determined by the number of flagella
There are four classifications…
Pili
Singular – pilus
Hairlike structures mainly on Gram-negative bacteria
Thinner than flagella, more rigid
Do not provide motility
Pili
(continued)
Serve three functions
Serve as a site for the attachment of particular types of other bacteria
Provide bacteria that have a sex pilus the ability to transfer genetic material to another bacteria through the process of conjugation
Provide the bacteria the ability to attach to other bacteria or surfaces, such as the lining of the intestine
Endospores
Several types of bacteria can form spores known as sporulation
When conditions do not allow the organism to survive it forms an endospore as a means of survival
Contains the genetic material, and is resistant to heat, dry conditions, and many chemicals
Can survive long periods of time
Spores are used to test the various methods of sterilization