Cells and organelles Flashcards
Define the term cell.
A cell is the fundamental unit of life
A cell is a semi independent living unit within the body
A cell is the site for mechanisms such as metabolism, growth and replication
A cell also consists of an aqueous solution and organic molecules with a membrane surrounding it
Define the term organelle.
A subunit of a cell found in the cytosol
Has defined structure and peforms specific activities
Can be membranous or non membranous
Define the term tissue.
An organised assembly of cells and the extra cellular products
Carries out specific,coordinated and similar activities
Eg. Connective, lymphoid
Define the term organ
An assembly of tissue
Coordinates to perform a specific function within the body
Eg. Ear,Heart,Lungs
Define the term system.
An assembly of tissue
Carries out specific related activities sharing REGULATORY influences
May also be a diffuse network of cells in multiple parts of the body e.g. immune
What is meant by the term prokaryote?
A single-celled organism
The chromosome is circular strand lying free in the cell
NO membranous organelles
What is meant by the term eukaryote?
One or more cells which :
The chromosomes are enclosed in a nucleus
typically have cytoplasmic, membrane bound organelles
DNA is divided series of linear chromosomes
What is a virus?
An assemblage of nucliec acid and proteins
It is parasitic on prokaryotes/eukaryotes
Summarise what a virus does?
Viruses invade cells
subvert the cell’s protein synthesis machinery to make more viruses
These then escape the cell in order to more cells
What is meant by cell theory?
The idea that cells have existed from pre existing cells which have duplicated
Explain how TEMs work?
Electrons go through the specimen- higher density areas will absorb electrons more so than other areas.
2D images
High resolution which enables us to see the ultra structure of the cell
Explain how SEMs work ?
Electrons fired at a specimen- scattered off the surface due to the heavy metal coating on the cells’ surface eg. Au
3D
What are the disadvantages to using electron microscopes?
Heavy duty preparation- is this what cells truly look like?!
Can only investigate Dead Samples
What limits the size of a cell?
Increasing the radius of a cell- both increases the SA and the volume of a cell but the the increases of the Volume is greater than the increase of SA. Therefore, the SA:V decreases
This means that the rate of diffusion decreases for materials such as intermediates, waste products and nutrients
How can cells overcome the diffusion distance issue?
Thin Processes- Direct transport of substances around the cell via cytoskeleton
Giant Multinucleate cells- since there is more than one nucleus- there is more gene expression hence more mRNA- more protein that can be translated (synthesise)- directed to the right areas
Gap Junctions- channels between cells which allows movement between cells
What are the advantages of having cellular organelles?
Within each cellular organelle ( since they are mostly bound by membranes) - there are different structure and different SPECIALISED internal conditions which allows them to have different functions. This means that ONE CELL can have multiple functional compartments- CELL= SPECIFIC
Allows for the regulation of movement of substances within the cell due to the membranes of the organelles
What is a cytoskeleton?
protein filaments :
actin- thinnest
microtubules-pulling apart chromosomes in cell division
Intermediate filaments= mechanical strength
What is a cytosol?
the aqueous environment within plasma membrane
Describe the nucleus.
Largest Organelle in the cell - 3-10 micrometers
Contains genetic information that is packaged into chromosomes:
DNA is wound around histones into nucleosomes
Chromatin- complex of DNA and histones and non-histone proteins
Nucleolus- where rDNA is transcribed
- ribosome submits are assembled
Nuclear Envelope- 2 layers of membrane
Nuclear Pores- allows the transport of substances in and out
Describe the SER.
Found continuous set of endosomes
Biosynthesis of steroids and lipids
Start of N-linked glycolysis
detoxification of xenobiotics
Describe the RER
Translation of mRNA to polypeptide (sequence of amino acids) The polypeptides used to make proteins for secretion and insertion into cell membranes.
These proteins then transported via vesicles to the golgi
Describe the Golgi
4-8 closely stacked cisternae, membrane bound channels
Modifies proteins delivered from the RER
e.g. Modification of N-linked carbohydrates
Glycolysation of O linked carbohydrates + lipids
synthesise and packages materials needed to be secreted
by directing new proteins into vesicles
Transport membrane lipids around the cell
Create lysosomes
Describe the mode of function of Secretory Vesicles
Bud off from Golgi
Fuses with inner surface of the plasma membrane
Releases contents- EXOCYTOSIS
eg. hormones
Describe the role of peroxisomes.
They contain many types of enzymes- involved in a variety of biochemical pathways. These can carry out
Detoxification
Phospholipids synthesis
Oxidation of a very long chain fatty acid - PROVIDING METABOLIC ENERGY
generating hydrogen peroxide- ( can also decompose it by converting it to water or oxidise into another compound - by an enzyme called catalase )
0.5-1.5 micrometers
