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
