Unit 1 Flashcards
Features that define a cell
1) membrane enclosed autonomous living unit
2) unit can maintain a stable internal environment with molecules and ions that differ from the external environment
3) capable of storing DNA and guiding the synthesis of RNA and protein
4) can convert energy from one form to another (ie carrying out metabolism to make ATP)
5) can grow and reproduce
Are viruses cells?
No - they are parasites of living cells and depend on the host cell for raw materials and energy for nucleic acid synthesis, protein synthesis, processing and transport, and other things that allows it to multiple and spread
Organelles
different structures within a living cell that perform specialized functions
Why are organelles important?
1) carry out unique function in the cell
2) provide optimal local environment for metabolic reactions and other functions
3) allow high local concentration of molecules, ions, etc. at a certain cellular location to be achieved
4) control passage of materials
Do all cells have organelles? Compare eukaryotic and prokaryotic cells
Yes
Euks: nucleus and other membrane-enclosed organelles/compartments
Proks: do not have membrane-enclosed organelles
Which organelles are membrane-enclosed?
membrane:
Nuc, mito, chloro, lysosome, peroxisome, ER, golgi
no membrane:
ribosomes, filaments, microtubules
What is an organism?
has/can develop the ability to act/function independently. They are capable of:
metabolism/homeostasis
growth and reproduction
responses to the environment
Cytosol
everything in the plasma membrane minus the organelles
Cytoplasm
everything within the plasma membrane
Cell theory
1) all living organisms are made of cells
2) cells are the basic building units of life
3) new cells arise by division of existing cells
Size of nucleus
approx. 6-10 micrometers
Magnification
expanding something in apparent size. It is the ratio of the size of an image to the size of the object
Resolution
defined as the closest spacing of two point which can be distinguished as separate entities. Major factor that determines it is the wavelength of the beam (light, electrons) used for imaging
Types of light microscopy and resolution limit. What is it used to visualize?
transmitted light microscopy (bright field microcopy)
emitted light microscopy (fluorescence microscopy)
resolution limit is 0.2 microm (200nm)
used to visualize whole tissues, fixed, often sectioned and stained (not alive)
colour
live cells
Types of electron microscopy
transmission electron microscopy
scanning electron microscopy
Limitation of light microscopy
live cells lack contrast
cells have to be “fixed”, thus killing them
Emitted light microscopy - fluorescence
Fluorescently labelled molecules/structures for localization in cells
Can use
Direct staining - using fluorochromes
Indirect staining - using fluorochrome-linked antibodies
Tagging of protein with GFP
Indirect staining - immunofluorescence. Name 3 limitations
Localizes proteins of interest using primary antibodies. Secondary antibodies covalently linked to a fluorochrome recognizes the primary antibody
Takes too long
May have issues
Cannot do it for live cells (not sure)
Direct staining
Gene for green fluorescent protein (GFP) can be fused with the gene of interest so when the gene is expressed, it’ll produce a protein with a GFP tag on it
Advantages/disadvantages of light microscopy
Adv: Colour Use live, whole cells Track cells Cheap and easy
Disadv:
Cannot see smaller structures
Lower resolution
When do you use transmitted or fluorescence light microscopy?
Transmitted:
Don’t need colour or use visible dyes
Visualize whole tissues
Cheap and easy to use
Fluorescence:
See the localization of specific protein
Need to see colour
Tracking proteins or organelles
Electron microscopy features
Res limit: 0.2 nm
Images are black and white
Uses electron beam (short wavelength) to illuminate sample
Tissues are fixed (dead)
TEM advantages and disadvantages
Adv:
High res such that details of cytoplasm can be seen
Disadv: Cells are fixed Complex specimen preparation Difficult to know 3D shape of structure Only shows a single slice (cross section)
Scanning electron microscopy advantages and disadvantages
Adv:
Can view surfaces (images appear 3D
Disadv:
Cells must be fixed
