TOPIC 2.1 Eukaryotic Cells Flashcards
Magnification of light microscopes
*1500
magnification of electron microscope
*500,000
define resolution
A measure of how close together two objects must be before we see them as one.
what do we call an image of an object as viewed through a microscope
micrograph
resolving power of light microscope
200nm
resolving power of electron microscope
0.5 nm
total magnification
eyepiece lens magnification*objective lens magnification
strengths and Limitations of Light Microscopes
S-
Cheap
can look at live cells with little prep
L-
lower Magnification and resolving power compared to EM
Instead of a beam of light like LM, EM uses a beam of…..
electrons
EM has a higher resolving power because the wavelength of electron beams is …..
Smaller than LM
Bane 2 types of EMs
TEM-transmission electron microscope
SEM- scanning electron microscope (produces 3D images)
Strengths and Limitations of Electron Microscopes
S-
high magnification and resolving power
L-
very expensive
specimens have to be examined in a vacuum so they have to be dead and dry
specialised skills required to prepare samples
the nucleus is surrounded by a double membrane called the…
nuclear envelope
define nucleolus
dense area almost pure DNA and protein, Produces ribosomes and RNA
What are ribosomes made of
ribosomal RNA and protein
what is a eukaryotic cell
genetic material is contained in a membrane bound nucleus
what are vesicles
membrane bags that hold secretions made in cells
what are gated channels
protein channels through the lipid bilayer of a membrane that are open or closed depending on the conditions in the cell
describe the fluid mosaic model
current model of the structure of the cell membrane including floating proteins forming pores, channels and carrier systems in a lipid bilayer
what is exocytosis
energy requiring process by which vesicle fuses with the cell surface membrane so that the contents are released to the outside of the cell
the cytoplasm and nucleus combined are called the…
protoplasm
what is chromatin
combination of DNA bonded to protein found in the nucleus when the cell is not actively dividing
what do you call the folding of the inner membrane of the mitochondria which provide a large surface area for the reactions of aerobic reactions
cristae
describe the endosymbiotic theory
the endosymbiotic theory–>
theory that suggests the mitochondria and chloroplasts originated as independent prokaryotic organisms that began living symbiotically inside other cells as endosymbionts
what are centrioles
bundles of tubules found near the nucleus and involved in cell division by the production of a spindle of microtubules that move the chromosomes to the ends of the cell
what do you call vacuoles that can fill and empty and why are they important
contractile vacuoles, they help control the concentration of cytoplasm of simple freshwater animals
purpose of apoptosis ?
break down worn out, damaged or diseased cells by lysomes
what is a lysome
an organelle full of digestive enzymes used to break down worn out cells/ digest food in simple organisms
80S ribosomes are made of a small sub unit and a large subunit.. they are…. and the ratio of RNA to protein is
80S=40S+60S
RNA:PROTEIN= 1:1
70S ribosomes made in the mitochondria are made up of… in the ratio…
70S=30S+50S
RNA:PROTEIN= 2:1
difference between Necrosis and Apoptosis
NECROSIS
-detrimental to body
-triggered when cells are exposed to extreme conditions
-passive random and unregulated
APOPTOSIS
-active and regulated process
-not detrimental to body
State the differences between Rough endoplasmic reticulum and Smooth endoplasmic reticulum
RER
-ribosomes on surface
- responsible for packing and processing of proteins made by the ribosomes
SER
-no ribosomes
-synthesises lipids, phospholipids and steroids
Describe the cell wall of a plant
Mostly insoluble cellulose. Freely permeable, it does not act as a barrier for substances entering the cell.
How does the cell wall prevent substances from getting into the cell
Cell wall can become impregnated with suberin and lignin, affecting permeability
the first layer to form when the plant cell divides in 2 is called______ it is made of ________ ___________ that binds the layers of ___________ together.
the first layer to form the plant cell divides in 2 is called the middle lamella it is made of calcium pectate that binds the layers of cellulose together
state and explain what polysaccharide holds the cells walls of neighbouring plant cells together.
PECTIN- pectin has lots of -COOH carboxyl groups that combine with positive calcium ions to form calcium pectate that binds to the cellulose on either side .
Why is the primary cell wall flexible
the cellulose microfibrils are all orientated towards the same direction
When does the secondary cell wall form
when the plant ages secondary thickening takes place
Difference between primary and secondary walls of plants in terms of flexibility
primary Cell wall is flexible as the cellulose microfibrils are all orientated in a similar direction while in the secondary cell wall cellulose microfibrils are laid densely at different angles to each other
the______ forms when the cell divides and the 2 cells do not separate fully-leaving cytoplasm bridges between them
the plasmodesmata forms when the cell divides and the 2 cells do not separate fully-leaving cytoplasm bridges between them
the symplast is…
the interconnected cytoplasm of cells. All the material contained within the surface membrane of a plant cell
the vacuole is surrounded by a membrane called the ______
tonoplast
the vacuole is filled with _________ , a substance of various substances in water, which causes water to move into the cell by _______
the vacuole is filled with Cell sap , a substance of various substances in water, which causes water to move into the cell by osmosis
similarities between chloroplasts and mitochondria
large organelles
contain their own DNA
surrounded by an outer membrane
folded inner membrane that gives them large surface areas
differences between chloroplasts and mitochondria
chloroplast-
site of photosynthesis
contain chlorophyll
are formed from leucoplast
what is an amyloplast
amyloplasts are plant organelles that store amylopectin (polysaccharide joined with amylose to form starch) which can be converted glucose to provide energy to the cells
define tissue
a group of specialised cells carrying out a particular function in the body
define organ
a structure made up of several different types of tissues grouped together to carry out a particular function in the body
define an organ system
a group of organs working together to carry out particular functions in the body
purpose of epithelial tissues
form the lining of surfaces inside and outside the body
what is the plasmodesmata
cytoplasmic bridges between plant cells that allow communication between the cells
what is pectin
a polysaccharide that holds the cell walls of neighbouring plant cells together and is part of the structure of the primary cell wall
____________ is a chemical that impregnates cellulose cell walls in cork tissues and makes them impermeable
SUBERIN is a chemical that impregnates cellulose cell walls in cork tissues and makes them impermeable
What type of ribosomes do eukaryotic cells have
80S—-> 60S and 40S
Describe how the electron microscope works
An Electron Microscope works by firing a beam of electrons at a biological sample, which then interacts with the sample and produces an image. The electrons are focused into a beam using magnetic lenses and are then directed towards the sample.
