Topic 2.1 - Structure of eukaryote and prokaryote cells Flashcards
List three ways eukaryotic cells differ from prokaryotic cells.
membrane bound organelles
DNA is enclosed in a nucleus
Have larger ribosomes (80S) than prokaryotic cells
Has a murein cell wall, a capsule and plasmid
Function of nucleus
containing chromosomes, consisting of protein-bound(histones) , linear DNA within the nucleoplasm.
Function of nuclear envelope
Double membrane surrounding the nucleus with nuclear pores to let molecules in and out
Plasma
Membrane
Involved in the transport of substances via diffusion or facilitated diffusion, active transport
Cytoplasm
Where chemical reactions take place
Ribosome
Where amino acids are joined together to make proteins (i.e. protein synthesis)
Mitochondria
Site of AEROBIC respiration
Produces ATP (releases energy)
Contains short, circular DNA (not associated with proteins)
Has a double membrane. The inner membrane is folded forming cristae.
Contains smaller (70S) ribosomes
Rough Endoplasmic Reticulum (RER)
Has ribosomes on their surface which are involved in protein synthesis
Proteins are also folded up inside the RER
Smooth endoplasmic reticulum
Synthesis and storage of molecules such as lipids, steroids and sterols
Golgi Apparatus and golgi vesicles
Modifies proteins (e.g. by adding carbohydrate groups to form a glycoprotein or lipid groups to make a lipoprotein)
Stores proteins
Packages proteins into vesicles
Transport vesicles to cell surface
Lysosomes
A vesicle that contains hydrolytic enzymes (lysozymes) which are used to digest molecules
Chloroplast
Chlorophyll absorb light for photosynthesis to produce carbohydrates
Has a double membrane. Inside there are thylakoid membranes which can form a stack called a granum (pl. grana). The grana are linked by lamellae.
Contain starch grains
Define resolution
Resolution is the minimum distance apart that the two objects can be in order for them to appear as separate items.
Describe the procedure to prepare a slide
Add a drop of water to the slide
Remove a thin section of tissue and place it onto the slide (flat as possible)
Add 1 drop of iodine dissolved in potassium iodide to stain the sample (This is only correct if it is plant tissue)
Lower a coverslip on top using a mounting needle
Explain why it was important that the sections of tissue were thin
A thin section allows more light through;
allows a single layer of cells to be viewed.
Why are electron microscopes used to view cells?
They have a HIGH resolution
because electrons have a shorter wavelength than light.
This allows you to view internal structures/organelles of a cell.
(Remember using this – Light microscope = Low resolution = Longer wavelength)
Name two structures in a eukaryotic cell that cannot be identified using an optical microscope.
Mitochondrion / ribosome / endoplasmic reticulum / lysosome / cell-surface membrane
Describe the limitations of using a transmission electron microscope to investigate cell structure.
Cannot look at living material / Must be in a vacuum;
Specimen must be (very) thin;
Artefacts present;
Complex staining method / complex / long preparation time;
Image not in 3D / only 2D images produced.
Write an equation to calculate magnification
Magnification = Image length / Actual Length
What is meant by ‘cell fractionation
Separating out the contents of a cell into the different ‘fractions’ (i.e. different parts).
This usually means separating out the different organelles by DENSITY.
This is useful for scientists because it allows them to study individual organelles
What is homogenisation?
Using a blender (or a homogenizer) to break open the cell membrane to release all of the organelles inside
Why is the solution filtered?
To remove any whole cells or large cell debris
Why is it cold?
To reduce enzyme activity TO prevent digestion of organelles
Why is it isotonic?
To prevent osmosis, SO that the ORGANELLES do not shrivel or burst/ lysis
