Cell Struture 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
Prokaryotic cells include bacterial cells. List the differences between Prokaryotic and Eukaryotic cells.
No membrane bound organelles (e.g. mitochondria, endoplasmic reticulum, golgi)
No nucleus - instead they have a single circular DNA molecule that is free in the cytoplasm and is not associated with proteins
Smaller ribosomes
Has a murein cell wall, a capsule and plasmids
What is the structure and function of nucleus?
ccontaining chromosomes, consisting of protein-bound, linear DNA within the nucleoplasm. Contains one (nucleolus) or more nucleoli
What is the structure and function of nuclear envelope?
Double membrane surrounding the nucleus with nuclear pores to let molecules in and out
What is the structure and function of plasma membrane?
Description of structure: A phospholipid bilayer with hydrophllic phosphate heads facing outwards and hydrophobic fatty acid tails facing inwards.
Function: Involved in the transport of substances via diffusion or facilitated diffusion, active transport (with the aid of proteins)
What is the structure and function of cytoplasm?
Where chemical reactions take place
What is the structure and function of 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 (thought to have evolved from prokaryotic cells.)
What is the structure and function of rough endoplasmic reticulum?
Has ribosomes on their surface which are involved in protein synthesis
Proteins are also folded up inside the RER
What is the structure and function of Smooth endoplasmic reticulum?
Synthesis and storage of molecules such as steroids and sterols
What is the structure and function of 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
What is the structure and function of Lysosomes?
A vesicle that contains hydrolytic enzymes (lysozymes) which are used to digest molecules
What is the structure and function of 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
What is the structure and function of Cell Wall
For strength and support
What is the structure and function of Vacuole
Tonoplast – a membrane surrounding the vacuole
When the vacuole is full of fluid the cell becomes turgid.
Temporary food store containing sugars and amino acids
Contains pigments (colour petals)
What is the structure and function of Flagella
For movement
What is the structure and function of Plasmids
Circular rings of DNA
(can reproduce independently and may give resistance to harmful chemicals such as antibiotics)
What is the structure and function of Slime layer (capsule)
A ‘slime’ layer on the outside of the cell, made of polysaccharides
It provides protection for the cell and might help cells stick together
What is the structure and function of Circular DNA (DNA in a loop)
Genetic material in a prokaryote (not enclosed in a nucleus)
Define magnification
Magnification is how much bigger the image is than the specimen
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.
Explain why you should push down hard on the cover slip, but should not push the cover slip sideways.
Push hard to squash the tissue to create a single layer of cells.
Do not push sideways as this will cause the cells to roll together.
A plant cell was observed with an optical microscope. Describe how the length of the cell could be estimated.
Use a stage micrometer to help us calibrate the size of the eyepiece graticule.
Measure the length of the plant cell with an eyepiece graticule.
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 principles and the limitations of using a transmission electron microscope to investigate cell structure.
- Electrons pass through / enter (thin) specimen;
- Denser parts absorb more electrons;
- (So) denser parts appear darker;
- Electrons have short wavelength so give high resolution;
Limitations: - 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.
What is the advantage of TEM (transmission) compared to SEM (scanning) is
Higher resolution
Allows internal structures within cells to be seen
What is the advantages of SEM (scanning) compared to TEM is
Thin sections do not need to be prepared
shows surface of specimen
can have 3-D images
