Chapter 2 Flashcards
DEFINE MAGNIFICATION
How much bigger an image is compared to the original object
DEFINE RESOLUTION
Ability to distinguish between two points.
DEFINE LIGHT MICROSCOPES
Rely on light and lenses to form an image.
Magnification: x1500
Resolution: 200nm (wavelength of light is large so lower resolution.)
STATE 5 ADVANTAGES OF LIGHT MICROSCOPES
Easy to use Cheap Portable Whole living organism studied Coloured 3D images
STATE TWO DISADVANTAGE OF LIGHT MICROSOCOPES
Low magnification
Low resolution
DEFINE LASER SCANNING MICROSCOPES
Use a light to scan an object point by point and assemble. Can focus on structures at different depths. Use a pinhole to get rid of any unfocused light.
STATE FOUR ADVANTAGES OF LASER SCANNING MICROSCOPES
High resolution
High contrast.
Coloured images,
3D images
STATE TWO DISADVANTAGES OF LASER SCANNING MICROSCOPES
Dead specimen
Expensive
TRANSMISSION ELECTRON MICROSCOPES - Define
Uses a beam of electrons which pass through the specimen and are then detected to produce a specimen.
Magnification: x2000000
Resolution:
STATE TWO ADVANTAGES OF TRANSMISSION ELECTRON MICROSCOPES
High magnification
High resolution
STATE 4 DISADVANTAGES OF TRANSMISSION ELECTRON MICROSCOPES
Produces a 2D black and white image.
Requires cells to be dehydrated, so they are dead. Hard to prepare specimen. Expensive and large.
DEFINE SCANNING ELECTRON MICROSCOPES
Electrons bounce of the surface of the specimen and are then detected.
STATE ONE ADVANTAGE OF SCANNING ELECTRON MICROSCOPES
3D image produced
STATE THREE DISADVANTAGES OF SCANNING ELECTRON MICROSCOPES
Dead specimen required.
Hard to prepare specimen.
Black and white image
EXPLAIN THE USE OF STAINING. EXPLAIN WITH EXAMPLE POSITIVE AND NEGATIVE STAINS.
Used to increase contrast and visibility. Allows differentiation between organelles.
Positively charged dyes - crystal violet and methylene blue.
- These are attracted to negatively charged organelles.
Negatively charged dyes - nigrosine and Congo red.
- Repelled by negative charge so stay away, increasing contrast.
EXPLAIN DIFFERENTIAL STAINING AND GIVE AN EXAMPLE
Can distinguish between two types of organelles.
- Sudan red stains lipids.
- Iodine stains starch granules blue/black.
EXPLAIN HOW A SLIDE IS PREPARED FOR VIEWING.
Before viewing slides must be prepared. They are dehydrated, waxed then very thinly sliced. The thin slices are stained and then mounted.
WHAT IS A GRATICULE IS AND HOW IT USED TO CALIBRATE A MICROSCOPE?
Graticules must be used, it is a mini ruler fixed to the eyepiece. As the specimen is viewed the ruler is imposed on to the specimen so measurements can be take. This must be calibrated with a ruler on the stage as the graticule is arbitrary. The eyepiece has to be calibrated for each objective lens.
To calibrate just align the graticules together, if the top one measures 10cm and aligns with the number 4, then for every 4 arbiter units, 10 cm is measured.
DEFINE NUCLEUS
Surrounded by nuclear envelope which has pores by which RNA can leave and hormones can enter etc.
Contains DNA in the form of chromatin which is loose and spread out
DEFINE NUCLEOLUS
Contains RNA which provides instructions for protein synthesis.
Is within the nucleus but has no membrane
DEFINE CYTOPLASM
Jelly like
Where all organelles are suspended
Where chemical reactions occur
DEFINE CYTOSKELETON
Network of protein filaments; actin and microtubules.
Allows organelles to move
Allows contraction of muscle cells.
DEFINE MITOCHONDRIA
Very small. Have two membranes, inner membrane folded into cristae. It is filled with matrix. Power house of the cell, produces ATP by aerobic respiration
DEFINE GOLGI APPARATUS
A stack of membrane bound flattened sacks. Have secretary vesicles which bring materials to and from the golgi apparatus. Folds, modifies and packages proteins
DEFINE ROUGH ENDOPLASMIC RETICULUM
This is a system of membranes containing fluid filled cavities (cisternae).
They are coated with ribosomes.
The cisternae from channels for transporting substances form one area of the cell to another.
DEFINE SMOOTH ENDOPLASMIC RETICULUM
A system of membranes, containing fluid filled cavities (cisternae).
No ribosomes on its surface. Contain enzymes that catalyse reaction involved with lipid metabolism. Involved with absorption, synthesis and transport of lipids.
DEFINE VESICLES
For transport
DEFINE CHLOROPLASTS
Surrounded by a double membranes. Inner membrane has stacks called thylakoids. Each stack is called a granum. Fluid filled matrix is called stroma. Contain loops of DNA and starch grains.
These are the site of photosynthesis. Light energy s trapped and used to make ATP. Water is also split to supply H+ ions (occurs in grana). Then the H- ions reduce CO2 with ATP making carbohydrates (this occurs in the stroma).
DEFINE VACUOLE
Surrounded by a membrane called the tonoplast. Filled with water and solutes to maintain stability by remaining turgidity,
DEFINE LYSOSOMES
Small bags formed by golgi apparatus. Contain hydrolytic enzymes. Can ingest and digest invading pathogens. Lysosomes keep the powerful digestive enzyme separate from the cell. They can engulf organelles and foreign matter and return waste to the cell.
DEFINE CILIA
Protrusions from the cell. Has microtubules. Formed from centrioles.
DEFINE RIBOSOMES
Small. Made of ribosomal RNA. Synthesise proteins to be exported out the cell.
DEFINE CENTRIOLES
Consists of two bundles of microtubules at right angles. They are made of tubulin and arranged into cylinders. They pull chromosomes apart during cell division. They are also involved in formation of the cilia.
DEFINE CYTOSKELETON
Network of protein structures. Rod like filaments made of actin. Gives support and mechanical strength. They form tracks for movement of substances. Form spindle before cell division. Also make up cilia.
WHAT IS A CELLULOSE CELL WALL?
Made of bundles of cellulose fibres. Only in plants. Provides strength and support. Permeable.
DESCRIBE THE 8 STEPS OF PHOTOSYNTHESIS
- The gene that has the coded instruction for a protein is housed on chromatin in the nucleus.
- It is transcribed into a length of RNA called mRNA.
- Many copies of mRNA are made and they pass out the nucleu pores to the ribosomes.
- At the ribosomes, the instruction is translated and the protein assembled for example insulin.
- Insulin will then pass into cisternae of the RER.
- Vesicles with insulin inside pinch of and pass via microtubules to the golgi.
- Vesicle fuses with golgi where insulin molecule may be modified for released.
- Vesicles pinch of and move to surface membrane.
Insulin released.
STATE AT LEAST 4 SIMILARITIES AND DIFFERENCES BETWEEN PROKARYOTIC CELLS AND EUAKRYOTIC CELLS
SIMILARITIES Have a plasma membrane Cytoplasm Ribosomes DNA and RNA
DIFFERENCES Much smaller Less well developed cytoplasm with no centrioles No membrane bound organelles like mitochondria, golgi, ER etc. No nucleus Cell wall made of peptidoglycan Have smaller ribosomes Naked DNA Flagella
HOW DO PROKARYOTES DIVIDE? EXPLAIN.
Prokaryotic cells divide by binary fission. This is because they do not have linear DNA that can divide by mitosis. The DNA is replicated exactly so that each daughter cell receives the same long strand of DNA and any smaller plasmids. They do not have any membrane bound organelles, simply too small.
