C1 - Cell Level Systems
- Created by: chelseaboy03
- Created on: 17-01-18 17:01
Eukaryotes
Animals, plants and fungi are eukaryotes
They have a membrane-bound nucleus and linear chromosomes
The DNA is tightly coiled
Nucleus - contains DNA in the form of chromosomes to control cell activity
Cytoplasm - gel-like substance where chemical reactions occur
Mitochondria - site of cellular respiration and contains enzymes
Cell Membrane - keeps the cell shape, controls what comes in and out, contains receptor molecules for cell communication
Cell Wall - made of cellulose and gives support
Chloroplasts - where photosynthesis occurs, they contain chlorophyll
Permanent Vacuole - filled with sap to keep the cell turgid
Ribosome - where protein synthesis happens
Prokaryoytes
Bacteria are prokaryotes
They do not have a membrane-bound nucleus and their DNA is free in the cytoplasm - this is called chromosomal DNA as it is one long circular chromosome
Plasmids - extra bits of DNA for genes like drug resistance
Pilli - the hair like extensions allow plasmids to be exchanged
Flagellum - tail so that they can move
Microscopy
They use lenses to magnify an image
Also, you can increase the resolution so you can see a picture clearer
1cm = 10000 micrometre
1cm = 10000000 nanometre
MAGNIFICATION = LENS MAGNIFICATION X OBJECTIVE LENS MAGNIFICATION
MAGNIFICATION = IMAGE SIZE / REAL SIZE
Light Microscopes
Eyepiece Lens - looked through to see image
Objective Lens - magnifies the image
Stage- supports the slide
Clip - holds the slide in place
Lamp - shines light so you can see the image
Coarse adjustment knob - adjusts to find a part of the specimen by moving the stage
Fine adjustment knob - used to finally see the image after a coarse adjustment
A stain, for example, a methyl blue can be used to see a specimen
A cover slip goes over the specimen - be careful to get no air bubbles
DNA
DNA is a double helix structure of paired bases that contains all of an organism's genetic material
Each of the two DNA strands is made up of nucleotides
Nucleotides consist of a base, sugar and phosphate - this forms a sugar-phosphate backbone
The sugar and phosphate group never change - only the base attached to the sugar varies
DNA is a polymer because it is made up of smaller nucleotides
Protein Synthesis - Transcription
DNA controls the production of proteins, and the section of DNA that does this is a gene
Transcription -
This occurs in the cell nucleus
The DNA of a gene unzips and one strand is used as a template
Complementary bases attach to the template - U joins to A instead of T
A strand of messenger RNA forms (mRNA)
It moves out of the cell nucleus and goes to ribosomes in the cytoplasm
WHAT ARE PROTEINS?
Proteins are polymers that are made of long chains of amino acids
The amino acids are made of carbon, nitrogen, hydrogen and oxygen
Proteins get broken down by enzymes that are located in the stomach and small intestine
HOW TO TEST FOR PROTEINS
To test for proteins you use the biuret test...
1. You add a few drops of sodium hydroxide so the solution is alkaline
2. Then add some copper sulfate solution
If there are proteins present it will turn purple. It will remain blue if there is no protein
WHAT ARE CARBOHYDRATES?
Carbohydrates are made of simple sugars in a polymer, they contain carbon, hydrogen and oxygen
Carbohydrates are then broken down back into the simple sugars when they are digested by enzymes
They are broken down by enzymes in the mouth and small intestine
HOW TO TEST FOR CARBOHYDRATES
To test for carbohydrates you use benedicts regent...
1. Add benedicts reagent and heat it in a bath
2. A coloured precipitate will form if the test for the sugars is positive
The higher the concentration of sugar, the further the colour changes
WHAT ARE LIPIDS?
Lipids are made up of fatty acids and glycerol
Lipids are NOT polymers because they don't form long chains of monomers
They contain carbon, hydrogen and oxygen
Lipids are broken down by enzymes in the small intestine
HOW TO TEST FOR LIPIDS
To test for lipids you use the emulsion test...
1. Add ethanol and shake until it dissolves
2. Pour the solution in water
If there are lipids present then there will be a milky emulsion
Protein Synthesis - Translation
This takes place in the ribosomes in the cytoplasm and mRNA is interpreted to form a protein
mRNA attached to a ribosome and decodes it into triplets which are complementary to the transfer RNA (tRNA)
The tRNA is specific to an amino acid and it returns it to the mRNA
The amino acids are lined up and bonds form to give a polypeptide chain
This folds and becomes a specific shape for a protein
Enzymes
Enzymes control cell reactions - they are biological catalysts
Enzymes are proteins that have a specific shape to do its jobs - substrates have to fit inside the active site
Factors that affect enzymes:
Temperature - A higher temperature can speed up a reaction because they have more energy but too hot will cause the enzymes to be denatured- the optimum temperature is the best temperature
pH - If it is too high or low it interferes with the bonds and can denature the enzyme - all enzymes have an optimum pH
Enzyme Concentration - The more enzymes in a solution, the rate of reaction increases but after a point it has no further increase as there is limited substrate
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