C1 - Cell Level Systems

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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

Image result for animal cell labelled diagram gcse

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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

Image result for bacteria cell gcse (http://www.frankswebspace.org.uk/ScienceAndMaths/biology/images/bacteria1.gif)

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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

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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

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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

A nucleotide consisting of a deoxyribose sugar, phosphate and base

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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

DNA helix unzipping and being copied (http://www.bbc.co.uk/staticarchive/5a6de6442a2225c1d1f6e801899cec515d31f0bc.jpg)

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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

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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

Image result for test for proteins

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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

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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

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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

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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

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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

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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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