DNA
-molecule is a double helix (shaped like twisted ladder)
-DNA stands for deoxyribonucleic acid
-two strands run antiparellel to each other (5' -> 3' and 3' -> 5')
-DNA is a polymer that consists of repeating units of nucleotides, the nucleotides in DNA consist of %-carbon sugar )deoxyribos, a phosphate and a nitrogenous base. There are 4 nitrogenous bases
-Nitrogen bases - A (adenine) (purine) = {double hydrogen bond} T (thymine) (pyrimidines)
G (guanime) (purines) =- {triple hydrogen bond} C (cytosine) (pyrimidine)
-DNA stands for deoxyribonucleic acid
-two strands run antiparellel to each other (5' -> 3' and 3' -> 5')
-DNA is a polymer that consists of repeating units of nucleotides, the nucleotides in DNA consist of %-carbon sugar )deoxyribos, a phosphate and a nitrogenous base. There are 4 nitrogenous bases
-Nitrogen bases - A (adenine) (purine) = {double hydrogen bond} T (thymine) (pyrimidines)
G (guanime) (purines) =- {triple hydrogen bond} C (cytosine) (pyrimidine)
DNA Replication
-DNA replication begins with the "unzipping" of the parent molecule as the hydrogen bonds between the base pairs are broken-Once exposed, the sequence of bases on each of the separated strands serves as a template to guide the insertion of a complementary set of bases on the strand being synthesized.
-A portion of the double helix is unwound by a helicase.-A molecule of a DNA polymerase binds to one strand of the DNA and begins moving along it in the 3' to 5' direction, using it as a template for assembling a leading strand of nucleotides and reforming a double helix.
-Because DNA synthesis can only occur 5' to 3', a molecule of a second type of DNA polymerase binds to the other template strand as the double helix opens. This molecule must synthesize discontinuous segments of polynucleotides . Another enzyme, DNA ligacse then stitches these together into the lagging strand.
-A portion of the double helix is unwound by a helicase.-A molecule of a DNA polymerase binds to one strand of the DNA and begins moving along it in the 3' to 5' direction, using it as a template for assembling a leading strand of nucleotides and reforming a double helix.
-Because DNA synthesis can only occur 5' to 3', a molecule of a second type of DNA polymerase binds to the other template strand as the double helix opens. This molecule must synthesize discontinuous segments of polynucleotides . Another enzyme, DNA ligacse then stitches these together into the lagging strand.
DNA Transcription
RNA polymerase is an enzyme that comes along to a strand of DNA and "unzips" it. it starts at the promoter strand, or the "TATAAA" box and breaks down the hydrogen bonds between the neucleotides. As it unzips the DNA, the enzyme reads the nitrogenous bases (the letters) and helps them find there match, replacing T (thymine) with U (uracil), and creating mRNA. As the polymerase moves along the DNA it re-zips it together and ends at the termination signal. The mRNA then exits the nucleus and enters the cytoplasm.
DNA Translation
Translation occurs inside of a ribosome. The mRNA strand enters the ribosome and a tRNA attatches to the matching nucleotides on the mRNA. they join together at the rRNA which is thebinding site". The tRNA has anti-codons which attatch to the codons of the mRNA. The codon on the tRNA starts reading the triplet codons on the mRNA at AUG and works its way down. On the opposite end of the codon, on the tRNA, is an amino acid. The amino acids bond together to form polypetide chains, which is the start of a new strand of DNA.
Fluid Mosaic Model
The fluid-mosaic model describes the plasma membrane of animal cells. The plasma membrane that surrounds these cells has two layers (a bilayer) of phospholipids (fats with phosphorous attached), which at body temperature are like vegetable oil (fluid). Each phospholipid molecule has a head that is attracted to water (hydrophilic) and a tail that repels water (hydrophobic). Both layers of the plasma membrane have the hydrophilic heads pointing toward the outside; the hydrophobic tails form the inside of the bilayer. Because cells reside in a watery solution (extracellular fluid), and they contain a watery solution inside of them (cytoplasm), the plasma membrane forms a circle around each cell so that the water-loving heads are in contact with the fluid, and the water-fearing tails are protected on the inside. The cholesterol that is stuck in there makes the membrane more stable and prevents it from solidifying when your body temperature is low.
Types of transport
The movement of substances in and out of the cell is called transport. Substances entering the cell go through a process called "endocytosis" and substances leaving the cell go through a process called "exocytosis". Some forms of transport require energy from the cell, these methods are called "Active Transport". ATP is usually the form of energy that helps the molecules move against the gradient. Some examples of active transport include
- Pumps- an example of a pump is the sodium potassium pump. This pumps sodium and potassium ions across a nerve cell membrane
- Pinocytosis- another type of active transport, and it is basically "cell drinking". Pinocyticis is the uptake of large dissolved particles. The Cell membrane uses energy to make a vesicle that encloses the particle and engulfs or "drinks" them into the cell.
- Phagocytosis- Pseudopods engulf large particles or even smaller cells. The cell membrane wraps around the particle and encloses it into a vacuole.
There is also Passive Transport which doesn't involve any energy at all. It is the movement of molecules from high concentration to low concentration until there is an equilibrium. Osmosis and diffusion are examples of this. Facilitated diffusion is a form of passive transport and the require hydrophobic protein channels that will transport materials across the membrane of a cell.
Tonicity
The solute and solvent are always trying to get to empty space, so when there is too much solvent in one place, the solute will rush across the gradient to get to empty space. Sometimes this work out making the cell and the solution are at equilibrium. But sometimes the solution doesnt know when to stop causing a hypotonic or hypertonic cell.
- Hypotonic- this word means that there is means that the cell inside the solution is more concentrated than the solution itself. This usually causes the cell to burst or rupture
- Isotonic- This is when the concentration inside the cell and the concentration of the solution is at equilibrium so everything is perfect.
- Hypertonic- When the concentration of the solution is greater than that of the cell, the cell will start to shrivel up, due to the lack of water inside of it.
Enzymes
Its important to understand that enzymes do not provide energy for a reaction nor do they enable that reaction to occur. Instead they act as a catalyst that speeds of the reaction by lowering the reactions action potential
Enzymes are effected by pH and by temperature. If the internal temperature of the body becomes higher than normal (37 degrees celsius) than the enzyme will denature and loose the ability to function. As well, if the pH raises or lowers, it will effect the enzymes activity in a negative way.
- Enzymes are globular proteins that have a tertiary structure
- Enzymes will only form to a substrate that is suited to the enzyme
- The enzyme will alter its shape slightly so that the substrate will fit a little better
- When the enzyme and substrate bind together, we get what is called the enzyme - substrate complex
- The binding of the enzyme and substrate places stress on the glucose - fructose bond, causing it to break apart.
- The reaction products are released and the enzyme can be used again.
Enzymes are effected by pH and by temperature. If the internal temperature of the body becomes higher than normal (37 degrees celsius) than the enzyme will denature and loose the ability to function. As well, if the pH raises or lowers, it will effect the enzymes activity in a negative way.
- Competitive Inhibitor- A competitive inhibitor is a compound that is similar to the substrate that is going to bind with the enzyme. This mimic substrates compete with the substrate for binding with the enzyme, lower the productivity of enzymes since the substrate cannot attatch. An increase in substrates can help overcome this problem.
- Non-competitive inhibitors- noncompetitive inhibitors or allosteric regulators bind to the enzyme, but not the active site. These inhibitors change the shape of the active site, which doesnt allow the substrate to bind to the active site. this causes a decrease in activity to the enzyme.