Biochemistry: Important Cellular Molecules and Their Functions, Slides of Biology

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Biochemistry

Important cellular chemicals.

Protein

• Proteins are made of chains of amino acids.
• There are 20 amino acids. 12 of these are called essential amino acids because we don’t have the ability to synthesize them inside our bodies.
• Protein have various functions:
  • Enzymes that catalyze (speed up or slow down) chemical reactions.
  • Structural proteins, like collegen, elastin, etc.
  • Hormones, chemical signals like insulin.
  • In rare cases as a source of energy. Docsity.com

Nucleic Acids

• Two types: DNA or Deoxyribonucleic Acid and RNA or Ribonucleic Acid.
• DNA carries genetic information it sort like the cell’s hard drive.
• Messenger RNA transfers information from the DNA to the protein making machinery. The three types of RNA are messenger RNA or mRNA, transfer RNA or tRNA and ribosomal RNA or rRNA.
• DNA is made of chains of nucleotides, they are made of a sugar (deoxyribose), nitrogenous base (adenine, guanine, thymine and cytosine) and phosphate group.
• RNA is made of chains of nucleotides, they are made of a sugar (ribose), nitrogenous base (adenine, guanine, uracil and cytosine) and a phosphate group.

Lipids: Fats and Oils

• Functions: Make up cell membranes, , insulation, energy source, hormones.
• Fats are solid – made from saturated fats.
• Oils are liquid – made from unsaturated fats.

Anabolic Pathways

• Are pathways where chemicals are synthesized from simpler chemicals.
• Memory device: Anabolic Steroids help build up muscles  Anabolic pathways help build up chemicals.
• Examples include:
  • building proteins from amino acids,
  • making complex carbohydrates from simple sugars
  • Making DNA from nucleotides

Catabolic Pathways

• Breaking down chemicals into simpler ones.
• Memory device: When things all fall apart or break down it is a CATASTROPHE
• Examples include:
  • The digestive system breaking proteins in amino acids, lipids into fatty acids an glycol, Starch in glucose and nucleic acids in nucleotides.

Question: Is this an Anabolic of catabolic reaction?

Enzymes continued

• The reason why enzymes have an optimum range is that the shape of proteins changes depending on their environment.
• If the shape of their active sites changes it will affect their ability to work.
• When a protein or enzyme changes from its working shape to a non-working shape it is said to be denatured. For example when you cook an egg it is denatured which why it goes hard and the egg white goes from clear to white.

Enzymes

• An important thing to note about enzymes, or any catalyst is that they are NOT used up during the reaction. Therefore the same enzyme can catalyse the same reaction over and over again.
• As a consequence to stop a particular reaction any enzyme will need to be deactivated. This is where feedback mechanisms come in.

Feedback mechanisms

• These mechanism apply to other biological processes not just chemical pathways. They help us maintain homeostasis.
• Sometimes the products or by-products of a chemical pathway will turn the pathway on or off or make it go faster or slower..
• The two main types of feedback mechanism are: - Negative feedback: this is where the products or by- products turn off the pathway or slows it down. - Positive feedback: the products or by-products signals the pathways to continue or speed up.
• Negative feedback is far more common than positive feedback.

Enzyme inhibition and feedback

• In addition to its active site and enzyme may have an allosteric site.
• An allosteric site fits a specific inhibitor molecule. When this inhibitor binds it changes the shape of the active site and therefore deactivates the enzyme.
• The inhibitor is often a product or by- product of the enzymes chemical pathway.

Competitive and Non Competitive

inhibition

• Inhibition via allosteric sites is called non- competitive inhibition because it doesn’t compete with the substrate for the active site.
• Competitive inhibition is therefore when a substance competes for a active site on and enzyme.
• Competitive inhibitors fit into the active site but do not react. The therefore block the reaction site.

Answer

• Competitive: Increasing the amount of substrate will increase the enzyme activity as it will overwhelm the competitive inhibitor
• Non-competitive: Increasing the amount of substrate will have no affect enzyme activity as the active site will still be the wrong shape fit the substrate.

Fun facts

• Poisons are often enzyme inhibitors.
• Cyanide, for example, inhibits an enzyme involved in cellular respiration.
• Heavy metals like mercury inhibit enzymes by binding to enzymes and changing their shape like a non-competitive inhibitor.