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Basics of Biochemistry: 4) Structure and function of Carbohydrates, Lipids, and Nucleic Acids

Carbohydrates, Lipids, and Nucleic Acids

This lesson will go over carbohydrates (sugars), lipids (fats), and nucleic acids (proteins). 

Carbohydrates: 

- Composition: C, H, and O. 

- Function: Quick energy (glucose), energy storage (starch, glycogen), structural materials (cellulose). 

- Types of carbs: Simple and complex sugars. 


Simple Sugars 

Provide the body with quick energy. 

    - Monosaccharides (monomers): 1 monomer of sugar (mono-saccharide = one-sugar). 

        - Glucose 
        - Fructose 
        - Galactose 

    - Disaccharides (oligomers - usually means 2 to 10 monomers, not yet a polymer): 2 monomers of sugar (di-saccharide = two-sugar). Linked by glycosidic bonds. 
        - Sucrose (Glucose + fructose) 
        - Lactose (Glucose + galactose) 
        - Maltose (Glucose + glucose) 


Complex Sugars 

Energy storage, cell structure. 

    - Polysaccharides (polymers): Many monomers (usually more than 10) of sugar (poly-saccharide = many-sugar). Linked by glycosidic bonds. 
        - Starch (energy storage in plants)
        - Glycogen (energy storage in animals)
        - Cellulose (cell structure in plants)
        - Chitin (cell structure in arthropods and fungi) 





- Isomers: Molecules with the same molecular formula, but different structure. 

    - Alpha-glucose vs beta-glucose 






Lipids: 

- Composition: C, H, and O (long hydrocarbon chains). 

- Function: Long term energy storage, cell membrane, organ cushioning, body insulation. 

- Types of lipids: Fats (triglycerides), phospholipids, steroids. 

- Does NOT form polymers. Monomers are repeated but do not form a chain of subunits. 


Triglycerides 

    - Composed of 1 glycerol molecule and 3 fatty acid chains. 
    - Serves to storm long term energy in the form of adipose (fat) cells 
    - Insulates and protects organs 




Phospholipids 

    - Composed of glycerol, 2 fatty acid chains, and phosphate group PO4(3-) — PO4 has a negative 3 charge 
    - Phosphate group (HEAD) is hydrophilic (attracted to water), due to the negative charge. 
    - Fatty acid (TAIL) is hydrophobic (not attracted to water), due to the fatty acids being a long chain of hydrocarbons that overrules the negative head; it is nonpolar. 
    - Phospholipids are arranged in a bilayer (2 layers) and are held together by hydrophobic interactions (the tails face each other; the heads face away). This creates a barrier (known as the cell membrane; more on that later). 





Steroids 

Although there are many types, they all share the same four-carbon-ring structure and have one of two functions: altering cell membrane rigidity and acting as signaling molecules. 

    - Cholesterol: Keeps the cell membrane fluid and flexible. 
        - In hot temperatures, when molecules are more agitated, it holds them together. 
        - In cold temperatures, cholesterol prevents molecules from clustering together and becoming stiff.

        - Cholesterol also is what makes up the majority of myelin sheaths, which protect neurons and increase their electrical charge signaling speed. 

    - Anabolic steroids: These are what athletes take to increase anabolic effects, like muscle building, as well as other effects. 





- Note: Fats are saturated or unsaturated, depending on their hydrogen density. 

    - Saturated fats: Have single bonds between carbons, allowing for maximal hydrogens to bond to the carbons (thus saturating the molecule). 





    - Unsaturated fats: Have double bonds between carbons. This creates a twist/bend that prevents tight packing of hydrogens. 





Nucleic Acids: 

- Composition: A 5-carbon sugar (such as deoxyribose in DNA and ribose in RNA), a phosphate group, and a nitrogenous base (adenine, guanine, cytosine, uracil, and thymine). 

- Function: Genetic material. DNA (deoxyribonucleic acid) stores information as genes and RNA (ribonucleic acid) transfers that information. 

- Types of nucleic acids: Nucleotides, DNA/RNA. 



Nucleotides 

Make up DNA/RNA. There are 5 possible nucleotides: Adenine, Guanine, Thymine, Cytosine, and Uracil.


    - Purines: Have a double ring N-base. Adenine and Guanine are the two purines. 
    - Pyrimidines: Have a single ring N-base. Cytosine, Thymine, and Adenine are the three pyrimidines. 





DNA & RNA 

Store and transmit genetic information. 

    - DNA: A:T and C:G (Adenine pairs with Thymine, Cytosine pairs with Guanine)
    - RNA: A:U and C:G (Adenine pairs with Uracil, Cytosine pairs with Guanine) 











Note that both DNA and RNA are made of A, C, and G! The only difference is that DNA has T while RNA has U. 

Adenine and Thymine/Uracil bond together with 2 hydrogen bonds (in both DNA and RNA) while Cytosine and Guanine bond together with 3 hydrogen bonds. Therefore, we can assume that C:G bonds are harder to break than A:T or A:U bonds because C:G have more bonds. 

In addition, the strands run anti-parallel to each other, meaning the end of one strand matches with the beginning of the other strand. Each DNA and RNA strand has a 5' end and a 3' end. The 5' end has a phosphate group attached to the 5' carbon. The 3' end has a hydroxyl (OH) group attached to the 3' carbon. So, DNA strands in anti-parallel formation will have the 5' and 3' ends next to each other, like so. 



Now for the joke! Which planet loves to sing? 



Nep-tune! 

(haha)

That's it for biochemistry! Next up we have a new unit: cells and their organelles! 




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Comments

  1. AnonymousJuly 20, 2024 at 8:50 AM

    so what makes up nucleic acids, nucleotides or the sugar/phosphate/base mix?

    ReplyDelete
    Replies
    1. Aspiring to be a rich doctorJuly 20, 2024 at 10:46 AM

      Nucleic acids are made up of nucleotides, which are made up of a sugar, phosphate, and base.
      Sugar + Phosphate + Base = Nucleotide
      Nucleotide + other Nucleotides = Nucleic Acid

      Delete
  2. AnonymousJuly 27, 2024 at 10:07 AM

    This is so comprehensive thanks for the resource!

    ReplyDelete
  3. AnonymousAugust 5, 2024 at 11:36 AM

    are the only structural differences between RNA and DNA the sugar and uracil?

    ReplyDelete
    Replies
    1. Aspiring to be a rich doctorAugust 5, 2024 at 11:47 AM

      There's a couple more that we'll get into (with a lot of detail!) when we cover molecular biology: RNA is typically single-stranded while DNA is double-stranded; DNA is typically longer than RNA; and DNA is typically more stable than RNA due to being double-stranded and the presence of thymine which makes it less prone to degradation. Hope this helps!

      Delete
  4. emmaAugust 16, 2024 at 6:37 PM

    If cellulose is made out of sugar could you make edible sugar out of cellulose?

    ReplyDelete
    Replies
    1. Aspiring to be a rich doctorAugust 16, 2024 at 6:44 PM

      Yes actually! It's a pretty long process though, because you have to break down the bonds in cellulose to get individual sugar molecules. If you're interested, a chemist on YouTube actually creates cotton candy from cotton balls. I found this a highly entertaining video, give it a watch! https://www.youtube.com/watch?v=vHuFizITMdA He explains the entire process while doing it.

      Delete

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