Understanding Biological Macromolecules: Structure, Function, and Metabolism
Biological Macromolecules
Carbohydrates
Structure
Glucose: a monosaccharide
Maltose: a disaccharide
Function
Monosaccharides: used as energy sources
Disaccharides: used as transport molecules to move carbohydrates around the body
Cellulose and Amylose
| Feature | Cellulose | Amylose |
|---|---|---|
| Source | Plants | Plants |
| Glucose Subunit | Beta glucose | Alpha glucose |
| Bonds | 1-4 glycosidic linkages | 1-4 glycosidic linkages |
| Branches | Linear | Linear |
Amylopectin and Glycogen
| Feature | Amylopectin | Glycogen |
|---|---|---|
| Source | Plants | Animals |
| Glucose Subunit | Alpha glucose | Alpha glucose |
| Bonds | 1-4 and 1-6 (every 20 monomers) glycosidic linkages | 1-4 and 1-6 (every 10 monomers) glycosidic linkages |
| Branches | Branched | Branched |
Cellulose Digestion
Which two types of animals can digest cellulose?
Ruminants (e.g., cows) and caeocotrophs (e.g., rabbits)
Lipids
Fatty Acids and Cholesterol
| Fatty Acid Type | Effect on Cholesterol |
|---|---|
| Cis unsaturated fatty acids | Raise HDL levels, eliminate cholesterol from the blood, and carry it back to the liver for disposal (HDL lipoproteins) |
| Saturated and trans unsaturated fatty acids | Raise LDL levels, carry cholesterol from the liver to the rest of the body (LDL lipoproteins) |
| Trans unsaturated fatty acids | Lower HDL levels AND raise LDL levels |
Sources of Fatty Acids
- Saturated fats: Meat products, eggs, cheese
- Cis-unsaturated fats: Olive oil, fish, avocado oil
- Trans-unsaturated fats: Deep-fried foods, some margarines, vegetable shortening
HDL and LDL Lipoproteins
HDL lipoproteins transport cholesterol from the blood vessels to the liver for disposal.
LDL lipoproteins transport cholesterol from the liver to blood vessels.
Importance of Regulating HDL and LDL Levels
Regulating HDL and LDL levels is crucial for overall health because high cholesterol levels can damage blood vessels. Cholesterol buildup in blood vessels can lead to clot formation, disrupting blood flow. Severe cases can result in:
- Atherosclerosis: narrowing/hardening of blood vessels
- Coronary heart disease: heart attacks
- Strokes
Proteins
Protein Structure
| Level | Bond | Location | Features |
|---|---|---|---|
| Primary | Peptide | Adjacent amine and carboxyl group | Linear order of amino acids |
| Secondary | Hydrogen | Non-adjacent amine and carboxyl group | Alpha helices, beta-pleated sheets |
| Tertiary | Hydrogen, ionic, covalent, disulfide bridges, polar associations | Between variable groups | Overall 3-D configuration of the polypeptide |
| Quaternary | Various | Between multiple polypeptide chains or with inorganic prosthetic groups | Multiple polypeptide molecules or the inclusion of inorganic prosthetic groups (e.g., hemoglobin) |
Protein Denaturation
Factors causing denaturation: Temperature and pH
Reason for denaturation: Hydrogen bonds break
Nucleic Acids
DNA Replication
- Semi-conservative: After replication, each new DNA molecule consists of one original strand and one newly synthesized strand.
- Anti-parallel: The two DNA strands run parallel to each other but in opposite directions.
Enzymes Involved in DNA Replication
- Primase: Attaches an RNA primer to the template strand, enabling DNA Polymerase III to bind.
- DNA Polymerase III: Adds complementary nucleotides to the new DNA strand.
- DNA Polymerase I: Replaces RNA primers with DNA nucleotides and proofreads the new strand.
- Ligase: Joins Okazaki fragments on the lagging strand.
- Helicase: Unwinds the DNA double helix at the replication fork.
- Gyrase: Relaxes supercoiling of the DNA molecule.
- Single-stranded binding proteins (SSBs): Prevent reannealing or degradation of separated DNA strands.
Leading and Lagging Strands
- Leading strand: Synthesized continuously towards the replication fork.
- Lagging strand: Synthesized discontinuously in Okazaki fragments, away from the replication fork.
Scientists Who Discovered DNA
Rosalind Franklin, James Watson, Francis Crick, and Maurice Wilkins
Metabolism
: Chemical reactions which are catalyzed by enzymes Active site:Site on enzyme where the substrate binds to Substrate: Reactant which will be catalyzed by an enzyme Enzyme: Catalyst in a chemical reaction. Made from proteins. Semi-Conservative: When DNA replication is complete, one of the two strands comes from the original molecule of DNA Anti-parallel:The orientation of both strands of DNA. The molecule is made from two strands which are parallel but run in opposite directions. Primase: Enzyme which attaches a short, RNA primer to the template strand. Helps DNA Polymerase III attach to the molecule to continue replication Okazaki fragments: Short, unconnected fragments of newly synthesized DNA. Only found on the lagging strand. Ligase: Enzyme which forms phosphodiester bonds, particularly between Okazaki fragments. Single stranded binding proteins: SSBs prevent the two recently separated strands of DNA from reannealing or breaking down. DNA Polymerase I:will replace the RNA primers, left from Primase, with DNA nucleotides. This enzyme will also proof-read the newly synthesized strand of DNA to ensure that no mistakes were made. DNA Polymerase III: This enzyme will pair up complementary bases with those found on the template strand. Helicase: breaks hydrogen bonds between complementary bases to form two, separate strands of DNA. Helicase also is where the replication fork is located. Gyrase: will flatten out the DNA molecule Leading strand: This is the strand which can be continuously synthesized towards the replication fork. Lagging strand: This strand must be synthesized in bits and pieces away from the replication fork. Okazaki fragments are found here. Which scientists discovering DNA? Rosalind Franklin, James Watson, Francis Crick, and Maurice WILKINS