Hello! As we keep learning about organic chemistry, it's essential to understand the key players in the game - carbohydrates, proteins, and lipids. These biomolecules are fundamental to life processes and understanding their structure and function will be crucial for your upcoming exam. Ready? Let’s dive in!

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🍚 Carbohydrates: The Energy Maestros

Structure of Carbohydrates

Carbohydrates are made up of carbon, hydrogen, and oxygen atoms arranged in rings or chains. They come in simple forms like sugars (glucose) and complex forms like starches (think pasta!) 🍝

• Simple Carbohydrates: Monosaccharides (glucose and fructose) and disaccharides (lactose and sucrose) are the two carbohydrate groups.
• Complex Carbohydrates: Consists of one group: Polysaccharides. The prefix poly- means a lot of, so the word's overall meaning is a lot of saccharides. These chains are made of monosaccharides, and some examples would be cellulose in plants and glycogen in humans.

Image Courtesy of Vibhi

Functions of Carbohydrates

1. ☀️ Energy Source: Glucose is a primary fuel for cells.
2. 🎒 Energy Storage: Starches in plants and glycogen in animals store energy for later use.
3. 🪜 Structural Role: Cellulose gives plant cells rigidity. Chitin also helps structural aspects of fungal cell walls.

Practice Question

1. Identify whether lactose is a mono-, di-, or polysaccharide and explain its role in biological systems.

Image courtesy of Wikimedia Commons.

Explanation: Lactose is a disaccharide, consisting of two sugar molecules (glucose and galactose) linked together. In biological systems, it serves as a primary carbohydrate in milk, providing energy for infants. Enzymes in or body break lactose into its components for absorption in the digestive system.

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⚙️ Proteins: The Doers

Structure of Proteins

Proteins are composed of amino acids linked together by peptide bonds forming complex structures:

• Primary Structure: A basic sequence of amino acids.
• Secondary Structure: Forms coils (alpha-helices) or folds (beta-sheets).
• Tertiary Structure: The overall 3D shape formed by interactions between amino acid side chains.
• Quaternary Structure: When two or more polypeptide chains join together.

Image Courtesy of Wikimedia Commons

Functions of Proteins

1. 🏃🏾‍♂️ Enzymes: Speed up chemical reactions without being consumed.
2. 💪🏽 Structural Components: Collagen strengthens bonds, and keratin protects hair.
3. 💬 Signaling Molecules: Hormones send messages throughout the body.
4. 🦠 Immune System: Antibodies recognize and bind to foreign substances.

Practice Question

1. Alpha-keratin, which is found in the outer layer of the skin, hair, nails, feathers, and horns of vertebrates, has alpha-helices. What type of structure does alpha-keratin have?

   Explanation: Secondary because of the alpha-helix structure.

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💧 Lipids: The Storers & Protectors

Structure of Lipids

Lipids vary widely but share an important trait – they don't mix well with water:

• Fats & Oils: Composed of glycerol attached to three fatty acid chains.
• Phospholipids: Similar to fats but one fatty acid is replaced by a phosphate group.
• Steroids: Four interconnected rings with various functional groups attached.

For example, we can look at the structure of a phospholipid!

Image Courtesy of Wikimedia Commons

Focusing on the hydrophobic tail, because there are so many fatty acids, the tail earns its "hydrophobic" name due to its poor compatibility with water.

Functions of Lipids

1. 🔋 Energy Storage: Fats hold more energy per gram than carbohydrates or proteins. Keeping this in mind, the body still uses carbohydrates because they are faster to break down, then lipids, and finally, proteins.
2. 🪜 Membrane Structure: Phospholipid bilayers form cellular membranes that act as boundaries.
3. 💬 Signaling Molecules: Steroids are permanent messengers to cells that need their message.

Practice Question

1. In water, phospholipids spontaneously form lipid bilayer membranes. Based on their form, demonstrated in the photo above, explain why this might occur.

   Explanation: Hydrophilic heads interact with water and hydrophobic tails repel it, which causes lipids to self-assemble into bilayers. This allows the hydrophobic tails to be sandwiched in between the hydrophilic heads, protecting them from water.

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🥣 Metabolism of Biomolecules

Understanding how these biomolecules are broken down and utilized is key! Here's what you should know about each of them:

Carbohydrate Metabolism

1. Glycolysis breaks down glucose into pyruvate while generating ATP (energy currency).
2. Gluconeogenesis forms glucose from non-carb sources when needed.
3. Glycogen synthesis/storage (glycogenesis) versus breakdown (glycogenolysis).

Protein Metabolism

1. Translation converts genetic information into polypeptides which fold into functional proteins.
2. Proteolysis breaks down proteins into amino acids for recycling or energy production.

Lipid Metabolism

1. Fatty acids break down through beta-oxidation for energy release while glycerol can enter glycolysis.
2. Triglyceride synthesis stores excess energy as fats within cells.

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Final Tips

Remember:

📔 Read all the study guides! 🤔 Understand concepts rather than just memorizing facts – ask "why" something happens! 🧪 Conduct experiments & visualize processes – become friends with lab work!

As you study these biomolecules, always relate structure to function – this understanding is critical both for your exams and your future scientific endeavors!

Keep questioning, keep exploring, and most importantly—keep enjoying chemistry! 🎉