Biological Macromolecules

Biological Macromolecules

• Large molecules essential for life.

• Built from smaller organic molecules (containing carbon).

• Constitute the majority of a cell's dry mass.

• Four types:

  • Carbohydrates

  • Lipids

  • Proteins

  • Nucleic Acids

Carbon-Based Life

• Life is constructed from carbon atoms linked to:

  • Other carbon atoms

  • Elements such as hydrogen, oxygen, and nitrogen

Why Carbon is Special

• Capable of forming 4 covalent bonds → resulting in strong and diverse molecules.

• Bonds with:

  • Itself (creating carbon chains and rings)

  • Other elements → forming complex structures.

Carbon’s Bonding Properties

• Allows for:

  • Long chains

  • Rings

  • Branches

  • Double/triple bonds

• This versatility facilitates the creation of complex molecules that make up:

  • Cells

  • Tissues

  • Organisms

Carbon Bonding

• Carbon possesses four electrons in its outer shell → forming four covalent bonds.

• Simplest carbon compound: Methane (CH_4) → one carbon atom bonded to 4 hydrogen atoms.

• Carbon atoms can bond with:

  • Other carbon atoms → forming long chains or branched structures.

  • Other elements such as nitrogen, oxygen, and phosphorus.

  • Themselves to form rings, which can connect with additional rings.

• This bonding flexibility generates a variety of molecular structures → responsible for the diversity of biological macromolecules.

• Example molecules:

  • Stearic acid: long carbon chain.

  • Glycine: includes C, H, N, O atoms.

  • Glucose: Ring structure with carbon atoms

Carbohydrates

• Macromolecules essential for energy and various biological functions.

• Serve as structural support (e.g., in plants: cellulose).

• Found in grains, fruits, and vegetables.

• Main energy source: glucose (a simple sugar).

• General Formula: (CH2O)n → Carbon:Hydrogen:oxygen ratio = 1:2:1

• Three types: Monosaccharides (monomer), Disaccharides (dimer), Polysaccharides (polymer).

• Examples:

  • Glucose (monosaccharide)

  • Sucrose (disaccharide)

  • Starch (plants store energy)

  • Glycogen (animals store energy)

  • Cellulose (plant cell walls)

Monosaccharides

• Mono= one, sacchar= sweet → simple sugars

• Most common: glucose

• Carbon atoms: typically 3 to 6 (trioses, pentoses, hexoses).

• Exists in linear or ring form (rings in aqueous solutions).

• Chemical formula for glucose: C6H{12}O_6

• Glucose is used in:

  • Cellular respiration → produces ATP.

  • Photosynthesis in plants → stored as starch.

• Other Examples:

  • Galactose (in lactose)

  • Fructose (in fruit)

• Glucose, galactose, fructose = isomers (same formula, different structures).

Disaccharides

• Di=two → formed by dehydration reaction (loss of water).

• Bond: covalent bond between two monosaccharides.

• Examples:

  • Lactose: glucose + galactose (in milk).

  • Maltose: glucose + glucose (malt sugar).

  • Sucrose: glucose + fructose (table sugar).

Polysaccharides

• Poly= many → long chains of monosaccharides.

• May be branched or unbranched.

• Examples:

  • Starch

    • Plant sugar storage (amylose and amylopectin).

    • Stored in roots/seeds.

    • Consuming starch → broken down into glucose.

  • Glycogen

    • Animal/human glucose storage.

    • Highly branched, stored in liver and muscle.

    • Broken down when glucose levels are low.

  • Cellulose

    • Provides structural support in plant cell walls.

    • Composed of flipped glucose monomers → rigid structure.

    • Indigestible by humans (called dietary fiber).

    • Herbivores can digest it via cellulose-secreting bacteria.

  • Chitin

    • Found in arthropod exoskeletons (insects, spiders, crabs).

    • Nitrogenous Carbohydrate made of modified sugars.

Functions of Carbohydrates

• Energy storage: Starch (plants), glycogen (animals).

• Structural support: Cellulose (plants), Chitin (Arthropods).

Lipids (Fats and Oils)

• Lipids = Diverse group of hydrophobic compounds due to nonpolar hydrocarbon structure (C-C and C-H bonds).

• Functions of lipids:

  • Long-term energy storage(fats)

  • Help with insulation (keep you warm).

  • Make up cell membranes.

  • Build hormones.

• Types of Lipids: Fats, Oils, Phospholipids, Steroids

Fat Molecules (Triglycerides)

• A fat is made of:

  • 1 glycerol (a small molecule).

  • 3 fatty acids (long chains of carbon and hydrogen).

• When they join together, 3 water molecules are released.

• This type of fat is called a triglyceride.

Types of Fatty Acids

• Saturated Fats

  • Have no double bonds.

  • Solid at room temperature.

  • Found in meat, fat, butter.

  • Can raise “bad” cholesterol.

• Unsaturated Fats

  • Have double bonds in their chains.

  • Liquid at room temperature (called oils).

  • Found in olive oil, canola oil, corn oil.

  • Healthier for the heart.

Trans-Fats and Hydrogenation

• Hydrogenation = Turning oil into a solid fat by adding hydrogen.

• This creates trans fats, which are:

  • Found in margarine, some peanut butters, and fast foods.

  • Food labels now show trans fat content.

Essential Fatty Acids

• Essential fatty acids are fats your body needs but can't make.

• You must get them from food like fish.

• Examples: Omega-3 and Omega-6

  • Help your brain, heart, and growth

Phospholipids

• Phospholipids are special fats that make up the cell membrane.

• Structure:

  • 2 fatty acid tails (don't like water= hydrophobic).

  • Phosphate head (likes water= hydrophilic).

• They form a double layer around cells

  • Tails face in, away from water.

  • Heads face out, toward water.

Steroids

• Steroids are fats with a ring shape.

• Examples:

  • Made in the liver.

  • Helps make hormones (like testosterone and estrogen).

  • Needed for vitamins and cell membranes.

Waxes

• Waxes are made of fatty acid + alcohol

• Used for:

  • Waterproofing (like in plant leaves or animal fur).

  • Examples: Beeswax, lanolin (in wool).

What are Proteins

• Important molecules found in all living things.

• They are made of amino acids (small building blocks).

• Each protein has a special job based on its shape and amino acid sequence.

• Proteins help with:

  • Building body parts (like muscle and skin).

  • Controlling body functions (hormones).

  • Speeding up reactions (enzymes).

  • Defending the body (antibodies).

  • Transporting things (like oxygen and blood).

Amino Acids - Building Blocks of Protein

• Proteins are made from 20 different amino acids.

• All amino acids have:

  • A central carbon

  • An amino group (-NH_2)

  • A carboxyl group (-COOH)

  • A hydrogen

  • An R group (This is the part that changes between amino acids).

How Proteins Are Made

• Amino acids link together using peptide bonds (by removing water).

• A chain of amino acids is called a polypeptide.

• One or more polypeptides that are folded and shaped correctly = a protein.

Protein Functions

• Enzymes: Speed up chemical reactions (like digestion).

  • Ex. Amylase in saliva breaks down starch

• Hormones: Send messages in the body.

  • Ex. Insulin controls blood sugar

• Transport: Move things in the body.

  • Ex. Hemoglobin carries oxygen in blood

• Structure: Builds body parts.

  • Ex. collagen in skin

• Protection: Fight illness (antibodies).

Protein Shapes

• Proteins can be:

  • Globular (round, like hemoglobin).

  • Fibrous (long and stringy, like collagen).

• Shape = Function

  • If a protein loses its shape, it stops working. This is called denaturation.

  • Denaturation happens because of:

    • Heat (like frying an egg)

    • Changes in pH

    • Harsh chemicals

Protein Structure Levels

1. Primary: The order of amino acids

2. Secondary: Folding into shapes like:

   • Alpha-helix (spiral)

   • Beta-Pleated sheet (zig-zag)

3. Tertiary: 3D shape caused by R group interactions

4. Quaternary: Multiple polypeptides joined together.

   • Ex. Hemoglobin has 4 subunits

Sickle Cell Disease (Example of proteins change)

• Caused by one amino acid change in hemoglobin.

• Changes the shape of red blood cells to a sickle shape.

• Can cause health problems like pain and trouble breathing.

Protein Evolution: Cytochrome c

• A protein that helps make energy from food.

• It’s almost the same in many species, showing a common ancestor.

• Human cytochrome c has 104 amino acids

  • Only 1 amino acid is different between humans and monkeys

  • 44 differences between humans and yeast

What are Nucleic Acids Made Of?

• Built from nucleotides (small building blocks).

• Each nucleotide has 3 parts:

  • 1 nitrogen base (like a letter in a code)

  • A sugar (5 carbon sugar)

  • A phosphate group

• Nucleotides link together to make a polynucleotide (long chain) which becomes DNA or RNA

DNA’s Double Helix Shape

• DNA looks like a twisted ladder or spiral staircase.

• It has 2 strands made of sugars and phosphate (like “slides” of a ladder).

• The “steps” are base pairs (nitrogen bases paired together with hydrogen bonds).

  • The bases always pair in a specific way:

    • A pairs with T

    • C pairs with G

  • This shape is called a double helix

What are Nucleic Acids

• Important molecules that store and pass on genetic info.

• They help the cell function properly and make proteins

Two Main Types

1. DNA (Deoxyribonucleic Acid)

   • Holds the genetic instructions for life

   • Found in all living things, from bacteria to humans

   • Stays inside the nucleus

2. RNA (Ribonucleic acid)

   • Helps make proteins using the instructions from DNA

   • Leaves the nucleus to do its job

   • Comes in different types, all involved in building proteins