Macromolecules Carbon and Life, Slides of Biology

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Macromolecules

carbon, and life Chapter 5

Stanley Miller’s Experiment (1953)

Can organic molecules form under conditions believed to simulate those on the early Earth? Yes!

Figure 4.

The (LARGE) Molecules of Life: Macromolecules

Macromolecules are large and complex molecules that are composed of many covalently connected atoms: carbohydrates ; lipids ; proteins ; nucleic acids (the 4 classes)

Molecular structure and function are inseparable

Figure 5.1 Why is the structure of a protein important for its function?

Concept: Macromolecules are Polymers, Built from Monomers Polymer: a long molecule consisting of many similar building blocks The smaller, repeating molecules that serve as building blocks are called monomers Three of life’s organic molecules are polymers:

• Carbohydrates
• Proteins
• Nucleic acids

Storage Polysaccharides (examples)

Starch , a storage polysaccharide of plants, consists entirely of glucose monomers (e.g. Plants store surplus starch as granules within chloroplasts and other organelles)

Figure 5.6a Polysaccharides of plants and animals.

Structural Polysaccharides

The glycosidic linkages of cellulose differ from those of starch because the ring forms of glucose in the two polymers are slightly different

Beta (β) bonds between glucose in cellulose (straight) instead of alpha (α) glucose as in starch (largely helical)

Figure 5.7 Starch and cellulose structures.

Concept: Lipids are a Diverse Group of Hydrophobic

Molecules

Lipids are the one class of large biological molecules that does not form polymers

• Unifying feature of lipids is little or no affinity for water
• Lipids are hydrophobic because they consist mostly of hydrocarbons which are nonpolar
• Biologically important lipids include fats, phospholipids, and steroids

Fats

Fats are constructed from glycerol and fatty acids Glycerol is a three-carbon alcohol with a hydroxyl attached to each carbon Fatty acids consist of a carboxyl group linked to a long hydrocarbon chain

Figure 5.9a The synthesis and structure of a fat, or triacylglycerol.

Phospholipids

In phospholipids , two fatty acids and a phosphate group are attached to glycerol

• The two fatty acid tails are hydrophobic
• The phosphate head group is hydrophilic

Figure 5.11a and b The structure of a phospholipid.

Phospholipids: major component of cell membranes When added to water, they spontaneously self- assemble into a bilayer

Steroids

Steroids are lipids with a carbon skeleton consisting of four fused rings

Cholesterol is a component in animal cell membranes

• Although cholesterol is an essential component of animal cell membranes, high levels in blood may contribute to cardiovascular disease

Figure 5.12 Cholesterol, a steroid.

Proteins are Polymers of Amino Acids

All proteins are polymers constructed from the same set of 20 amino acids… linked together into unbranched polymers called polypeptides (few to >1000 monomers)

A protein is a biologically functional molecule that consists of one or more polypeptide

Four Levels of Protein Structure: Primary structure of a protein is its unique amino acids sequence Secondary structure are coils and folds within the polypeptide chain Tertiary structure is determined by interactions among various side chains (R groups) Quaternary structure is when a protein consists of multiple polypeptide chains

• Figure 5.

Protein Structure and Function

The sequence of amino acids determines a protein’s three- dimensional structure

• Protein structure determines its function
• Function usually depends on ability to recognize and bind other molecule(s)

Figure 5.17 Complementarity of shape between two protein surfaces.

Protein Functions: Enzymatic proteins

Figure 5.