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What property of water allows it to absorb a large amount of energy without a significant increase in temperature?
Ice is denser than liquid water.
False
What type of substances can dissolve easily in water due to its polar nature?
Polar and charged substances
The ph of blood must be kept between ______ and ______.
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Match the following classes of biological monomers with their examples:
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Which of the following statements correctly describes hydrophilic substances?
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Functional groups do not affect the properties of organic molecules.
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How do buffers help maintain pH levels in bodily fluids like blood?
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What is the primary role of enzymes in biological reactions?
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Cofactors are only inorganic molecules that assist in enzyme catalysis.
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What is the term for the inactive forms of enzymes?
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Enzymes lower the __________ required for a chemical reaction to occur.
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Match each type of RNA with its primary function:
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Which of the following bases is found in RNA but not in DNA?
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All nucleic acids have a backbone made of phosphate groups and pentose sugars.
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What are the monomers of nucleic acids called?
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DNA replication produces two identical __________ strands.
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What is the function of ATP in cells?
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What type of linkage connects monosaccharides in carbohydrates?
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Cellulose can be broken down by the enzymes present in humans.
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What is the primary storage polysaccharide in animals?
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Phospholipids have a ___________ head and ___________ tails.
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Match the types of fats with their characteristics:
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Which of the following is NOT a type of lipid?
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Eicosanoids are 20-carbon compounds that serve as immune signaling molecules.
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What are the monomers of proteins called?
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A __________ protein is water-soluble and often has functions like enzyme activity.
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Match the following protein structures with their descriptions:
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Which of the following statements is true regarding triglycerides?
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Denatured proteins retain their biological activity.
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What is the role of cholesterol in cellular membranes?
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Fatty acids consist of a long hydrocarbon chain with a ___________ group.
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Study Notes
Water Properties
- Water molecules stick to one another due to cohesion.
- Water can absorb a lot of energy before its temperature increases, helping moderate temperature.
- Water releases heat back into the environment at night, keeping temperatures stable.
- Sweat is an example of how water controls temperature through evaporation.
- Ice floats on liquid water because water expands when it freezes.
- The hydrogen bonds between water molecules in ice force them into a lattice structure.
- Liquid water is less ordered, resulting in a higher density than ice.
- Water is a polar molecule, making it an excellent solvent.
- Hydrophilic substances dissolve easily in water, while hydrophobic substances (like oils and lipids) do not.
- Buffers minimize changes in pH levels, maintaining a stable environment for biological processes.
- Blood is a buffer, with a pH maintained between 7.35-7.45.
Organic Chemistry
- All living things are made of matter, which is subject to the same chemical and physical laws.
- Organic molecules contain carbon.
- Carbon skeletons are held together by covalent bonds.
- Molecules containing only carbon and hydrogen are called hydrocarbons.
- Functional groups are atoms or molecules attached to the carbon skeleton.
- Different functional groups lead to different chemical properties and influence the function of molecules in cells.
- Biological molecules are complex organic compounds.
- Most organic molecules are polymers built from monomers.
Carbohydrates
- Carbohydrates consist of carbon, hydrogen, and oxygen.
- They make up 2-3% of total body mass.
- Monosaccharides, simple sugars, are the monomers of carbohydrates.
- Dehydration synthesis joins monosaccharides together, forming a glycosidic linkage.
- Disaccharides are two monosaccharides joined together.
- Polysaccharides are made of many monosaccharides.
- Glycogen is a branched chain of glucose monomers, the storage polysaccharide in animals.
- Starches are linear chains of glucose monomers, the storage polysaccharide in plants.
- The stereochemistry of glycosidic bonds between monomers differs in glycogen and starch.
- Humans lack enzymes to break down cellulose.
Lipids
- Lipids are hydrophobic molecules made primarily of carbon, hydrogen, and a small amount of oxygen.
- They make up 18-25% of total body mass in humans.
- Fatty acids have a hydrocarbon chain with a carboxyl group at one end.
- Saturated fatty acids contain only single C-C bonds.
- Unsaturated fatty acids have one or more C-C double bonds.
- Triglycerides are three fatty acids bonded to a glycerol backbone by ester bonds.
- Fats are solid at room temperature, while oils are liquid.
- Triglycerides are stored in fat cells.
- Phospholipids have a glycerol backbone linked to two fatty acids and a phosphate group.
- The phosphate "head" is hydrophilic, and the fatty acid "tails" are hydrophobic, making them amphipathic molecules.
- Steroids are made from four fused carbon rings.
- Cholesterol is the starting molecule for synthesizing other steroids.
- Sterols are steroids with at least one hydroxyl group, making them slightly amphipathic.
- Eicosanoids are 20-carbon compounds involved in immune signaling.
- Fat-soluble vitamins (D, E, K) are essential for human health.
Proteins
- Proteins are large molecules made of carbon, hydrogen, oxygen, and nitrogen.
- They make up 12-18% of total body mass in humans.
- Amino acids are the monomers of proteins.
- Each amino acid has a central carbon atom bonded to an amino group, a carboxyl group, and a R group, which determines its unique properties.
- Dehydration synthesis forms peptide bonds between amino acids.
- Polypeptides are formed by chains of many amino acids.
- Proteins can be single or multiple polypeptide chains.
- Protein structure determines function.
- Primary structure is the amino acid sequence, determined by genes.
- Secondary structure involves repeated folds (α-helices or β-sheets) stabilized by hydrogen bonds.
- Tertiary structure is the three-dimensional shape, influenced by primary and secondary structure, bonds, and atomic forces.
- Disulfide bridges are covalent S-S bonds between sulfhydryl groups.
- Quaternary structure is the arrangement of polypeptide chains in multi-peptide proteins.
- Fibrous proteins form long bundles and are water-insoluble, such as keratin (hair) and actin (muscle thin filaments).
- Globular proteins are round and water-soluble, such as antibodies and enzymes.
- When proteins lose their structure, they become denatured and inactive.
Enzymes
- Enzymes are biological catalysts that increase the rate of chemical reactions without being consumed.
- Cofactors are nonprotein molecules that assist enzyme catalysis, including coenzymes, which are organic molecules.
- Substrates bind to the active site of enzymes, forming a substrate-enzyme complex.
- Enzymes lower the activation energy of reactions.
- Enzymes are highly specific for their substrates.
- Enzymes are efficient, increasing the rate of chemical reactions.
- Enzymes are regulated through the synthesis and activity control.
- Proenzymes are inactive forms of enzymes that are activated under specific conditions.
Nucleic Acids
- Nucleic acids are made of carbon, hydrogen, oxygen, nitrogen, and phosphorus.
- DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the two types.
- Genes are sections of DNA that encode specific proteins.
- DNA is transcribed into RNA, which is translated by ribosomes into proteins.
- Nucleotides are the monomers of nucleic acids, consisting of a nitrogenous base, a pentose sugar, and a phosphate group.
- DNA contains the bases A, G, C, and T.
- RNA contains the bases A, G, C, and U.
- Purines (A and G) have double-ring bases.
- Pyrimidines (T/U and C) have single-ring bases.
- Base pairing involves a purine pairing with a pyrimidine (A-T or A-U, G-C).
- The backbone of the DNA and RNA molecule is formed by phosphate groups and pentose sugars.
- DNA forms a double helix, with the bases forming the "rungs"
- DNA replication makes a new copy of the double helix using one strand as a template.
- A change in the nucleotide sequence of DNA is called a mutation.
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RNA is single-stranded and exists as three major types:
- Messenger RNA (mRNA)
- Ribosomal RNA (rRNA)
- Transfer RNA (tRNA)
- Adenosine triphosphate (ATP) is the energy currency of cells.
- ATP consists of three phosphate groups bound to adenosine (adenine + ribose).
- ATP is produced by exergonic cellular reactions and consumed by endergonic cellular reactions.
- Hydrolysis of the terminal phosphate group in ATP releases a large amount of energy.
- ATP is regenerated by ATP synthase during aerobic cellular respiration.
Summary
- Biological molecules are diverse organic molecules.
- Four main classes: carbohydrates, lipids, proteins, and nucleic acids.
- All are polymers of monomers except lipids.
- Function is closely related to structure.
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