40 Questions
Which of the following elements is NOT mentioned as a component of living organisms?
Barium
What is the general term for the chemical activities that occur within cells?
Metabolism
What is the percentage of fresh weight of cells that water makes up?
60-95%
Why is water considered essential for life?
All of the above
What type of bonds are formed between water molecules?
Hydrogen bonds
What is the role of water in transporting substances?
It transports substances into and out of cells
What is the term used to describe the large molecules that carry genetic information?
Informational molecules
Why do evolutionists believe that life evolved in water?
Because without water, life as we know it would not exist
What is the primary function of cellulose and chitin in living organisms?
Providing structure
What is characteristic of lipids in comparison to carbohydrates?
Lower oxygen content
What is the primary difference between fats and oils?
Type and saturation of fatty acids
Why are fats a good source of energy?
They produce more energy on oxidation
What is the function of phospholipids and steroids in living organisms?
Components of the plasma membrane
Why are lipids insoluble in water?
They lack polar groups
What is the significance of fatty acids in lipids?
They determine the physical properties of lipids
Why are fats and oils good insulators?
They have low thermal conductivity
What type of specificity is shown by enzymes that can distinguish one enantiomer from another?
Stereochemical specificity
What is the term for the non-protein prosthetic group that binds to an enzyme to make it active?
Cofactor
Which of the following enzymes is an example of a protease that selectively hydrolyse peptide bonds?
All of the above
What is the role of coenzymes in biochemical reactions?
To donate groups to the substrate or serve as recipients of groups removed from the substrate
What is the term for the active enzyme that consists of the polypeptide portion and the non-protein prosthetic group?
Holoenzyme
Which vitamin is not associated with a coenzyme?
Vitamin C
What is the effect of inhibitors on enzymes?
They eliminate or drastically reduce the catalytic ability of the enzyme
What is the term for the enzyme that lacks the non-protein prosthetic group?
Apoenzyme
What is the primary function of catabolic reactions in a cell?
To break down complex materials into simpler ones
What type of organisms use sunlight or chemical energy to build up their required macromolecules?
Autotrophs
Why do metabolic reactions involve a series of steps?
To prevent the release of excess energy and to allow for efficient use of energy
What is the term for reactions that build up complex molecules from simpler ones?
Anabolism
What is the purpose of catabolic reactions in heterotrophs?
To break down food molecules to release energy
Why do anabolic reactions tend to be endothermic?
Because they require energy input
What is the term for the breakdown of complex materials into simpler ones?
Catabolism
What is the purpose of coupling anabolic and catabolic reactions in biological systems?
To prevent the wastage of energy and to allow for efficient use
What is the primary role of the pentose phosphate pathway?
Anabolic
What is the reduced form of NADP+ produced in the pentose phosphate pathway?
NADPH
What is the precursor for the synthesis of nucleotides produced in the pentose phosphate pathway?
Ribose-5-phosphate
Where does the pentose phosphate pathway take place in plants?
Plastids
What is the name of the pathway that is also known as the pentose phosphate pathway?
Warburg-Dickens pathway
Which tissues have high levels of PPP enzymes?
Liver and adipose tissue
How many molecules of NADP+ are reduced to NADPH in the oxidative stage of the pentose phosphate pathway?
Two
What is the starting molecule in the oxidative stage of the pentose phosphate pathway?
Glucose-6-phosphate
Study Notes
Biologically Important Molecules
- Living organisms are made up of a limited number of atoms, including carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus, and ions like Na+, Mg2+, Cl-, K+, and Ca2+.
- These elements combine to form molecules, which are the building blocks of life, varying in size from simple molecules like carbon dioxide and water to macromolecules like proteins and nucleic acids.
Water
- Water is the most abundant small molecule, making up 60-95% of the fresh weight of all cells/organisms.
- It is a vital constituent of living cells, forms part of the extra-cellular fluid of multicellular organisms, and serves as an environment for unicellular organisms.
- Water is the medium in which the majority of metabolic reactions take place, a reactant in some metabolic reactions, and a solvent for a wide variety of chemicals found in cells, including wastes.
- Its unique combination of properties makes it essential to the continuance of life.
Lipids
- Lipids are a group of compounds with no general formula, sharing the property of being insoluble in water due to the lack of polar groups.
- They contain carbon, hydrogen, and oxygen, but with a lower proportion of oxygen than in carbohydrates.
- Some lipids also contain phosphorus.
- Fats and oils are familiar lipids, formed from fatty acids and glycerol.
- Fats are solid at room temperature, found in animals, and contain mainly saturated fatty acids.
- Oils are liquid at room temperature, found in plants, and contain mainly unsaturated fatty acids.
Enzymes and Cofactors
- Some enzymes need an additional non-protein prosthetic group to function, called the cofactor.
- The polypeptide portion of the enzyme is called the apoenzyme, and the combination of the two is the active enzyme, called the holoenzyme.
- Cofactors may be metal ions, organic compounds, or organometallic compounds.
- Coenzymes are low-molecular-weight organic molecules that serve as carriers of electrons or chemical groups.
Inhibitors and Metabolism
- Inhibitors are chemicals that can bind to enzymes and either eliminate or drastically reduce their catalytic ability.
- Metabolism can be divided into catabolism and anabolism.
- Catabolic reactions break down complex materials, producing raw materials for building new cellular materials and providing energy for these processes.
- Anabolic reactions build complex molecules from simpler molecules, requiring energy.
The Pentose Phosphate Pathway
- The pentose phosphate pathway (PPP) is an alternative pathway for the oxidation of glucose, also known as the Warburg-Dickens pathway or the phosphogluconate pathway.
- Its primary role is anabolic, generating NADPH and pentoses (5-carbon sugars), as well as ribose 5-phosphate, a precursor for the synthesis of nucleotides.
- The PPP is most active in tissues involved in cholesterol and fatty acid syntheses, requiring abundant NADPH.
This quiz covers the introduction to biologically important molecules, exploring the atoms and ions that form the building blocks of life.
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