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Questions and Answers
Which cell type is characterized by a membrane-bound nucleus?
What is the primary role of DNA in a cell?
What is the primary component of the cell membrane?
Which type of evolution describes changes that occur over many generations?
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What structural role do polysaccharides have in plants?
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What type of bond links monosaccharides together to form disaccharides?
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Which process involves converting the information from a gene into a cellular product?
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Which macromolecule is primarily involved in speeding up chemical reactions in the body?
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What is the simplest form of carbohydrates?
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Which of the following are considered lipids?
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Which of the following structures is the primary determinant of a protein's function?
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What best describes the term 'emergent properties' in biological systems?
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Which of the following is NOT considered a domain in biological classification?
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What is the primary role of DNA in cells?
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Which sugar is present in ribonucleic acid (RNA)?
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Which base pairs with adenine in DNA?
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What does denaturation refer to in proteins?
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What is the main function of mitochondria in cells?
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What is the structure of a nucleotide?
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Which statement accurately describes the endosymbiotic theory?
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What type of reaction is hydrolysis?
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What distinguishes purines from pyrimidines?
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What is the primary energy carrier produced during cellular respiration?
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Which components are found in the double membranes of mitochondria and chloroplasts?
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Which base is unique to RNA as opposed to DNA?
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What major synthesis process does dehydration synthesis involve?
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What defines the antiparallel nature of DNA strands?
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What is the primary role of the cytoskeleton in a cell?
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Which type of cytoskeletal fiber is the thickest?
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How do motor proteins interact with the cytoskeleton?
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What are desmosomes primarily responsible for?
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Which component is essential for the formation of the extracellular matrix in animal cells?
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What do microfilaments primarily help with in a cell?
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What is the function of tight junctions in animal cells?
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What role do aquaporins play in cell membranes?
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How does passive transport differ from active transport?
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Which type of cytoskeletal fiber interacts with myosin for muscle contraction?
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What distinguishes the cell walls of plant cells from the extracellular matrix of animal cells?
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During which process do microtubules play a critical role in animal cells?
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Why can hydrophobic molecules easily cross the plasma membrane?
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What is a defining characteristic of intermediate filaments?
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Study Notes
Emergent Properties
- The arrangement and interaction of parts within a system result in emergent properties.
- Emergent properties are a characteristic found in a system that is not present in any of the system’s individual components.
Biological Organization
- Life can be studied at different levels of organization, starting with the smallest unit of life - the cell, and progressively increasing in complexity.
- The organization of living things is hierarchical, with each level building upon the previous one.
- Here is an example of the hierarchy of biological organization:
- Molecules
- Organelles
- Cells
- Tissues
- Organs
- Organisms
- Populations
- Communities
- Ecosystems
- Biosphere
The Cell
- Cells are the smallest unit of life.
- Cells share certain basic characteristics.
- Cells can be classified as prokaryotic or eukaryotic.
- Eukaryotic cells have membrane-bound organelles, including a nucleus that contains DNA.
- Prokaryotic cells lack a nucleus and other membrane-bound organelles.
- Prokaryotic cells are generally smaller than eukaryotic cells.
Genetic Material
- Chromosomes contain a cell's genetic material in the form of DNA (deoxyribonucleic acid).
- DNA holds genes, which are units of inheritance that transmit information from parents to offspring.
- DNA is made of two long chains arranged in a double helix.
- Each link in a chain is made of one of four nucleotides: adenine (A), cytosine (C), thymine (T), and guanine (G).
- DNA provides blueprints for making proteins.
- Proteins are major players in building and maintaining cells.
Gene Expression
- Gene expression is the process of converting information from a gene to its cellular product.
- This process involves the use of RNA (ribonucleic acid).
Energy Transfer
- Life requires the transfer of energy.
- The input of energy is mainly from the sun.
- Plants and other producers convert energy from the sun into chemical energy.
- This chemical energy is then passed to consumers.
- Energy flows through ecosystems.
- Generally, energy is transferred from sunlight to heat.
- Energy is not recycled.
Organism Interactions
- Every organism interacts with other organisms and with physical factors in its environment.
Evolution
- Evolution is the process of biological change in which differences between organisms accumulate gradually from their ancestors.
- Evolution is the primary cause of the diversity of life on Earth.
Classifying Diversity
- Organisms are grouped by similarities, both physical and molecular.
- The three main domains of life are Bacteria, Archaea, and Eukarya.
- Bacteria are the most diverse and are classified into various kingdoms.
- Archaea are prokaryotes that live in extreme environments.
- Eukarya includes the kingdoms Plantae, Fungi, Animalia, and protists.
Darwin
- Darwin proposed the theory of natural selection.
- Darwin’s theory of evolution includes the concept of “descent with modification.”
- Natural selection is the primary cause of descent with modification.
- Darwin observed that individuals vary in traits that are heritable, that more offspring are produced than can survive, and that species generally suit their environment.
- Darwin reasoned that individuals best suited for their environment are likely to survive and reproduce, and that over time, more individuals will have the advantageous trait.
The Tree of Life
- Natural selection can cause ancestral species to give rise to two or more descendant species.
- This process can be visualized as a tree of life, with the branches representing the diversification of organisms over time.
Macromolecules
Carbohydrates
- Carbohydrates include sugars and polymers of sugars.
- The simplest carbohydrates are monosaccharides (simple sugars).
- Carbohydrate macromolecules are polysaccharides.
- Polysaccharides are polymers composed of many sugar building blocks.
Monosaccharides
- Monosaccharides have molecular formulas that are usually multiples of CH2O.
- The most common monosaccharide is glucose (C6H12O6).
- Monosaccharides are classified by the number of carbons in the carbon skeleton and the placement of the carbonyl group.
Disaccharide Synthesis
- Disaccharides are formed by the joining of two monosaccharides via a glycosidic bond.
Polysaccharides
- Polysaccharides are polymers of sugars that have storage and structural roles.
- Storage polysaccharides include starch (in plants) and glycogen (in animals).
- Structural polysaccharides include cellulose (in plants) and chitin (in arthropods and fungi).
Lipids
- Lipids are diverse group of hydrophobic molecules.
- Lipids do not form true polymers.
- Lipids have little to no affinity for water and are hydrophobic due to nonpolar covalent bonds.
- The most important types of lipids include fats, phospholipids, and steroids.
Fats
- Fats are constructed of glycerol and fatty acids.
- Glycerol is a three-carbon alcohol with a hydroxyl group attached to each carbon.
- Fatty acids consist of a carboxyl group attached to a long carbon skeleton.
- Fats store energy.
- Fats are compact.
Phospholipids
- Phospholipids have a hydrophilic head and hydrophobic tails.
- Phospholipids create a bilayer, which is a key component of cell membranes.
Steroids
- Steroids are lipids characterized by a carbon skeleton consisting of four fused rings.
- Cholesterol is an important steroid; it is a component of animal cell membranes.
- High levels of cholesterol can be dangerous.
Proteins
- Proteins make up the majority of the dry mass of cells.
- Proteins act as catalysts (enzymes).
- A catalyst speeds up chemical reactions without being consumed.
Amino Acids
- Amino acids are the basic building blocks of proteins.
- Amino acids are organic molecules with both an amino group and a carboxyl group.
- Amino acids differ in properties due to differing R groups.
Polypeptides
- Polypeptides are unbranched polymers built from the same set of 20 amino acids.
Protein Structure
- A protein’s biologically functional model consists of one or more polypeptides.
- A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape.
- A protein’s structure determines its function.
- The amino acid sequence is the most important aspect of protein function.
Levels of Protein Structure
- Proteins have four levels of structure:
- Primary
- Secondary
- Tertiary
- Quaternary (more than one polypeptide chain)
Factors Affecting Protein Structure
- Physical and chemical conditions can affect protein structure.
- These conditions include pH, salinity, and temperature.
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