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Questions and Answers
What is the smallest chemical unit of a type of pure substance?
Which of the following is characterized as the fundamental unit of life?
What term describes characteristics that arise from the interaction of a system’s components?
Which process describes how energy enters ecosystems?
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Which of the following is NOT one of the properties of life?
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What role do decomposers play in an ecosystem?
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What is the definition of a nutrient?
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In which level of organization do populations belong?
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What is the primary structure of a protein?
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Which of the following components is not found in a nucleotide?
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What is a peptide bond formed from?
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Which base is found in RNA but not in DNA?
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Which of the following describes the tertiary structure of a protein?
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What is one reason cells are too small to be seen with the naked eye?
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What is the role of proteins in cells?
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What is the quaternary structure of a protein?
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What is the function of ribosomes in cells?
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Which feature distinguishes a nucleus from a nucleoid?
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What is the primary role of the plasma membrane?
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Which of the following is NOT a component of the nucleus?
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What is the function of mitochondria in eukaryotic cells?
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Which statement about prokaryotic cells is true?
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Which organelle is responsible for breaking down waste materials in eukaryotic cells?
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What is one of the primary functions of the cytoplasm?
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Which organelle is responsible for modifying, sorting, and packaging proteins and lipids?
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What characterizes rough endoplasmic reticulum?
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Which statement about mitochondria is true?
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Which of the following is NOT a component of the endomembrane system?
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What is the primary function of the smooth endoplasmic reticulum?
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How do mitochondria and chloroplasts support the endosymbiotic theory?
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What is the function of tight junctions in animal cells?
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In chloroplasts, what are thylakoids organized into stacks called?
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What characterizes a redox reaction?
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What process describes the movement of water across a selectively permeable membrane?
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Which of the following best describes a coenzyme?
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How does the sodium-potassium pump function in a cell?
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What is the role of the electron transfer chain in cellular processes?
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What happens to a cell placed in a hypertonic solution?
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Which of the following correctly defines facilitated diffusion?
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What distinguishes endocytosis from exocytosis?
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Study Notes
Levels of Life's Organization
- Atom: The simplest unit of a pure substance (element).
- Molecule: Two or more atoms joined together.
- Organelle: A membrane-bound structure within a cell with a specific function.
- Cell: The basic unit of life.
- Tissue: A group of similar cells working together to perform a specific function.
- Organ: Made up of different tissues that cooperate for a common purpose.
- Organ System: A group of organs that work together to carry out major bodily functions.
- Organism: An individual living being.
- Population: A group of the same species living in the same area at the same time.
- Community: All the populations of different species living in a particular area.
- Ecosystem: Includes all living organisms (biotic) and their nonliving environment (abiotic) in a specific area.
- Biosphere: The global ecosystem encompassing all life and its environments.
Emergent Properties
- Emergent properties arise from the interactions of a system's components.
- The whole is greater than the sum of its parts.
- Example: Individual brain cells cannot think, but their interconnected network gives rise to consciousness.
Properties of Life
- Organization: Living things exhibit complex organization.
- Energy Requirements: Organisms need energy to maintain life processes.
- Homeostasis: Living things maintain stable internal conditions.
- Reproduction, Growth, and Development: Life replicates, increases in size, and undergoes changes over time.
- Evolution: Organisms change over generations.
Energy Flow and Material Cycling
- Energy Flow: Sunlight is captured by producers (plants) through photosynthesis, converting light energy into chemical energy. Consumers obtain this energy by feeding on other organisms. Energy is lost as heat during each energy transfer.
- Material Cycling: Nutrients are recycled within ecosystems. Decomposers break down dead organisms, returning nutrients to the soil, which are then absorbed by producers.
Key Terms
- Energy: The ability to do work or cause change.
- Nutrient: A substance essential for organism growth, reproduction, and survival.
- Producers: Organisms that make their own food using energy from nonliving sources (e.g., plants).
- Consumers: Organisms that obtain energy and nutrients by eating other organisms.
- Receptors: Structures that detect stimuli and aid in maintaining homeostasis.
Proteins
- Proteins are polymers made up of amino acids.
- They have numerous functions, including structural support, enzyme activity, and transport.
Amino Acid Structure
- The basic structure of an amino acid consists of a central carbon atom bonded to:
- An amino group (NH2)
- A carboxyl group (COOH)
- A hydrogen atom (H)
- A variable side chain (R group) that distinguishes different amino acids.
Protein Structure
- Primary Structure: The linear sequence of amino acids in a polypeptide chain.
- Secondary Structure: Local folding of the polypeptide chain into structures like alpha helices or beta sheets, stabilized by hydrogen bonds.
- Tertiary Structure: The overall three-dimensional shape of a single polypeptide chain.
- Quaternary Structure: The arrangement of multiple polypeptide chains into a functional protein.
Peptide Bond Formation
- A peptide bond is formed through a dehydration synthesis reaction between the amino group of one amino acid and the carboxyl group of another, releasing a water molecule.
Nucleotides
- Nucleotides are the building blocks of nucleic acids.
- Made up of three components:
- A phosphate group
- A 5-carbon sugar (deoxyribose or ribose)
- A nitrogenous base (adenine, guanine, cytosine, thymine, or uracil).
Nucleic Acids
- Two primary types of nucleic acids:
- DNA (Deoxyribonucleic acid): Stores genetic information.
- RNA (Ribonucleic acid): Plays a role in protein synthesis.
Nitrogenous Bases
- Four bases found in nucleotides:
- Adenine (A)
- Guanine (G)
- Cytosine (C)
- Thymine (T) in DNA or Uracil (U) in RNA.
Cell Theory
- All living organisms are composed of one or more cells.
- The cell is the fundamental unit of life.
- All cells come from preexisting cells.
- Additional key principles:
- All cells share a basic chemical composition.
- All cells use energy.
- All cells contain DNA that is duplicated and passed on during cell division.
Cell Size
- Cells are generally microscopic because a high surface area-to-volume ratio is essential for efficient exchange of materials with their environment.
Features Common to All Cells
- Genetic Material (DNA): Carries hereditary information.
- Ribosomes: Sites of protein synthesis.
- Cytoplasm: The fluid inside the cell where organelles are located.
- Cell Membrane: A boundary that separates the cell's interior from its external environment and controls what enters and exits.
Functions of the Plasma Membrane
- Forms a boundary between the cell and its environment.
- Regulates the passage of substances into and out of the cell, helping maintain homeostasis.
Nucleus vs. Nucleoid
- Nucleus: A membrane-bound organelle in eukaryotic cells containing DNA.
- Nucleoid: A region within prokaryotic cells where DNA is located, but it is not enclosed by a membrane.
Prokaryotic Cell Structure
- Nucleoid: Contains DNA.
- Cell Membrane: Encloses the cell.
- Cytoplasm: Contains ribosomes.
- Cell Wall: (Optional) Provides protection.
- Flagella: (Optional) Aid in movement.
- Pili: (Optional) Help with attachment.
Eukaryotic Organelles
- Nucleus: Contains genetic material and controls cell activities.
- Mitochondria: Produce energy through cellular respiration.
- Endoplasmic Reticulum (ER): Synthesizes proteins and lipids.
- Golgi Apparatus: Processes, sorts, and packages proteins and lipids.
- Lysosomes: Break down waste materials.
- Chloroplasts: (In plant cells) Carry out photosynthesis.
- Vacuoles: Store substances and assist with waste disposal.
- Cytoskeleton: Provides structure and aids in cell movement.
Nucleus Components and Functions
-
Components:
- Nuclear Envelope: Double membrane surrounding the nucleus.
- Nucleolus: Produces ribosomes.
- Chromatin: DNA-protein complex.
-
Functions:
- Houses the cell's genetic material (DNA).
- Controls cellular activities by regulating gene expression.
Endomembrane System
- A network of internal membranes that work together to modify, package, and transport proteins and lipids.
- Major components:
- Nuclear Envelope
- Endoplasmic Reticulum (ER)
- Golgi Apparatus
- Lysosomes
- Vesicles
- Plasma membrane
Endoplasmic Reticulum (ER)
- A network of membranes involved in protein and lipid synthesis.
- Rough ER: Studded with ribosomes, involved in protein synthesis.
- Smooth ER: Lacks ribosomes, synthesizes lipids, and detoxifies harmful substances.
Golgi Apparatus and Vesicles
- Golgi Apparatus: Stack of membrane sacs that modify, sort, and package proteins and lipids for transport.
- Vesicles: Small membrane-bound sacs that transport materials within the cell and to the plasma membrane for secretion.
Mitochondria Structure and Function
- Have a double membrane with the inner membrane folded into structures called cristae.
- The space inside is called the matrix.
- Mitochondria produce energy for the cell through cellular respiration, converting sugar into ATP.
Endosymbiotic Theory
- Proposes that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by ancestral eukaryotic cells.
- Evidence includes:
- Both organelles have their own DNA.
- They reproduce independently of the cell.
- They have double membranes, suggesting an engulfing event.
Chloroplast Structure and Function
- Have an inner and outer membrane with internal structures called thylakoids arranged in stacks called grana.
- The space around the grana is called the stroma.
- Chloroplasts convert light energy into chemical energy (sugar) through photosynthesis.
Cell Junctions
-
Animal cells:
- Tight Junctions: Prevent leakage between cells.
- Adhering (Anchoring) Junctions: Provide strong mechanical attachments.
- Gap Junctions: Allow the passage of materials between cells.
-
Plant Cells:
- Plasmodesmata: Channels that connect the cytoplasm of adjacent cells.
Redox Reactions
- Redox reactions involve the transfer of electrons from one molecule (oxidation) to another (reduction).
- Oxidation: Loss of electrons.
- Reduction: Gain of electrons.
- Redox reactions are often coupled.
Electron Transfer Chain
- A series of proteins embedded in a membrane that transfer electrons through redox reactions, releasing energy in small steps.
- This energy is used to form ATP.
Cofactors and Coenzymes
- Cofactors: Non-protein molecules (e.g., metal ions) that assist enzyme function.
- Coenzymes: Organic cofactors (e.g., vitamins) that aid enzyme function.
Types of Diffusion and Passive Transport
- Diffusion: Movement of molecules from an area of higher concentration to lower concentration.
- Simple Diffusion: Movement of small, nonpolar molecules through the membrane.
- Facilitated Diffusion: Movement of larger or polar molecules through a transport protein.
- Passive Transport: The movement of substances across a membrane without using energy, following the concentration gradient.
Osmosis
- The diffusion of water across a selectively permeable membrane.
- Hypotonic Solution: Water enters the cell, causing it to swell (may burst).
- Hypertonic Solution: Water exits the cell, causing it to shrink.
- Isotonic Solution: Water moves in and out at equal rates, maintaining cell stability.
Active Transport
- Requires energy (ATP) to move substances against their concentration gradient.
- Calcium Pump: Moves calcium ions across the membrane using ATP.
- Sodium-Potassium Pump: Exchanges sodium (Na⁺) and potassium (K⁺) ions across the cell membrane, essential for nerve and muscle function.
Endocytosis and Exocytosis
- Endocytosis: The process by which cells engulf materials from their environment by forming vesicles.
- Exocytosis: The process where cells expel materials by merging vesicles with the plasma membrane.
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Description
Explore the different levels of life's organization, from atoms to the biosphere. This quiz tests your knowledge on emergent properties and how various biological structures and systems interact within ecosystems. Perfect for biology enthusiasts and students.
