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Questions and Answers
What is the primary function of lysosomes in a cell?
Which type of vacuole is responsible for getting rid of excess water in protists?
What is the main function of peroxisomes within a cell?
How are peroxisomes formed?
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What is a major role of the plasma membrane?
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What distinguishes semiautonomous organelles like mitochondria and chloroplasts?
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Which organelle is primarily responsible for ATP synthesis?
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What is the primary byproduct produced during the breakdown of harmful molecules in peroxisomes?
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What structure in plant cells is responsible for photosynthesis?
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Which part of the chloroplast contains stacks of thylakoids?
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What is the initial process for co-translational sorting?
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What role does signal peptidase play in protein sorting?
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What must happen for a vesicle to successfully transport materials to the Golgi?
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Which of the following proteins remain in the cytosol due to lack of a sorting signal?
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What is the main function of chaperone proteins during post-translational sorting?
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What is the fluid found inside the inner membrane of a chloroplast called?
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What defines organic molecules?
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What is an example of a functional group?
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Which process describes the formation of polymers from monomers?
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What type of macromolecule are carbohydrates classified as?
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What distinguishes structural isomers from stereoisomers?
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Which carbohydrate is classified as a hexose?
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What type of bond connects two monosaccharides in a disaccharide?
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Which of the following correctly represents the general formula for carbohydrates?
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What role do enzymes play in chemical reactions?
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Which statement correctly describes ATP synthesis?
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What is the term for the site where substrates bind on an enzyme?
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What is the primary requirement for a reaction to proceed concerning activation energy?
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Which of the following statements is true about ribozymes?
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What are the primary roles of motor proteins in cellular movement?
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Which of the following describes the endomembrane system?
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What is the function of the nuclear envelope?
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What comprises the structure and function of the endoplasmic reticulum (ER)?
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Which region of the Golgi apparatus faces the endoplasmic reticulum?
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Which of the following correctly describes lysosomes and their function?
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What role does the nucleolus play within the nucleus?
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What distinguishes rough endoplasmic reticulum from smooth endoplasmic reticulum?
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Study Notes
Organic Molecules and Macromolecules
- Organic molecules contain carbon and are abundant in living organisms.
- Macromolecules are large, complex organic molecules.
- Carbon has four valence electrons and can form four bonds (single, double, or triple).
- Molecules with polar bonds are water-soluble (hydrophilic), while nonpolar molecules are not (hydrophobic).
- Functional groups are groups of atoms with special chemical features important for their function.
- Isomers are molecules with the same chemical formula but different structures and characteristics.
- Structural isomers have the same atoms but different bonding relationships.
- Stereoisomers have atoms in the same bonding relationships but different spatial positioning.
- Cis-trans isomers involve positioning around a double or triple bond.
- Enantiomers are mirror-image molecules.
- Organic molecules and macromolecules form through dehydration or condensation reactions, where a water molecule is removed.
- Organic molecules and macromolecules are broken down through hydrolysis, where a water molecule is added.
- These reactions are catalyzed by enzymes.
Types of Macromolecules
- There are four types of macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
Carbohydrates
- Contain carbon, hydrogen, and oxygen with the formula Cn(H2O)n.
- Are classified as monosaccharides, disaccharides, and polysaccharides.
- Monosaccharides are the simplest form of sugar, usually containing five or six carbons.
- Pentoses (5 carbons) include ribose and deoxyribose.
- Hexoses (6 carbons) include glucose.
- Disaccharides are composed of two monosaccharides joined together by a glycosidic bond.
- Polysaccharides are complex carbohydrates made of many monosaccharides linked together.
Lipids
- Are a diverse group of molecules that are hydrophobic.
- Include fats, oils, waxes, phospholipids, and steroids.
- Fats and oils are composed of glycerol and fatty acids.
- Phospholipids have a hydrophilic head and a hydrophobic tail, making them important components of cell membranes.
- Steroids are characterized by their four-ring structure and include cholesterol, which is a precursor to other steroids.
Proteins
- Are polymers of amino acids.
- Have diverse functions, including structural support, catalysis, transport, defense, and regulation.
- The amino acid sequence determines the protein's three-dimensional structure and function.
- Protein structure can be described at four levels: primary, secondary, tertiary, and quaternary.
Nucleic Acids
- Are polymers of nucleotides.
- Two types: DNA and RNA.
- DNA stores genetic information and is responsible for heredity.
- RNA is involved in protein synthesis and other cellular processes.
Motor Proteins
- They carry cargo along filaments.
- They remain in place while the filament moves.
- They and the filament are both restrained; the motor protein exerts a force that causes the filament to bend.
- Steps in their movement include the head detaching from the filament, cocking forward, reattaching to the filament, and cocking backwards.
Endomembrane System
- Network of membranes enclosing the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.
- Components may be directly connected or pass materials via vesicles.
Nucleus
- Double membrane structure enclosing the nucleus.
- Outer membrane continuous with the ER membrane.
- Nuclear pores provide passageways.
- Contains chromatin (DNA and proteins).
- Consists of a filamentous network (nuclear matrix) that organizes chromosomes.
- Contains the nucleolus where ribosome assembly occurs.
Endoplasmic Reticulum (ER)
- Network of membranes forming flattened, fluid-filled tubules or cisternae.
- ER membrane encloses a single compartment called the ER lumen.
- Two types: smooth ER and rough ER.
- The rough ER is studded with ribosomes and is involved with protein synthesis and sorting.
- The smooth ER lacks ribosomes and is involved with detoxification, lipid synthesis, carbohydrate metabolism, calcium balance, and modification of lipids.
Golgi Apparatus
- Stacks of membrane-bound compartments (cisternae).
- Divided into three regions: cis, medial, and trans.
- Involved with protein and lipid sorting, processing, and secretion.
Lysosomes
- Membrane-bound organelles containing acid hydrolases for breaking down macromolecules.
- Involved in autophagy and degradation of materials taken in by endocytosis.
Vacuoles
- Membrane-bound organelles with diverse functions depending on cell type and conditions.
- Central vacuoles in plants regulate volume, store materials, and have digestive functions.
- Contractile vacuoles in protists remove excess water.
- Phagocytic vacuoles in protists and white blood cells degrade foreign bodies.
Peroxisomes
- Membrane-bound organelles involved in breaking down harmful molecules.
- Catalyze reactions that remove hydrogen or add oxygen to molecules, producing hydrogen peroxide as a byproduct.
- Catalase breaks down hydrogen peroxide into water and oxygen.
- Form from vesicles budding off the Golgi and fusing.
Plasma Membrane
- The boundary between the intracellular and extracellular environments.
- Controls what enters and exits the cell (selective permeability).
- Involved in cell signaling and adhesion.
Semiautonomous Organelles
- Mitochondria and chloroplasts.
- Grow and divide to reproduce themselves.
- Rely on the cell for synthesis of internal components and membrane maintenance, making them not completely autonomous.
Mitochondria
- Membrane-bound organelles responsible for ATP synthesis.
- Divided into regions: outer membrane, inner membrane, intermembrane space, and mitochondrial matrix.
- Involved in the modification, synthesis, and breakdown of several cellular molecules.
- Have their own DNA and divide by binary fission.
- The mitochondrial chromosome is located in the nucleoid region.
Chloroplasts
- Membrane-bound organelles found in plant cells responsible for photosynthesis.
- Capture light energy and synthesize organic molecules like glucose.
- Found in nearly all plant and algae species.
- Structure: outer membrane, inner membrane, intermembrane space, and thylakoid membrane.
- Stacks of thylakoids are called grana.
- Stroma is the fluid inside the inner membrane.
Protein Sorting in Eukaryotes
- Two types: co-translational and post-translational sorting.
- Co-translational sorting begins in the cytosol and involves ER, Golgi, lysosomes, vacuoles, plasma membrane, and secretion.
- Post-translational sorting happens after translation and is for the nucleus, peroxisome, and semiautonomous organelles.
Co-translational Sorting
- The ribosome encounters an ER sorting signal, pauses translation, and travels to the rough ER.
- The signal is recognized, and the polypeptide is synthesized into the ER lumen.
- The protein may remain in the ER due to an ER retention signal or travel to the Golgi through vesicles.
- Further modifications may occur in the ER and Golgi.
- The protein may remain in the Golgi or be sorted to its final destination.
- Proteins may be secreted outside the cell.
Post-Translational Sorting
- Proteins (cytosolic proteins) that lack a signal remain in the cytosol.
- Proteins destined for other locations have sorting signals recognized by protein receptors.
Vesicle Formation and Transport
- Vesicles bud off the ER membrane with the help of coat proteins and V-snares.
- After release, the coat proteins are shed, and the V-snares connect to the T-snares of the target organelle, allowing the vesicle to fuse and deliver its contents.
Catalysts and Enzymes
- Catalysts speed up the rate of a chemical reaction without being consumed.
- Enzymes are protein catalysts, and ribozymes are RNA molecules with catalytic properties.
- Activation energy is the initial input of energy required to start a reaction.
How Enzymes Lower Activation Energy
- By straining bonds in reactants to facilitate the transition state.
- By positioning reactants together to facilitate bonding.
- By changing the local environment.
Enzyme Terms
- Active site: where the reaction takes place.
- Substrates: reactants that bind to the active site.
- Enzyme-substrate complex: formed when the enzyme and substrate bind.
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Description
Test your knowledge on organic molecules and macromolecules with this quiz. Learn about carbon's role, functional groups, isomers, and the formation of these complex structures. This quiz covers essential concepts crucial for understanding biology and chemistry.
