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Questions and Answers
Which of the following correctly describes the hierarchy of biological organization?
Which of the following correctly describes the hierarchy of biological organization?
What is the significance of biogenesis in cell theory?
What is the significance of biogenesis in cell theory?
Which of the following macromolecules is NOT considered a carbohydrate?
Which of the following macromolecules is NOT considered a carbohydrate?
What type of cells lack a nucleus?
What type of cells lack a nucleus?
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Which of the following best describes the process of dehydration synthesis?
Which of the following best describes the process of dehydration synthesis?
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Which of the following statements correctly identifies characteristics of organic compounds?
Which of the following statements correctly identifies characteristics of organic compounds?
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What is the role of functional groups in organic compounds?
What is the role of functional groups in organic compounds?
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What is the primary function of RNA in the cell?
What is the primary function of RNA in the cell?
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Which of the following best describes the composition of carbohydrates?
Which of the following best describes the composition of carbohydrates?
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Which component is part of the structure of a nucleotide?
Which component is part of the structure of a nucleotide?
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What type of bond links nucleotides together in nucleic acids?
What type of bond links nucleotides together in nucleic acids?
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What type of nucleic acid has deoxyribose as its sugar?
What type of nucleic acid has deoxyribose as its sugar?
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During ATP hydrolysis, what is released that powers cellular work?
During ATP hydrolysis, what is released that powers cellular work?
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Which base is exclusive to RNA?
Which base is exclusive to RNA?
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What is the primary site of cellular respiration in eukaryotic cells?
What is the primary site of cellular respiration in eukaryotic cells?
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What substance is detoxified in peroxisomes?
What substance is detoxified in peroxisomes?
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What occurs during telophase in the cell cycle?
What occurs during telophase in the cell cycle?
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What is the main purpose of the G1 checkpoint?
What is the main purpose of the G1 checkpoint?
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How does cytokinesis differ between animal and plant cells?
How does cytokinesis differ between animal and plant cells?
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What initiates the binary fission process in bacteria?
What initiates the binary fission process in bacteria?
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What happens if DNA damage is detected at the G1 checkpoint?
What happens if DNA damage is detected at the G1 checkpoint?
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What defines the M checkpoint in the cell cycle?
What defines the M checkpoint in the cell cycle?
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In which phase do animal cells undergo cleavage furrow formation?
In which phase do animal cells undergo cleavage furrow formation?
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Which of the following statements about cell division checkpoints is true?
Which of the following statements about cell division checkpoints is true?
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What is the main function of the plasma membrane?
What is the main function of the plasma membrane?
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Which of the following statements about prokaryotic cells is true?
Which of the following statements about prokaryotic cells is true?
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What is the purpose of transport proteins in the plasma membrane?
What is the purpose of transport proteins in the plasma membrane?
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What structural features help solve the upper limit of cell size?
What structural features help solve the upper limit of cell size?
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Which process describes the transport of secretory proteins within the endomembrane system?
Which process describes the transport of secretory proteins within the endomembrane system?
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What defines the lower limit of cell size?
What defines the lower limit of cell size?
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Which of the following describes fluorescence microscopy?
Which of the following describes fluorescence microscopy?
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What is a key characteristic of eukaryotic cells compared to prokaryotic cells?
What is a key characteristic of eukaryotic cells compared to prokaryotic cells?
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What is the primary function of meiosis in the context of gamete formation?
What is the primary function of meiosis in the context of gamete formation?
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During which stage of meiosis do homologous chromosomes undergo crossing over?
During which stage of meiosis do homologous chromosomes undergo crossing over?
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What happens to chromosome pairs during metaphase I of meiosis?
What happens to chromosome pairs during metaphase I of meiosis?
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What results from independent assortment during meiosis?
What results from independent assortment during meiosis?
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In human beings, how many chromosomes do gametes contain?
In human beings, how many chromosomes do gametes contain?
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What is the outcome of meiosis II?
What is the outcome of meiosis II?
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What role does crossing over play in meiosis?
What role does crossing over play in meiosis?
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Which of the following describes the chromosome configuration at the end of Prophase I?
Which of the following describes the chromosome configuration at the end of Prophase I?
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Study Notes
Biological Organization
- Cells are fundamental units of life, organized hierarchically.
- From atoms to molecules, macromolecules, organelles, cells, tissues, organs, organ systems, and ultimately, organisms.
- Human physiology focuses on organs and organ systems.
- Ecology and evolution concern populations, communities, and ecosystems.
Macromolecules
- All organisms share the same four major macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
Cell Theory
- All organisms are composed of cells, the smallest units of life.
- New cells arise only from pre-existing cells, the basis of biogenesis.
- Cell division serves reproduction, growth, and repair in multicellular organisms.
Cell Types
- Two fundamental cell types exist: prokaryotes and eukaryotes.
- Prokaryotes (bacteria and archaebacteria) are small (10-6m) and lack a nucleus.
- Eukaryotes (protists, fungi, plants, and animals) are larger (100µm) and possess a nucleus and organelles.
Carbon Compounds and Macromolecules
- Organic compounds are based on carbon atoms covalently bonded to hydrogen atoms, forming backbones.
- Common elements like oxygen, nitrogen, phosphorus, and sulfur are also linked to the carbon backbone.
- Functional groups attached to the carbon backbone confer diverse properties to organic compounds, essential for life.
- Macromolecules or polymers are large organic compounds assembled by living cells.
Carbohydrates
- Most abundant macromolecules, primarily composed of carbon, hydrogen, and oxygen (with nitrogen in chitin).
- Monosaccharides (simple sugars) have the general formula (CH2O)n, where n represents the number of carbon atoms.
- Examples of monosaccharides include glucose, fructose, galactose, and glucosamine.
- Disaccharides (two sugars) store energy, such as maltose, sucrose, and lactose.
- Dehydration synthesis joins monosaccharides to form disaccharides.
Microscopy
- Microscopes are crucial for visualizing cells.
- Light microscopes utilize visible light optics, allowing observation of live specimens with limited resolution and magnification.
- Electron microscopes employ electron optics, enabling observation of fixed specimens with higher resolution and magnification.
Cell Size Limitations
- Cell size is limited by the surface area to volume ratio.
- Large cells face challenges in efficient nutrient uptake and waste removal.
- Solutions include compartmentalization (organelles) and elongated shapes (microvilli).
- Larger organisms have more cells, not larger cells.
Minimal Cell Components
- All cells, prokaryotic or eukaryotic, share basic components.
- These include a cell membrane (plasma membrane), DNA, ribosomes, cytoplasm, and protein synthesis machinery.
Plasma Membrane
- A thin (9nm) phospholipid bilayer embedded with proteins.
- Acts as a semipermeable barrier, favoring the passage of hydrophobic molecules while restricting hydrophilic molecules.
- Transport proteins facilitate the passage of hydrophilic substances.
Prokaryotic Cells
- Prokaryotes lack membrane-bound cytoplasmic organelles like a nucleus, mitochondria, and Golgi apparatus.
- Smaller than eukaryotes, typically 10-100 times smaller.
- Key features include:
- Nucleoid (DNA-containing region, not membrane-bound)
- Single circular chromosome
- Cell wall (peptidoglycan: protein + carbohydrate)
- Capsule (sticky polysaccharide for attachment, found in pathogenic bacteria)
- Pili (extensions for attachment, found in pathogenic bacteria)
- Flagella (for locomotion)
Endomembrane System
- A network of interconnected membranes involved in protein transport and secretion.
- Ribosomes on the rough endoplasmic reticulum (RER) synthesize proteins.
- Secretory proteins move from RER to Golgi, then to secretory vesicles, and finally to the plasma membrane.
- Other functions include synthesis of cytoplasmic proteins, lipid synthesis, cleavage, and degradation (lysosomes).
Nucleic Acids
- Informational macromolecules composed of carbon, hydrogen, nitrogen, oxygen, and phosphorus.
- Monomers are nucleotides, linked by phosphodiester bonds.
- Two types:
- DNA (deoxyribonucleic acid): stores genetic information, composed of four deoxyribonucleotides.
- RNA (ribonucleic acid): involved in protein synthesis, composed of four ribonucleotides.
DNA vs. RNA Comparison
| Criteria | DNA | RNA |
|---|---|---|
| Overall structure | Double helix, antiparallel, complementary (G=C, A=T) | Single stranded |
| Monomers | Deoxyribonucleotides | Ribonucleotides |
| Pentose sugar | Deoxyribose | Ribose (extra OH) |
| Bases | G, A, T, C | G, A, U, C |
| Function | Store genetic information | Carry genetic info for protein synthesis |
| Location in cell | Euk. nucleus, cytoplasm | Euk. nucleus, cytoplasm |
| Chromatin | Form of DNA packaged/complexed with proteins |
Nucleotide Structure
- Composed of a phosphate group, a sugar, and a nitrogenous base.
- Phosphate groups are ionized (–O–).
- Sugar is either deoxyribose (DNA) or ribose (RNA).
- Nitrogenous bases are either:
- Purines (adenine (A), guanine (G))
- Pyrimidines (cytosine (C), thymine (T, in DNA) uracil (U, in RNA)
DNA Structure
- Two antiparallel and complementary strands linked by phosphodiester bonds.
- Base pairing follows purine-pyrimidine rules (A with T or U, G with C)
ATP
- Is a high energy molecule due to unstable phosphate bonds.
- Broken bonds release free energy useful for cellular work.
ATP Hydrolysis
- The breakdown of ATP into ADP and Pi is a spontaneous and exergonic reaction.
- Energy released powers:
- Chemical work (anabolic reactions)
- Mechanical work (cellular movement)
- Transport (molecular movement across membranes)
The ATP Cycle
- ATP is continuously cycled:
- Dehydration synthesis (endergonic) generates ATP.
- Hydrolysis (exergonic) releases energy from ATP.
- Energy from cellular respiration (glucose) drives the ATP cycle.
Cellular Respiration
- The process of breaking down glucose to generate energy (ATP).
- Occurs primarily within mitochondria.
Photosynthesis
- The process of converting light energy into chemical energy (glucose).
- Happens in chloroplasts, specifically within thylakoid membranes.
- Chlorophyll, a pigment within chloroplasts, plays a central role in photosynthesis.
Peroxisomes
- Organelles responsible for detoxification of reactive oxygen species (O2).
- Play a role in alcohol detoxification in liver cells.
- Involved in fatty acid catabolism.
Cell Shape and Structure
- Cell shape is determined by internal structures like cytoskeleton and external constraints.
- Cell walls provide structural support and protection.
Cell Walls
- Plant cell walls are composed of cellulose (β-glucose polymer).
- Fungal cell walls utilize chitin (N-acetylglucosamine polymer).
- Bacterial cell walls are made of peptidoglycan, a polymer of sugars and linked peptides.
Cell Division
- The process of creating new cells from existing ones.
- Two primary types: mitosis and meiosis.
Mitosis
- Cell division for growth and repair in multicellular organisms.
- Produces two identical daughter cells.
- Four phases:
- Prophase: chromosomes condense, nuclear envelope breaks down, spindle forms.
- Metaphase: chromosomes align at the equator, attached to spindle fibers.
- Anaphase: sister chromatids separate and move to opposite poles.
- Telophase: chromosomes decondense, nuclear envelope reforms, two nuclei appear.
- Cytokinesis (division of cytoplasm) follows mitosis.
Cytokinesis in Animals and Plants
- Animals: cleavage furrow forms, pinching the cell membrane.
- Plants: cell plate forms, derived from Golgi vesicles, eventually fusing with the plasma membrane, creating a new cell wall.
Bacterial Cell Division (Binary Fission)
- Single circular chromosome replicates at the origin of replication.
- Two origins separate as the bacterium elongates.
- Cell membrane grows inward, creating a new cell wall.
- DNA replication is not always synchronized with separation.
Checkpoints in Cell Cycle
- Monitor progression of the cell cycle, ensuring proper completion of preceding phases:
- G1 (restriction) checkpoint in late G1.
- G2 checkpoint.
- M checkpoint.
The G1 Checkpoint
- Ensures cell size and environmental conditions are favorable for entering the S phase.
- Controls processes like:
- Anchorage dependence (division requires attachment to a surface).
- Density dependent inhibition (division stops when a surface is fully covered).
- DNA damage (division halts until damage is repaired).
Diploid and Haploid Cells
- Somatic cells are diploid (2n), containing two copies of each chromosome.
- Gametes (sperm and egg) are haploid (n), containing one copy of each chromosome.
- Human diploid number is 2n=46.
- Human haploid number is n=23.
Meiosis
- Cell division that reduces the chromosome number by half, producing haploid gametes.
- Consists of two nuclear divisions (meiosis I and meiosis II) but only one DNA replication in the S phase.
Meiosis I
- Prophase I: chromosomes condense and pair up (synapsis), crossing over occurs.
- Metaphase I: tetrads (paired chromosomes) align at the equator, independent assortment occurs.
- Anaphase I: homologous chromosomes separate but not sister chromatids.
- Telophase I: chromosomes decondense, nuclear envelope reforms, resulting in haploid nuclei.
Meiosis II
- Prophase II: chromosomes recondense, no DNA replication.
- Metaphase II: chromosomes align at the equator.
- Anaphase II: sister chromatids separate, no longer identical due to crossing over.
- Telophase II: chromosomes decondense, cytokinesis occurs, forming 4 haploid gametes (sperm or egg).
Variation in Offspring
- Meiosis and random fertilization contribute to genetic variation:
- Crossing over creates unique combinations of genes.
- Independent assortment shuffles homologous chromosomes.
- Random combination of egg and sperm at fertilization produces genetically diverse offspring.
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Description
Explore the fundamental concepts of biological organization, including cell theory and the role of macromolecules in living organisms. From cells to organ systems and the differences between prokaryotes and eukaryotes, this quiz covers essential topics in biology. Test your knowledge of the building blocks of life and their significance in ecology and evolution.
