Questions and Answers
What type of transport does not require ATP?
Animal cells can swell and burst in hypotonic solutions.
True
Which of the following factors affect simple diffusion?
What is tonicity defined as?
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What is the function of enzymes?
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Enzymes are used up in reactions.
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What are the three types of RNA?
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The process of converting DNA to RNA is called ______.
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What are the phases of the cell cycle?
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What is the role of ribosomes?
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Which structure is primarily responsible for ATP production?
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The molecular structure that facilitates cellular transport is called ______.
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What is the function of checkpoints in the cell cycle?
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Study Notes
Cell Membrane Transport
- All cells require transport to intake and release substances for survival, growth, and reproduction.
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Passive Transport (requires no ATP):
- Simple diffusion: movement of molecules from high to low concentration.
- Osmosis: diffusion of water across a semi-permeable membrane.
- Facilitated diffusion: molecules move across membrane via transport proteins.
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Active Transport (requires ATP):
- Pumps: proteins that transport molecules against their concentration gradient.
- Exocytosis: process where substances are expelled from the cell.
- Endocytosis: process where substances are taken into the cell.
Factors Affecting Diffusion
- Concentration gradient: difference in concentration across a membrane.
- Temperature: higher temperatures increase the kinetic energy of molecules, enhancing diffusion.
- Type of diffusing molecule: size and polarity influence how easily a molecule can cross the membrane.
- Diffusion medium: the medium (gas, liquid) can affect the rate of diffusion.
Tonicity and Cell Behavior
- Tonicity refers to the ability of a solution to cause a cell to gain or lose water.
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Animal Cells:
- Hypotonic solution: cells swell and may burst due to increased water intake.
- Hypertonic solution: cells shrink and may die from water loss.
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Plant Cells:
- Hypotonic solution: cells become turgid due to water influx, but do not burst due to the cell wall.
- Hypertonic solution: cells undergo plasmolysis where the cell membrane pulls from the cell wall due to water loss.
Enzymes
- Enzymes function as biological catalysts, accelerating reactions without being consumed.
- They lower activation energy, allowing chemical reactions to proceed more favorably.
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Structure of Enzymes:
- Primary: amino acid sequence.
- Secondary: folding into alpha-helices or beta-sheets.
- Tertiary: complete three-dimensional shape necessary for function.
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Types of Enzymes:
- Intracellular: function within the cell (e.g., cytoplasm).
- Extracellular: function outside the cell.
Properties of Enzymes
- Enzymes act quickly and are proteins essential in small amounts.
- They exhibit specificity, targeting specific substrates.
- Enzymes are not damaged during the reaction, allowing reuse.
Enzyme Inhibition
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Reversible inhibitors bind temporarily and include:
- Competitive inhibitors: compete for the active site.
- Non-competitive inhibitors: bind to an allosteric site, changing enzyme shape.
- Lock and Key hypothesis: enzyme active site specifically fits substrate; Induced Fit hypothesis suggests enzyme and substrate adjust to fit.
Transcription and Translation
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Transcription: DNA → RNA conversion.
- Involves three stages: Initiation, Elongation, Termination.
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Translation: RNA → Protein process.
- Involves codons, tRNA, ribosomes, and stages: Initiation, Elongation, Termination.
Mitosis
- Humans possess 46 chromosomes (23 pairs).
- Mitosis is essential for growth, tissue repair, and asexual reproduction.
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Interphase Phases:
- G1: cell growth and function preparation.
- S: DNA replication.
- G2: final growth and error checking before mitosis.
- Four phases of Mitosis:
- Prophase: chromosomes condense and nuclear envelope breaks down.
- Metaphase: chromosomes align at the cell's equator.
- Anaphase: sister chromatids separate and move apart.
- Telophase: chromosomes reach poles and nuclear membranes reform, followed by cytokinesis.
Checkpoints in Cell Cycle
- Checkpoints ensure accurate completion of each phase before proceeding and play a role in cancer prevention.
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Phases of Checkpoints:
- G1: checks DNA integrity and cell conditions.
- G2: checks for DNA damage.
- M: ensures chromosomes are properly attached to spindle fibers.
Ribosomes and Protein Synthesis
- Eukaryotic ribosomes: 80s (40s small + 60s large); Prokaryotic: 70s (30s small + 50s large).
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Ribosome Types:
- Free (float): synthesize proteins for internal use.
- Bound: attached to the ER for export proteins.
Organelles and Their Functions
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Endoplasmic Reticulum (ER):
- Smooth ER: lipid synthesis and detoxification.
- Rough ER: protein synthesis and modification.
- Golgi Apparatus: processes and sorts proteins received from the ER for transport.
- Mitochondria: produce ATP through chemiosmosis and electron transport chain; contain their own DNA and ribosomes.
Membrane Structure and Communication
- Phospholipid bilayer: fundamental structure of cell membranes.
- Peripheral proteins: loosely bound to the membrane surface.
- Integral proteins: embedded within the bilayer.
- Facilitate signal transduction for communication and responsiveness to outside signals.
- Cell recognition markers include glycoproteins and glycolipids, allowing interaction and responses between cells.
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Description
Test your knowledge on the various processes involved in cell membrane transport. This quiz covers both passive and active transport mechanisms, along with factors affecting diffusion. Perfect for students studying biology or related fields.
