Chp.8 Cells 2B Flashcards

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Leeuwenhoek

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Anton van Leeuwenhoek invented the single-lens microscope and was among the first to observe microscopic life. His improvements in lens-making allowed detailed observations of cells and microorganisms.

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Hooke

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Robert Hooke examined a slice of cork with a microscope and coined the term “cell” after noticing box-like structures. His observations described dead plant cell walls and helped spark interest in cell studies.

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Schleiden

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Matthias Schleiden concluded that all plants are made of cells after microscopic studies of plant tissues. His work contributed to the formulation of the cell theory.

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Schwann

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Theodor Schwann concluded that all animals are made of cells, extending Schleiden’s plant findings to animals. This helped establish the universality of cellular organization in living things.

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Virchow

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Rudolf Virchow proposed that all cells arise from preexisting cells, emphasizing cell division as the source of new cells. This idea completed a key element of modern cell theory.

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Cell Theory

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The cell theory states three main ideas: all living things are made of one or more cells, cells are the basic units of structure and function, and new cells come from existing cells. These principles form the foundation for modern biology.

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Prokaryote

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A prokaryote is a small, simple cell type that lacks a nucleus and membrane-bound organelles. Prokaryotes include all bacteria and have cytoplasm, a cell membrane, and ribosomes.

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Eukaryote

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A eukaryote is a larger, more complex cell type that contains a nucleus and membrane-bound organelles. Eukaryotes include plants, animals, fungi, and protists and house DNA inside the nucleus.

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Organelle

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An organelle is a specialized structure within a eukaryotic cell that performs a specific function, like an organ inside the cell. Organelles include the nucleus, mitochondria, ER, Golgi apparatus, and others.

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Cytoplasm

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The cytoplasm is the semifluid region inside the cell membrane where chemical activities and many metabolic processes occur. It contains organelles in eukaryotes and provides a medium for molecular movement.

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Cell Membrane

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The cell membrane is a selectively permeable phospholipid bilayer that regulates what enters and leaves the cell and provides protection and support. It contains proteins, cholesterol, and carbohydrates that contribute to transport, signaling, and recognition.

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Cell Wall

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A cell wall is a rigid outer layer found outside the cell membrane in many prokaryotes and some eukaryotes such as plants and protists. It provides structural support and protection and helps maintain cell shape.

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Nucleus

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The nucleus is a membrane-bound organelle that stores the cell’s DNA and controls cellular activities. It contains chromatin, chromosomes, the nucleolus, a nuclear envelope, and nuclear pores for transport and communication.

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Chromatin

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Chromatin is the complex of DNA and proteins found in the nucleus during interphase. It is the less condensed form of genetic material that allows access for transcription and replication.

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Chromosome

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A chromosome is tightly coiled chromatin visible during cell division that packages DNA for equal distribution to daughter cells. Chromosomes ensure accurate genetic inheritance during mitosis and meiosis.

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Nucleolus

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The nucleolus is a dense region within the nucleus where ribosomal RNA is synthesized and ribosome subunits are assembled. It is not membrane-bound but is essential for protein production machinery.

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Nuclear Envelope

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The nuclear envelope is a double membrane that surrounds the nucleus, protecting the DNA and defining the nuclear compartment. Nuclear pores in the envelope allow regulated movement of molecules between the nucleus and cytoplasm.

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Ribosomes

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Ribosomes are the cell structures that synthesize proteins by translating mRNA. They may be free in the cytoplasm or attached to the rough ER and are found in both prokaryotic and eukaryotic cells.

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Smooth ER

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The smooth endoplasmic reticulum (SER) synthesizes lipids and detoxifies harmful substances, with prominent roles in cells like liver cells. It lacks ribosomes and is involved in lipid metabolism and calcium storage.

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Rough ER

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The rough endoplasmic reticulum (RER) is studded with ribosomes and synthesizes proteins that will be secreted, incorporated into the plasma membrane, or sent to lysosomes. It works closely with the Golgi apparatus for protein processing.

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Golgi Apparatus

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The Golgi apparatus modifies, sorts, and packages proteins and lipids received from the rough ER, often attaching carbohydrates or lipids to proteins. It then directs these molecules to their final destinations inside or outside the cell.

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Lysosome

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Lysosomes are membrane-bound organelles containing enzymes that break down lipids, carbohydrates, and proteins for recycling or disposal. They act as the cell’s cleanup crew and are especially common in animal cells.

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Vacuole

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A vacuole is a membrane-bound sac that stores water, salts, proteins, and carbohydrates and helps transport substances. Plant cells typically have a large central vacuole that aids in storage and turgor pressure.

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Mitochondria

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Mitochondria are the organelles where cellular respiration occurs and ATP is produced, earning them the nickname “powerhouse of the cell.” They have their own DNA and a double membrane structure specialized for energy conversion.

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Chloroplast

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Chloroplasts are organelles in plants and some protists that perform photosynthesis, converting sunlight into chemical energy and food. They contain chlorophyll and have a double membrane plus internal thylakoid structures.

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Cytoskeleton

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The cytoskeleton is a network of protein fibers that maintains cell shape, provides mechanical support, and enables movement. It includes microtubules, microfilaments, and intermediate filaments that organize organelles and mediate transport.

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Microtubules

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Microtubules are hollow protein tubes that determine cell shape, provide tracks for organelle movement, and form structures like cilia, flagella, and centrioles. They are essential for chromosome movement during cell division.

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Microfilaments

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Microfilaments are thin actin protein fibers that function in cell movement, muscle contraction, and structural support. They are important for changing cell shape and enabling cell motility.

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Fluid Mosaic

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The fluid mosaic model describes the cell membrane as a dynamic, fluid phospholipid bilayer with embedded proteins, cholesterol, and carbohydrates. This model explains membrane flexibility, lateral movement of components, and diverse functions such as transport and signaling.

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Phospholipid Bilayer

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The phospholipid bilayer consists of polar phosphate heads that interact with water and nonpolar fatty acid tails that repel water. The arrangement creates a selective barrier that restricts passage of polar molecules while allowing lipid-soluble substances to pass.

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Membrane Proteins

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Membrane proteins serve multiple roles including channels for transport, receptors for signal transduction, cell surface markers for recognition, and structural anchors for the cytoskeleton. Their polar and nonpolar regions allow them to associate with both the lipid core and the aqueous environments.

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Cholesterol

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Cholesterol molecules in the membrane help maintain appropriate fluidity, especially at lower temperatures, by preventing tight packing of phospholipids. This stabilizes membrane dynamics across temperature changes.

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Carbohydrates

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Carbohydrates on the cell surface are often attached to proteins or lipids as markers that aid cell-to-cell recognition and communication. These ‘name tags’ are important for immune recognition and tissue organization.

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Diffusion

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Diffusion is the passive movement of molecules from regions of higher concentration to regions of lower concentration, driven by random molecular motion. It requires no cellular energy and leads to equilibrium over time.

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Osmosis

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Osmosis is the diffusion of water across a selectively permeable membrane from regions of lower solute concentration to regions of higher solute concentration. It influences cell volume and can cause cells to swell or shrink depending on external conditions.

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Facilitated Diffusion

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Facilitated diffusion is passive transport that uses specific transmembrane proteins to carry large or charged molecules across the membrane down their concentration gradient. It allows substances that cannot cross the lipid bilayer directly to move without energy input.

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Isotonic

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An isotonic solution has equal concentrations of dissolved particles inside and outside the cell, resulting in no net water movement across the membrane. Cells maintain their size and volume in isotonic conditions.

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Hypotonic

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A hypotonic solution has a lower concentration of dissolved particles outside the cell than inside, causing water to move into the cell by osmosis. This influx can make animal cells swell and burst, while plant cells develop turgor pressure and become rigid.

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Hypertonic

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A hypertonic solution has a higher concentration of dissolved particles outside the cell than inside, causing water to move out of the cell by osmosis. Cells placed in hypertonic solutions typically shrink or crenate due to water loss.

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Turgor Pressure

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Turgor pressure is the hydrostatic pressure exerted by the central vacuole against the plant cell wall when the vacuole is full of water. It helps maintain plant rigidity and structural support.

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Active Transport

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Active transport moves materials from lower to higher concentration using cellular energy, often in the form of ATP. It relies on transport proteins like pumps to maintain concentration gradients essential for cell function.

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Endocytosis

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Endocytosis is an active transport process where the cell membrane folds inward to bring large particles or fluids into the cell inside vesicles. It includes specialized forms such as phagocytosis and pinocytosis.

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Phagocytosis

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Phagocytosis is a type of endocytosis where extensions of the cytoplasm surround and engulf large particles or even whole cells, forming a food vacuole. It is used by some single-celled organisms and immune cells to ingest solids.

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Pinocytosis

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Pinocytosis is a form of endocytosis in which the cell membrane engulfs droplets of extracellular fluid to take in dissolved substances. It is often described as ‘cell drinking.’

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Exocytosis

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Exocytosis is the active process by which cells expel materials in vesicles that fuse with the plasma membrane. It is used for secretion of hormones and enzymes and for excretion of cellular waste.

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Cell Specialization

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Cell specialization means cells become adapted to perform specific functions, often by expressing particular genes and forming unique structures. This specialization is fundamental to multicellular organisms and enables tissues and organs to carry out complex roles.

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Levels of Organization

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Biological organization in multicellular organisms progresses from cell to tissue to organ to organ system to organism. Each level represents increasing complexity and coordinated function among specialized units.

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Electron Microscope

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Electron microscopes use electron beams with much shorter wavelengths than visible light, enabling much higher resolution and revealing fine cellular details. They typically cannot be used to view live specimens and require specialized preparation.

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Light Microscope

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Light microscopes use visible light to magnify specimens and can be used to observe living cells and tissues, though at lower resolution than electron microscopes. They are useful for studying overall cell structure and dynamics in real time.

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Prokaryote Example

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A bacterium is a classic example of a prokaryote; it lacks a nucleus and membrane-bound organelles. Bacteria carry out all necessary life processes within a simpler cellular organization.