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Chapter 3 Part 1
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Gravity
Terms in this set (53)
Typical cell
-Smallest living unit in the body
~0.1 mm in diameter
-Could not be examined until invention of microscope in 17th century
Cell theory
1. Cells are building blocks of all plants and animals
2. All new cells come from division of preexisting cells
3. Cells are smallest unit that perform all vital physiological functions
Cell cooperation
-Each cell maintains homeostasis at cellular level
-Coordinated activities of cells allow homeostasis at higher organizational levels
Cell differentiation
-All cells in the body come from a single fertilized ovum (Start with a single cell, yet end with wide variety of cell size, shape, and function)
-Fertilized ovum contains genetic potential to become any cell
-First cell divisions create smaller parcels of cytoplasm
-Regional differences in original ovum cytoplasm means now different composition of cytoplasm in resulting daughter cells
-Cytoplasmic differences affect DNA in daughter cells and cause specific genes to turn on or off: Result is specialization of cells. Process of gradual specialization is called differentiation. Specialized cells form tissues of the body
Body fluid distribution
-Cells surrounded by extracellular fluid: Watery medium surrounding cells. Called interstitial fluid (interstitium, something standing between) in most tissues
-Fluid inside cell is intracellular fluid or cytoplasm
-Cell plasma membrane separates intracellular from extracellular fluid
Basic cell structure
-Surrounded by a plasma membrane
-Contains cytoplasm. Material of varying consistency found between cell membrane and nuclear membrane. Subdivided into:
Cytosol (intracellular fluid, the fluid part of cytoplasm) Organelles ("little organs",intracellular structures with specific functions)
Organelles
Divided into membranous and nonmembranous
Nonmembranous
-Not completely enclosed by membranes
-In direct contact with cytosol
Examples: Cytoskeleton, Microvilli, Centrioles, Cilia, Ribosomes
Membranous
-Enclosed in a phospholipid membrane
Isolated from cytosol
-Examples: Mitochondria, Nucleus, Endoplasmic reticulum, Golgi apparatus, Lysosomes, Peroxisomes
Peroxisome Structure/Function
STRUCTURE: Vesicles containing degradative enzymes
FUNCTION: Break down organic compounds
Neutralize toxic compounds
Lysosome: Structure/Function
STRUCTURE: Vesicles containing digestive enzymes
FUNCTION: Break down organic compounds and damaged organelles or pathogens
Microvilli: Structure/Function
STRUCTURE: Membrane extensions containing microfilaments
FUNCTION:Increase surface area for absorption
Golgi apparatus: Structure/Function
STRUCTURE: Stacks of flattened membranes (cisternae) containing chambers
FUNCTION: Store, alter, and package synthesized products
Nucleus: Structure/Function
STRUCTURE: Fluid nucleoplasm containing enzymes, proteins, DNA, and nucleotides
Surrounded by double membrane called nuclear envelope
FUNCTION: Controls metabolism
Stores and processes genetic information
Controls protein synthesis
Endoplasmic reticulum (ER): Structure/Function
STRUCTURE: Network of membranous sheets and channels
FUNCTION: Synthesizes secretory products; stores and transports within cell; detoxifies drugs and toxins
-Smooth ER: No attached ribosomes. Synthesizes lipids and carbohydrates
-Rough ER: Attached ribosomes. Modifies/packages newly synthesized proteins
Ribosomes: Structure/Function
STRUCTURE: RNA and proteins
Fixed: attached to endoplasmic reticulum
Free: scattered in cytoplasm
FUNCTION: Synthesize proteins
Mitochondrion: Structure/Function
STRUCTURE: Double membrane
Inner membrane contains metabolic enzymes
FUNCTION: Produces 95 percent of cellular ATP
Cytoskeleton: Structure/Function
STRUCTURE: Proteins organized into fine filaments or tubes
Centrosome
Organizing center containing pair of centrioles
FUNCTION: Strengthens and supports cell
Moves cellular structures and materials within the cell
Plasma membrane
-Selectively permeable barrier separating inside of cell from extracellular fluid
Controls: Entry of ions and nutrients. Elimination of wastes. Release of secretions
Composed of: Phospholipid bilayer. Proteins. Glycocalyx
Plasma membrane components
1. Phospholipid bilayer
2. Proteins
a.Integral proteins
b.Peripheral proteins
3. Glycocalyx
Phospholipid bilayer
-Measures 6-10 nm
-Two layers of phospholipids: Hydrophilic heads at membrane surface. Hydrophobic tails facing each other on the inside
-Phospholipids interspersed with cholesterol molecules: Cholesterol has hydrophilic and hydrophobic portions (amphipathic). Functions to "stiffen" the plasma membrane
Proteins
-Integral proteins: Part of cell membrane and cannot be removed without damaging cell. Often span entire cell membrane (these are called transmembrane proteins). Can transport water or solutes
-Peripheral proteins: Attached to cell membrane inner or outer surface. Easily removable
Fewer than integral proteins. May have regulatory or enzymatic functions
Glycocalyx
-Superficial membrane carbohydrate layer
-Components of complex molecules: Proteoglycans (carbohydrates with protein attached). Glycoproteins (protein with carbohydrates attached). Glycolipids (lipids with carbohydrates attached)
-Functions: Cell recognition, Binding to extracellular structures, Lubrication of cell surface
Plasma membrane functions
-Physical isolation
-Regulation of exchange with external environment
-Sensitivity to environment
-Structural support
-Lipid bilayer provides isolation
-Proteins perform most other functions
Cytoskeleton
Functions as cell's skeleton
Provides internal protein framework
Gives cytoplasm strength and flexibility
Components include:
1. Microfilaments
2. Intermediate filaments
3. Microtubules
Cytoskeleton components
1. Microfilaments (microvilli, terminal web)
2. Intermediate filaments
3. Microtubules
Microfilaments
-<6 nm in diameter
-Typically composed of actin
-Commonly at periphery of cell
Microvilli: Finger-shaped extensions of cell membrane. Have core of microfilaments to stiffen and anchor. Enhance surface area of cell for absorption
Terminal web: (layer inside plasma membrane in cells forming a layer or lining)
Intermediate filaments
-7-11 nm in diameter
-Strongest and most durable cytoskeletal elements
Microtubules
~25 nm in diameter
-Largest components of cytoskeleton
-Extend outward from centrosome (near nucleus)
Centrioles
-Cylindrical structures
-Composed of microtubules (9 groups of triplets)
-Two in each centrosome
-Control movement of DNA strands during cell division: Cells without centrioles cannot divide (Red blood cells, Skeletal muscle cells)
Cilia
-Long, slender plasma membrane extensions
-Common in respiratory and reproductive tracts
-Also composed of microtubules (Nine groups of pairs surrounding a central pair)
-Anchored to cell surface with basal body
-Beat rhythmically to move fluids or secretions across cell
Ribosomes
-Responsible for protein synthesis
-Two subunits (1 large, 1 small) containing special proteins and ribosomal RNA (rRNA): Must join together before synthesis begins
-Free ribosomes: Throughout cytoplasm, Manufactured proteins enter cytosol
-Bound or fixed ribosomes: Attached to endoplasmic reticulum, Synthesize proteins for export out of cell
Endoplasmic reticulum (ER)
-Network of intracellular membranes continuous with nuclear envelope, which surrounds nucleus
-Forms hollow tubes, sheets, and chambers (cisternae, singular, cisterna, reservoir for water)
-Synthesizes and stores proteins, lipids, and carbohydrates
Two types of endoplasmic reticulum (ER)
1. Smooth (SER)
Lacks ribosomes
Cisternae are often tubular
2. Rough (RER)
Has attached (fixed) ribosomes
Modifies newly synthesized proteins
Exports those proteins to Golgi apparatus
-Proportion of SER to RER depends on the cell and its functions
Functions of the smooth endoplasmic reticulum
-Synthesizes phospholipids and cholesterol for cell and organelle membranes
-Synthesizes steroid hormones in the reproductive organs
-Synthesizes and stores glycerides
-Synthesizes and stores glycogen
Polypeptide formation in rough endoplasmic reticulum (RER)
-Polypeptide synthesized on attached ribosome: Growing chain enters cisterna of RER
-Polypeptide assumes secondary/tertiary structures
-Completed protein may become enzyme or glycoprotein
-Products not destined for RER are packaged into transport vesicles: Deliver products to Golgi apparatus
Golgi apparatus (Golgi complex)
-Functions
1. Renews or modifies plasma membrane
2. Modifies or packages secretions into secretory vesicles for release from cell (exocytosis)
3. Packages special enzymes within vesicles for use in cytosol
-Typically consists of 5-6 flattened discs (cisternae)
-May be more than one apparatus in a cell
-Situated near nucleus
Golgi apparatus process
1. Transport vesicles filled with proteins and/or glycoproteins from rough ER arrive at cis face ("receiving side") of Golgi apparatus.
2. Transport vesicles fuse, forming new cisternae. Enzymes in Golgi apparatus modify arriving products.
3. Products modified and re-packaged as they move toward trans face ("shipping side").
4. Finalized products packaged in secretory vesicles and released from trans face.
Golgi apparatus products
1. Membrane renewal vesicles: Add to plasma membrane, Allow alteration of plasma membrane properties, changing sensitivity and functions of cells
2. Secretory vesicles
Contain hormones or enzymes for extracellular release
3. Lysosomes
Contain digestive enzymes for intracellular use
Lysosomes
-Vesicles that isolate digestive processes from the rest of the cytoplasm
Three basic functions:
1. Fusion with another organelle and digestion of contents
2. Fusion with another vesicle containing fluid or solid extracellular materials and digestion of contents
3. Release of digestive enzymes within the cytoplasm when cell is injured or dying, resulting in autolysis (enzymes destroy cytoplasm): Leads to "suicide packets" name for lysosomes
Membrane flow
-Continuous movement and exchange of materials between organelles using vesicles
-Can replace parts of cell membrane to allow cell to grow, mature, or respond to changing environment
Mitochondria (mitos, thread + chondrion, granule)
-Produce energy (ATP) for cells
-Vary widely in shape
-Vary in number per cell depending on cell's energy requirements (more energy needs = more mitochondria): Mitochondria account for 30 percent of volume of cardiac muscle cells, Red blood cells have no mitochondria
-Contain their own DNA (mtDNA) and ribosomes
Mitochondrial double membrane
-Outer membrane surrounds organelle
-Inner membrane contains folds called cristae: Inner membrane encloses liquid called matrix, Cristae increase surface area exposed to matrix, Metabolic enzymes in matrix catalyze reactions providing energy for cellular function
Steps of ATP production
1. Glycolysis (glycos, sugar + -lysis, a loosening): Occurs in cytosol, 1 glucose → 2 pyruvate, Pyruvate absorbed into mitochondria
2. In mitochondrial matrix: CO2 removed from pyruvate, Enters citric acid (or TCA, tricarboxylic acid) cycle: Systematically removes CO2 and hydrogen atoms
3. Enzymes and coenzymes use hydrogen atoms to catalyze ATP from ADP: Also forms H2O
4. ATP leaves mitochondrion
Aerobic metabolism or cellular respiration
-ATP production that requires oxygen
-Occurs in the mitochondria
-Much more efficient than ATP production without oxygen (e.g., glycolysis)
-Produces about 95 percent of ATP needed by cell: Remaining 5 percent produced by enzymatic reactions in the cytoplasm
Nucleus
-Usually largest cellular structure
-Control center for cellular operations: Can direct synthesis of >100,000 different proteins, Genetic information coded in sequence of nucleotides, Determines cell structure and function
-Usually only one per cell
Exceptions: Skeletal muscle cells have many, Mature red blood cells have none (Because of no nucleus, they disintegrate within 3-4 months)
The nucleus directs cellular responses to environmental (ECF) changes
-Short-term adjustments: Enzyme activity changes
-Long-term adjustments: Changes in enzymes produced, Changes in cell structure from changes in structural proteins, Often occur as part of growth, development, and aging
Nuclear structures and functions
-Nuclear envelope: Separates nucleus from cytoplasm, Double membrane (Perinuclear space (peri-, around)
Space between layers)
Nuclear pores
-Passageways that allow chemical communication between nucleus and cytoplasm
-Movement of ions and small molecules regulated by proteins at the pores
-Account for about 10 percent of the surface of the nucleus
Nucleoplasm
-Fluid contents of nucleus
-Contains network of fine filaments for structural support
-Also contains ions, enzymes, nucleotides, and small amounts of RNA and DNA
Nucleoli
-Transient nuclear organelles
-Composed of RNA, enzymes, and proteins (histones)
-Assemble RNA subunits
-Most prominent in cells manufacturing large amounts of proteins : Examples: liver, nerve, muscle cells
DNA in the nucleus
-Stores instructions for protein synthesis
-Strands in nucleus coiled, allowing much to be packed in small space: Wrap around histone molecules forming nucleosomes, Loosely coiled (chromatin) in non dividing cells, Tightly coiled (chromosomes) in dividing cells
DNA during cell division
-Starts by becoming tighter and more complex, forming chromosomes
-Two copies of each chromosome held together at centromere
-23 paired chromosomes in somatic (general body) cells: One each from mother/father
-Carry instructions for proteins and RNA
-Also some regulatory and unknown functions
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