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90 Cards in this Set
- Front
- Back
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The cell
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The Basic Structural and functional unit that is considered “living"
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Parts of a Cell
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The plasma membrane
The cytoplasm The nucleus |
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The Plasma Membrane
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The flexible outer surface of the cell that separates the contents of the cell from the external environment
Composed of phospholipid bilayer Performs many functions -two layers of phospholipids -Also has cholesterol, protein membrane, glycolipid, glycoprotein |
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The Cytoplasm
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The content between plasma membrane and nucleus
Two components: Cytosol, Organelles Cytosol: the fluid portion of cytoplasm, contains water and dissolved solutes Organelles: molecular machines that perform various functions for the cell |
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Nucleus
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A large organelle that has the place for cell’s DNA
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The Phospholipid Bilayer
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Two layers of phospholipids
Polar heads: face watery fluid on both sides (hydrophilic) Nonpolar tails: orient away from water (hydrophobic) |
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Membrane Proteins
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Firmly embedded within the phospholipid bilayer
Integral proteins: extend into (through) the lipid bilayer Peripheral proteins: located at either extracellular or intracellular side of the lipid bilayer |
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Functions of Membrane Proteins
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Ion Channels
Carriers (Transporters) Receptors Enzymes Identity markers Linkers |
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Ion Channels
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Pores or holes in the channel serve as a pathway for the movement of ions
Are often selective: allow specific ion to move through Examples:Na+ channels K+ channels Ca++ channels |
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Carriers (Transporters) Channels
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Transport specific substances across the membrane by changing shape
Transport is either passive or active Example:Transporter for amino acids |
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Receptors
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Serve as cellular recognition sites
The specific molecule that binds to the receptor is called “ligand” Binding ligand to receptor changes cell’s function in some way Example:insulin receptors |
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Enzymes
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Catalyst specific chemical reactions
Reactions can occur at the extracellular or intracellular surface of the membrane Example:Lactase in small intestine cells |
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Identity Markers
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Enable cell to identify same cells or potentially dangerous foreign cells (identify self vs. non-self)
Examples: ABO blood types |
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Linkers
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Link to membrane proteins of neighboring cells (intercellular junction)
Link to protein filaments inside and outside the cell Provide structural stability and maintain the shape |
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Membrane Fluidity
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Most membrane lipids and proteins rotate and move sideways in their own half of the bilayer
Enable cells to move, grow, divide, and secret |
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Membrane Permeability
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Selective permeable
Permeable to nonpolar, molecules: O2, CO2 Slightly permeable to small, polar molecules: water, urea Impermeable to ions, large and polar molecules: glucose, Na+, K+, Ca++ |
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Gradients Across Membranes
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Selective movement through the bilayer establishes differences between the extracellular and intracellular fluid
Gradient: the different concentrations of the substance on both sides of the membrane Two types of gradients: Concentration gradient Electrical gradient |
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Concentration Gradients
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The difference in concentration of a chemical between extracellular and intracellular fluids
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Electrical Gradients
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The difference in the number of positively and negatively charged ions between extracellular and intracellular fluids
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Electrochemical Gradients
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The combined influences of the concentration gradient and electrical gradient on movement of a particular ion
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Transport Across the Plasma Membrane
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Mediated: helped by a carrier or transporter
Non-mediated: no carrier or transporter is required Passive: no energy is required (moving from high to low concentration) Active: energy is required (moving from low to high concentration) |
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Diffusion-Passive transport processes
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Movement of a solute from high to low concentration
Three types: Simple diffusion Diffusion through a channel Facilitated diffusion |
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Simple Diffusion
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Substances move directly through the bilayer
Does not require carrier or channels Example: transport of gases, small polar molecule like water, urea |
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Diffusion Through a Channel
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Channel transport the substances through the bilayer
Channels may be gated, so they may open or close Example: transport of ions like Na+, K+, Ca++ Different permeability is based on different numbers of channels |
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Facilitated Diffusion
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Carrier binds to substance, undergoes change in shape, then release it to the opposite side of the bilayer
When substances are too polar or highly charged Example: Transporting glucose, fructose, galactose, and some vitamins |
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Transporting Glucose into Cells
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Transporting glucose into cells
Insulin promotes glucose transport into cells by stimulating the movement of more transporters to plasma membrane |
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Osmosis-Passive transport processes
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The diffusion of water molecules across a selectively permeable membrane
Occurs when a membrane is permeable to water molecules, but not permeable to solute molecules Water moves from its area of high concentration to its area of low concentration |
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Red Blood Cell in Hypertonic ECF
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A red blood cell is placed in concentrated NaCl solution
Cell loses water cellular shrinkage occurs (crenation) -has a higher solute concentration than cytosol |
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Red Blood Cell in Hypotonic ECF
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-has a lower solute concentration than cytosol
-A red blood cell is placed in distilled water Cell gains water cellular bursting occurs (lysis) Hemolysis is lysis of red blood cells |
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Isotonic ECF
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-has the same solute concentration as cytosol, in this ECF cells remain the same size
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Active Transport Processes
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Solutes are pumped from low concentration to high concentration
Use a protein membrane as a pump Require ATP Two types: Primary active transport Secondary active transport |
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Primary Active Transport
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ATP is used directly to change the shape of a carrier which pumps a solute from its low to high concentration
Example: the sodium-potassium pump |
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Secondary Active Transport
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ATP is used indirectly
The passive transport of a solute is coupled to the active transport of another solute Symporters: two solutes move the same direction Antiporters: two solutes move in opposite direction |
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Vesicular Transport
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Used to transport solutes or solids in a small, spherical sac called vesicle
ATP is used Two types: Endocytosis Exocytosis |
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Endocytosis-vescular transport
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Movement of solutes or solid particles into the cells
Vesicle is formed from the plasma membrane Vesicle buds away from the membrane and carries packaged material into the cytoplasm |
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Types of Endocytosis
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Phagocytosis: cellular “eating”
Pinocytosis: cellular “drinking” Receptor-mediated: endocytosis that requires a membrane receptor |
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Phagocytosis
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A vital defense mechanism of the body
Transport of a large solid particles (bacteria, virus, dead cell) into the cell |
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Pinocytosis
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Transport of fluid and dissolved solutes into the cell
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Receptor-Mediated Endocytosis
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Highly selective
Substance to be transferred must first bind to a receptor Endocytosis occurs Receptors are recycles back to the plasma membrane |
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Exocytosis
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Movement of solutes or solid particles out of the cell
Intercellular vesicle fuses to the plasma membrane Contents of vesicle are expelled into the extracellular space This is the way that secretory cells release secretory products |
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The Cytoskeleton
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The cell’s internal skeleton
Composed of a network of protein fibers criss-crossing throughout the cytosol Fibers maintain cell shape and strength, guide the movement of organelles |
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Protein Fibers of the Cytoskeleton
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Microfilaments: composed of the protein called actin
Intermediate filaments: composed of many different proteins; including keratins, lamins Microtubules: composed of the protein called tubulin |
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Microfilaments
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The thinnest
Found primarily at the cell’s borders Maintain cell shape, muscle contraction, provide mechanical strength for microvilli Microvilli increase the surface area of the cells |
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Intermediate Filaments
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Thicker than microfilaments
Many types Found throughout the cytoplasm Help to stabilize the positions of organelles such as nucleus Help attach cell to the neighboring cells |
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Microtubules
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The largest cytoskeleton components
Help determine cell shape Provide a set of tracks for organelles and vesicles to move on Form the spindle fibers during mitosis Primary components of cilia and flagella |
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Centrosome
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An organelle located near the nucleus
Site of microtubule synthesis and assembly Two components: A pair of centrioles Pericentriolar material |
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Functions of the Centrosome
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Centrosome replicates before mitosis begins
The centrosomes move to the opposite poles of cell Microtubules continually grow from each centrosome forming the spindle fibers Spindle fibers move the chromosomes |
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Cilia and Flagella
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Composed of microtubules
Arranged to form hair like projections Used for movement |
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Cells with Cilia
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Cilia move secretions across the cell surface
Cilia in the respiratory tract move mucus across the surface of cells |
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Cells with Flagella
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Flagella move the entire cell
Flagella are found on sperm cells that “swim” through the male and female reproductive tracts |
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The Ribosome
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The factory for protein synthesis
May be free in the cytoplasm or bound to another organelle called the endoplasmic reticulum (ER) |
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Free vs. Bound Ribosomes
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Free ribosomes synthesize proteins that will be used by the cell
Example: cellular enzymes, cytoskeleton proteins Ribosomes bound to the ER synthesize proteins that will be exported out of the cell by exocytosis Examples: membrane proteins, secretory proteins: hormones, enzymes |
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Ribosome Structure
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Composed of large and small ribosomal subunits
They are made in nucleolus (a spherical body in the nucleus) When they exit nucleus, they come together in cytoplasm |
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The Endoplasmic Reticulum
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A network of membranes in the form of sacs, vesicles, and tubules
Two types: Smooth ER Rough ER |
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Smooth Endoplasmic Reticulum
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Smooth external surface with many internal spaces called cisternae
Does not have ribosomes does not synthesize proteins Functions:lipid synthesis (all cells), detoxification (liver cells), storage of Ca++ ions (muscle cells) |
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Rough Endoplasmic Reticulum
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An elaborate network membranous passageways with cisternae
External surface is studded with ribosomes Function:modification, storage and transport of secretory proteins , membrane proteins |
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The Golgi Complex (Apparatus)
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A series of flattened membranes that are stacked on top of each other
Vesicle may be seen on both sides |
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Structure of the Golgi Complex
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Two faces:
Cis (receiving) face: faces the rough ER Trans (shipping) face: faces the plasma membrane |
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Function of the Golgi Complex
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The “UPS” of the cell
Cis face receives newly manufactured proteins from the rough ER Chemical modification and packaging occur inside the Golgi space Trans face ships the modified product to the exterior |
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The Lysosome
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The garbage disposal system of the cell
A membrane-enclosed vesicle which forms from the Golgi complex Contains enzymes that are capable of digesting all types of macromolecules |
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Function of Lysosome
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Fuse with a vesicle formed during phagocytosis
Enzyme in the lysosome digest the material in the vacuole |
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Autophagy
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Lysosomal enzymes can also digest worn out organelles
This process is called autophagy |
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Cellular Death
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Lysosomes are “suicide sacs”
They are activated during apoptosis or programmed cell death, and after cellular injury |
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The Mitochondrion
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The “powerhouse” of the cell
Contains numerous enzymes for cellular respiration and generation of ATP The numbers of mitochondrion shows level of activity of cell |
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Structure of the Mitochondrion
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Two membranes:
Outer: smooth Inner: folded to form cristae Inner space called matrix Numerous enzyme in the cristae and in the matrix Ribosomes |
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Function of the Mitochondrion
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Generation of ATP via cellular respiration
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The Nucleus
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The largest organelle
Acts as the “control center” for the cell |
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Structure of the Nucleus
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A double-layered membrane called the nuclear envelope
Openings called nuclear pores extend through the envelop One or more nucleolus Nucleoplasm |
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The Nuclear Envelope
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Selectively permeable
Numerous nuclear pores which are large central opening surrounded by proteins Nuclear pores control the movement of substances into and out of the nucleus |
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The Nucleolus
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Condensed area inside the nucleus
Site of synthesis of rRNA and assembly of rRNA and proteins into ribosomal subunits |
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Chromatin
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A long molecule of DNA folded and twisted into a structure called a chromosome
Nucleosome: a double-strand DNA wrapped twice around a core of eight histones Nucleosomes > Chromatin> Chromatin fibers> chromatid> Chromosome |
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Chromosomes
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23 pairs in human body cells = 46 total
Pairs are numbered 1 22 #23: the X and Y chromosomes are the sex chromosomes Chromosomes contain region of DNA called genes |
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Genes
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Genes control cellular structure and direct cellular activities.
They are code for specific proteins and are responsible for many human characteristics and diseases |
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Protein Synthesis
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The formation of proteins from the information encoded in DNA
Two steps: Transcription Translation |
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Transcription-Protein Synthesis
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Occurs in nucleus
DNA serves as a template for mRNA synthesis The enzyme RNA polymerase is required Required nucleotides: Adenine, Uracil, Cytosine, Guanine |
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Translation-Protein Synthesis
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mRNA leaves the nucleus, enters cytoplasm, and attaches to ribosome
Ribosome reads the mRNA tRNA brings amino acids to the ribosome In the ribosome, amino acid combine to form polypeptide chain |
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Cell Division
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A cell cycle is a “day” in the life of a cell
Two phases: Interphase Mitosis |
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Interphase
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The cell is performing its daily activities
Three Subphases: G1 > S > G2 |
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G1 Phase
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The cell is metabolically active
Cellular growth and differentiation occur Cell duplicates its cellular organelles Centrosome replication begins |
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S Phase
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The synthesis phase
The cell duplicates its DNA through DNA replication Each old strand of DNA is copied to form a new strand |
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G2 Phase
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Another growth phase
Cell prepares for mitosis Replication of centrosomes is completed |
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G0 Phase
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From G1, the cell exits from the cell cycle
Cell remains metabolically active but no cell division occurs |
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Mitosis
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A parent cell divides to form two new daughter cells (two identical cells)
Involves separation and redistribution of the chromosomes Four phases: Prophase Metaphase Anaphase Telophase and cytokinesis |
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Before Mitosis Begins
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The cell is in interphase G2
Nucleus and nuclear envelop are intact Chromatin in the nucleus is finely granular |
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Prophase
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Nucleus and nuclear envelope disappear
Chromatin condenses to form thread-like chromosomes Spindle fibers are beginning to attach to the chromosomes |
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Metaphase
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Chromosomes migrate to the center of the cell and line up along the metaphase plate
Each chromosome is attached to spindle fibers on both sides of the metaphase plate |
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Anaphase
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Pulling and tugging by the spindle fibers forces the chromosomes to separate
Spindle fibers split chromosomes to opposite poles of the cell |
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Telophase and Cytokinesis
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Chromosomal movement stops
The identical chromosomes are at opposite poles of cells The nucleus and nuclear envelop reappear The cytoplasm begins to separate Two identical cells are produced |
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Embryonic Cells
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Spend more time dividing than they do in the interphase
Egg units with sperm to form zygote Zygote begins to divide rapidly to form blastocyst |
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Tumor Cells
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Divide rapidly in an uncontrolled, unregulated manner
Have lost check mechanisms that normally prevent uncontrolled division Spend little time in interphase and generally are unfunctional |
