The Cell Flashcards
Where are all organisms on Earth descended from?
They descended from a common prokaryotic ancestral cell about 3.5 billion years ago.
Theory of Endosymbiosis
About 1.5 billion years ago. Eukaryotic cells emerged when mitochondria and chloroplasts, once free-living prokaryotes, took up permanent residence inside larger cells.
Eukaryotic Cell
Complex cell with nucleus and internal membranes that compartmentalize the cell. They led to the evolution of multi-celled organisms. They make up every other form of life.
Cell Size
10-100 micrometers; human red blood cells are about 8 micrometers
Cell Theory: Schleiden and Schwann
All living things are composed of cells; Cells are the basic unit of all organisms; All cells arise from preexisting cells
Cells in General
Cells are enclosed by a membrane that regulates the passage of material between the cell and tis surrounding. They also contain nucleic acid which directs the cell’s activities and controls inheritance.
Prokayotic Cells
Have no nucleus or other internal organs.
Eukaryotic Cell
Complex cell with nucleus and internal membranes that compartmentalize the cell. They led to the evolution of multi-celled organisms. DNA wrapped with histone proteins into chromosomes, ribosomes are larger, metabolism is aerobic, cytoskeleton present, mainly multicellular with differentiation and cells are larger.
Prokayotic Cells
Have no nucleus or other internal organs. Circular, naked DNA. Ribosomes are small, metabolism in anaerobic/aerobic, cytoskeleton is absent, mainly unicellular and cells are very small.
Prokayotic Cells
Have no nucleus or other internal organs. Circular, naked DNA. Ribosomes are small, metabolism in anaerobic/aerobic, cytoskeleton is absent, mainly unicellular and cells are very small.
Microscopes
Main tool for studying cells. They magnify an image over 100,000 times. Resolution, high magnification and high resolution are characteristics of a good microscope.
Microscrope: Resolution
clarity of the image
Microscopes and People to Know
Antoine van Leeuwenhoek developed the first microscope and Robert Hooke advanced it which enabled him to study and name cells in a cork.
Microscopes and People to Know
Antoine van Leeuwenhoek developed the first microscope and Robert Hooke advanced it which enabled him to study and name cells in a cork.
Light Microscopes
Microscopes that use light passing through a living/dead specimen to form an image. Cells/tissue can be staines to make organelles easier to see however stains may kill cells.
Electron Microscopes
Microscopes that use electrons passing through a specimen to form an image. They have superior revolve and magnification power. However, they cannot be used to view live specimens because the specimen preparation kills the cells.
Transmission Electron Microscopes
Used to study the interiors of cells. The images appear flat and 2D. The tissues must be cut into very small pieces and exposed to a fixative that stops all biochemical activity. The tissue is then dehydrated, embedded in a polymer, cured overnight and sliced on an ultramicrotome.
Scanning Electron Microscopes
Used to study the surface of cells. The images appear 3D. Specimens are coated with a heavy metal such as gold and are placed directly on the microscopes for observing. Specimens are not alive.
Phase-Contrast Microscopes
Used to examine unstained, living cells. It is often used to examine cells growing in tissue culture.
Phase-Contrast Microscopes
Used to examine unstained, living cells. It is often used to examine cells growing in tissue culture.
Cell Fractionation
Using an ultracentrifuge to spin liquids at high speeds and separate them based on differences in density. Tissues/cells are first mashed up in a blender to form a homogenate. The most dense particles such as nuclei are pushed to the bottom, followed by mitochondria and ribosomes. The supernatant, liquid above the pellet, can be poured off an re-spun.
Cell Fractionation
Using an ultracentrifuge to spin liquids at high speeds and separate them based on differences in density. Tissues/cells are first mashed up in a blender to form a homogenate. The most dense particles such as nuclei are pushed to the bottom, followed by mitochondria and ribosomes. The supernatant, liquid above the pellet, can be poured off an re-spun.
Freeze Fracture and Freeze-Etching
Multistep techniques used to prepare a detailed cast of the membrane. The tissue is then digested away leaving only the cast which can be examined under the electron microscope.
Tissue Culture
Used to study the properties of specific cells in vitro. Cell lines can be grown in culture for years and while the cells are growing they can be studied with a phase-contrast microscope.
Tissue Culture
Used to study the properties of specific cells in vitro. Cell lines can be grown in culture for years and while the cells are growing they can be studied with a phase-contrast microscope.
Tissue Culture
Used to study the properties of specific cells in vitro. Cell lines can be grown in culture for years and while the cells are growing they can be studied with a phase-contrast microscope.
Nucleus
Contains chromosomes
Nucleus
Contains chromosomes which are wrapped with special proteins into a chromatin network. It’s surrounded by a selectively permeable membrane or envelope that contains pores to allow for the transport of molecules which are too large to diffuse directly through the envelope.
Nucleolus
An interphase in the nucleus contains this region where components of ribosomes are synthesized. 1 to 2 nucleoli may be visible. Nucleoli are not membrane-bound structures but are actually a tangle of chromatin and unfinished ribosome precursors.
Ribosomes
The site of protein synthesis. They can be found free in the cytoplasm or attached to the endoplasmic reticulum.
Endoplasmic Reticulum
A membranous system of channels and flattened sac that traverse the cytoplasm.
Rough ER
The site of protein synthesis resulting from the attached ribosomes.
Smooth ER
Assists in the synthesis of steroid hormones and other lipids; connects rough ER to the Golgi apparatus; Carrier out various detoxification processes
Golgi Apparatus
Lies near the nucleus and consists of flattened membraneous sacs stacked net to one another and surrounded by vesicles. They package substances produced in the rough ER and secrete them to other cell parts or the cell surface for export.
Golgi Apparatus
Lies near the nucleus and consists of flattened membraneous sacs stacked net to one another and surrounded by vesicles. They package substances produced in the rough ER and secrete them to other cell parts or the cell surface for export.
Lysosomes
Sacs of hydrolytic (digestive) enzymes surrounded by a single membrane. They are a site of intracellular digestion. The cells can continually renew itself by breaking down and recycling its parts. Apoptosis occurs with a cell’s own hydrolytic enzymes which is essential for multi-celled organisms.
Peroxisomes
Found in both plant and animal cells. They contain catalase which converts hydrogen peroxide (waste product of cellular respiration) into water with the release of oxygen atoms. They also detoxify alcohol in liver cells.
Mitochondria
The site of cellular respiration. All cells have them but a very active cells could have 2,000+. They have an outer double membrane and an inner series of membranes called cristae. They contain their own DNA.
Vacuoles
Single, membrane-bound structure for storage. Vesicles are smaller version of these. Contractile vesicles pump out extra water; they’re found in freshwater protista.
Plastids
Only found in plants and algae. Have a double membrane.
Plastids: Chloroplasts
Site of photosynthesis. In addition to the double outer membrane so they have an inner one that forms a series of structure called grana. The grana consist of thylakoids and lie in the stroma. They contain their own DNA.
Plastids: Leucoplasts
Store starch and are found in roots like turnips or in tubers like the potato.
Plastids: Chromoplasts
Store carotenoid pigments and are responsible for the red-orange-yellow of carrots, tomatoes and daffodils.
Cytoskeleton
Complex network of protein filaments that extend through the cytoplasm and gives the cell its shape and enables it to move. It also anchors organelles to the plasma membrane.
Cytoskeleton: Microtubules
Hollow tubes made of the protein tubulin that make up the cilia, flagella, and spindle fibers. Cilia and Flagella help with locomotion. Spindle fibers help to separate chromosomes during meiosis and mitosis.
Spindle Fibers: Structure
Microtubules organized into 9 triplets with no microtubules in the center.
Cytoskeleton: Microfilaments/Actin Filaments
Help support the shape of the cell. They enable animal cells to form a cleavage furrow during cell division; amoebas to move by sending out pseudopods; and skeletal muscle to contract at they slide myosin filaments.
Centrioles, Centrosomes or Microtubules Organizing Centers
Non-membranous structure that lie outside the nuclear membranes. They organize spindle fibers and give rise to the spindle apparatus required for cell division. Two centrioles oriented at right angles to each other make up one centrosome and consists of 9 triplets of microtubules arranged in a circle. Plants lack centrosomes but have MTOCs.
The Cell Wall
Not found in animal cells. The primary cell wall is immediately outside of the plasma membrane. Some cells have a secondary cell wall outside the primary cell wall. When a cell divides a thin gluey layer is formed which becomes the middle lamella.
Cell Wall: Structure
Plants and algae have cell walls made out of cellulose. The cell walls of fungi are usually made of chitin. The average membrane is the consistency of olive oil and is 40% lipid and 60% protein.
Fluid Mosaic Model
S.J.Singer’s description of the cell membrane. The eukaryotic plasma membrane consists of a phospholipid bilayer with proteins dispersed through the layers. Phospholipids move along the plane of the membrane rapidly while some proteins are kept in place by attachment to the cytoskeleton.
Amphiphatic
A characteristic of phospholipids. This means it has both a hydrophilic and hydrophobic regions.
Integral Proteins
Proteins that have non-polar regions that completely span the hydrophobic interior of the plasma membrane.
Peripheral Proteins
Proteins that are loosely bound to the surface of the plasma membrane.
Cholesterol Molecules
Molecules embedded in the interior of the bilayer to stabilize the membrane.
Glycocalyx
The external surface of the plasma membrane also has carbohydrates attached to it. This is important of cell to cell recognition.
Glycocalyx
The external surface of the plasma membrane also has carbohydrates attached to it. This is important of cell to cell recognition.
Plasma Membrane: Proteins as Transport Molecules
They transport ions, molecules, and electrons through channels, pumps, carriers and electron transport chains.
Plasma Membrane: Proteins as Enzymes
Ex. One membrane-bound enzyme located within the cell membrane that synthesizes cyclic AMP (c-AMP) from ATP is adenylate cyclase.
Plasma Membrane: Proteins as Receptors
They act as receptors for hormones, neurotransmitters, receptor-mediated endocytosis, and for cells of the immune system.
Plasma Membrane: Proteins in Cell to Cell Attachment
Ex. Desmosomes serve as anchors for filaments and river cells together.
Cell Transport
Movement of substances into and out of a cell. Either active which requires energy (ATP) or passive which requires no energy.
Passive Transport
Movement of molecules down a concentration gradient from a region of high concentration to a region of low concentration. Ex. diffusion and osmosis
Diffusion: Simple
Does not involve protein channels. Ex. in the glomerulus of the human kidney, where solutes dissolved in the blood diffuse into Bowman’s capsule of the nephron.
Diffusion: Facilitated
Required hydrophilic protein channels that will passively transport substances. Ex. one channel transports single ions.
Countercurrent Exchange
The flow of adjacent fluids in opposite direction that maximizes the rate of simple diffusion.
Countercurrent Exchange: Fish Gills
Blood flows toward the head in the gills while water flows over the gills in the opposite direction. This maximizes the diffusion of respiratory gases and wastes between the water and the fish.
Countercurrent Exchange: Fish Gills
Blood flows toward the head in the gills while water flows over the gills in the opposite direction. This maximizes the diffusion of respiratory gases and wastes between the water and the fish.
Osmosis
Term for diffusion of water across a membrane.
Solvent
Substance that does the dissolving.
Solute
Substance that dissolves
Hypertonic
Having greater concentration of solute that another solution.
Hypotonic
Having lesser concentration of solute than another solution.
Isotonic
Two solutions containing equal concentration of solutes.
Osmotic Potential
The tendency of water to move across a permeable membrane into a solution.
Water Potential
Movement of water. Results from two factors: solute concentration and pressure. Water potential for pure water is zero. The addition of solutes lowers water potential to a value less than zero. Water will move across a membrane from the solution with higher water potential to a solute with lower water potential.
Water Potential Values
Water potential for pure water is zero. The addition of solutes lowers water potential to a value less than zero. Water potential inside a cell is a negative value.
Water Potential Values
Water potential for pure water is zero. The addition of solutes lowers water potential to a value less than zero. Water potential inside a cell is a negative value.
Hypotonic Solution
The concentration of solute in the beaker is less than the concentration of solute in the cell. Water will flow into the cell causing the cell to swell.
Turgid
A cell that is swelled. What keeps plant crisp. If a plant cell dehydrates it will lose turgor pressure and wilt.
Hypertonic Solution
The concentration of solute in the beaker is greater than the concentration of solute in the cell. Water will flow out of the cell from high concentration of water to low concentration of water.
Plasmolysis
A cell that shrinks due to flow of water out of the cell.
Plasmolysis
A cell that shrinks due to flow of water out of the cell.
Aquaporins
Specialized water channel proteins that facilitate the diffusion of massive amounts of water across a cell membrane. They don’t affect the water potential gradient or the direction of water flow but affect the rate at which water diffuses down its gradient.
Aquaporins as Gated Channels
Gates that open and close in response to changes in tonicity. A sudden change in a cell in response to changes in tonicity may be results of aquaporins.
Aquaporins as Gated Channels
Gates that open and close in response to changes in tonicity. A sudden change in a cell in response to changes in tonicity may be results of aquaporins.
Active Transport
The movement of molecules against a gradient which requires energy (ATP). Examples are pumps or carriers that carry particles across the membrane by active transport.
Plastoquinone
Active transport occurs in the thylakoid membrane of chloroplasts by this mobile electron carrier.
Sodium-Potassium Pump
Pumps Na+ and K+ ions across a nerve cell membrane to return the nerve to resting state. They move against a gradient. Two K+ ions for very three Na+ ions.
Electron Transport Chain
Active transport in mitochondria consists of proteins that pump protons across the cristae membrane.
Contractile Vacuole
In freshwater Protista this pumps out excess water that has diffused inward because the cell lives in a hypotonic environment.
Exocytosis
Active transport occurs in nerve cells as vesicles release neurotransmitters into a synapse.
Pinocytosis
Active transport in the uptake of large, dissolved particles. (AKA cell drinking). The plasma membrane invaginated around the particles and encloses them in a vesicle.
Phagocytosis
The engulfing of large particles or small cells pseudopods. The cell membrane wraps around the particle and encloses it into a vacuole. This is the way white blood cells engulf bacteria.
Receptor-Mediated Endocytosis
Enables a cell to take up large quantities of a specific substance through active transport. It is a process by which extracellular substances bind to receptors on the cell membrane.
Receptor-Mediated Endocytosis Process
Once a ligand binds to the receptors, endocytosis begins. The receptors, carrying the ligand, migrate and cluster along the membrane. The receptors turn inward and become coated vesicles that enter the cell. Ex. How cholesterol is taken in from the blood.
Ligan Define
Any molecule that bind specifically to a receptor site of another molecule.
Ligan Define
Any molecule that bind specifically to a receptor site of another molecule.
Bulk Flow
Term for the overall movement of a fluid in one direction in a organism. Bulk flow movement is always from source to sink.
Bulk Flow: Blood
In humans blood moves around the body by bulk flow as a results of blood pressure created by the pumping heart.
Bulk Flow: Sap
Sap in trees moves by bulk flow from the leaves to the roots due to active transport in the phloem.
Glycocalyx
The external surface of the plasma membrane also has carbohydrates attached to it. This is important of cell to cell recognition.
Bulk Flow: Sap
Sap in trees moves by bulk flow from the leaves to the roots due to active transport in the phloem.
Cell Communication
In multi-celled organisms individual cells work together through cell junctions, signal transduction pathway, and cell-to-cell recognition.
Cell Junction: Tight Junctions
Belts around epithelial cells that line organs and serve as a barrier to prevent leakage into/out of those organs. In the urinary bladder, they prevent urine from leaking out the bladder to the surrounding body cavity.
Cell Junction: Desmosomes
They are found in many tissues and have been compared to spot welds that rivet cells together. They consist of clusters of cytoskeleton filaments looped together. They occur in tissues that are subjected to mechanical stress such as skin epithelium or neck of the uterus.
Cell Junction: Gap Junction
Permit the passage of materials from the cytoplasm of one cell to the cytoplasm of an adjacent cell. In the middle tissue of the heart, the flow of ions through the gap junctions coordinate the contraction of the cardiac cells.
Cell Junction: Plasmodesmata
Connect one plant cell to the next and are similar to gap junctions in animal cells.
Signal Transduction Pathway
It relied on plasma membrane proteins in a multistep process in which a small number of extracellular signal molecules produce a major cellular response.
Three Stages of Cell Signaling
Reception, Transduction, and Response
Signal Transduction Pathway: Reception
Signal molecules (usually a protein that doesn’t enter the cell) binds to a specific receptor on the cell surface causing the receptor molecule to change in conformation.
Signal Transduction Pathway: Transduction
After the change in the cell surface receptor this leads to transduction. This is a change in signal form where the receptor relays a messages to a secondary messenger.
Signal Transduction Pathway: Response
After transduction, the secondary signaling molecule gets the message, it induces a response within the cell.
Cell-to Cell Recognition
The cell’s ability to distinguish one type of neighboring cell from another is crucial to the function of multi-celled organism. The glycocalyx is a feature that aids in this.
Cell-to-Cell Recognition: Glycocalyx
Consists of oligosaccharides (small chains of sugar molecules) attached to integral proteins within the plasma membrane. This is responsible for a phenomenon called contact inhibition.
Contact Inhibition
Caused by glycocalyx which causes the normal trait of cells to stop dividing when they become too crowded.
