Chapter 3 Flashcards
What are the common cellular functions?
Cell metabolism / energy use Synthesis of molecules Communication Reproduction Inheritance
What are the functions of the plasma membrane?
Boundary - separates intracellular/extracellular
Determines what moves into/out of cells
What is membrane potential?
The charge difference across the plasma membrane. Outside is more positively charged than inside due to gathering of ions on plasma membrane.
Describe the glycocalyx.
A collection of glycolipids (carb + lipid), glycoproteins (carb + protein) and carbohydrates on the outer surface of the PM (plasma membrane).
What is the lipid bilayer?
A double layer of phospholipid molecules. Have polar (hydrophilic) head and nonpolar (hydrophobic) tail.
What does hydrophilic mean?
Water loving. Heads of lipids are positively charged and exposed to extracellular and intracellular fluids of cell.
What does hydrophobic mean?
Water fearing. Tails face the interior of the plasma membrane.
What is cholesterol’s function inside the plasma membrane?
Interspersed among phospholipids and accounts for 1/3 total lipids in plasma membrane.
What does the fluid nature of the phospholipid bilayer allow for?
Distribution of molecules in the membrane.
Phospholipids can automatically reassemble with damage.
Membranes can fuse.
What are the two major types of membrane proteins?
Integral (intrinsic) - penetrates deeply into lipid bilayer
Peripheral (extrinsic) - attached to either inner/outer surfaces of lipid bilayer
What are the five types of membrane proteins?
Marker molecules Attachment proteins Transport proteins Receptor proteins Enzymes
Where are marker molecules located? What is their function?
Located on cell surface.
Allows cells to identify other molecules/cells. Usually glycoproteins or glycolipids
What is the function of attachment proteins?
Allow cells to attach to each other or to extracellular molecules.
Cadherins: cells to other cells
Integrins: cellular membrane proteins to extracellular molecules
What are the three types of channel proteins?
Non-gated: always open
Ligand-gated: open/closed in response to chemical signals
Voltage-gated: open/close in response to change in charge across plasma membrane
What are carrier proteins?
Transporters.
Move molecules from one side of plasma membrane to the other by changing shape.
Uniporters - moves one particle
Symporters - 2 particles in same direction
Antiporters - 2 particles in opposite direction
What are the four ways that molecules can pass through the plasma membrane?
Diffusion
Osmosis
Mediated transport
Active transport
What is the difference between diffusion and osmosis?
Diffusion - movement of solutes from high concentration to low concentration.
Osmosis - diffusion of solvent (water) across a selectively permeable membrane (allows water but not all solutes in water).
What is osmotic pressure?
The force required to prevent water from moving across a SP membrane.
Isosmotic - same concentration of solutes/same pressure
Hyperosmotic - greater concentration of solute particles, higher osmotic pressure.
Hypoosmotic - lesser concentration of solute particles, lower osmotic pressure (more dilute solution)
What are the three types of tonicity of cells?
Isotonic - cell placed in solution, neither shirnks nor swells
Hypertonic - cell placed in, water moves OUT, cell shrinks (crenation)
Hypotonic - cell placed in, water moves INTO cell and cell bursts (lysis)
IMPORTANT FOR FLUID ADMINISTRATION IN DEHYDRATED PATIENTS.
What is mediated transport?
Process by which transport proteins mediate or assist, movement of large water soluble molecules or electrically charged molecules/ions across plasma membrane.
What are the three characteristics of mediated transport?
Specificity - each transport protein binds to/transports only one ion/molecule
Competition - result of similar molecules binding to transport protein
Saturation - rate of movement of molecules across membrane is limited by number of available transport proteins
What is the difference between passive and active transport?
Passive transport - cell does not expend metabolic energy. (diffusion, osmosis, facilitated diffusion)
Active transport - cell expends metabolic energy. (can move substances from low to high with ATP and high to low)
What is facilitated diffusion?
A carrier-mediated or channel-mediated passive membrane transport process that moves substances into or out of cells from high to low. Does not require ATP.
What is secondary active transport?
Active transport of an ion out of a cell from low to high concentration. The tendency for the inos to move back provides energy necessary to move a different ion or other molecule into the cell.
Moves by symport or antiport.
Sodium/Potassium or glucose movement.
What is the difference between endocytosis and exocytosis?
Endocytosis - uptake of material into cell by formation of a vesicle. PM wraps around particle/droplet and fuses so the membrane “eats” the particle/droplet.
Exocytosis - secretions that accumulate within vesicles cause these vesicles to fuse to the PM and the vesicle contents are expelled from cell.
What is the cytoplasm?
Cellular material outside the nucleus but inside plasma membrane. Composed of cytosol, cytoskeleton, cytoplasmic inclusions and organelles.
What is cytosol?
Fluid portion of cytoplasm. Contains cytoskeleton/cytoplasmic inclusions.
What is the cytoskeleton?
Supports the cell and holds nucleus and other organelles in place.
Responsible for allowing movement of cell organelles and changes in cell shape.
What is the cytoskeleton made of?
Microtubules - internal scaffolding, assist with transport/cell division
Actin filaments - offers support, supports microvilli, helps with contractibility/movement
Intermediate filaments - offer mechanical strength to cells
What are cytoplasmic inclusions?
Aggregates of chemicals either produced or taken in by cell. Includes chemicals for energy storage, pigmentation or for transporting other molecules.
What is the nucleus?
Large, membrane-bound structure near center of cell. Houses majority of DNA - organized into structures called chromosomes.
Nucleoplasm - cytoplasm of nucleus
Nuclear envelope - PM of nucleus
Nucleolus - nucleus of nucleus
What is a chromosome?
Fibrous structures of DNA and protein called chromatin.
Chromatids joined together by centromere and become a chromosome.
What is the ribosome?
Site of protein synthesis.
FREE or ATTACHED (to ER)
What is the endoplasmic reticulum?
(makes packages)
Consists of broad, flat interconnected sacs/tubules - cisternae - separate from rest of cytoplasm.
Rough ER - ribosomes attached; protein production
Smooth ER - no ribosomes; lipid production
What is the golgi apparatus?
(ships packages)
Packaging/distribution center for proteins/lipids manufactured by ER.
Create lysosomes - membrane bound vesicles that may include hydrolytic enzymes that function as digestive enzymes.
What is the mitochondria?
POWERHOUSE!
Provides energy for cell with ATP synthesis.
Inner foldings - cristae…make up the matrix.
Mitochondria increase in # when cell energy requirements increase.
What are the centrioles and spindle fibers?
Located close to nucleus in centrosome - specialized zone for microtubule formation.
Centrioles - move to poles before cell division and organize spindle cell fibers.
Spindle cell fibers - bind to chromosomes to facilitate movement of chromosomes toward two centromeres.
What are the cilia?
Structures that project from the surface of cells and are capable of movement.
1-1000’s per cell.
What is the flagella?
Longer cilia - sperm cells are only human cells that possess flagella. One per cell.
What are the microvilli?
Extension of plasma membrane that increases surface area. Not used for movement. Much smaller than cilia.
What are genes?
Functional units of hereditary (transmission of traits from parents to offspring)
What is gene expression?
Production of proteins from information stored in DNA.
What is gene regulation?
All nucleated cells (except germ cells) have full complement of DNA. During development, differentiation occurs and some segments are turned off.
What is transcription?
“copying the recipe”
Synthesis of types of RNA based on DNA sequence. One DNA strand serves as template for transcription.
What is translation?
“making the cake”
Synthesis of a protein at the ribosome in response to codons of mRNA.
Explain how genetic code works.
The sequence of bases on a DNA strand.
Bases (letters) Codons (three letter words) Protein (words into sentences) Chromosomes (sentences into book) Genome (books of library)
What are the phases of a cell’s life?
Interphase - 90% of time
Mitosis - 10% of time
What happens in interphase?
G1 (1st gap phase) - cell carries out routine metabolic activities
S (synthesis phase) - new DNA synthesized
G2 (2nd gap phase) - cell prepares for division
What happens in mitosis?
Prophase: chromatin condenses and forms mitotic chromosomes
Metaphase: chromosomes align near center
Anaphase: chromatids separate
Telophase: nuclear envelope forms, two separate nuclei
What is cytokinesis?
Occurs after mitosis - separation of cytoplasm between two new cells.
What is meiosis?
A type of cell division specialized for sexual reproduction.
One cell undergoes two divisions to produce four genetically different daughter cells. One homolog from each homologous pair.
Diploid (2 chromosomes: 2n) - first division - 2 cells
Haploid (1 chromosome: 1 n) - second division - 4 cells - EGG/SPERM
What is the difference between a genetic disorder and a birth defect?
Genetic disorder is an abnormality in DNA. A birth defect is due to developmental problems.
What causes birth defects?
Teratogens (radiation, drugs, alcohol, etc.)
Do not cause abnormalities in DNA.
What causes genetic disorders?
Mutagenes - agents that cause mutations
Oncogenes - DNA replication on steroids (some genetic and some from exposure to carcinogens)
What is a carcinogen?
Anything that increases the risk of cancer.
