physiology Flashcards
what is a cell?
a functional and structural unit of life
what are the three basic parts of a human cell?
nucleus, cytoplasm, and plasma membrane
what are extracellular materials?
substances found outside of cell:
extracellular fluids (blood plasma, cerebrospinal fluid)
cellular secretions(mucus, saliva)
extracellular matrix(glue that holds cells together)
what is the plasma membrane?
acts as an active barrier that separates intracellular fluid from extracellular fluid.
phospholipids that form a flexible bilayer
controls what enters and leaves the cell
what are the structures of the plasma membrane?
fluid mosaic, glycocalyx
-membrane structures help to hold cells together through cell junctions
what are the 4 major functions of the plasma membrane
1.physical barrier
2.selective permeability
3.communication
4.cell recognition
what do phospholipids contain?
phosphate heads (hydrophilic)
fatty acid tails (hydrophobic)
what are the plasma membrane components?
glycolipids, cholesterol, and membrane proteins
what are integral proteins?and their functions?
-most are transmembrane proteins
-have both hydrophobic(embedded in membrane)and hydrophilic regions ( in the intra and extracellular space)
-functions as transport protein, enzymes, or receptors
what are peripheral proteins?functions?
-not embedded in membrane, loosely attached to the membrane or integral proteins
-include filaments on intracellular surface used for plasma membrane support
-functions as enzymes, motor proteins for shape during cell division and muscle contraction
how do membrane proteins function as transporters?
-the left protein spans across the membrane and provides a hydrophilic channel across the membrane that is selective for a particular solute
-the right transport proteins hydrolyze ATP as an energy source to actively pump solute across the membrane
how do membrane proteins function as receptors?
-a membrane protein exposed to the outside of the cell may act as a binding site for specific chemical messenger(hormones)
-when bound the chemical messenger may cause a change in shape in the protein that initiates a chemical reaction in the cell
what are ligands?
molecules that bond to receptors (hormones, neurotransmitters, growth factors)
-binding of ligand leads to downstream signalling cascade
how do membrane proteins act as enzymes?
-a membrane protein may be an enzyme when its active site is exposed to substances in the adjacent solution
-a team of several enzymes in a membrane may catalyze sequential steps of a metabolic pathway
what are glycoproteins?
proteins bonded to short chains of sugars which help to make up the glycocalyx
how do cell proteins use cell-cell recognition?
some glycoproteins serve as identification tags that are specifically recognized by other cells
how do membrane proteins function in attachment to the cytoskeleton and ECM
-elements of the cytoskeleton and ECM may anchor to membrane proteins
-helps maintain cell shape, fixes the location of certain membrane proteins, and play a role in cell movement
how do membrane proteins function in cell-cell joining?
-membrane proteins of adjacent cells may be hooked together in various kinds of intracellular junctions
-some membrane proteins(cell adhesion molecules) of this group provide temporary binding sites that guide cell migration and other cell-cell interactions
what is the glycocalyx and its function?
-consists of sugars sticking out of cell surface
-attached to proteins and lipids (glycolipids and glycoproteins)
-every cell type has different patterns of sugar coating
-functions as specific biological markers for cell to cell recognition
what are cell junctions?
most cells are bound together to form tissues and organs
what are the three ways that cells can be bound together?
tight junctions, desmosomes, and gap junctions
what are tight junctions?
what are tight junctions?
-integral proteins on adjacent cells fuse to form an impermeable junction that encircles whole cell
-prevent fluids and most molecules from moving inbetween cells (creates continuous seal around cell)
what are desmosomes?
-formed when linker proteins of neighboring cells interact with similar types of linker protein
-linker protein is anchored to its cell through thickened plaques
-keratin filaments anchor plaques internally
what are gap junctions?
-transmembrane proteins allow small molecules to move from cell to cell
-used to spread ions, simple sugars, or other small molecules between cells
-allows electrical signals to be passed quickly (used in cardiac and smooth muscle contractions)
what are the 2 types of membrane transfer?
passive processes:no energy required
active processes:energy(ATP)required
what are the two major types of passive transport?
diffusion an filtration
what is diffusion?
molecules move from high concentration to low concentration, down the concentration gradient
explain diffusion in cells?
very small, lipid soluble may freely pass through plasma membrane via passive diffusion
what is facilitated diffusion?
some molecules passed down the concentration gradient with assistance
what is carrier mediated diffusion?
-binding of molecule causes carrier to change shape, moving the molecule
-molecules still move down the concentration gradient
-carriers can become saturated
what is channel-mediated diffusion?
through a channel protein, mostly ions selected on basis of size and charge
two types:
leakage channels:open gates
gated channels:controlled by chemical or electrical signals
what is channel-mediated osmosis?
diffusion of a solvent such as water through a specific channel protein (aquaporin) or through the lipid bilayer
what is hydrostatic pressure
pressure of water inside cell pushing on membrane
what is osmotic pressure?
tendency of water to move into cells by osmosis;the more solutes inside a cell the higher the osmotic pressure
what is a isotonic solution?
cells retain their normal size and shape in isotonic solutions (same solute/water concentration as inside cells;still water moves in and out but the net movement equals zero because it is equal)
what is a hypertonic solution?
has higher osmolarity (more solutes) than inside the cell, water flows out of the cell
what is a hypotonic solution?
has lower osmolarity (fewer solutes) than inside the cell, water flows into the cell, can cause cells to burst (lyses)
what is secondary active transport?
-depends on the ion gradient that was created by primary active transport system
-energy used in gradient is indirectly used to drive transport of other solutes
what is active transport?
-requires carrier proteins
-move solutes against their concentration gradient (move from low to high) requires ATP
what is vesicular transport?
-second type of active transport membrane
-involves transport of large particles, macromolecules, and fluids across membrane in vesicles
-requires ATP
what are peroxisomes?
membrane sacs containing detoxifying substances that neutralize toxins, such as free radicals (highly reactive molecules, by-products of metabolism
-they also play a role in breakdown and synthesis of fatty acids
what are lysosomes?
membranous structures containing digestive enzymes (acid hydrolases)
-digest ingested bacteria, viruses, and toxins
-degrade organelles
includes autophagy(cell digests itself)
what are the functions of the endomembrane system?
-produce, degrade, store, and export biological molecules
-degrade potentially harmful substances
what are the three types of cytoskeleton?
-microfilaments
-intermediate filaments
-microtubules
what are microfilaments?
-strands made of spherical protein subunits called actin
-cross linked network attached to cytoplasmic side of plasma membrane
-strengthens cell surface
-involved in cell mobility, changes in cell shape, and exocytosis and endocytosis
what are intermediate filaments?
-tough, insoluble protein fibers constructed like woven ropes composed of tetramer fibrils
-help cell resist pulling forces
-some have special names (neurofilaments in nerve cells/keratin filaments in skin)
what are microtubules?
-hollow tubes composed of protein subunits called tubulins, constantly assembled and disassembled
-determine overall shape of cell and distribution of organelles
-microtubules act as tracks for motor proteins
-many organelles are tethered to microtubules
what are motor proteins?
function in motility:
-movement in organelles and other substances around cells
-use microtubules as tracks to carry their cargo
-powered by ATP
what are centrosomes?
located near the nucleus, “cell center”
-newly assembled microtubules radiate from centrosomes to the rest of the cell
what are centrioles?
microtubule organizing center, consisting of centrioles
centrioles form the base of cilia and flagella
what are the 3 structures of the nucleus
-nuclear envelope
-nucleolus
-chromatin
what is the nuclear envelope?
-double membrane barrier that encloses the nucleoplasm
-surface of nuclear envelope is rough ER with ribosomes
-inner layer is a network of proteins that supports nuclear shape and holds DNA in
-nuclear pores allow substances to move in and out of the nucleus
what is the nucleolus?
involved in ribosomal RNA synthesis and ribosome subunit assembly
what is chromatin?
-arranged in fundamental units called nucleosomes
-chromosomes are condensed chromatin(helps protect during DNA division)
what is the process from DNA to proteins?
-DNA is transcribed to RNA
-RNA is translated to proteins
what is autophagy?
-self eating
what are proteasomes?
unneeded proteins are marked by ubiquitins
-proteosomes disassemble ubiquitin tagged proteins and recycles amino acids and ubiquitin back into the body
what is apoptosis?
-programmed cell death
what is hyperplasia?
-is accelerated cell growth that increases cell numbers when needed
what is atrophy?
is a decrease in size that results from lack of stimulation or use
what are telomeres?
strings of nucleotides that protect ends of chromosomes , shorten when divide
what is telomerase?
enzyme that lengthens telomeres after division
what are the 3 main functions of blood?
-transport
-regulation
-protection
how does the blood function with transport?
-delivers O2 and nutrients to body cells
-transporting CO2 and wastes to lungs and kidneys for elimination
-transporting hormones from endocrine to target organs
how does the blood function with regulation?
maintains body temp, pH, and fluid volume
how does the blood function with protection?
-preventing blood loss (platelets, and proteins initiate clotting)
-prevent infection (antibodies, blood cells, complement proteins)
what type of connective tissue is found in blood?
plasma:non-living fluid matrix
formed elements:living blood cells
-leukocytes, erythrocytes, platelets
what does hematocrit mean?
percentage of erythrocytes in blood volume
what is plasma and what is it comprised of?
-straw colored sticky fluid
-over 100 dissolved solutes (nutrients, electrolytes, gases, hormones, proteins, etc)
what is albumin?
-important carrier protein found in plasma
-maintains osmotic balance
what are the characteristics of erythrocytes?
-concave shape, small diameter
-transport gas
-no mitochondria, no nucleus
-filled with hemoglobin
-contains spectrin (protein that maintains RBC shape)
what is hemoglobin?
-binds reversibly with O2
-has two alpha and two beta chains (quaternary level)
what is oxyhemoglobin?
produced when O2 is loaded into the lungs
what is deoxyhemoglobin?
produced when O2 is unloaded into the tissue
what is carbaminohemoglobin?
produced when CO2 in blood binds to Hb
what is hematopoiesis?where does it occur?
-formation of all red blood cells
-occurs in red bone marrow
what are hematopoietic stem cells?
hemocytoblasts:give rises to all formed elements
hematopoietic stem cells turn into RBCs
what is hypoxia?
low levels of oxygen in body tissues
what does erythropoietin do?
stimulates the formation of RBCs
-hypoxia inducible factor increases synthesis of EPO
what are the causes of hypoxia?
-decreased RBCs due to hemorrhage, blood loss, or increased RBCs destruction
-insufficient hemoglobin per RBCs (iron deficiency)
-reduced availability of oxygen (high altitude or pneumonia)
explain how erythrocytes are destructed
-old RBCs become weak and Hb begins to degenerate
-macrophages in spleen engulf and break down RBCs
-iron in RBC is stored for use
-heme is degraded to to bilirubin (leaves body in feces)
-globin is metabolized into amino acids and released back into the blood stream
what are the three types of anemia?
-blood loss
-not enough RBCs produced
-too many RBCs being destroyed
what is iron-deficiency anemia?
-not enough RBCs being produced
-low iron intake or decreased absorption
-RBCs produced are called microcytes
what is pernicious anemia?
-destroys stomach mucosa that produces intrinsic factor(needed to absorb B12)
-without B12 RBCs become enlarged but cannot divide (macrocytes)
-can also be caused by low B12 intake
what is hemolytic anemia and what is it caused by?
-premature lysis of RBCs
-caused by: incompatible transfusions or infections
-hemoglobin abnormalities
-sickle cell anemia
what is sickle cell anemia?what is it caused by?
-mutated hemoglobin
-one amino acid residue is altered
-RBCs become crescent shaped when O2 levels are too low
-misshaped RBCs cause them to rupture and block small blood vessels
what are the benefits of sickle cell anemia?
-people with sickle cell anemia cannot contract malaria
what is polycythemia?
-abnormal excess of RBCs(increased blood viscosity causes sluggish blood flow)
what is polycythemia vera?
bone marrow cancer leading to excess RBCs
what is secondary polycythemia?
-caused by low O2 levels (high altitude)or increased EPO production
what are leukocytes?
-white blood cells
-function in defense of disease
