chapter 3-cellular organization Flashcards
cytology
study of cells
cytosol
fluid part of the cytoplasm
phospholipids
molecules that self-assemble into a bilayer to make up the majority of the plasma membrane
glycocalyx
-coating on the outside of the cell membrane
-functions for protection, anchoring, and recognition by the immune system
peripheral membrane proteins
adheres to only one side of the cell membrane
integral membrane proteins
span the whole width of the bilayer
osmotic lysis of a cell could occur in a strongly WHAT solution?
hypotonic
During phagocytosis, a cell reaches out with WHAT to grab onto a
large object and internalize it in a phagosome?
mircofillaments
transmembrane potential
-unequal charge distribution of positive on the outside and negative on the inside across the cell membrane
-ranges from -10 to -100mV
cisternae
membrane sacs of the endoplasmic reticulum
the Golgi functions to modify and sort proteins that are synthesized by the fixed
ribosomes on the WHAT ORGANELLE?
rough endoplasmic reticulum
three types of vesicles are produced at the trans face of the Golgi: secretory
vesicles, membrane renewal vesicles and WHAT?
lyosomes
peroxisomes
membrane sacs that contain oxidases and catalases to neutralize free radicals
proteins tagged with ubiquitin will be sent to the WHAT for recycling?
proteasome
cristae
inner folds of membrane in the mitochondria
aerobic cellular respiration
glucose is catabolized in the mitochondria into water and carbon dioxide in orderto create ATP
nucleolus
dense/dark spot in the nucleus where rRNA
synthesis is occurring
chromatin
loose open form of DNA
nucleosome
formed by DNA wound around histone proteins
in a gene, three bases of DNA make up a WHAT which is the instructions for one amino acid in the protein?
codon
transcription
process of making an RNA copy of a DNA gene
RNA polymerase binds to the WHAT on the template strand of DNA to begin the process of synthesizing RNA?
promoter
AUG
start codon for translation
if an mRNA has the codon CAU, the anticodon of the corresponding tRNA would
be WHAT?
GUA
why does translation stop at the stop codon?
no tRNA with anticodon to stop codon, no new amino acid arrives at ribosomes so the polypeptide chain is terminated
point mutation
-change in one base
-can be a silent mutation if the amino acid is not changed (common at the 3rd base in a codon)
apoptosis
the process of controlled cell death where lysosomes are neutralized
G1 phase
a cell duplicates its cytoplasm during interphase
During the S phase, DNA WHAT unwinds the DNA to allow copying of the information for replication?
helicase
DNA polymerase can add nucleotides only to the WHAT end of a growing DNA molecule
3’
DNA ligase functions to assemble the WHAT fragments into a
continuous lagging strand during DNA replication
okasaki
metaphase
the phase of mitosis where the chromosomes are lined up in the middle of the cell
the two sister chromatids are held together by a WHAT at the kinetochore?
centromere
cancer
caused by abnormal proliferation of cells due to mutations in oncogenes
how many cells does a human have?
~75 trillion cells & ~200 different types
sex cells
sperm and oocyte (eggs)- half of DNA (23)
somatic cells
-every other cell
-all contain full amounts of DNA
-unique morphology is related to function
-all cells surrounded by plasma membrane
cytoplasm
consists of cytosol (fluid) and organelles (structure)
interstitial fluid (outside membrane)
surrounds body cell
plasma/cell membrane
-phospholipids bilayer dynamic
-6 to 10 mm thick
-interface between cell and environment
-selective permeability of membrane allows
different conc. of molecules in/outside cells
-the inside surface is negatively charged due to the abundance of proteins
-outside surface is positively charged due to cations in extracellular fluids
functions of the plasma/cell membrane
-the physical barrier that maintains homeostasis
-regulates exchange with the environment
-provides sensitivity via receptors: cell communication
-provides structural support
phospholipids (membrane)
self assemble into bilayer
cholesterol (membrane)
resist osmotic lysis, stiffens
carbohydrates (membrane)
-linked to other molecules such as proteoglycans, glycoproteins, and glycolipids
-The carb part protrudes from the extracellular side creating outer carb layer called glycocalyx
functions of glycocalyx
-lubrication & protection
-anchoring & locomotion
-binding specificity (receptor bind ligands)
-self recognition by immune system
proteins (membrane)
-1/2 mass of membrane
-contain integral & peripheral proteins
integral proteins
-most common
-span within membrane
peripheral proteins
adhere to inner/outer surface
anchoring proteins
attachment
recognition proteins
self-identification by the immune system (glycoproteins)
enzymes
catalyzer in cytosol or extra cellular fluid
receptors
-binds ligands for signaling or import/export
-ex: ions, nutrient molecules, hormones
carrier proteins
transport solutes in/out
channels
moves ions & H20 in/out
passive tranport
require no energy from the cell, rely on diffusion principles
active transport
requires a transport protein which uses energy from ATP to pump a particular substance against its diffusion gradient
simple diffusion
-net movement of molecules from an area of high concentration to an area of low concentration across a diffusion gradient toward equilibrium
-transport of nonpolar & lipid soluble
rates of simple diffusion
-distance: shorter the distance, faster
-molecule size: smaller the molecule, faster
-temperature: hotter it is, faster
-gradient size: larger difference, faster
-electrical forces: opposite charge, faster
facilitated diffusion
-diffusion through a transporter substances
-rate of diffusion depends on the number of carrier molecules for the specific substance
carriers (facilitated diffusion)
proteins that bind a particular large or polar molecule
channels (facilitated diffusion)
proteins that act as selective pores for water or ions
leak channels
always open
gated channels
regulated
osmosis
diffusion of water through a semi permeable membrane
osmolarity
solute concentration of a solution
tonicity
how the solute concentration affects the shape of cell
tonos
tension
isotonic solutions
contain solute concentration equal to that of the cell, no net movement of water into or out of the cell, no osmotic pressure
hypotonic solutions (crenation)
contain less solutes than the cell, net movement of water into the cell
hypertonic solutions (lysis)
contain more solutes than the cell, net movement of water out of the cell
vesicular transport
allows bulk of small molecules or internalization of large particles
endocytosis
transport into the a cell via a vesicle
exocytosis
transport out of a cell via a vesicle
receptor-mediated endocytosis
membrane receptors bind substrate (ligand) and are internalized as an endosome to be fused with the lysosome
*specifically collected things from environment
pinocytosis
“cell drinking” interstitial fluid is internalized as an endosome to be fused with the lysosomes
* random
phagocytosis
“cell eating” large particles or cells are engulfed by pseudopods and internalized as a phagosome to be fused with the lyosomes
pseudopods
a temporary growth on a cell that allows it to be mobile, almost like a little foot
microvilli
ruffles and folds of cell membrane containing a web of microfilaments and cytoplasm, anchored to the cytoskeleton, corrugations maximize the surface of a cell
cytoplasm
-enclosed by plasma membrane
-occupies space between the plasma membrane and nuclear membrane
-components are cytosol, inclusions, organelles
cytosol
-fluid
-high K +, low Na +!
-colloid solution: proteins and enzymes
-nutrient reserves: carbohydrates, lipids,
-amino acids
inclusions
-type and number vary with cell
-e.g. glycogen, melanin, steroids, etc.
organelles
-carry out cellular functions
-each has separate functions
-some have membranes
contact cytosol
organelles free in cytosol
membranous organelles
-ER
-Golgi
-lysosomes
-peroxisomes
-mitohondria
-nucleus
nonmembranous organelles
-cytoskeleton
-centrioles
-ribosomes
-proteasomes
cytoskeleton
-internal framework
-organizes cell contents and functions
-4 possible types of filaments: microfilaments, intermediate, mircotubles, thick
microfilament
~5nm diameter
-composed of actin protein
-usually at periphery of cell
microfilament functions
- attach integral membrane proteins to the cytoskeleton to keep the membrane around the cytoplasm
- control the consistency of cytoplasm
- in muscle cells interact with myosin to produce movement
intermediate filaments
~9-11nm
-the type varies with cell (e.g. collagen, elastin, keratin) all are insoluble and durable
intermediate filament functions
- strengthen cells and maintain shape
- stabilize the position of organelles
- stabilize the cell relative to other cells
microtubules
~25nm diameter
- hollow tubes composed of tubulin protein!
- originate from the centrosome
- very dynamic
microtubule function
- forms main portions of the cytoskeleton, contributes to rigdity of cell and anchoring organelles
- allows the cell to change shape andassists in mobility
- involved in transport: molecular motors travel along microtubule “tracks”
- makes up the spindle apparatus for nuclear division (mitosis) !
- structural part of some organelles and cellular projections (centrioles, cilia, flagella)
thick filaments
- 15nm diameter
- composed of myosin protein
- muscle cells only!
function of thick filaments
to interact with actin to produce movement
centrosome
-located near the nucleus
-consists of dense cytoplasm & two centrioles arranged at right angles
function of centrosome
-microtubule organizing center
-assembling spindle apparatus during mitosis
cilia & flagellum
-cellular appendages
-contain a microtubule core with cytoplasm covered in plasma membrane
-beating or waving motions
cilia
-short, numerous
-function to sweep substances over cell surface
flagellum
-very long, singular
-function to propel cells through environment
ribosomes
-site of protein synthesis
-contain 2 subunits: large and small, composed of 60% of rRNA & 40% protein
protein synthesis
enzymes to peptide bond amino acids
free ribosomes
in cytoplasm and manufacture protein for use in cytoplasm
fixed ribosomes
attached to endoplasmic reticulum, manufacture proteins for export or for in the membrane
endoplasmic reticulum
-a network of membranes made up of tubes, sacs & chambers called cisternae!
-attached to the nuclear envelope
-transport vesicles from RER dock on the cis face or forming face of Golgi and release contents into Golgi
- 2 forms: RER & SER
rough endoplasmic reticulum (RER)
-studded with fixed ribosomes!
-ribosomes synthesize proteins and feed! them into RER cisternae to be modified (e.g. + carbs = glycoprotein)
-modified proteins put into transport vesicles to go to Golgi
-these proteins for exocytosis or use in membrane
smooth endoplasmic reticulum
-tubular membranes
-no ribosomes
-near nucleus but not attached
functions of SER
- synthesis of phospholipids & cholesterol for membrane
- synthesis of steroid hormones
- synthesis & storage of triglycerides
- synthesis & storage of glycogen
- storage of Ca2+ ions in muscle cells
- detoxification/inactivation of drugs in kidney and liver cells
functions of the ER
A. modifies and packages secretions
B. renews or modifies the cell membrane!
C. packages enzymes within vesicles to create a temporary digestive organelle called the lysosome
golgi apparatus
-stack of cisternae with associated transport vesicles (vesicles composed of lipids & proteins from the ER)
-proteins (and glycoproteins) are modified (phosphate, carbohydrate, or lipids attached, polypeptides refolded)
-modified proteins transit between cisternae via vesicles from cis face (forming) to trans
face (maturing) and are concentrated and sorted by final function and destination
-at trans face, proteins are packaged into one
of three types of vesicles for transport: secretory, membrane renewal & lysosomes
secretory vesicles
carry products to be exocytosed for use outside of cell
membrane renewal vesicles
carry products to be incorporated into the plasma membrane
lysosomes
temporary organelles, membrane bound sac of digestive enzymes
lysosomes
-digestion center for large molecules or structures, cells can have many
-endosomes or phagosomes containing endocytosed things, and organelles and molecules targeted for destruction fused with the lysosome and enzymatically broken down
-some solutes diffuse into the cytoplasm for use, remaining debris is exocytosed
-failure of lysosomes results in buildup in cells that eventually prevents cell functions
tay sach’s disease
-example of lysosome failure when lysosomes fail to break down glycolipids in nerve cells
-accumulation of glycolipids disrupts nerve function
peroxisomes
-membrane sac containing oxidases and
catalases to neutralize free radicals
-free radicals (e.g. H2O 2) form during the catabolism of organic molecules
-not made by Golgi but by enzymes produced by free ribosomes
proteasomes
-cylindrical structure composed of protein-digesting enzymes called proteases!
-functions to degrade and recycle damaged, denatured, or abnormal proteins
-hydrolyzes peptide bonds of proteins tagged
with ubiquitin to recycle amino acids
mitochondria
-sausage-shaped double membrane
-outer membrane: smooth
-inner membrane folded
-folds called cristae
-center = matrix (fluid)
-aerobic cellular respiration occurs on the surface of cristae where glucose is catabolized creating CO2 & H2O waste to convert ADP into ATP
-have their own DNA
-can replicate independent of the cel
nucleus
-control center of cell: directs protein synthesis (proteins are responsible for the structure and function of the cell)
-contains DNA: genetic material
-surrounded by nuclear envelope: double membrane, outer layer connected to ER
-has nuclear pores with regulator proteins that control exchange of molecules between cytoplasm and nucleus
-inside is DNA floating in nucleoplasm, with nucleotides, RNA, and protein enzymes!
the DNA-RNA hybrid
16-18 base pairs of DNA are unwound and the most recently made RNA is still bound to DNA
genetic code
-the language of the DNA that is read off a gene to assemble a protein
-3 bases of DNA = 1 codon
-each codon gives the instructions for one amino acid!
genetic information
-this is only 1.5% of total DNA
-the remainder is involved with the control of genes, some appear to be junk (25%)
-noncoding parts of DNA (non-genes) are highly variable from one person to the next
-variability allows for the identification of an individual by DNA fingerprinting!
-for a gene to be expressed (used to make a product) it must be unwound from the histone proteins so it can be read
gene activation (transcription)
-disassembly of the nucleosomes and unwinding of the DNA to copy the information
-controlled by signals from outside the nucleus, either from within the cell or in response to external cues (e.g.hormones)
transcription (DNA -> RNA)
-DNA unwounded and separated into coding strand and template strand and RNA polymerase binds to promoter on template strand
-RNA polymerase uses free nucleotides from nucleoplasm to complenmentary base pair to template strand of DNA to build RNA copy
transcription RNA process
-RNA produced exits the nucleus to the cytoplasm
-rRNA is assembled into ribosomes
-tRNA picks up amino acids!
-mRNA attaches to a ribosome
translation (mRNA -> protein)
-making a protein using the mRNA blueprint
-occurs in the cytoplasm on free ribosomes or fixed ribosomes on the RER
1. two ribosomal subunits make a ribosome to read the codons on the mRNA and facilitate peptide bonds
2. mRNA contains the codons from start to stop to encode all the amino acids in the primary structure of a protein
3. tRNA carries an amino acid prescribed by anticodon, and then the anticodon base pairs with the correct mRNA codon to ensure delivery of the correct amino acid
insertion mutation
add a base and change the reading frame; the whole protein after the mutation is wrong
sickle cell anemia
-point mutation in DNA: A->T
-changes one codon: GAG->!GTG
-changes one amino acid: glutamic acid (- charged) -> valine (neutral)
-alters the 3D shape of the whole hemoglobin protein: globular -> fibrous
-changes the shape of red blood cell:
disc ->crescent
-prevents the RBC from carrying oxygen, and causes it to block capillaries
deletion mutation
remove a base, alter reading frame, protein wrong
life cycle of a cell
-life depends on the type of cell
-all cells eventually die
-lysosomes are defused to prevent damage to other cells
-stem cells
-to divide, DNA must be replicated and equally distributed between the stem cell and the new daughter cell
stem cells
divide to replace dying cells
mitosis
nuclear division
interphase
-time that a cell performs its normal functions
-if a cell never divides, it remains in the G0 phase of interphase
-if the cell is preparing to divide, it will go through 3 stages in interphase: G1, S phase, G2
G1 phase (interphase)
cell doubles organelles and synthesizes enough cytoplasm for two cells
S phase (interphase)
cell duplicates DNA
G2 phase (interphase)
copious protein synthesis: cell generates enough enzymes for two cells, centrioles are replicated
DNA replication
- DNA helicases unwind the DNA and separate strands
- DNA polymerase binds to DNA and synthesizes complementary antiparallel strands
- DNA rewinds into double helix molecules, each new molecule contains one strand of original DNA and one new one
okasaki fragments
-DNA polymerase can only add to the 3’ end of a molecule so one strand (leading) is synthesized continuously while the other strand (lagging) is synthesized in pieces
-attached end to end into one strand by DNA ligase
prophase
-chromosomes condense and pair with duplicate sister chromatids attached by a centromere at the kinetochore
-nuclear envelope breaks down
-centrioles migrate to opposite poles
-spindle fibers form and attach to kinetochores
metaphase
-chromosomes align on the metaphase plate (middle)
anaphase
-centromeres split and sister chromatids are pulled to opposite poles by the spindle apparatus
telophase
-nuclear membrane forms
-chromosomes decondensed into chromatin
-spindle dissassembles
-cytokinesis occurs
cytokinesis
cytoplasm constricts at the metaphase plate forming a cleavage furrow that pinches the cell apart
cell division
-cell division is controlled by both internal and external factors
-in adults cell growth = cell death
-if growth exceeds death a tumor can form
benign tumor
grow in a connective tissue capsule and remain in one place!
malignant tumor
ignore growth control mechanisms: invade surrounding tissue and can metastasize to other locations in the body
primary neoplasm (1° tumor)
cells grow uncontrolled, usually appear and behave abnormally
2° tumor
cells metastasize in blood and lymph to establish new growth elsewhere
oncogenes
genes involved in cell growth, differentiation or division
spontaneous mutation
error rate of DNA polymerase, ~ 1 in 1 billion!
tumors
-tumors trigger the growth of blood vessels to support the cells (for diffusion to bring nutrients and remove wastes all cells have to be within 125μm of a vessel)!
-eventually, the tumor will crowd out normal cells and deprive normal tissues of nutrients causing organ failure and death!
mutagens
agents that can cause mutations in DNA (e.g. UV, cigarettes)
carcinogens
agents that cause cancer (e.g. UV is both a mutagen and carcinogen estrogen is carcinogenic but not mutagenic)
cell differentation
-all somatic cells in the body have the same DNA but different sizes, shapes, and functions
-differentiated cells only express genes related to their function; make a specific subset of all possible proteins, these limited proteins dictate the structure and function of the cell
differentation
as cells specialize to become a specific cell type many genes get turned off; cells can no longer make those proteins, usually this is permanent
embryotic stem cells
express all of their genes and become any cell type
partial differentiation
stem cells that are limited in what cell type they can become
