Chapter 3 Flashcards
prokaryotic cells
simple cells with no nucleus
eukaryotic cells
complex cells with a nucleus & sub cellular structures (organelles)
all eukaryotic cells are composed of (3) main parts
1) plasma membrane
2) cytoplasm
3) nucleus
1) plasma membrane
2) cytoplasm
3) nucleus
1) outer boundary & separates cells internal environment from outside
2) gelatin-like substance + structural fibers b/w pm & nucleus - includes organelles (not nucleus)
3) contains genetic library of cell
cytoplasm
(2) components
1) cytosol - fluid portion
2) organelles - subcellular structure embedded in cytosol
Plasma Membrane - functions
covers, protects, controls in/outflow, links to other cells, tells other cells who it is (flying flags)
Fluid Mosaic Model
arrangement of molecules within the membrane
- resembles sea of phospholipids with protein “icebergs” floating in it
- Lipids act as barrier to certain polar substances
- proteins act as gatekeepers, allowing passage of specific molecules/ions
phospholipids
form lipid bilayer - cholesterol & glycolipids
Integral proteins
extend into/through bilayer
(2) Integral proteins
transmembrane
peripheral
Transmembrane proteins
(most integral proteins) span the entire lipid bilayer.
Peripheral proteins
attach to inner or outer surface but don’t extend through membrane
Structure of the membrane
phosphlipids
integral proteins
2 back-2-back layers of phospholipid molecules (& cholesterol & glycoproteins)
polar head faces water on inside & outside
the plasma membrane’s arrangement is due to…
amphipathic nature of lipid molecules
Glycoproteins
membrane proteins with carb group attached that protrude into ECF
Glycocalyx
entire sugar-coating surrounding membrane
- carb portion of glycolipids & glycoproteins
-
Glycocalyx enables…
WBCs to detect foreign organisms, allows cells to adhere to one another & protects cells from enzymes in ECF
Functions of the membrane (5)
ion channels carrier receptor enzymes cell-identity markers
Examples of different membrane proteins include (6)…
1) ion channels (integral)
2) carriers (integral)
3) receptors (integral)
4) enzymes (integral & peripheral)
5) linkers (int. & perip)
6) cell-identity markers (glycoprotein)
1) ion channels (integral)
allow ions to move through water-filled pore
2) carriers (integral)
aka transporters
carries specific substances across membrane by changing shape
(ex. amino acids)
3) receptors (integral)
recognizes specific ligand & alters cells functions in some way.
4) enzymes (integral & peripheral)
catalyzes rxn inside or outside cell (depending on which direction active site faces)
5) linkers (int. & perip)
anchors filaments inside & outside PM providing structural stability & shape for cell
- may also help movement or link 2 cells together
6) cell-identity markers (glycoprotein)
distinguishes your cells from anyone else’s
selective permeability
membrane allows some substances across (small, non polar) but not others (large, polar)
Rule of Thumb about Selective Permeability
small neutrally-charged lipid-soluble substances can freely pass
Exception to the Rule of Thumb about Selective Permeability
Water is a special case
- highly polar but still can pass b/c of its small size
How do impermeable substances cross the PM?
transmembrane proteins that act as channels & transporters
[O2] & [Na+]
a) inside cell (cytosol)
b) outside cell (ECF)
a) [lower]
b) [higher]
[CO2] & [K+]
a) inside cell (cytosol)
b) outside cell (ECF)
a) [higher]
b) [lower]
Charge of:
a) inner cell surface
b) outer cell surface
a) negatively charged
b) positively charged
the negative charged inner surface and the positively charged outer surface creates a…
electrochemical gradient (membrane potential)
Transport Processes
passive processes
active processes
Passive processes (3)
a) diffusion of solutes
b) diffusion of water (osmosis)
c) facilitated diffusion
Diffusion
passive spread of particles through random motion from areas of [high] to [low]
Diffusion is affected by the amount of ___ & ___ of ___ ___
substance & steepness of concentration gradient
Diffusion is also affected by (3)
1) temperature (fever)
2) surface area (emphysema)
3) diffusion distance (pneumonia)
Passive Transport Processes - types of diffusion (3) (not including osmosis)
a) simple diffusion
b) channel-mediated facilitated diffusion
c) carrier-mediated facilitated diffusion
a) simple diffusion
when substances move through lipid bilayer without transport proteins
- non-polar hydrophobic molecules move this way
b) channel-mediated facilitated diffusion
process where solutes move down [gradient] through membrane channel
- small hydrophillic molecules
- gates operate randomly or mediated by electrical/chemical changes
c) carrier-mediated facilitated diffusion
process where carrier protein moves solute down [gradient]
- solute binds to carrier on one side & is released on other side when carrier changes shape
(# of carriers limit speed)
Is Simple Diffusion or Channel-Mediated Facilitated Diffusion slower? Why?
Channel-mediated facilitated diffusion is slower b/c of small SA of transmembrane protein
Example of channel-mediated facilitated diffusion
passage of K+ ions through gated K+ channel
Example of carrier-mediated facilitated diffusion
glute 4 transportes
- passage of glucose across cell membrane
Osmosis
net movement of water through selectively permeable membrane from area of high [water] concentration to one of lower [water]
Osmosis only occurs when..
membrane is permeable to water & not solute
water can pass through PM in (2) ways
1) through lipid bilayer (by simple diffusion)
2) through aquaporins (integral membrane proteins)
osmotic pressure
force generated by movement of water from [high] to [low] of water
minimum pressure which needs to be applied to solution to prevent inward flow of water across a semipermeable membrane
Active transport processes
transportation of solutes against concentration gradient by using energy
Primary active transport
ATP changes shape of carrier protein which pumps substance across membrane against gradient
Primary active transporters are also known as…
pump
Cells expend __%of the ATP they produce on primary active transport
~40%
Primary active transport
- pushes __ out & __ into cell in order to maintain…
Na+ out
K+ in
to maintain low [Na+] inside cell & [K+] outside
secondary active transport (co-transport)
energy stored in Na+ or H+ gradient is used to drive other substances across their own gradients
- indirectly uses energy from ATP
Secondary Active Transport Mechanisms (2)
1) Antiporters
2) Symporters
1) Antiporters
carry 2 substances across membrane in opposite directions
2) Symporters
carry 2 substances across membrane in same direction
Example of Antiporter
Na+ in
Ca2+ out
Na+ in
H+ out
Example of Symporter
Na+ & glucose/amino acid in
Vesicle
small spherical sac formed by budding off from membrane
Endocytosis
materials move into a cell in a vesicle formed from the plasma membrane
(3) types of Endocytosis
1) receptor-mediated endocytosis
2) phagocytosis
3) bulk-phase endocytosis (pinocytosis)
Exocytosis
materials move out of cell by fusion of vesicle formed inside cell with PM - releases contents into ECF
Transcytosis
combination of endocytosis & exocytosis
Receptor-Mediated Endocytosis - steps
1) binding
2) vesicle formation
3) uncoating
4) fusion with endosome
5) recycling of receptors to PM
6) degradation in lyosome
Receptor-Mediated Endocytosis
1) binding
2) vesicle formation
3) uncoating
4) fusion with endosome
5) recycling of receptors to PM
6) degradation in lyosome
1) LDL particle binds to receptor
2) invagination of clathrin-coated PM to form vesicle
3) uncoating of clathrin
4) fusion of vesicle with endosome
5) receptors are recycled back to PM
6) lysosomes degrade remaining molecules
Phagocytosis
pseudopods engulf microbe attached to
- forms phagosome, fuses with lysosome
lysosomal enzymes digest leaving residual body
- secreted via exocytosis or remain stored in cell as lipofuscin granules
Pinocytosis (bulk-phase endocytosis)
non-specific - inward folding of PM forms vesicle containing droplet of ECF
- vesicle detaches from PM & enters cytosol
-fluid & dissolved solutes in vesicle
fusion of lysosome & vesicle -
digestion of solutes by lysosmal enzymes
(2) Components of the cytoplasm
1) cytosol
2) organelles
1) cytosol
intracellular fluid surrounding organelles
75-90% water
- site of many chemical rxns which provide building blocks for cell maintenance, structure, function & gowth
2) organelles
Specialized structures within the cell, each with specific enzymes
Cytoskeleton
network of protein filaments throughout cytosol
that provides structural support for cell
(3) types of protein filaments of the Cytoskeleton
1) microfilaments
2) intermediate filaments
3) microtubules
1) microfilaments
thinnest
- composed of proteins actin & myosin
functions in structure (provides support) & movement (muscle contractions)
2) intermediate filaments
second largest/widest
- help stabilize organelles & attach cells to one another
3) microtubules
Largest
- composed of protein tubulin
- attached to centromeres
- help determine cell shape
- function in movement of organelles/xsomes/cilia/flagella
Centrosome
located near nucleus, consists of 2 centrioles (right angles) & periocentriolar material
- organizing centre important in cell division
Cilia
short, hair-like projections from the cell surface, move fluids along a cell surface
Flagella
longer than cilia, move an entire cell
only example is the sperm cell’s tail
endoplasmic reticulum
network of membrane in shape of flattened sacs/tubules
ribosomes
site of protein synthesis
Rough ER
series of membrane sacs connected to nuclear envelope
- surface studded with ribosomes to produce proteins
Smooth ER
network of membrane tubules, no ribosomes but contains enzymes that play key role in synthesis of FAs & steroids, detox of certain drugs (alcohol)
Golgi complex
consists of 3-20 flattened, membranous sacs called cisternae
Cisternae
the flattened, membranous sacs of the Golgi Complex
Golgi Complex - proteins & packaging
1) transport vesicle from rough ER transported to cis face
2) fuse with cis face membrane & empty contents into lumen
3) proteins are modified (enzymes add carbs (glycoprotein) or lipids (lipoprotein) in the medial cistern
4) sort & package proteins for transport to different destinations on trans face
proteins are sorted & packaged into (3) vesicles
1) secretory - proteins exported from cell by exocytosis
2) membrane - proteins in vesicle membrane merge with PM
3) transport - to bind with lysosome
Lysosomes
vesicles formed from Golgi complex that contain powerful digestive enzymes that break down molecules within vesicles formed during endocytosis
(2) mechanisms of lysosomes
1) autophagy
2) autolysis
1) autophagy
the process of engulfing other organelles, digesting them & returning their components to the cytosol
2) autolysis
process of destroying cells that contain them
Peroxisomes
found where?
organelles smaller than lysosomes that detoxify (contain oxidases) several toxic substances
- abundant in the liver
Proteasomes
- function
- location
- contain
continuously destroy unneeded, damaged or faulty proteins
- found in cytosol & nucleus
- contain proteases that breakdown proteins in aa for recycling
Mitochondria
generate. .
have. .
powerhouse of cell
- generate ATP through aerobic respiration
- self-replicate
- contain own DNA (from mother)
- have inner & outer mito. membrane with folds in inner membrane (cristae) & a central fluid-filled cavity (matrix)
Mitochondria are more prevalent in which cells?
physiologically active cells such as muscle, liver & kidney cells
– How would you increase the # of mitochondria in muscle cells?
aerobic activity/exercise at a lower intensity
Cristae
series of folds of the inner membrane
Matrix
large central fluid-filled cavity
Mitochondria self-replicate when? (2)
during times of increased cellular demand or before cell division
Mitochondria are located ?
within cell where O2 enters or ATP is used
Where are the enzymes that catalyze cellular respiration located in the mitochondria?
located on the cristae & in matrix
Nucleus
spherical/oval structure with a nuclear envelope, nuclear pores, nucleoli, genes & chromosomes
Nuclear Envelope
double membrane that separates nucleus from cytoplasm (outer membrane continuous with rough ER)
Nuclear pores
numerous opening in nuclear envelope that control movement of substances b/w nucleus & cytoplasm
Nucleoli
spherical body in nucleus that produces ribosomes
Genes
cells hereditary units arranged along xsomes
- that control activities & structure of cell
Chromosomes
long molecules of DNA combined with protein molecules
Transcription
DNA → RNA → mRNA
promotor region initiates transcription of gene
RNA polymerase unwinds double helix and adds matching RNA nucleotides until terminator sequence is reached
Translation
(1) initiation
mRNA → protein
initiation begins when small subunit of ribosome attaches to 5’ end cap & moves to initiation site
- tRNA with complementary anticodon binds to start codon (AUG).
- large subunit now binds to create P & A site.
Translation
(2) elongation
- a 2nd tRNA occupies P site.
- aa from first tRNA (met) is transferred to A site aa & then exits.
- ribosome moves along mRNA (shifting 2nd tRNA to P site) & next tRNA enters
- growing peptide continuously transferred to A-site tRNA
Translation
(3) termination
- continues until stop codon is encountered & release factor enters A site
- translation terminated →ribosome dissociates & newly formed polypeptide (protein) is released
Somatic Cell Division - Mitosis
each daughter cell is genetically identical to the parent cell
Somatic cells
any cell other than a germ cell (reproductive cell)
Cell Cycle
sequence of events in which a body cell duplicates its contents & divides into 2
Human somatic cells contain ___ pairs of xsomes
23
total of 46
homologous xsomes (homologs)
the 2 xsomes that make up each pair
diploid cells
somatic cells that contain 2 sets of xsomes
Cell Division - Cell Cycle
(2) phases
1) Interphase
2) Mitotic phase
1) Interphase
cell is NOT dividing
- replicates its DNA
consists of (3) phases
(3) phases of Interphase
1) G1
2) S
3) G2
1) G1
1) metabolically active, duplicates organelles & cytosolic components, centrosome replication begins
2) S
DNA replicated
3) G2
reaches max size
- centrosome replication completed
- enzymes & proteins synthesized
length of time for
1) G1
2) S
3) G2
a) 8-10 hours
b) 8 hours
c) 4-6 hours
2) Mitotic Phase
consists of nuclear division (mitosis) & cytoplasmic division (cytokinesis) to form 2 identical cells
Nuclear Division: MITOSIS
(4) phases
1) prophase
2) metaphase
3) anaphase
4) telophase
1) prophase
chromatin fibers condense into xsomes
2) metaphase
microtubules align centromeres of chromatid pairs at metaphase plate
3) anaphase
chromatid pairs split at centromere & move to opposite poles of cell
4) telophase
2 identical nuclei are formed around identical sets of xsomes now in their chromatin form
Cytokinesis
division of cells cytoplasms to form 2 identical cells
When do Cytokinesis begin?
usually in late anaphase (before telophase)
Cytokinesis: process
plasma membrane constricts at its middle forming a CLEAVAGE FURROW
- cells eventually splits into 2 daughter cells
Once Cytokinesis is complete, what happens?
Interphase begins
average adult has __ __ cells
nearly 100 trillion
__ different types of cells
200
cellular diversity permits __ of cells into more __ __ & __
organization
complex tissues & organs
largest human cell
female egg cell - about the diameter of a human hair
telomeres
DNA sequences found at tips of each xsome
Telomeres - function/purpose
protect xsomes from sticking to one another & from erosion
Aging & Telomeres - shortening
normal cell divison shortens telomeres & after many years telomeres become significantly shorter
- also stress shortens telomeres
Aging & Glucose
glucose is added to proteins creating crosslinks with neighbouring proteins - decreases elasticity
Immune System & Aging
may attack bodies cell
- caused by changes in cell-indentity markers thus marking cell for destruction
Hydrostatic pressure
pressure which is exerted on portion of a column of water as a result of the weight of the fluid above it
pressure exerted by a fluid at equilibrium at given point within the fluid, due to force of gravity
Sodium-Potassium Pump
works to maintain a [low Na+ ] and a [high K+] in cytosol
- binding of 3 Na+ triggers hydrolysis of ATP & phosphorylates pump protein
- reaction changes shape of pump protein, expelling 3 Na+ into ECF & binds 2 K+
- triggers release of P which causes shape change & releases the 2 K+ into cytosol
