lecture 3 minus cell parts Flashcards
eukaryotic cells
cells that possess membranous organelles
makeup of the lipid bilayer (%)
75% phospholipids
20% cholesterol
5% glycoproteins
why must membranes be fluid?
- permits self healing
- allows for membrane growth
- permits fusion with other membranes
how is membrane fluidity regulated? (3)
- cells change the saturation of fatty acids
- saturated = straight
- unsaturated = “kinked”
- unsaturated allows for more space between fatty acids = more fluid - cells change cholesterol amount in membranes
- cholesterol acts as a fluidity buffer
- bulky molecule = increases fluidity
- planar nature of rings prevent movement = lower fluidity - temperature
- high temp - more fluid
why can only non polar molecules cross the membrane?
because non polar things are hydrophobic, things must be hydrophobic to cross
the membrane is impermeable to polar and charged things
integral membrane proteins
anchored to hydrophobic centre of membrane
assist in transport
integral membrane proteins
anchored to hydrophobic centre or membrane
assist in transport
transmembrane proteins
integral proteins that go all the way through
amphipathic
peripheral membrane proteins
bound to membrane by electrostatic interactions
hydrophilic
glycoproteins
membrane proteins bound to saccharides
only found on the outer side
glycocalyx
formed when the saccharides on glycoproteins and glycolipids join
receptors
bind specific molecules and send signals to the inside of the cell to change behavior
receptors
bind specific molecules and send signals to the inside of the cell to change behavior
linker proteins
connect cells and facilitate locomotion
cell identity markers
usually glycoproteins, help body cells or invaders identify cell types
passive transport
diffusion, osmosis
any type of transport that requires, no ATP
passive transport is driven by kinetic energy and concentration gradients
rate of diffusion is effected by: (2)
size of the particles
- bigger = slower
temperature
- high temp = faster molecules = more kinetic energy
diffusion
movement of particles down its concentration gradient
facilitated diffusion
the use of carrier proteins or ion channels (and aquaporins) to help substances cross the bilayer
this is how polar and charged substances can get through
ion channels
passage for facilitated diffusion
may be gated (require a signal before opening)
passive
can only transport one type or ion
carrier proteins
change shape to move solutes across membrane
specific to shape
passive
ex. used to bring glucose into the cell
aquaporins
channels to bring water into the cell
water can diffuse, but these are 50000 time faster
passive
active transport
transport needed to keep concentration gradients (CG) from diffusing
moves substances UP the CG
requires energy (ATP for primary, electrochemical potential for secondary)
how do cells maintain a negative membrane potential
sodium/potassium pump pumps Na out and K in in a 2:3 ratio, keeping the inside negative
primary active transport
moves solutes UP the CG using ATP hydrolysis
secondary active transport
uses electrochemical potential set up by primary active transport as energy
move two solutes at the same time
one solute flows down its CG and releases free energy for the second solute to move UP its CG
antiporters
when solutes in secondary active transport flow in opposite directions
symporters
when both solutes in secondary active transport flow in the same direction
endocytosis
movement into cells via a vesicle
active transport
exocytosis
movement out of cells via a vesicle
also called secretion in some cells
active transport
receptor mediated endocytosis
imports specific molecules into cells
phagocytosis
“eating” of molecules or invaders by phagocytic cells
important process for immune system
pinocytosis
“drinking” of dissolved tissues
cell takes in interstitial fluid and test for invaders (via lymphocytes)
transcytosis
movement of substances through the cells by endocytosis then exocytosis
osmosis
water moving from low solute concentration to high across a semipermeable membrane
isotonic
a solution with the same concentration as as cell in it
hypertonic
solution outside of the cell has a higher solute concentration compared to the inside
water will move out of the cell, and the cell will crenate
crenate
when a red blood cell shrinks due to osmosis in a hypertonic solution
hypotonic
solution outside of the cell has a lower concentration compared to in the cell
water will move into the cell, and the cell will lyse (hemolysis in RBCs)
hemolysis
when a red blood cell lyses or bursts
how to calculate if a solution is hyper, hypo, or isotonic
- add all percentages of ALL solutes (osmolarity)
- compared and determine what the environment is
- determine outcome of situation
osmolarity and what it determines
osmolarity is the total solute concentration of a solution, and it determines tonicity
tonicity
how a cell behaved when it is placed in a solution (shrink, lyse, …)
chromatin
transcriptionally active DNA that is loosely packed
where does transcription occur?
the nucleus
where does translation occur?
in ribosomes
chromosomes
Chromatin that has been supercoiled and condensed into a compact form
cytokinesis
division of the cellular components excluding the nucleus
interphase stages
g1, S, g2
g1 phase
cell growth and preparation for DNA replication
duplicates organelles and cytosolic components
centrosome replication begins
S phase
DNA replication happens in this phase
in preparation for mitosis
g2 phase
enzymes and other proteins are synthesized in preparation for division
cell growth continues
replication process is completed
prophase
nuclear envelope dissolves and chromatin condenses into chromosomes
mitotic spindle starts to form
clump of stuff under microscope
metaphase
chromosomes align at the equatorial plate
chromosomes in a line under microscope
anaphase
chromosomes are pulled by the mitotic spindle to either sides of the cell
appears to be being pulled under microscope
cleavage furrow starts in late anaphase
telophase
begins once chromosomes are at either side of the cell
nuclear envelopes form around new cells
cytokinesis
the division of the cytoplasm
starts in late anaphase with the cleavage furrow and ends after telophase
completes cell division
anatomy of a chromosome (in mitosis)
an unreplicated or replicatted chromosome are both called chromosomes
the two halves are called sister chromatids
chromatids are only existent in replicated chromosomes. if there is only one “strand,” it is a chromosome
pinched centre of a chromosome in mitosis
centromere
a complex of proteins that serves as the site of attachment for the mitotic spindle
kinetochore
telomeres
pieces of DNA at the ends of chromosomes that protect the ends from shortening
protect against nucleolytic degradation
how are telomeres added to chromosomes?
telomerase
diploid cell
a cell with 2 sets of chromosomes
formed during mitosis
haploid cell
a cell with only 1 set of chromosomes
haploid cell
a cell with only 1 set of chromosomes
formed during meiosis
full mitosis process
g1
S
g2
prophase
metaphase
anaphase (cytokinesis starts)
telophase
cytokinesis ends
meiosis 1
homologous chromosomes are segregated
crossing over happens, and recombination occurs to create genetic diversity
homologous chromosomes align at equatorial plate and separate
we are left with two nonidentical cells with a haploid set of chromosomes
meiosis 2
sister chromatids are segregated
chromosomes align at plate
chromosomes split
we are left with 4 nonidentical cells with a haploid set of chromosomes
prophase 1
tetrads form by synapsis of sister chromatids of homologous chromosomes
crossing over between non sister chromatids occurs
genetic recombination occurs
metaphase 1
homologous chromosomes align at equatorial plate
anaphase 1
separation of homologous chromosomes
telophase 1
cell splits
nuclear envelops form
creates two haploid cells
prophase 2
nuclear envelops dissolve
mitotic spindle starts to form
NO interphase between 1 and 2
metaphase 2
chromosomes align at equatorial plate
anaphase 2
chromosomes are pulled to either side
cytokinesis starts
telophase 2
Cells split
cytokinesis finishes
we are left with now 4 haploid daughter cells
synapsis
the joining of two homologous chromosomes during meiosis 1
facilitates genetic exchange
