Cell biology Flashcards
cell
Structural and functional
unit of living organisms
* All human cells originate
from a single fertilized egg
Development involves cell
replication & specialization
four main types of tissue in humans
connective tissue
epithelial
muscle
nervous tissue
what is epithelial tissue
Epithelial cells make up the epithelium. The cells come
from the surfaces of your body, like skin, digestive tract and
organs
how is cell diversity determined
genes -> proteins -> determined cell structure and function
each cell expresses only a subset of its genes
how big are cells (4)
cell sizes range from 5 to 100 micrometers
average cell nucleus is around 5 micrometers in diameter
micrometer = 1 - 1,000,000 of a meter
and 1 - 1000 of a millimeter
how small is a nanometer
1 nanometer = 1000 micrometers
viewing power of the human eye
down to 0.2mm
viewing power of light microscope
down to 0.2um
viewing power of the electron microscope
down to 0.2nm
what is mitosis needed for (4)
growth and repair
remember this
some cells are just too specialised to divide, and some cells divide very rapidly
explain G1 (first gap phase) of cell cycle (4)
growth and normal metabolic roles
explain S (synthesis phase) of cell cycle
DNA replication
explain G2 (second gap phase) of cell cycle (4)
growth and preparation for mitosis
what is interphase made up of
G1 - 2 - G2
In a normal human cell there are 46 chromosomes, also
called 23 pairs of chromosomes
In a cell in S phase, each chromosome doubles it’s DNA,
forming 2 chromatids, joined by a centromere
A DIPLOID cell has the full complement of chromosomes, a
HAPLOID cell has half
G1 phase (gap phase 1)
- growth & normal
cellular activity
S phase (synthetic phase)
- DNA replication
- 6-8 hours
G2 phase (gap phase 2)
brief, final preparation
for cell division
3-4 hours
prophase (4) (first part)
chromosomes condense and become visible
- nuclear membrane disappears
- mitotic spindle starts to form from centrioles
metaphase
chromosomes line up on equator
the spindle is fully formed
anaphase
chromosomes split at centromeres
Telophase
decondensation of chromatin
reformation of nuclear envelope
- cytokinesis
plasma membrane of cell
outer boundary of the cell, lipid bilayer (polar/non-polar) + proteins
highly dynamic and fluid structure
how is the phospholipid bilayer fluid in nature
because of chlorestrol, which is imbedded within the phospholipid bilayer, gives it a lot of its fluidity
Control centre of the cell
- control is mediated via
the DNA
nuclear envelope
chromatin
nucleolus
nuclear envelope
- double-membrane
- nuclear pores
- outer membrane is
continuous with Rough ER
chromatin (4)
- DNA / histone proteins
nucleolus
- produces ribosomes
rough ER
- cisternae/lamellae (sheets)
- studded with ribosomes
(protein/RNA subunits) - Site of protein synthesis
smooth (4)
tubular network (remember this 1)
steroid synthesis
- cholesterol synthesis
- drug metabolism
first thing the mRNA will encounter when leaving nucleus is _______ (4) (4)
rough ER
lysosomes
contain enzymes that “digest” unwanted molecules
what does the golgi apparatus do (4)
transport and sort the proteins made in the endoplasmic reticulum
what does cis mean in cellular biology (4)
close to in terms of proximity
what does trans mean in cellular biology
further way in terms of proximity
golgi apparatus and glucose transport
how can cells do bulk export (exocytosis)
secretory granule
nucleus, RER, and golgi interactions (4, the last part)
Nucleus - DNA directs
protein synthesis by
transcribing DNA into RNA
* RER - site of
translation/protein
synthesis by ribosomes
* Protein transported
to Golgi apparatus
* Proteins processed,
exit within lysosomes
or secretory granules
explain purpose of mitochrondia
Inner/Outer membranes
- form cristae
- high surface area
explain membrane of mitochondria
provides the energy
supply for the cell
* energy is adenosine
triphosphate (ATP)
cellular inclusions (4)
miscellanous components of cell
name some cellular inclusions (4)
pigments (e.g. melanocytes of the skin)
glycogen (e.g. liver cells)
lipid droplets (e.g. in fat cells)
cell projections
microvilli
cilia
microvilli
Increase the surface area
of a cell
Commonly involved in
absorption
Microfilaments for rigidity
cilia (4 last part)
Used for moving material along
(motility)
More rare
Microtubules for strength
Attached to a basal body
three man types of cytoskeletal structures
microfilaments (tinnest)
intermediate filaments (give the cell strength, they are thicker than microfilaments)
microtubules (like the train tracks for movement of molecules around the cell)
cell-cell connections
- tight junction
tight junction
intimate association
between membranes
of adjacent cells
-
* prevents substances
passing between cells,
forces them to go
through cells
* prominent in epithelial
cells (eg, lining the gut)
desmosome (4)
spot welding
providing attachment
strength linking
two cells
* Intermediate filaments
provide strength
* prominent in skin cells
gap junction (4)
“channels connecting
cytoplasm of two cells
proteins called
“connexins
prominent in cells
that work together
(eg, smooth muscle)
diffusion
The movement of atoms or small molecules from
an area of high concentration to an area of low
concentration, such that an equal and uniform
concentration is achieved
osmosis
is through a semi-permeable membrane (meaning that water can enter cell)
hypertonic
a solution that has a greater amount of solute than the solution you are comparing it to
hypotonic
a solution that has a lesser amount of solute than the solution you are comparing it to
three main transport mechanisms (4)
diffusion
facilitated diffusion
active transport
what can move through diffusion (4)
steroid hormones and water
facilitated diffusion (4) (4)
have a concentration gradient but the molecule cant get in because its incompatible with the environment of the membrane
does require a channel protein, but doesn’t require energy, but is also limited by the amount of components doing this facilitated diffusion
what is a rate limiting factor for facilitated diffusion
amount of channel proteins in membrane
active transport (4)
carrier-mediated
* energy required (from ATP)
* enables transport AGAINST
a concentration gradient
* eg: amino acids, ions
carrier vs channel protein
carrier will change shape when the molecule moves through but the channel is just open or shut and the shape doesn’t change whether or not a molecule is moving through
Channel Proteins: do NOT change
conformation when
molecule passes through
Passive transport
Carrier Proteins: change of conformation
when molecule passes
through
Active OR passive transport
sodium potassium pump carrier
- used to pump Na+ out of the cell against a concentration gradient
- ATP energy is used to force the Na+ out of the cell
*The pump protein changes conformation allowing K+ to
bind
- ATP energy is used to force the Na+ out of the cell
- the K binds
- the K+ is imported passively (no energy required)
- the cycle resumes
vesicular transport
exocytosis: explusion of bulk molecules from a cell
endocytosis: bringing in of bulk molecules into a cell
what are receptors (4)
integral membrane proteisn, but they do not do transport molecuels acvross the membrane
receptors are required to ‘signal’ to the cell interior that a molecule is docked on the outside of the cell
two types of endocytosis
pinocytosis:
phagocytosis:
cell signalling
cell signalling is a part of a complex system of cell communication that governs basic cellular activities and coordinates cell actions
ligand
is a signal that is bound by a receptor
the shape of a receptor only matches the ligand that binds it
two types of hormones
steroid hormones
peptide hormones
steroid hormones
bind intercellular receptors
e.g. estrogen, testosterone, cortisol
peptide hormones
bind membrane receptors
e.g. oxytocin, insulin, growth hormones
exocrine signalling
signalling/secreting to ducts/lumens and outside the body
exocrine glands:- salivary, sweat, gastrointestinal
contrast to endocrine signalling into the bloodstream where the target of signals is inside the body
the membrane of a resting cell is what
polarised (i.e. it is negative inside relative to outside)
electrical signal passes along the cell by a wave of + charge ion transport
Electrical Signals: controlling
channels by electricity
The sodium gate is a channel protein that is responsible for
propagating an electrical signal down a neuron. It opens in
response to a voltage change
Both The potassium gate AND the sodium/potassium
pump restore the resting membrane potential
Electrical signaling involves changing the
resting membrane potential (eg, depolarization)
* Local depolarization
action potential
(if magnitude of depolarization large enough)
Action potentials are a propagation of the
depolarization
