Chapter 3 - Cell Structure Flashcards
cells
- basic functional unit of the body
- variety of shapes and sizes
- similar cells grouped together to form tissue
phospholipid bilayer
- semi-permeable double sided membrane
- barrier seperating the intracellular from extracellular environment
- made up of phospholipids and proteins
Plama Membrane
phospholipids
- arrangment based on affinity of polarity
- polar head groups: form the exterior (next to polar water)
- nonpolar fatty acids: form hydrophobic center
Plasma Membrane
Hydrophobic center restricts the movement of:
polar molecules: water
hydrophilic: water soluble molecules
charged molecules: ions
steriods can pass through on their own
integral proteins
span the entire plasma membrane (channels, carriers, transporters)
peripheral proteins
found on either side of the plasma membrane (enzymes, receptors, structural support)
fluid mosaic model
proteins and phospholipids are not trapped in the membrane but move laterally
(not static, they can change as needed)
(localized distribution of proteins aids in function)
cilia
tiny, hair-like structures composed of microtubules that project from the plasma membrane
* found in respiratory tract and uterine tubes (eggs travel by using the cilia)
* found in almost every cell in the body
cystic fibrosis
- hereditary disease in which cells make chloride pumps, but fail to install them in the plasma membrane
- thick mucus plugs pancreatic ducts and respiratory tract
flagellum
- a single whip/tail like structure that can propel a cell forward
- composed of microtubules
- sperm is the only cell in the human body with a flegellum
microvilli
folds in the plasma membrane that increase the surface area for rapid diffusion
* examples: intestines and kidney tubules
phagocytosis
- process by which manipulation of the entire cell structure allows for cell to extend around large substances
pseudopods
- pseudopods engluf bacteria and dead cells and then fuse together to form a food vacuole
- the food vacuole fuses with a lysosome and the bacteria is digested
- white blood cells can perform amoeboid movement by extending pseudopods (false feet) to pull the cell forward
endocytosis
- another strategy for bringing large materials (extracellular fluid) into the cell
- a small part of the membrane surrounding the substances pinches off and is brought in as a vesicle
pinocytosis vs receptor-mediated
pinocytosis: non specific endocytosis
receptor-mediated: specific endocytosis
exocytosis
- large cellular products (proteins) are moved out of the cell
- the golgi apparatus packages proteins into vesicles that fuse to the plasma membrane and concents spill out of the cell
exocytosis - nerve endings
synaptic transmission: neuronal communication
critical for our nervous system (used in signals)
cell transport
what structure is selectively permable?
the plasma membrane is selectively permable, meaning that it allows some molecules to cross but not others
- nutrients in, harmful substances out
- keeps needed substances for cellular function inside
passive transport
- does not require energy
- molecules move from higher to lower concentration
(down the concentration gradient)
active transport
- requires energy in the form of ATP
- molecules move from lower to higher concentration using ATP (against its concentration gradient)
examples of passive transport
- simple diffusion
- lipid soluble molecules
- ions - channel mediated
- water - osmosis
- facilitated diffusion
simple diffusion
- solution: consists of a solvent (water) and a solute (molecules dissolved in water)
- occurs when there is a concentration difference between 2 regions, random motion will establish equilibrium via diffusion
- move solute (molecules) down its concentration gradient from high to low
- net diffusion becomes zero, when the concentration of molecules becomes equal on both sides
gated channels
- gated channels need a stimulus to open them, so ions can freely flow through
- from high to low
- example of passive transport
Passive Transport
facilitated diffusion
- movement of large, polar substances across the plasma membrane by carrier proteins
- ineract with molecules that are too large to cross the membrane on their own.
* conformational change in structure of carrier protein upon binding - net movement from high to low concentration (down the gradient)
Osmosis
- the diffusion of water across the plasma membrane
-
diffusion of a solvent instead of a solute
Requirements: - there must be a solute concentration difference on either side of a membrane permable to water
- the membrane must be impermeable to the solute, or the concentration difference will not be maintained
water moves from area of low solute to an area of high solute concentration
osmotically active
solutes that cannot cross and permit osmosis are called osmotically active
osmolality
- used to determine the direction of water movement during osmosis
- osmolality: total molality of a solution when you combine all the molecules within it
- no net movement of water
tonicity
the effect of a solute concentration on the osmosis of water
isotonic
a solution with the same osmolality as the inside of a cell
hypotonic
a solution with a lower osmolality than the inside of a cell
hypertonic
a solution with a higher osmolality than the inside of a cell
active transport
- moves large polar molecules and ions using carriers (pumps)
- movement from an area of low to high concentration (against gradient)
- requires energy: ATP
- 2 forms: primary + secondary active transport
primary active transport
- directly unitlizes the energy released by the hydrolysis of ATP
- pump is activated by phosphorylation using a phosphate (Pi) from ATP
- hydrolysis ATP -> ADP
steps of primary active transport
- Ca2+ binds
- activates the ATPase function
- Pi bonds and ADP is released causing a shape change and Ca2+ to be released extracellularly
- Pi is removed and the carrier protein goes back to its orginal shape, ready for Ca2+ to bind again
Na+/K+ Pump
- found in all body cells
- ATPase enzyme that pumps 3 Na+ out of the cell and 2 K+ into the cell, both moved against thier concentration gradients
3 functions of Na+/K+ Pump
- provides energy for coupled transport of other molecules (used in secondary active transport)
- produces electrochemical impulses in neuron and muscule cells (keeps membrane potential negative)
- maintains osmolality (promotes water movement)
steps of Na+/K+ Pump
- 3 Na+ bind activate ATPase
- Pi bonds ADP released causing a conformational change, 3 Na+ released extracellularly
- 2 K+ bind, Pi released
- Conformational change again and 2 K+ released intracellularly
secondary active transport
- indirectly utilizes the energy released by the hydrolysis of ATP
- The Na/K pump maintains a high extracellular concentration
- as Na+ moves back into the cell other molecules are transported by the same carrier protein (cotransport)
sccondary active transport
cotransport:
the other molecule is moved with sodium (moved in the same direction)
* common way to transport glucose
sccondary active transport
countertransport
the other molecule is moved in the opposite direction from sodium
carrier-mediated transport characteristics:
specificity
carrier proteins interact only with specific molecules
carrier-mediated transport characteristics:
competition
2 different molecules can be transported by the same carrier, but they compete for the carrier protein
carrier-mediated transport characteristics:
saturation
when all the carrier proteins in a cell are being utilized to move molecules, they are said to be saturated and have reached the Transport Maxium (Tm)
working as hard as possible, similar to enzymes (can only work so fast before they plateau
cytoplasm
- cellular region between the nucleus and the plasma membrane
- has a combination of organelles and cytosol (fluid)
cytosol
- fluid that suspends the organelles
- composed of water and many dissolved substances
- comprised of protein fibers - microfilaments and microtubules (which act as a cytoskeleton)
cytoskeleton proteins
- support cells shape
- quick reorganization of intracellular environment (contraction of muscle cells)
- form the spindle apparatus that pulls
- serves as a “railroad system” for vesicles and organelles to move along
lysosomes
- package of enzymes bond by a membrane
- tend to be acidic
- has lots of different enzymes so it can metabolize many different things
autophagy
digestion of cell’s surplus organelles
apoptosis
programmed cell death
(lysosomes burst, release all its acid to kill the cell
peroxisomes
- resemble lysosomes but contain differnt enzymes and produced by ER
- rxns produce hydrogen peroxide
- catalase breaks down excess peroxide to H2O and O2
- neutralize free radicals, detoxify alcohol, other drugs
- break down fatty acids into acetyl groups for mitochondrial use in ATP synthesis
mitochondria
- sites of energy production
- has an inner and outer membrane which is separated by an intermembranous space
- inner membrane is folded into cristae
- most cells have mitochondria
ribosomes
- protein factories of the cell
- messenger RNA (mRNA) takes genetic info to the ribosome so a protein can be assembled (protein synthesis)
- found free in the cytoplasm or with the rough ER
- broken into 2 subunits composed of proteins and ribosomal RNA (rRNA) while not in use
mRNA vs rRNA vs tRNA
mRNA: messanger RNA (takes genetic info form the nucles into the cytoplasm to be transcribed into protein (by the ribosome)
rRNA: ribosomal RNA (subunit of ribosome)
tRNA: transfer RNA (adds aa to the mRNA at the site of the ribosometo make protein strand)
rough ER
- rough ER is also called the granular ER
- has ribosomes
- functions in protein modification
smooth ER
- smooth ER also called agranular ER
- has many functions depending on the cell
golgi apparatus
- consists of stacks of flattened sacs
- modifies proteins receieved from the ER
- these are packaged in vesicles and bud off to fuse with the plasma membrane for exocytosis
cell nucleus
most cells have 1 nucleus, mucle cells have hundreds, RBC’s none
* the nucleus is enclosed by the nuclear envelope made of 2 membranes:
1. outer: continuous with rough ER
2. inner
* nuclear pores, join the 2 membranes together
functions of nucleus
- control center of the cell
- transmits genetic information (cell division)
- DNA –> DNA (replication)
- initiation of protein synthesis
- DNA –> mRNA (protein synthesis)
