LECTURE 5 Flashcards
What are three ways for molecules to move across the membrane
1) diffusion (active transport)
2) facilitated diffusion
3) active transport
Diffusion (active transport)
Occurs best with small hydrophobic molecules (O2), which are soluble in the bilayer.
(Active transport) When a molecule is more once treated on one side of a membrane
Diffusion occurs until equilibrium is reached
Which molecules are from best to warts at diffusing across the membrane in active transport
Hydrophobic = BEST
Small uncharged polar = POOR
Large uncharged polar - RARE
Charges (small or large) = NEVER
Osmosis
Diffusion of water, but solute (sugar) cannot pass.
During osmosis, where dos water move from
Water moves from a place of Low solute concentration to higher clout ion concentration
Tonicity
The relative contraction of a solute in two solution separated by age range that it cannot pass.
- hypotonic
- isotonic
- hypertonic
Hypotonic (less solute)
ANIMAL: influx of water causes osmotic lysis (Lysed). Water going in
PLANT: turger pressure, turgid (normal)
Isotonic
ANIMAL: normal (water going in and out)
PLANT: flaccid (water going in and out)
Hypertonic (more solute)
ANIMAL: shriveled (water going out)
PLANT: plasmolyzed, cell shrinks, membrane pulls always from cell wall = plasmolysis
Types of diffusion or active transport
- osmosis
- tonicity
Facilitated diffusion
Passive transport aided by proteins (transport proteins)
Two types of transport proteins
- channel proteins
- carrier proteins
Channel proteins
A specific channel protein per one type of molecule, cell conditions determine whether closed or open
Two examples of channel proteins
Aquaporins: facilitates osmosis
Ion channel: allows specific ions
Carrier proteins
- undergo change in shape to trans locate a solute across a membrane.
- specific molecule transported down its concentration gradient.
Active transport
Used to move a substance against the concentration gradient
Active transport requires energy, which kind?
ATP
Why do cells do active transport
- to concentrate nutrients in the cell
- to expel waste
- establish (chemical/voltage) gradients
What kinds of proteins are involved in active transport
Carrier proteins, each septic to one substance
Animal cells Martin a high concentration of ____ and a low concetration of _____
High concentration of K+ and a low concentration of Na+
How do cells maintain Na and K levels, and what kind of energy does it use?
Sodium-potassium pump, uses ATP
ATP
Adenosine triphosphate, breaks down ADP +Pi and released energy
ADP
Adenosine diphosphate
Pi
Phosphate
Active trap org allows cells to establish and maintain
Concentration gradients
What are the steps (6) to the sodium-potassium pump?
1) cytoplasmic Na+ binds to the sodium-potassium pump.
2) Na+ blinding stimulates phosphorylation by ATP.
3) phosphorylation causes the protein to change its shape. Na+ expelled
4) K+ bonds and triggers release of phosphate groups
5) loss of phosphate restore proteins original shape
6) K+ released, cycle repeated
Because there are 3 Na going out for every 2 K going in, what does this cause
An imbalance in charge across the membrane, (more negative inside), causing ions to move
Membrane potential
The unique distribution of anions and cations across the plasma membrane.
Tow forces drive the diffusion of ions across the membrane
- a difference in concentration (chemical force)
- a different in charge (electrical force)
What do the 2 forces that drive ions to diffuse across membrane make
Electrochemical gradient
What kind of molecule flow done the electrochemical gradient
Charged molecules
Pumps are responsible for creating
Electrogenic pumps
For animals, an important electrogenic pump is the
Sodium-potassium pump
For planets, fungi, and bacteria the electrogenic pump is a
Proton pump.
Cotransporters
Transports a second substance against its own concentration gradient.
How can Big molecules (polysaccharides) be transported? And what does it involve?
Bulk transporting mechanisms involving the formation of vesicles
The membrane for bulk transport is
flexible and can bend into different shapes- pinching off into vesicles. This requires energy
Exocytosis
Exporting substances out of the cell
Processes of bulk transport
Exocytosis and endocytosis
3 types of endocytosis
1) phagocytosis
2) pinocytosis
3) receptor-mediated
Phagocytosis
Cell eating (vacuole)
Pinocysis
Cell drinking (vesicle)
Receptor-mediated
A mechanism involving receptors to import specific things
Recpetors are a sspecofc type of
Protein
Receptors receive chemical signals from _____
Ligands
Receptors-mediated endocytosis
Receptors binds to a ligand that the cell needs to uptake. Clathrin binds to these receptors on the inside of the cell, gathering them into a pit shape which forms the vesicle. Clathrin is released, ligand is consumed, receptors make their way back to the membrane.
Clathrin is a
Coat protein that helps facilitate vesicle formation
An example of receptor-mediated endocytosis is
Fat delivery to cells.
What kind of proteins transport fat to cells via the bloodstream
Lipoproteins
A lipoproteins has a surface
Monolayer of phospholipid and cholesterol
Lipoprotiens core consists of
Triacylglycerols and/or cholesterol
Which specific proteins associate with the fat droplet
Apolipoprotiens
When recpetors on the recipients cell recognize the apoprotein they promote
Endocytosis and the uptake of the fats.
LDL means
Low density lipoprotein
HDL means
High density lipoproteins
LDL
Low in density, high in cholesterol
HDL
High in density due to high protein / lipid ratio.
What do the proteins and lipid in HDL do?
They remove access cholesterol from blood vessels and transport it to the liver.
Which cholosterol is good / bad
HDL= good
LDL = bad
Primary active transport
Systems that perform active transport using ATP directly mediate
(EXAMPLE: Na+ / K+ pump)
Secondary active transport
Systems that use carrier proteins driven by ion gradients
Three descriptions of carrier proteins
1) uniporters
2) symporters
3) antiporters
Aniporters
transports only one type of molecule
Symporters
Transports two different molecules in the same direction
Antiporters
Transports two different molecule in opposite directions
Types of transport review card
1) passive transport -diffusion across membrane, NO energy use
2) active transport - uses energy to move solute against gradients
3) bulk transport - diffusion across plasma membrane using exocytosis and endocytosis
The cell membrane is a
Fluid barrier that separates the cell interior from the exterior
Is the cell membrane strong?
NO
Bacterial cell walls
Provides shape and protection.
Both bacteria and animal cells both contian a
Much higher concentration of many molecules, compared with their environment.
Bacterial cells walls are made of
Peptidoglycan
What are the tow major classes of cells walls and how are they distinguished?
1) gram positive
2) gram negative
They are distinguished based on how they are stained
Gram positive bacteria
- simple cell wall structure
- thick layer of peptidoglycan
- NO outer layer
Gram negative bacteria
- complex cell wall structure
- thinner layer of peptidoglycan
- outer membrane
- carbohydrate portion of lipopolysacchrdies.
(Causes fever due to lipopolysacchrides)
