Lecture 7: Cell Phy 3 Flashcards
What cellular functions is ATP needed for?
- Membrane transport
- Synthesis of chemical compounds
- Mechanical work
What’s an example of membrane transport?
Example: sodium transport
What’s an example of synthesis of chemical compounds?
Example: protein synthesis by ribosomes
What’s an example of mechanical work?
Example: supply energy needed for muscle contraction
What are the types of transport through the membrane?
- Diffusion
- Active transport
What are the types of transport proteins?
Channel proteins
Carrier proteins
What are channel proteins?
Watery spaces to allow movement of certain ions
What are carrier proteins?
Bind with molecules or ions to be transported
What is the function of transport proteins?
penetrate the membrane
What are examples of channel proteins?
Aquaporins
Aquaglyceroporins
Ion channels
How does diffusion occur.
- Occurs down a concentration gradient.
- Either through lipid bilayer or involves a protein “channel” or “carrier”
- No additional energy required
How does active transport occur?
- Occurs against a concentration gradient.
- Involves a protein “carrier.”
- Requires energy (ATP)
Sometimes transport of ions through a channel
protein is called ____ not ____.
facilitated diffusion not simple
diffusion
What type of transport moves molecules/ions without carrier proteins?
Simple diffusion
What type of transportation requires interaction of carrier protein with molecules or
ions?
facilitated diffusion
How do lipid-soluble move through the lipid bilayer?
Lipid soluble moves quickly through lipid bilayer
How does water move through the lipid bilayer?
Water is insoluble to lipid cell membrane, but travels quickly through channels in protein molecules
True/False: Protein channels are usually selectively permeable to certain substances
true
What are the two types of gates that open and close protein channels?
Voltage and chemical gates
How do voltage gates work?
Molecular conformation of gate responds to electrical potential
across cell membrane
Give an example of a voltage gate.
Example: strong – charge inside cell so Na-gates remain closed,
but when lose negative charge with action potential, gates open
and Na enters cell
How do chemical gates work?
chemical (ligand) binds to protein, changes conformation to protein which opens or closes gate
Give an example of a chemical gate.
Example: Acetylcholine channel – Ach binds to channel and opens
it to allow certain molecules and ions to enter
What is the most abundant substance to diffuse through the cell membrane?
Water; But normally it is balanced in both directions so there is essentially zero NET movement of water
What is osmosis?
concentration difference develops, the net movement of water = osmosis
What is osmotic pressure?
the amount of pressure required to stop osmosis
What causes osmotic pressure?
- caused by particles in a solution
- Equals the number of particles per unit volume
True/False: Each particle in a solution, regardless of mass, exerts the same amount of pressure against the membrane
True
What is osmolarity?
number of particles per liter of solution (e.g. osmoles per liter of solution)
What is osmolality?
= concentration of solution per unit of particles (e.g osmoles per kilogram of water)
What is more common in clinical practice osmolarity or osmolality?
osmolarity
What are two examples of substances that need to be transported via facilitated diffusion?
Glucose and amino acids
Explain Primary Active Transport.
- Molecules are “pumped” against an electrochemical gradient at the expense of energy (ATP).
- direct use of energy
Explain secondary active transport.
- Transport is driven by energy stored in ionic concentration differences between two sides of membrane in the electrochemical gradient of another molecule (usually Na+).
- indirect use of energy
True/False: Both primary and secondary active transport depend on carrier proteins that penetrate through membrane
True
Where is the sodium-potassium pump located in animal cells?
On plasma membrane
What is the function of the sodium-potassium pump?
- Pumps sodium ions OUT of cell membrane
- Pumps potassium ions INTO the cell
- Regulates osmotic balance by maintaining Na+ and K+ balance across cell membrane
- Basis of nerve function for transmitting nerve signals
What is the basis of nerve function for transmitting nerve signals?
sodium-potassium pump
How much energy does the sodium-potassium pump use?
Requires about 1/5 of typical cell’s energy and up to 2/3 of neuron’s energy
How is the sodium-potassium pump activated?
Pump is activated by an increase in cell volume
What controls the volume of the cell so it doesn’t burst?
Sodium-potassium ion pump
Describe the structure of the sodium-potassium ion pump.
- Three receptor sites bind sodium inside cell
- Two receptor sites bind potassium outside cell
How does the sodium-potassium ion pump work?
- When ions are bound, activates ATPase part of protein, cleaving ATP and releasing energy, extruding 3 sodium out
of cell (and water passively) and bringing 2 potassium into cell - Creates negative electrical voltage inside cell interior, creating electrical potential across cell membrane as it pumps
Is the sodium-potassium ion pump primary or secondary active trasnport?
Primary active transport
What is counter-transport
- Transport in the opposite direction of the primary ion
- Sodium (retained) and hydrogen (excreted) (e.g. in renal tubule)
What are the protein cotransporters in secondary active transportation?
symporters or antiporters
What do symporters do?
transport substance in same direction as a “driver” ion like Na+.
What do antiporters do?
transport substance in opposite direction of a “driver” ion like Na+
Where does active transport occur in the human body?
This type of transport occurs in intestine, renal tubules, gallbladder
RNA controls ___ formation.
protein
Cellular proteins are either ___ or ___.
structural or enzymes catalyzing cellular reactions
Which is more common: structural proteins or enzymes catalyzing cellular reactions?
enzymes
Proteins provide ___ to a membrane.
specificity
What is the function of Messenger RNA?
Carries genetic code to cytoplasm to control protein formation
What is the function of transfer RNA?
Transports activated aa to the ribosomes to be used in assembling protein molecules
What is the function of ribosomal RNA?
Forms ribosomes where protein is assembled
True/False: Most mutated cells die
True
How to cells control their growth?
Growth factors from blood or adjacent tissue and they stop growing when there is no more room to grow
Negative feedback with ___ cellular secretions
increased
What causes cancer?`
- abnormal cell growth and mitosis
- Mutation/abnormal activation of cellular genes for Loss/inactivation of antioncogenes -> oncogenes ->cancer
What is the function of feedback mechanisms?
prevent excessive growth and make it so that only a few cells which survive become cancerous
True/False: A lack of sleep has links to cancer?
True
What happens during facilitated diffusion?
substance diffuses through a membrane with carrier protein
How does insulin affect glucose?
insulin increases the rate of glucose diffusion by 10-20 fold
What are common carrier proteins in facilitated diffusion?
glucose and amino acids
