Maintaining Homeostasis: Control of the Cell's Internal Environment Flashcards
Phospholipid Head region
polar (slightly charged), hydrophilic “water-loving”
Tail region
non-polar (no charge), hydrophobic “water-fearing”
cholesterol molecule
helps maintain the fluid conditions of the bilater
integral protein
channel for ions + larger molecules to get into and out of the cell
peripheral protein
connected to cytoskeleton filament
alphahetic protein
channel for nutrients entering the cytoplasm
gycoprotein
protein with attatched carbohydrates
carbohydrate
involved in cell recognition as receptors for things like hormones + insulin
In order for the ___to survive. it needs to ___what goes in and out of it.
cell
control
Cell membrane is set up to do?
hydrophilic
hydrophobic
What will hydrophilic heads do?
repel uncharged molecules, like CO2
What will hydrophobic tails do?
repel charged molecules, like NA2+
Will small particles pass through the cell membrane freely?
yes
The cell needs to allow certain things inside (food, water, hormones, ions, etc) and things to leave (wastes, poisons, etc.). It does this either___(__ __ __), or ___(__ __)?
passively (without using energy)
actively (requires energy
What is passive transport?
The movement of molecules across the cel lmembrane without the expenditure of chemical energy (ATP).
Why does passive transport take place?
Some molecules are able to apss through tiny gaps in the cell membrane.
What are the four types of passive transport?
diffusion
osmosis
facilitated diffusion
ion channels
What is the concentration gradient?
all particles will naturally move from an area of high concentration to an area of low concentration.
What is diffusion?
The movement of small molecules (oxygen, carbon dioxide) from an area of high concentration to an area of low concentration.
What is concentration?
The number of molecules divided by the volume.
Diffusion occurs in___and___via random movement (collisions, bouncing).
liquids and gases
Diffusion requires only the energy provided by what? Why?
heat since a large amount of motion cannot occur in frozen cells.
What does increasing temperature cause the molecules to do in diffusion?
causes the molecules to move more rapidly therefore they collide more often and diffuse more rapidly
Diffusion will occur until there is no what? At this point, we say that___has been reached?
no net movement from one area to another
equilibrium
What is osmosis?
The natural movement of water across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.
What is the opposite of osmosis?
diffusion
How many different types of solutions are there that effect the movement of water in and out of a cell?
three
What is a solution
solvent (water) + solute (dissolved materials, like salt)
What are the three types of solutions with osmosis?
1) Isotonic Solution
2) Hypertonic Solution
3) Hypotonic Solution
What is an isotonic solution?
Total dissolved solutes is equal in both environments (inside and outside the cell).
What is a hypertonic solution?
A greater solute concentration outside of the cell results in a lower concentration of water outside of the cell, water moves to the areas of lower concentration, thereby leaving the cell.
What is a hypotonic solution?
Less solute concentration on the outside of the cell, therefore water moves into the cell.
What is a solute?
A substance tha tis dissolved in a fluid. Example, sugar is a solute that is dissolved in water.
What is a solvent?
Is the fluid that a solute is dissolved into. Example, sugar is the solute tha is dissolved in water (solvent).
What is a solution?
The outcome of the solute (sugar) being dissolved in a solvent (water). Example, sugar dissolved in water would make a solution of “sugar-water”.
What is diffusion?
movement of molecules (particles) from an are of high concentration to another area of lower concentration. (spreading out evenly+equilibrium).
What is osmosis?
Diffusion of water through a cell membrane from an area of high (water) concentration to an area of low (water) concentration.
Hypertonic means the solution has ___solvent and___solute than inside the cell.
less
more
Hyoptonic means the solution outside the cell has___solvent and___solute than inside the cell.
more
less
When the solvent and solute concentration inside a cell is the same as the solution outside the cell- the outside solution is called___?
isotonic solution.
In an isotonic solution, will water still diffuse in an out of a cell?
Yes, but the % concentration will always be equal between inside and outside of the cell.
relationship between concentration gradient and diffusion?
concentration gradient: particles will naturally move from high to low concentration
diffusion: the movement of particles from high to low concentration
the relaionship between osmosis and turgor pressure?
osmosis: diffusion of water through a cell membrane from an area of high to low concentration
turgor pressure: pressure that water molecules exert against a cell wall in plants
relationship between hypertonic and plasmolysis?
plasmolysis: water leaves the cells through osmosis; the cells shrink away from the cell walls and turgor pressure is lost; the reason that plants wilt if they don’t receive enough water.
hypertonic: when the concentration of solute molecules outside the cell is higher than the concentration inside
Substances that can pass through cell membranes by diffusion include
a. Na+ ions
b. Cl- ions
c. glucose
d. oxygen
d
The contractile vacule of a paramecium should be active when the paramecium is in
a. an isotonic environment
b. a hypotonic environment
c. a hypertonic environment
d. any environment
b
When a human red blood cell is placed in a hypotonic environment, it will
a. undergo cytolysis
b. undergo plasmolysis
c. experience a decrease in turgor pressure
d. be at equilibrium
a
Facilitated diffusion is often used to transport
a. ions
b. water
c. molecules that are not soluble in lipids
d. molecules that are too small to diffuse across the membrane
c
Na+ ions enter cells by
a. diffusing across the lipid bilayer
b. diffusing through Na+ ion channels
c. binding to Na+ carrier proteins
d. binding to Cl- ions
b
What is facilitated diffusion?
This process is used for molecules tha cannot diffuse rapidly through cell membrances. Such molecules may not be soluble in lipids or may be too large to pass through pores in the membrane. Example: glucose.
What assists the molecules across the cell membrane in facilitated diffusion?
special proteins in the cell membrane called carrier proteins
Why can’t ions such as sodium, potassium, calcium and chloride diffuse through the lipid bilayer without assistance?
Becasue they are not soluble in lipids.
What do ion channels provide?
small passage ways for ions to diffuse through the cell membrane; each ion has its own passage way that will not accept any other kind of ion
What is active transport?
The movement of molecules across the cell membrane with the expenditure of chemical energy (ATP). Materials are moved through the cell membrane from an area of lower concentration to an area fo hight concentration (up the concentration gradient).
What are the two mechanisms for active transport?
1) inpocketing
2) carrier molecules
What is inpocketing?
Liquids and solids are taken in or expelled from the cell by a bending of the cell membrane.
What are the two types of inpocketing?
1) endocytosis
2) exocytosis
What is endocytosis?
When materials are brought into the cell. The cell membrane folds in and forms a small pouch. The pouch then pinches off from the cell membrane to ceomone a cesicle.
What is phagocytosis in endocytosis?
When large particles (solids) are brought in.
What is pinocytosis in endocytosis?
When liquid with dissolved materials are brought in.
What is exocytosis?
When amterials are pushed out of the cell. Vesicles in the cytoplams fuse with the cell membrane, releasing their contents into the cells external environment.
What are carrier molecules?
There are proteins that are buried in the phospholipid bilayer. Using energy from ATP, they latch onto a molecule and pump it through the membrane.
What is a vesicle?
Membrane bound organelle that is filled with fluid. Pouch formed as a result of endocytosis as cell membrance folds in.
Facilitated-diffusion carrier proteins and cell -membrane pumps both
a. require an input of energy
b. are specific for the kinds of substances they transport
c. transport substances up their concentration gradients
d. carry out active transport
b
The sodium-potassium pump transports
a. Na+ out of the cell and K+ into the cell
b. Na+ annd K= in both directions across the cell membrane
c. K+ out of the cell and Na+ into the cell
d. Na+ during some cycles and K+ during other cycles.
a
The enrgy needed to power the sodium-potassium pump is provided by the
a. binding of ATP to the pump
b. transport of ATP by the pump
c. splitting of ATP
d. formation of ATP
c
Exocytosis is a
a. tyype of passive transport
b. mechanisms by which cells ingest other cells
c. transport process in which vesicles are formed from pouches in the cell membrane
d. way for cels to release large molecules, such as proteins
d
