Homeostasis and Cellular Transport in Eukaryotic Cells Flashcards
the tendency of living things to maintain internal dynamic equilibrium
Homeostasis
the state when forward progress reactions and reverse progress reactions result in stable conditions when put together
Dynamic Equilibrium
the value around which a specific condition fluctuates
Set Point
moves the body away from a set point which causes the body to act to re-establish equilibrium
Stimulus
a homeostatic process that reduces the stimulus
Negative Feedback Loop
What is an internal and environmental example of a Negative Feedback Loop?
Internal - high blood sugar > pancreas releases insulin > blood sugar levels return to normal levels
Environmental - heat causes dog body temp to rise > dog pants to cool down > body temp returns to normal levels
animals that depend on the external environment to set their body temperature
Ectotherm
animals that can maintain their body temperature at set points
Endotherms
the most effective and ongoing stimulus response and is how endotherms regulate internal temperature
Thermoregulation
Give examples of ectotherms vs endotherms
Ectotherms - fish, amphibians, reptiles
Endotherms - mammals, birds
What are the 4 ways that endotherms AND ectotherms exchange heat with their environment?
- Evaporation
- Radiation
- Convection
- Conduction
the loss of heat as a liquid becomes a gas
Evaporation
the loss or gain of electromagnetic radiation as heat waves
Radiation
the loss of heat due to air or fluid movement
Convection
the direct transfer of heat by molecules of an organism or object that’s in direct contact
Conduction
Give an example of:
Evaporation
Radiation
Convection
Conduction
Evaporation - dog panting to cool down
Radiation - lion seeking shade to cool down / snake basking in the sun to warm up
Convection - air from a fan cooling the skin on a hot day
Conduction - sitting on a rock that has been warmed by the sun
a homeostatic process that maintains or enhances a stimulus
Positive Feedback Loop
Give an example of a Positive Feedback Loop
Giving Birth - Lamb’s head puts pressure on the ewe’s uterus > uterus contracts > uterine pain receptors prompt oxytocin production > oxytocin stimulates uterine contractions during birth > contractions increase in strength > help the ewe deliver the lamb
the primary way that cells maintain internal stability typically achieved by moving liquids, molecules, proteins, ions, and other solutes into and out of the cell
Cellular Transport
any substance that has been dissolved in another substance
Solute
a group of atoms bonded together
Molecule
an atom or molecule with an electric charge caused by a loss or gain of an electron
Ion
Give an example of a solute vs a solvent
Saltwater
Solute - Salt
Solvent - Water
the selectively permeable membrane that controls the entering or exiting of specific ions, proteins, molecules, solutes, and liquids for the cell through active or passive transport
Plasma Membrane (Phospholipid Bilayer)
What does the double-layer system of the phospholipid bilayer allow for?
It allows the membrane to be selectively permeable
model that recognizes that (1) the phospholipids are held together by hydrophobic interactions that are much weaker than covalent bonds and (2) the membrane is made up of different proteins clustered in groups and embedded in the fluid matrix of the lipid layer
Fluid Mosaic Model
The membrane is more like a crowd of people that can shift and move when perturbed > making room for another person or closing behind as one leaves the line
The “Fluid Aspect” of the Fluid Mosaic Model
What are the 3 major populations of polymers in the “Mosaic Aspect” of the Fluid Mosaic Model?
- Integral Proteins
- Peripheral Proteins
- Carbohydrate Molecules
proteins in the cell membrane that shuttle molecules and ions in and out of the cell
Integral Proteins (Transmembrane Proteins)
proteins on the cell membrane that add structure to the cells by binding with fibers and serve as attachment sites for enzymes or as cell-recognition sites
Peripheral Proteins
Form specialized sites on the cell surface that allow cells to recognize each other and bond to either the lipid or integral proteins
Carbohydrate (Sugar) Molecules
the movement of ions and other substances across a cellular membrane without the input of energy
Passive Transport
Passive Transport consists of what 3 processes?
- Diffusion
- Facilitated Diffusion
- Osmosis
the process by which substances move from areas of high concentration to areas of low concentration and continues until the concentration becomes equal throughout a space
Diffusion
the relative concentration difference between a region with high concentration and a region with low concentration
Concentration Gradient
the process by which certain insoluble molecules that are unable to pass through the selectively permeable membrane due to their size, charge, or polarity are moved using transport proteins
Facilitated Diffusion
What are the 2 types of transport proteins used in facilitated diffusion?
- Channel Proteins
- Carrier Proteins
proteins that facilitate the movement of certain molecules through a semipermeable membrane by forming special pores and pathways that are big enough to accommodate large molecules or have polarity that accepts the polar or charged molecule
Channel Proteins
proteins embedded in the plasma membrane that change shape to bind to a substance and help it across a semipermeable membrane
Carrier Proteins
How many different substances can bind to carrier proteins so they can cross the plasma membrane?
1 - these proteins are generally specific to one substance
the diffusion of water from areas of high water concentration to areas of low water concentration across a selectively permeable membrane in order to equalize the concentration of water and solutes present
Osmosis
a determining force in water movement and causes water to move from areas of high concentration to areas of low concentration
Osmotic Pressure
What causes osmotic pressure?
differences in water concentration within and outside the cell
What are 3 types of solutions related to osmosis?
- Isotonic
- Hypotonic
- Hypertonic
a solution where the concentration of solutes within and outside the cell is equal
Isotonic
a solution where the concentration of solutes [outside] the cell is [lower] than the concentration of solutes [inside] the cell
Hypotonic
the concentration of solutes [outside] the cell is [higher] than the concentration of solutes [inside] the cell
Hypertonic
What could happen to a cell if osmosis occurs in excess for hypotonic vs hypertonic solutions?
Hypotonic - Water present outside the cell will move down its concentration gradient into the cell > will cause the cell to swell or burst
Hypertonic - Water will move down its concentration gradient out of the cell > causes cells to shrink
the movement of ions, molecules, proteins, liquids, or solutes into regions that already have a high concentration of these substances in order to maintain homeostasis and require the use of energy to do this
Active Transport
Active transport is required for cells in order to maintain what?
A membrane potential
the presence of a difference in electrical charge between one side of the selectively permeable membrane and the other
Membrane Potential
a voltage difference on 2 sides of a semipermeable membrane
Electrical Potential
What is the normal cellular membrane potential between?
-40 and -80 millivolts
The minus refers to inside the cell
How is a membrane potential created?
By active transport pushing ions and other molecules against their gradients
the difference in concentration of a specific molecule, protein, or liquid on either side of a membrane
Chemical Gradient
the difference in concentration of electrical charges on either side of a membrane
Electrical Gradient
the combined effects of an electrical gradient and a chemical gradient on the movement of substances, their effects may combine or negate
Electrochemical Gradient
when the chemical and electrical gradients encourage movement in the same direction
Combined Electrochemical Effects
when the chemical and electrical gradients oppose one another
Negated Electrochemical Effects
one of the most common energy currencies used in cells
Adenosine Triphosphate (ATP)
molecule used to help power active transport against gradients
Adenosine Triphosphate (ATP)
mechanism that uses active transport to keep the concentration of potassium inside the cell high and the concentration of sodium inside the cell relatively low + ensures the concentration of potassium outside the cell remains low and the concentration of sodium outside the cell remains high
Sodium-Potassium Pump
Why is it important that the Sodium-Potassium Pump helps a cell remain more negative inside than outside?
This feature is important to signal transmission
Why does the movement of sodium and potassium across membranes contribute to the electrochemical gradient?
Because sodium and potassium are both ions
What are the 6 steps of active transport in the sodium-potassium pump?
- Pump is opened toward the inside of the cell > 3 sodium ions bind to it
- 1 molecule of ATP is split to provide the energy for active transport > ATP becomes ADP + a phosphate group > the phosphate group is attached to the pump
- Attaching the phosphate group causes the enzyme to change shape > Enzyme reorients itself to open towards the outside of the cell > the 3 sodium ions are released outside of the cell
- Pump is open to the outside of the cell > 2 potassium ions bond to the pump + the phosphate group detaches
- Loss of the phosphate group > enzyme returns to its original shape > opens toward the inside of the cell
- The 2 potassium ions are released inside of the cell > cycle is ready to start over
How many sodium ions and potassium ions are moved during active transport? What is the net loss inside the cell? Why is this important?
- 3 (+) sodium out + 2 (+) potassium in
- Net loss of 1 (+) ion on the inside
- This maintains the electrochemical membrane potential - the cell is slightly (-) on the inside compared to the outside
the process of bulk transport of molecules, food, and other substances across a membrane into the cell
Endocytosis
Endocytosis consists of what 3 processes?
- Phagocytosis
- Pinocytosis
- Receptor-Mediated Endocytosis
the movement of food or other particles from the extracellular fluid through the cell membrane into the cell
Phagocytosis
What are the 4 steps of Phagocytosis?
- Cell plasma membrane wraps around the food particle outside the cell > creates a food vacuole
- The newly formed food vacuole is moved into the cytoplasm of the cell
- Vacuole fuses with a lysosome
- Lysosome’s enzymes break down the food into useable materials for the cell
the movement of extracellular liquid through the cell membrane into a cell
Pinocytosis
What are the 3 steps of Pinocytosis?
- Cell plasma membrane wraps around the liquid outside the cell > creates a vesicle
- The vesicle is nonspecific and contains dissolved molecules and ions (as opposed to a solid particle)
- The vesicle moves into the cytoplasm of the cell
the movement of substances through the cell membrane that requires the recognition of a molecule by receptors on the cell membrane
Receptor-Mediated Endocytosis
What are the 5 steps of Receptor-Mediated Endocytosis?
- Outward-facing receptors create pits in the cell plasma
- Receptor is filled by a specific molecule
- A signal is sent
- The pit closes off
- Pit with the molecule is ingested by the cell
