2.5 Homeostasis And Cellular Transport In Eukaryotic Cells Flashcards
Homeostasis
Tendency of living things to maintain a steady state of internal conditions
In a living system it is the maintenance of a dynamic equilibrium
Dynamic equilibrium
A point at which the rate of the forward process matches the rate of the reverse process
Stimuli
Changes that cause reactions
Feedback loop
Homeostatic process that changes the direction of the stimulus
Negative feedback loop
Changes the direction of the stimulus
Reduces the stimulus
Positive feedback loop
Maintains the stimulus and sometimes even enhances it
Thermoregulation
Ongoing stimulus response that allows warm-blooded animals to regulate internal temp
Ectotherms
Depend on the external environment to set their body temperatures
Endoderms
Maintain their body temperature at set points through thermoregulation
Radiation
Loss of electromagnetic radiation as heat waves
Evaporation
Loss of heat as a liquid becomes a gas
Convection
Loss of heat due to air movement
Conduction
Direct transfer of heat by molecules of an organism or object that’s in direct contact
Cellular transport
Moving liquids, molecules, proteins, ions, and other solutes into and out of the cell
Solute
Any substance that has been dissolved in another substance
Hydrophilic
Water-attracting
Hydrophobic
Water-repelling
Fluid mosaic model
Phospholipids are held together by hydrophobic interactions that are much weaker than covalent bonds so they can shift and move when perturbed, making room for other things to move through and close behind them
Proteins are embedded in the fluid matrix of the lipid layer
Carbohydrates are bonded to either the lipid or proteins of the membrane
Integral proteins
Often span the entire membrane (AKA transmembrane proteins)
Hydrophilic regions stick out and hydrophobic regions are between the lipids
Important for transport
Peripheral proteins
Not part of the cell membrane but appendages on surface of cell
Add structure by binding with fibers
Attachment sites for enzymes or cell-recognition sites
Role of carbohydrates on cell membrane
Bone to either the lipid or the proteins of the cell membrane
Allow cells to recognize each other
Can tell the difference between body cells and foreign invaders
Stimulate the immune system when foreign cells detected
Passive transport
The movement of ions and other substances across a cellular membrane along the concentration gradient without the input of energy
Includes diffusion, facilitated diffusion and osmosis
Diffusion
Substances move from areas of high concentration to areas of low concentration until concentration is equal throughout a space
Concentration gradient
Relative concentration difference between a region with high concentration and a region with low concentration.
Semipermeable
Will let only certain substances pass through regardless of the concentration gradient
Facilitated diffusion
Transport protein are used as channels or carriers for certain insoluble molecules that are too large or unable to pass through membrane due to charge or polarity
Channel proteins
Facilitate movement of molecules through membrane by forming special pores and channels that are big enough to accommodate large molecules or have polarity that accepts polar or charged molecules
Carrier proteins
Bind to substances to help them across the membrane
Generally specific for one substance
Osmosis
Diffusion of water from areas of high water concentration to areas of low water concentration
Isotonic
Concentration of solutes within and outside the cell is equal
Water moving in and out at equal rates
Hypotonic
Concentration of solutes outside cell is lower than inside the cell
Water outside the cell will move into the cell
Hypertonic
Concentration of solutes outside cell is higher than inside the cell
Water will move outside of the cell
Osmotic pressure
Caused by differences in water concentration within and outside the cell
Active transport
Cells must use energy to move molecules, ions, proteins, liquids, or solutes into regions that already have high concentration of these substances
Membrane potential
Electrical potential or voltage difference between one side of the selectively permeable membrane and the other
Difference usually falls between -40 and -80 millivolts (cells typically more negative on inside than outside)
Chemical gradient
Difference in concentration of a specific molecule, protein, or liquid on either side of a membrane
Electrical gradient
Difference in the concentration of electrical charges on either side of a membrane
Electrochemical gradient
Combined effects of electrical and chemical gradients
Sodium-potassium pump
One of the most common active transport found in eukaryotic cells
Keeps concentration of potassium inside the cell high and the concentration of sodium inside the cell relatively low and vice versa
For every 3 sodium ions pumped out of the cell, 2 potassium ions are pumped in
Sodium potassium pump steps
- Open to inside of cell, 3 sodium ions bind to inside
- ATP binds to pump and energy is used by splitting into ADP and a phosphate group
- The ADP is released and the phosphate group caused the pump to change shape and open to the outside
- Sodium ions released and 2 potassium ions attach causing the phosphate group to detach
- Loosing the phosphate group causes pump to change back to being open to the inside
- The potassium ions are released to the inside of the cell
Endocytosis
Bulk transport of molecules, food and other substances across a membrane into the cell
Phagocytosis
Movement of food or other particles through the cell membrane
Cell membrane encases the particle in a food vacuole and eventually fuses with a lysosomes to break it into usable materials
Pinocytosis
Plasma membrane wraps itself around liquid outside the cell to absorb dissolved molecules and ions
Non-specific
Receptor-mediated Endocytosis
Requires the recognition of the molecule by receptors on a pit in the cell membrane. Once the receptor have filled a signal is sent to close off the pit and the contents are ingested.
