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Fluid Mosaic
membranes that are composed of a bilayer of phospholipids with embedded and attached proteins.
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Plasma Membrane
- Boundary that encloses a living cell (the edge of life)
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What is constantly moving in and out of cells?
"Fluid"
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In animal cell membranes, what does cholesterol help out with?
- helps to stabilize the membrane at warm temperatures and
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also helps keep the membrane fluid at lower temperatures.
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What are membranes composed of?
A bilayer of phospholipids with embedded and attached proteins in a "fluid mosaic"
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Why are phospholipids made from unsaturated fatty acids that have kinks in their tails?
To prevent phospholipids from packing together tightly and it keeps them in liquid form.
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Name the six functions that proteins perform.
- Maintain cell shape; coordinate changes inside and outside of the cell through attached cytoskeleton and extracellular matrix.
- Receptors for chemical messengers from other cells.
- Function as an enzyme.
- membrane glycoproteins are involved in cell-cell recognition.
- Intercellular junctions that attach adjacent cells to each other.
- Some may allow selective permeability.
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Selective Permeability
allowing some substances to cross more easily than other to maintain an equal cell balance.
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Phospholipids
Key ingredients of biological membranes, possibly first organic molecules on early Earth.
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Diffusion
Tendency for particles of any kind to spread out evenly in an available space.
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Concentration Gradient
particles diffuse until they reach equilibrium where the concentration of particles is the same throughout.
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Passive Transport
diffusion across a membrane does not require energy.
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Osmosis
Diffusion of water across a selective permeable membrane.
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Tonicity
ability of a surrounding solution to cause a cell to gain or lose water.
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Isotonic Solution
- Solute concentration of a cell.Animal Cell ~ it gains water at the same rate that it loses it. Remains Normal
- Plant Cell ~ Becomes flaccid
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Hypotonic Solution
- a solution with a solute concentration lower that that of the cell. Animal Cell ~ gains water and may burst.
- Plant Cell ~ turgid/normal
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Hypertonic Solution
- Solution with a higher solute concentration.
- Animal Cell ~ can shrivel and die from water loss.
- Plant Cell ~ same as animal cell.
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Facilitated Diffusion
- Process where polar or charged substances can move across a membrane with the help of specific transport proteins. Does not require energy, it uses concentration gradient like other passive transports.
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Osmoregulation
Control of water balance for an animal cell to survive in a hypotonic or hypertonic environment.
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Aquaporin
A protein channel made possible by the very rapid diffusion of water into and out of certain cells.
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Active Transport
- A cell must expend energy to move a solute against its concentration gradient.ATP supplies the energy
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Exocytosis
is used to export bulky molecules such as proteins and polysaccharides.
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Endocytosis
Used to import substances useful to the livelihood of the cell.
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What are the two mechanisms that move large molecules across membranes?
Exocytosis and Endocytosis.
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What are the three types of Endocytosis?
- PhagocytosisPinocytosis
- Receptor Mediated Endocytosis
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Phagocytosis
- the engulfment of a particle by wrapping cell membrane around it, forming a vacuole.Cell Eating
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Pinocytosis
- the engulfment of a particle by wrapping cell membranes around it, fluids are taken into small vesicles.
- Cell Drinking
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Receptor Mediated Endocytosis
uses receptors in a receptor coated pit to interact with a specific protein, initiating the formation of a vesicle.
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Energy
Capacity to cause change or produce work.
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What are the two forms of Energy?
Kinetic and Potential
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Kinetic Energy
- Energy of motion.
- Moving objects can perform work by transferring motion to other matter.
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Heat (Thermal Energy)
- type of kinetic energy associated with the random movement of atoms or molecule.
- (Light energy can power photosynthesis)
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Potential Energy
- Second main form of energy, energy matter possesses as a result of its own location or structure.
- (water behind a dam)
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Chemical Energy
- potential energy available for release in a chemical reaction.
- most important type of energy for living organisms.
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Thermodynamics
The study of energy transformations that occur in a collection of matter.
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The First Law of Thermodynamics
(Law of Energy Conservation)
the energy in the universe is constant, it cannot be created or destroyed. it can only be transferred.
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Entropy
Measure of disorder or randomness (since some energy is converted to heat, causing a disorder of energy)
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The Second Law of Thermodynamics
Energy conversions increase the entropy (disorder) of the universe.
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Cellular Respiration
Chemical energy stored in organic molecules in converted to a form that the cell can use to perform work.
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Exergonic Reaction
A chemical reaction that releases energy (energy outward)
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Endergonic Reactions
- (energy inward) yield products that are rich in potential energy.
- Photosynthesis is an example, the process where plant cells make sugar.
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Metabolism
the total of an organisms chemical reactions.
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Metabolic Pathway
A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.
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Energy Coupling
The use of energy released from exergonic reactions to drive essential endergonic reactions. Usually uses the energy stored in ATP molecules.
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ATP (Adenosine Triphosphate)
- powers nearly all forms of cellular work.Adenosine part consists of nitrogenous base adenine, five carbon sugar ribose.Triphosphate part consists of three phosphate groups which are negatively charged.
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Phosphorylation
A process where hydrolysis of ATP releases energy by transferring its third phosphate from ATP to some other molecule.
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What are the three main types of cellular work driven by ATP?
- chemical-provides energy to drive the endergonic synthesis of products.
- mechanical-muscle cells cause proteins to change shape and pull protein filaments.
- transport-phosphorylating transport proteins.
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Adenosine Disphosphate (ADP)
- Bonds connecting phosphate groups are unstable and be readily broken by hydrolysis (water)
- when the bond of the third group is broken, a phosphate group leaves ATP and becomes ADP and energy is released.
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Activation Energy EA
- The energy barrier that must be overcome before a chemical reaction can begin.
- Bc energy must be absorbed to contort or weaken bonds in reactant molecules so that they can break and new bonds can form.
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What is one way to speed up reaction in molecules?
- by adding heat.
- but heat is then added to all chemical reactions and may be too much, causing the cell to die.
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Enzymes
- Is usually a protein but can be RNA molecules.
- Used to speed up a reaction by lowering the EA needed for a reaction to begin.
- i.e. table sugar, without water it stays same shape unless water is added, then it becomes completely dissolved.
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Enzyme's Subtrate
the specific reactant that an enzyme acts on.
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Enzyme's Active Site
typically a pocket or groove on the surface of the enzyme formed by only a few of the enzymes amino acids.
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Cofactors
- Non protein helpers, which bind the active site and function in catalysis.
- They are inorganic, such as ions of zinc, iron, and copper.
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Coenzyme
is what you call a cofactor if its an organic molecule, such as vitamins.
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Inhibitors
- A chemical that interferes with an enzyme's activity.
- Cells use them as important regulators of cellular metabolism.
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Competitive Inhibitor
- Reduces an enzyme's productivity by blocking substrate molecules from entering the active site.
- It can be overcome by increasing the concentration of the substrate.
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Noncompetitive Inhibitor
Does not enter the active site, it binds to the enzyme somewhere else in a place called Allosteric Site and its binding changes the shape of the enzyme that the active site no longer fits the substrate.
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Feedback Inhibition
- A cell is producing more of that product than it needs, the product may act as an inhibitor of one of the enzymes early in the pathway.
- only weak interactions bind inhibitor and enzyme, and its reversible.
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