Chapter 5 Notes
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membranes that are composed of a bilayer of phospholipids with embedded and attached proteins.
- Boundary that encloses a living cell (the edge of life)
What is constantly moving in and out of cells?
In animal cell membranes, what does cholesterol help out with?
- helps to stabilize the membrane at warm temperatures and
- also helps keep the membrane fluid at lower temperatures.
What are membranes composed of?
A bilayer of phospholipids with embedded and attached proteins in a "fluid mosaic"
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.
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.
allowing some substances to cross more easily than other to maintain an equal cell balance.
Key ingredients of biological membranes, possibly first organic molecules on early Earth.
Tendency for particles of any kind to spread out evenly in an available space.
particles diffuse until they reach equilibrium where the concentration of particles is the same throughout.
diffusion across a membrane does not require energy.
Diffusion of water across a selective permeable membrane.
ability of a surrounding solution to cause a cell to gain or lose water.
- Solute concentration of a cell.Animal Cell ~ it gains water at the same rate that it loses it. Remains Normal
- Plant Cell ~ Becomes flaccid
- a solution with a solute concentration lower that that of the cell. Animal Cell ~ gains water and may burst.
- Plant Cell ~ turgid/normal
- Solution with a higher solute concentration.
- Animal Cell ~ can shrivel and die from water loss.
- Plant Cell ~ same as animal cell.
- 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.
Control of water balance for an animal cell to survive in a hypotonic or hypertonic environment.
A protein channel made possible by the very rapid diffusion of water into and out of certain cells.
- A cell must expend energy to move a solute against its concentration gradient.ATP supplies the energy
is used to export bulky molecules such as proteins and polysaccharides.
Used to import substances useful to the livelihood of the cell.
What are the two mechanisms that move large molecules across membranes?
Exocytosis and Endocytosis.
What are the three types of Endocytosis?
- Receptor Mediated Endocytosis
- the engulfment of a particle by wrapping cell membrane around it, forming a vacuole.Cell Eating
- the engulfment of a particle by wrapping cell membranes around it, fluids are taken into small vesicles.
- Cell Drinking
Receptor Mediated Endocytosis
uses receptors in a receptor coated pit to interact with a specific protein, initiating the formation of a vesicle.
Capacity to cause change or produce work.
What are the two forms of Energy?
Kinetic and Potential
- Energy of motion.
- Moving objects can perform work by transferring motion to other matter.
Heat (Thermal Energy)
- type of kinetic energy associated with the random movement of atoms or molecule.
- (Light energy can power photosynthesis)
- Second main form of energy, energy matter possesses as a result of its own location or structure.
- (water behind a dam)
- potential energy available for release in a chemical reaction.
- most important type of energy for living organisms.
The study of energy transformations that occur in a collection of matter.
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.
Measure of disorder or randomness (since some energy is converted to heat, causing a disorder of energy)
The Second Law of Thermodynamics
Energy conversions increase the entropy (disorder) of the universe.
Chemical energy stored in organic molecules in converted to a form that the cell can use to perform work.
A chemical reaction that releases energy (energy outward)
- (energy inward) yield products that are rich in potential energy.
- Photosynthesis is an example, the process where plant cells make sugar.
the total of an organisms chemical reactions.
A series of chemical reactions that either builds a complex molecule or breaks down a complex molecule into simpler compounds.
The use of energy released from exergonic reactions to drive essential endergonic reactions. Usually uses the energy stored in ATP molecules.
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.
A process where hydrolysis of ATP releases energy by transferring its third phosphate from ATP to some other molecule.
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.
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.
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.
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.
- 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.
the specific reactant that an enzyme acts on.
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.
- Non protein helpers, which bind the active site and function in catalysis.
- They are inorganic, such as ions of zinc, iron, and copper.
is what you call a cofactor if its an organic molecule, such as vitamins.
- A chemical that interferes with an enzyme's activity.
- Cells use them as important regulators of cellular metabolism.
- 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.
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.
- 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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