Midterm Review Flashcards

Question

Explain the various methods cells use to transport materials across membranes

Answer 1

Through endocytosis large particles are brought into cells across the membranes, through exocytosis large particles are removed from cells, by the formation of vesicles, active transport requiring ATP, uses protein pumps to move materials against concentration gradients , the molecules are too large or too charged to diffuse directly through the membrane, small polar and non-polar molecules / gases, can diffuse directly through the membrane from an area of high concentration to an area of low concentration / down the concentration gradient, osmosis is the passive movement of water molecules across a partially / selective permeable membrane from a region of lower solute concentration to a region of higher solute concentration

Answer 2

vesicle is made by pinching off a piece of membrane, fluidity of membrane allows this, vesicles can be used to transport material around inside cells, proteins are transported in vesicles, from the rough ER to the Golgi Apparatus, from the Golgi apparatus to the plasma membrane, formation of vesicle from plasma membrane allows material to be taken in, endocytosis / phagocytosis / phagolysosome is absorption of material using a vesicle, fusion of vesicle with plasma membrane allows the material to be secreted / passed out, exocytosis is secretion of material using a vesicle, named example of endocytosis

Answer 3

A solution that has the same salt concentration as cells and blood. Isotonic solutions are commonly used as intravenously infused fluids in hospitalized patients.

Answer 4

If concentrations of dissolved solutes are greater outside the cell, the concentration of water outside is correspondingly lower. As a result, water inside the cell will flow outwards to attain equilibrium, causing the cell to shrink. As cells lose water, they lose the ability to function or divide. Hypertonic environments such as concentrated brines or syrups have been used since antiquity for food preservation because microbial cells that would otherwise cause spoilage are dehydrated in these very hypertonic environments and are unable to function.

Answer 5

If concentrations of dissolved solutes are less outside the cell than inside, the concentration of water outside is correspondingly greater. When a cell is exposed to such hypotonic conditions, there is net water movement into the cell. Cells without walls will swell and may burst (lyse) if excess water is not removed from the cell. Cells with walls often benefit from the turgor pressure that develops in hypotonic environments.

Answer 6

endocytosis- an energy-using process by which cells absorb molecules (such as proteins) by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane exocytosis- a process in which an intracellular vesicle (membrane bounded sphere) moves to the plasma membrane and subsequent fusion of the vesicular membrane and plasma membrane ensues.

Answer 7

alpha helix or beta pleated sheets

Answer 8

fibrous proteins have a long and narrow shape, globular protein have rounded shapes, fibrous mostly insoluble in water, globular protein soluble in water, fibrous: collagen / silk / keratin, globular: immunoglobulin / hemoglobin / catalase / named enzyme /

Answer 9

polar amino acids are hydrophilic / "water loving", polar amino acids form hydrophilic proteins / channels allowing hydrophilic / polar / charged particle acids on the surface proteins make them water soluble

Answer 10

DNA wraps around 8 histone proteins 1.65 times, and remains bound via hydrogen bonds and an H1 linker protein. This complex is known as a nucleosome. Nucleosomes condense some more to create chromatin which eventually condenses even more to form chromosomes.

Answer 11

a gene is "a locatable region of genomic sequence, corresponding to a unit of inheritance, which is associated with regulatory regions, transcribed regions, and or other functional sequence regions. Segments of DNA carry codes for specific proteins and thus code for various biological traits. The region of the chromosome at which a particular gene is located is called its locus.

Answer 12

Single copy genes are found only once and code for proteins, while repetitive sequence genes are found multiple times and do not code for proteins.

Answer 13

enzymes are high molecular mass soluble globular proteins that act as catalysts as living systems, increasing the rate of the reaction they catalyze without being used up.

Answer 14

enzymes possess an active site where substrate binds to form an enzyme-substrate complex which induces stress in the substrate thereby lowering the energy required for the reaction. They are very efficient catalysts that cause very high reaction rates at low temperatures. The active site has a particular shape and enzymes can therefore only react with substrates that have a certain shape and can enter a bind with the active site. They are specific to either one substrate where only a single substrate can bind or a chemical group where a particular chemical group can bind

Answer 15

They have optimum conditions of temperature and pH for maximum activity and activity can be lowered or cease altogether in extreme conditions. The rate of reaction also depends upon concentrations of enzyme, substrate, product and inhibitor. As proteins, they denature temporarily or permanently at higher temps. Temperature and pH changes cause bond changes affecting conformation of the protein molecule and therefore the shape of the active site, the substrate can no longer bind to the site and the reaction is no longer catalyzed.

Answer 16

Denaturation is a change in the shape of an enzyme which prevents it from fulfilling its function. Enzymes can be denatured by heat, pH changes, or certain chemicals.