exam 2 flashcards

Lipids

hydrophobic carbon-containing compounds characterized by their insolubility in water. Their insolubility results from a high proportion of nonpolar C-C and C-H bonds relative to polar functional groups.

Steroids

four ring hydrocarbon structure; contain hydroxyl group 

Fats

consist of three fatty acid molecules joined by ester linkages to a glycerol molecule containing three hydroxyl groups; energy storage

Phospholipids

contain hydrophilic head with a phosphate group and a hydrophobic tail with two hydrocarbon chains; major component of plasma membrane and organelle membranes

Why are some lipids liquid at room temperature whereas other lipids are solid at room temperature?

Some lipids are liquid at room temperature whereas other lipids are solid at room temperature due to bond saturation of fatty acids. There are two types of fatty acids: unsaturated and saturated. Unsaturated fats have a low melting point, so they are liquid at room temperature, whereas saturated fats have a high melting point, so they are solid at room temperature.

Hydrophilic 

water loving; polar compounds with partial or fully charged atoms  

Hydrophobic

water fearing; nonpolar molecules

Amphipathic; Why do amphipathic lipids play such a central role in biology?

1. substances that contain both hydrophilic and hydrophobic regions 

   1. Amphipathic lipids play a central role in biology because they make up the phospholipid bilayer which allows the cells to have selective permeability, so only certain substances can move in and out of the cell. 

what molecules can readily diffuse across the plasma membrane of a cell?

water, gasses, fatty acids, and glycerol

What variables could affect membrane permeability (and membrane fluidity) in a consistent way?

1.  length and saturation state of the hydrocarbon tails and the presence of cholesterol molecules influence membrane permeability 

Unsaturated hydrocarbon tails

double bonds produce spaces among the tails which reduce van der waals reactions and weakens the barrier to solutes making membrane more permeable

Saturated hydrocarbon tails

contain fewer spaces and have more van der waals reactions increasing the length of tails making the membrane less permeable

what happens to the molecules in the bilayer after temp drops?

as temp drops the molecules in the bilayer move slowly causing the membrane to be less fluid, so the tails pack tightly causing the membrane to have lower permeability.

Diffusion

spontaneous movement of molecules from one region to another with a net movement from a region of high concentration to low concentration; concentration gradient

Osmosis

diffusion of water across a selectively permeable membrane from lower solute concentration with high water concentration to higher solute concentration and lower water concentration

Hypertonic

1. solution outside the cell has a higher concentration of solutes than the interior; water moves outside and cell shrinks

Hypotonic

solution lower concentration of solutes outside the cell than the interior: water moves inside and cell swells and bursts

Isotonic

solute concentration are equal on both sides of of the membrane; cell maintains shape and size

Fluid Mosaic Model

cellular membranes that consist of proteins embedded in a fluid phospholipid bilayer; membranes are a fluid mosaic of phospholipids and different types of proteins

Integral membrane proteins

1. (transmembrane proteins) any membrane protein that spans the entire lipid bilayer; have segments that faced the interior and exterior of the cell

Peripheral membrane proteins

any membrane protein that doesn’t span the entire bilayer but binds to one side of the bilayer; binds to membrane lipids of integral membrane proteins without passing through the membrane; either only interior or only exterior

Side Chains

1. proteins can be amphipathic, so they have side chains that range from highly nonpolar to highly polar or charged; nonpolar residues are more stable in the interior of the bilayer, whereas the polar residues would be stable along the polar lipid heads and surrounding water

Carrier Proteins

1. Ions and large polar molecules get into cells through carrier proteins which are integral membrane proteins that facilitate diffusion of a small molecule across a membrane by a process involving a reversible change in the shape of a protein

   1. Carrier picks up a solute on one side of the membrane to the other 

   2. Glucose: GLUT-1 is a carrier protein that that binds to glucose, changes its shape, so it can move through the hydrophobic region of the membrane and releases it on the other side

Channel Proteins

1. integral membrane protein that forms a pore inside the cell membrane that can open or close by a signal; permits only a particular type of ion or small molecule to pass through it 

Aquaporin

“water pore” type of channel protein that facilitates the movement of water across a plasma membrane

Gated Channels

type of channel protein that opens and closes in response to a stimulus

Passive transport

doesnt require energy

Facilitated diffusion

1. facilitated diffusion is the passive movement of a substance across a membrane with the assistance of a transmembrane carrier or channel proteins 

Active transport

1. transport against a gradient; requires energy and transport protein, whereas diffusion and passive transport do not require energy

1. How can dissolved materials be moved from the outside to the inside of a cell when the inside concentration of the material is already high?

1. ATP sends a phosphate group to a pump, which is a membrane protein that uses energy to change shape and power active transport. 

   1. The Sodium Potassium Pump: transmembrane protein that uses the energy of ATP to move sodium ions outside the cell and potassium ions inside the cell

Prokaryotic

single celled; no nucleus; Bacteria and archaea

Eukaryoticmulticellular

multicellular; compartmentalization; nucleus; eukarya  

Ribosomes

synthesize proteins

Cytoplasm

all contents of the cell bounded by the plasma membrane 

Plasma membrane

selective barrier allowing for the passive of O2, nutrients, and waste

Cell wall

rigid structure outside the plasma membrane  that supports the cell

Flagellum

propels the cell (up and down in pro and rotates in euk)

Cytoskeleton

involved in cell shape, support, and transport of materials within the cell (pro have less extensive network and euk have more)

Mitochondria

where ATP is made because cells require energy

Nucleus

contains DNA; Nuclear envelop with nuclear pores 

Endomembrane system

protein processing and other metabolic activities occur; contains rough er, golgi, lysosomes, and smooth er  

Rough ER

covered with ribosomes; new proteins grow and move to the edge of ER and depart in vesicle to golgi

Golgi Apparatus

proteins undergo further processing and bud off and transported to lysosomes

Lysosomes

 contain digestive enzymes

Smooth ER

 lacks ribosomes and where lipids are made

Cell wall

outside plasma membrane and made from strong cellulose fibrous

Central vacuole

 regulates the composition of the cytoplasm

Chloroplasts

where plants make their own food through photosynthesis

Two advantages of compartmentalization:

1. Incompatible chemical reactions can be separated 

2. Chemical reactions become more efficient

Significance of SA-to-volume ratio

As cell size increases its, its surface area to volume ratio decrease, meaning the cell has less SA available for substances to diffuse through slowing the rate of diffusion

Nuclear envelope

double layer membrane enclosing nucleus; studded with nuclear pores

Plasma membrane

selective barrier allowing for the passive of O2, nutrients, and waste; holds the cell together

Nuclear Pore Complex

1. allows molecules to move between the cytoplasm and the nucleus 

   1. About 30 proteins that form an opening in the nuclear envelope connecting the inside of the nucleus with the cytosol and allows for diffusion of small molecules and ions 

   2. Regulates transport of RNA proteins

Nuclear Localization Signal

short amino acid sequence that marks a protein to be delivered to the nucleus

substrate

molecule upon which an enzyme acts to catalyze a chemical reaction. In enzyme-catalyzed reactions, the substrate is the specific molecule or molecules that the enzyme binds to and acts upon to facilitate a specific chemical transformation. 

Enzyme

An enzyme is a biological macromolecule, typically a protein, that acts as a catalyst in chemical reactions. Enzymes facilitate and accelerate specific reactions by lowering the activation energy required for the reaction to occur. 

Active Site

The active site is a specific region on an enzyme where substrates bind and the chemical reaction takes place.

how does temp affect enzyme activity?

1. Enzyme activity typically increases with temperature, up to an optimal point, and then decreases as the temperature exceeds the optimal range.

   1. Lower temperature= less kinetic energy, less collisions between enzyme and substrates

   2. Increased temperature= more kinetic energy, more collisions

   3. Temperature too high= enzyme denatures and there is little to no collisions

pH

1. Enzymes have an optimal pH range at which they exhibit maximum activity. Deviating from this pH range can reduce enzyme activity.

   1. Optimal pH= the active site is at its most functional and binds the most

   2. Too low/ high pH= the enzyme/active site will denature, reducing collisions

Competitive Inhibition

mechanism of enzyme regulation where a molecule, known as a competitive inhibitor, competes with the substrate for binding to the enzyme's active site. Competitive inhibitors are structurally similar to the substrate and can bind to the enzyme's active site, blocking the substrate from binding. 

Allosteric Regulation

 mechanism of enzyme regulation where a molecule, known as an allosteric regulator, binds to a specific regulatory site on the enzyme, not the active site. This binding can either enhance or inhibit the enzyme's activity, depending on the nature of the allosteric regulator