cell bio exam 1

roles of aquaporins

1. Kidney nephrons 2. epithelial fluid secretion 3. brain water balance 4. cell migration 5. neurosensory function

vesicle-mediated transport

1. cargo selection 2. budding 3. scision 4. uncoating 5. transport 6. tethering 7. docking 8. fusion 9. disassembly

cell theory

1. cells are the fundamental units of life 2. all living things are composed of cells 3. new cells must come from existing cells

name two types of protein modification that can occur in the ER but not in the cytoplasm

1. disulfide bond formation (can't occur in cytosol because it is a reducing environment) 2. Protein glycosylation (glycosylating enzymes not found in cytosol)

step 6 of glycolysis

1. gylceraldehyde-3-phosphate oxidized by NAD 2. glyceraldehyde-3-phosphate phosphorylated by addition of a free phosphate group 3. dehydrogenase takes away a hydrogen

basic lipid structure

1. head group 2. phosphate group 3. glycerol backbone 4. fatty acid tails

step 3 of glycolysis

1. irreversible transfer of a phosphate from ATP to fructose-6-phosphate 2. Mg atom is a cofactor 3. PFK is an allosteric enzyme that regulates the pace of glycolysis

basic functions of plasma membrane

1. receive information 2. import and export small molecules 3. capacity for movement and expansion

propose four vesicle properties that could be used to differentiate one type of vesicle from another

1. shape/size 2. motor protein attachment 3. coat proteins 4. targeting and tethering proteins

citric acid cycle regulated by

1. substrate availability 2. product inhibition 3. competitive feedback inhibition

step 7 of glycolysis

1. transfer phosphate group to ADP to form ATP 2. Mg atom cofactor of PKG enzyme

how vesicles move around the cell

1. vesicle specificity 2. specific cargo binds to a cargo receptor 3. protein coat

mechanisms of channel regulation

1. voltage 2. ligand-gated extracellular 3. ligand-gated intracellular 4. mechanically gated

glycolysis

6-carbon glucose split into two 3-carbon pyruvate; net gain of 2 ATP and 2 NADH

Human infants have a much larger portion of brown adipose tissue than adult humans. It was found that the mitochondria in brown adipocytes (brown fat cells) have a novel protein in the inner mitochondrial membrane. This protein, called the uncoupling protein (UCP), was found to transport protons from the intermembrane space into the matrix. A. What is the impact of UCP on oxidative phosphorylation in the mitochondria of brown fat? B. Propose an explanation for the higher proportion of brown fat cells in infants compared to adults.

A. A protein that pumps protons into the matrix would diminish the gradient. Without the gradient, ATP cannot be formed. The electron transport chain can still work though in the presence of oxygen. The UCP is an uncoupler of oxidative phosphorylation, causing the electron transport chain to run a cycle producing heat instead of ATP. B. The heat produced from oxidative phosphorylation in the presence of UCP helps infants maintain a constant body temperature. As body mass increases with age, we are less susceptible to temperature fluctuations and therefore adults do not require as much brown fat as infants.

COP II

ER to golgi

Glycolysis and the citric acid cycle comprise two different sets of oxidation reactions. The reaction sequence for glycolysis is linear, whereas the reaction sequence for the citirc acid cycle forms a circle. How does this difference in the arrangement of reactions influence the rate of these processes when an excess amount of a single intermediate is added?

If one intermediate is added to the citric acid cycle, it will cause an increase in all intermediates since it will be continuously be cycled through. If one intermediate is added to glycolysis, it will not cause an increase in all intermediates as the process ends once the two pyruvates are formed. The intermediate will build up and will not be cycled through to form more product.

provide a brief description of the process by which the body derives energy from food

In the first stage, polymers are broken down into smaller subunits by the digestive system. Proteins to amino acids, carbohydrates to simple sugars (glucose) and fatty acids to glycerol. In the second stage, these subunits are further broken down to produce the carrier acetyl CoA, which is the molecular precursor to stage three. In stage three of catabolism, acetyl CoA is converted to CO2, coupled with the production of ATP

do you expect the cell to produce more ATP per molecule of glucose or or one fatty acid molecule?

More ATP is produced from fat catabolism than glucose catabolism. The citric acid cycle relies on an input of acetyl CoA. Two molecules of acetyl CoA are produced from one glucose molecule while nine molecules of acetyl CoA are produced from the triacylglycerol, which has more carbons than glucose.

Explain how the F0 complex of ATP synthase harnesses the proton-motive force to help synthesize ATP. What would happen if the proton gradient were reversed?

Protons flow through a channel composed of subunits of the transmembrane H+ carrier that form a ring. As protons flow through, the gradient causes the ring and stalk to rotate and rub against the F1 complex of ATP synthase. This causes a conformation change of the F1 ATPase, forming ATP. When the proton gradient is reversed, the F1 ATPase hydrolyzes ATP into ATP and a phosphate group, pumping protons into the matrix against their concentration gradient and causing the stalk to rotate in the opposite direction.

saturated fatty acid

all single bonds; fluid

inhibitor molecules

bind to a site on an enzyme distinct from substrate site, making the enzyme assume an inactive conformation

catabolic pathways

breaking down of polymers to their constituent parts; releases energy

endomembrane system

budding goes from rough ER to smooth ER to golgi to plasma membrane

phospholipids

build cell membrane; prevent hydrophilic substances from crossing the cell membrane

glycogen

can be mobilized for quick energy

carrier proteins

change conformation when bound to solute; never open space directly from outside to inside

cell membrane

clear boundary between inside and outside of the cell

lipids

components of cell membranes; energy storage; cell signaling

nucleic acids

contain and help express genetic code

enzymes

convert molecules into forms to help the cell meet energy needs, build support structures, or pump out wastes

third transporter

coupled transport moves two molecules in opposite directions

symporter

coupled transport moves two molecules in the same direction

unsaturated fatty acid

double bonds; rigid

cholesterol

fill gaps between phospholipids; make membrane more fluid; made in the liver; lipid monolayer

amino acids

form chains to make proteins

importance of oxygen in glycerol backbone

form polar bonds with carbon which take less energy to break; always reactive

membrane proteins

gate keepers, markers, fasteners, communicators

citric acid cycle

generates 3 NADH, FADH2, and GTP

what is a major problem at the end of the citric acid cycle?

huge amount of high energy electrons

membrane channels

hydrophobic outside and hydrophilic inside; only facilitate gradient-driven transport

fermentation

in absence of oxygen, intermediates are formed rather than CO2

complex carbohydrates

intracellular energy storage; play a key role in cell recognition

clathrin

leaving the golgi

activator molecules

make the enzyme assume an active conformation

simple carbohydrates

meet cell's immediate energy demands

electron transport chain

mitochondrial inner membrane

COP I

move vesicles in golgi

uniporter

moves one type of molecule

glucosyl transferase

puts glucose back on incompletely folded proteins, allowing more chances to fold properly

calnexin

removes glucose that was placed by glucosyl transferase

oxidation

shift electrons away from central atom

chemical potential energy

splitting of covalent bonds produce energy (more covalent bonds, more energy); high energy bonds oxidized in a stepwise process to generate as little heat as possible

anabolic pathways

synthesis of macromolecules; requires energy

oxidative phosphorylation

transfers electrons from NADH to FADH2 to O2 to eventually form water; proton gradient formed and produces 2 ATP per electron

acetyl CoA

two-carbon energy carrier formed from breakdown of pyruvate

cytoplasm

water based interior of the cell; 30: of cell's energy spent maintaining cytoplasm