Biology Unit 2 Flashcards

fluid mosaic model

fluid mosaic model

mosaic of proteins floats in or on the fluid lipid bilayer like boats on a pond

mosaic

proteins, cholesterol, and carbs are embedded among the phospholipid

plasma membrane functions

1. defining the outer border of all cells and organelles

2. managing what enters and exits the cell

3. adhering to neighboring cells

4. receiving external signals and initiating cellular responses

cellular membranes have four components:

1. phospholipid bilayer

2. transmembrane proteins

3. interior protein network

4. cell surface markers

function of phospholipid bilayer

defining the outer border of all cells and organelles

function of transmembrane proteins

managing what enters and exits the cell

function of interior protein network

adhering to neighboring cells

function of cell surface markers

receiving external signals and initiating cellular responses

what are some influences on fluidity?

1. phospholipid type

2. temp

3. cholesterol

what is in the inner surface of membrane?

1. interior proteins

2. exterior proteins

3. glycoproteins

interior proteins

anchor fibers of the cytoskeleton to the membrane

exterior proteins

bind to the extracellular matrix

glyoproteins

bind to substances the cell needs to import

selectively permeable

allows some molecules to pass but not others

what is the major barrier to crossing a biological membrane?

the hydrophobic interior bc it repels polar molecules but not nonpolar molceules

passive transport

requires no energy or ATP and goes down concentration

active transport

requires energy and goes against concentration

diffusion

simplest type of passive transport and it moves from high to low concentration

what are some examples of things that go through diffusion?

O2, CO2, lipids, and hormones

what are factors that affect diffusion rates?

1. concentration gradients

2. mass of molecules

3. temp

4. solvent density

5. solubility

6. surface area

7. distance travelled

8. pressure

facilitated diffusion

molecules that cannot cross membrane easily may move through proteins, and ions and small polar molecules move this way

what are some things that assist facilitated diffusion?

channel proteins and carrier proteins

channel proteins

hydrophilic channel when open, some are always open, some are gated and open when there is a signal

carrier proteins

bind specifically to molecules they assist, they change shape and “carry it” to the other side after they bind to substance

uniporters

move one molecule at a time

symporters

move two molecules in the same direction

antiporters

move two molecules in opposite directions

Sodium-potassium pump

-direct use of ATP for active transport

-uses an antiporter to move 3 Na+ out and 2 K+ in

Osmosis

net diffusion of water across a membrane toward a higher solute concentration

Hypertonic solution

more solutes than solvent in the cell (water goes out of the cell so it shrinks)

hypotonic

fewer solutes than solvent (water goes in and cell swells)

isotonic

same amount of solute and solvent

aquaporins

-specialized channels for water in the cell membrane

-facilitate osmosis

osmotic pressure

cell wall can reach balance of osmotic pressure driving water in with hydrostatic pressure driving water out

extrusion

water is rejected through contractile vacuoles

isosomotic regulation

involves keeping cells isotonic with their environment

freshwater osmotic balance

trying to keep solute level inside “high”

saltwater osmotic balance

trying to dilute the solute water inside

turgor pressure

plant cells push the cell membrane against the cell wall and keep the cell rigid

electrochemical gradients

combined effects of concentration gradients and electrical gradients

electrical gradient

when the cytoplasm contains more negatively charged molecules than the extracellular fluid

Secondary active transport

-uses ATP indirectly

-uses the energy released when a molecule moves by diffusion to supply energy to the active transport of a different molecule

-symporter is used

exocytosis

movement of substances out of the cell, requires energy

endocytosis

movement of substances into the cell

what are the three types of endocytosis?

1. phagocytosis

2. pinocytosis

3. receptor-mediated endocytosis

phagocytosis

cell take in particulate matter, cell “eating”

pinocytosis

cell take in only fluid, dissolved substances, cell “drinking”

receptor-mediated endocytosis

specific molecules are taken in after they bind to a receptor

bioenergetics

the study of energy flow through a living system

metabolism

refers to all chemical reactions of a cell or organism

what are the two types of reactions/pathways required to maintain the cells energy balance?

1. anabolic

2. catabolic

anabolic reaction

requires energy and synthesize larger molecules

catabolic reaction

releases energy and break down large molecules into smaller molecules

how did organisms evolve their metabolic pathways?

as they evolved, they developed specialized enzymes to help them adapt to their enviornment

kinetic energy

objects in motion

energy

ability to do work

potential energy

objects that have the potential to move

Gibb’s Free Energy

amount of energy available to do work (aka usable energy)

endergonic reaction

require an input of energy to produce product

exergonic reaction

releases energy as the substrate becomes a product

activation energy

the energy required for a reaction to proceed

ATP

the common currency of energy transactions within the cell, it is composed of an adenosine molecule, and three phosphate groups

ATP hydrolysis

ATP is an unstable molecule and will hydrolyze quickly

enzymes

are protein catalysts that facilitate reactions without being destroyed in the process, they reduce the amount of activation energy required to begin a reaction

inhibitors

at the active site or an allosteric site they can inhibit enzyme function

competitive inhibition

inhibitors at the active site (directly blocks the active site)

non-competitive inhibition

inhibitors at the allosteric site (changes the shape of active site)

what are helper molecules that help enzymes work?

cofactors and coenzymes

example of coenzyme

vitamins act as precursors or coenzymes

feedback inhibition

where the end product of the pathway inhibits an upstream step, it is an important regulatory mechanism in cells

cellular respiration

series of redox reactions that occur

oxidized

loss of electrons (gets more positive)

reduced

gains electrons (gets more negative)

dehydrogenation

lost electrons are accompanied by protons

NAD+

an electron carrier and enzymatic cofactor it accepts 2 electrons and 1 proton to become NADH

aerobic respiration

final electron receptor is oxygen (O2)

anaerobic respiration

final electron acceptor is an inorganic molecule

fermentation

final electron acceptor is an organic molecule

oxidative phosphorylation

ATP synthase uses energy from proton gradient, during the electron transport chain

what is the complete oxidation of glucose?

1. glycolysis

2. pyruvate oxidation

3. citric acid cycle

4. electron transport and chemiosomosis

glycolysis

occurs in the cytoplasm and the net production is 2 ATP and 2 NADH and 2 pyruvate, has a 10 step biochemical pathway (both prokaryotes and eukaryotes) (6 carbons from glucose turns into 2× 3 carbon pyruvates)

What are the two ways that NADH can be recycled?

1. aerobic respiration (produces ATP and pyruvate is oxidized to acetyl-CoA which enters the citric acid cycle

2. fermentation (occurs when there’s no oxygen and organic molecule is the final electron acceptor)

pyruvate oxidation

in the presence of oxygen, pyruvate is oxidized, which occurs in mitochondria in eukaryotes and at the plasma membrane in prokaryotes (step #2 of cellular respiration)

products of pyruvate oxidation

produces:

2 CO2, 2 NADH, and 2 acetyl-CoA from 2 pyruvate

aerobic respiration overview

the complete oxidation of glucose proceeds in stages:

1. glycolysis

2. pyruvate oxidation

3. citric acid cycle

4. electron transport chain and chemiosmosis

structure of a cell membrane

1. phospholipid bilayer

2. transmembrane proteins

3. interior protein

4. cell surface markers

functions of cell membrane

1. defining the outer border of all cells and organelles

2. managing what enters and exits the cell

3. adhering to neighboring cells

4. receiving external signals and initiating cellular responses

what influences fluidity?

phospholipid type, temperature, and chlosterol

citric acid cycle (Krebs cycle)

-occurs in the matrix of the mitochondria

-biochemical pathway of 9 steps in three segments

what are the 3 segments of the citric acid cycle?

1. Acetyl-COA + oxaloacetate turns into citrate

2. Citrate rearrangement and decarboxylation

3. regeneration of oxaloacetate

products and reactants of the citric acid cycle

each Acetyl-CoA entering the citric acid cycle:

-releases 2 molecules of CO2

-reduces 3 NAD+ to 3 NADH

-reduces 1FAD to FADH2

-produces 1 ATP

-regenerates oxaloacetate

Electron Transport Chain

-series of membrane-bound electron carriers embedded in the inner mitochondrial membrane

-electrons from NADH and FADH2 are transferred to complexes of ETC

Chemiosmosis

-accumulation of protons in the intermembrane space drives protons into the matrix via diffusion

-moves slowly since the membrane is relatively impermeable to ions

tiny rotary motor

-carries out ATP synthesis driven by a proton gradient, when protons travel through the channel it causes the rotation

-mechanical energy changes the confirmation of the catalytic domain

Aerobic respiration in mitochondria

1. oxidation of NADH and FADH2

2. pump H+ across the membrane

3. electrons are shuttled to Complex III

4. Electrons from complex 3 are picked up by cytochrome C

5. Cytochrome C carries the electrons to the final complex

6. H+ gradient dries ATP synthesis

Energy Yield of respiration (whole process)

-32 ATP per glucose for bacteria

-30 ATP per glucose for eukaryotes (loses 2 ATP for transporting NADH from cytoplasm into mitochondria)

substrate level and oxidativefor each step

glycolysis: yes and no

Pyruvate ox.: no and no

Citric acid cycle: yes and no

ETC: no and yes

Electron tower

-bacteria go for the electron acceptor that yields the highest energy and then move down the tower when they are depleted: aerobic, anoxic, anaerobic

anaerobic respiration

-use of inorganic molecules (other than O2) as final electron acceptor

-many prokaryotes use sulfur, nitrate, carbon, dioxide or even inorganic metals

methanogens

-CO2 is reduced to CH4 (methane)

-found in diverse organisms including cows