Biology Midterm 2

metabolic pathways are regulated by ______.

feedback inhibition

Membrane Functions

1. controls transport

2. compartmentalizes the cell

3. signaling

4. enzymatic activity

5. attachment/recognition

Controlling transport includes:

• maintains an intracellular environment

• creates ion gradients

• nutrients + waste

Compartmentalizing cells:

• increase surface area to volume ratio

• increase efficiency

Signaling

point of contact for information

Plasma Membrane

Lipid bilayer

Fluid mosaic model

• components constantly in motion

• diverse protein, lipid and carbohydrates

Lipids

non polar and hydrophobic

the 3 types of lipids

1. fats

2. steroids

3. phospholipids

Fats

3 fatty acids linked to glycerol

e.g. triglycerides

Steroids

lipids with 4 ring structure

e.g. cholesterol

Phospholipids

(amphipathic) contain phosphate as a part of a polar head and 2 hydrophobic tails. They spontaneously form micelles or bilayer in water.

Micelles

single hydrocarbon tail (low energy stable) ring like structure

Bilayers

2 hydrocarbon tails (low energy stable)

Unsaturated vs saturated fats

saturated: straight

unsaturated: has double bonds and kinks (bent)

do all phospholipids contain fatty acids?

No. Bacteria and eukaraya do. Archaea has isoprenoid tails.

Membranes are asymmetric

types of phospholipids differ between monolayers. This is important for function.

Eukaryotic membranes contain what sterols?

animals = cholesterol

fungi = egosterols 

plants = phytosterols

but are absent in prokaryotes

why are membranes flexible, repairable and expandable?

because they are fluid

what factors affect membrane fluidity and permeability?

1. ratio of saturated vs unsaturated fat

2. temperature

3. cholesterol

Ratio of saturated and unsaturated fatty acids

unsaturated: higher permeability and fluidity because they are not tightly packed together

saturated: lower permeability and fluidity because they are packed tightly

which fatty acids solidifies in lower temperature first?

saturated

how do organisms maintain optimum fluidity

by adjusting their fatty acid composition to allow more unsaturated fatty acids to be present.

how does cholesterol affect permeability and fluidity?

decreases fluidity at higher temp by reducing phospholipid movement

increases fluidity at lower temp by reducing packing opportunities

what is the membrane permeable to?

it blocks out large, polar and charged molecules and lets in small, non polar molecules.

why can ions pass through the membrane?

ions are always incapsulated by hydrogen and oxygen so its not as small.

Simple Diffusion (passive)

net movement from high concentration to low concentration (spontaneous)

Osmosis (movement of water)

diffusion of water due to different solute concentrations across a selectively permeable membrane. Water goes to the side with high solute concentration.

Tonicity effect on water movement

Hypertonic: water moves outwards (shrinks) - high solute concentration

Hypotonic: water moves inwards (swells) - high solvent concentration

Isotonic: water moves in and out.

Membrane Protein Functions

• transport

• enzymatic activity

• signal transduction

• cell - cell recognition

integral vs pheripheral membrane protiens

Integral: inside bilayer

Pheripheral: on top of bilayer

What traverse the hydrophobic core?

Alpha helices or beta sheets

multipass transmembrane protein

help other substances cross the membrane

Facilitated diffusion (passive)

substances diffuse across membrane with the help of membrane transport proteins along their concentration gradients.

Channel protein

creates hydrophilic pathways without conformational changes or energy for specific ions or water. (e.g.. aquaporin protein)

Many channel proteins are ____.

Gated

what causes the channel to switch to an open state

ATP and addition of phosphate

Nerve impulse transmission relies on?

gated ion channels

Diffusion rate through channels depend on:

1. state of protein (open or closed)

2. concentration gradient

3. number of gated channels at the plasma membrane.

Carrier Proteins

use conformational change ot move specific solute along its concentration gradient

Steps of carrier proteins

1. molecule attaches to transporter binding site

2. carrier protein changed conformation

3. transporter opens to the other side and solute diffuses

Active transport

Using energy to move solute AGAINST its concentration gradient.

pumps

use ATP or light for energy

Coupled transporters

use an ion gradient as a source of energy

Pumps use _____ to power conformational changes that moves _____.

energy; solute

Steps of active transport

1. ATP phosphorylates protein so protein is in high energy state

2. solute binds to protein to cause a conformational change

3. binding site opens to other side, shape change causes reduced binding affinity

4. ion and phosphate removed

5. protein reverts to original shape

e.g. acid in stomach

membrane potential

different charge across membrane

what are chemical gradients based on

voltage + concentration

The Sodium Potassium Pump

movement of Na+ out of the cell

Steps of the sodium potassium pump

1. unbound protein: 3 binding sites within the protein have high affinity

2. sodium binding: 3 Na+ bind to those sites

3. Shape change: P group from ATP binds and protein changes shapes

4. Release

5. unbound protein: now protein has 2 binding sites for K+

6. All steps repeat but for K+

how does the Sodium Potassium Pump create a concentration gradient?

because 3 sodium get released and 2 potassium go in. There for the outside is more positive than the inside.

Potential difference

the difference between inside charge and outside charge

Nerve impulse

electrical current travelling along axon due to ion moving through volted gated channel proteins in the neuron membrane

what creates the nerve impulse?

pumps and gated channels

coupled transport uses _______

ion gradients as energy

how does a coupled transport use ion gradients as energy?

it uses the potential energy in an ion concentration gradient to move another molecule against its concentration gradient.

Symport

2 molecules in membrane move in the same direction

Antiport

2 molecules in the membrane move in different directions.

Na+/Glucose Co transporter

binding of Na+ of Glucose causes a conformational change which leads to an affinity change too.

when affinity decreases…

glucose is needed (symport)

The 2 metabolic pathways

Respiration and Fermentation

Cellular Respiration

Series of metabolic reactions that convert energy in organic molecules like glucose.

Fuel Molecules

provide energy

Activated Carrier Molecules

Move energy around the cell

the 3 activated carrier molecules

ATP, FADH2, NADH

Energy is transferred via _______

Redox Reactions

Substrate phosphorylation

enzyme catalyzes transfer of phosphate from high energy substrate to ADP

Oxidative Phosphorylation

ATP is made with ADP + Pi by ATP synthase using proton gradient for energy.

Glycolysis

involves partial oxidation of glucose to form pyruvate and generates ATP + NADH

The first 5 steps of glycolysis is

energy investment phase

what is the end result of glycolysis?

a 6 carbon glucose coverts in to a 3-carbon sugar phosphate (G3P!!)

The first 5 steps of glycolysis:

1. adding a phosphate to glucose

2. rearranging it

3. adding another phosphate

4. splitting the molecule in half

The last 5 steps of glycolysis is…

the energy payoff phase

the last 5 steps of glycolysis:

1. G3P is oxidized and phosphorylated

2. a phosphate group is transferred to ADP to create the first ATP molecule

3. rearrangement

4. a water molecule is removed

5. the energy of glucose goes to the bonds in pyruvate and ATP is released as heat

is glycolysis aerobic or anaerobic?

aerobic

2 pyruvate converts into…

2 Acetyl-CoA

what complex oxidizes pyruvate to Acetyl-CoA in the mitochondrial matrix?

Pyruvate Dehydrogenase

Acetyl-CoA enters the…

Citric Acid Cycle

steps of Citric Acid Cycle

1. acetyl-coa and oxaloate combine to form citrate 

2. Citrate is rearranged

3. its then oxidized and loses 1 carbon and produced NADH

4. its oxidized again losing another carbon and producing another NADH.

5. GTP/ATP is formed

6. FADH2 is created

7. water is added to make malate which is reused to start the cycle again

outcomes of citric acid cycle

1 ATP

3NADH

1 FADH2

1 CO2

The citric acid cycle oxidizes…

Acetyl-CoA

where does glycolysis occur?

cytosol

pyruvate processing and citric acid cycle occurs in…

matrix of mitochondria or cytosol

where does the ETC occur?

inner membrane or plasma membrane

Steps of pyruvate oxidation

1. carbon removed from pyruvate and released as co2

2. remaining 2 carbon molecule is oxidized and the electrons released go to NAD+

3. Coenzyme A attaches to the 2 carbon molecule to form acetyl-CoA

what are the products of pyruvate oxidation?

2 acetyl-coa, 2 co2 and 2 NADH.

which type of phosphorylation does the CAC use

substrate level phosphorylation

steps of the CAC

1. acetyl coa attaches to a 4 carbon molecule (oxaloate) to form citrate (6 carbon)

2. citrate is taken through a series of enzyme catalyzation reactions.

3. during the steps, energy is released and captured by the formation of NADH and FADH2

4. 2 carbon atoms release at co2

5. the co2 attaches toa new acetyl-coa

products of the CAC

1 ATP, 3 NADH, 1 FADH2, 1CO2

what is the ETC

a group of integral membrane proteins in the inner membrane of the mitochondria

Components of the ETC:

complex 1-4 = protein complexes with redox capability (3 proton pumps)

ubiquinone = small lipid soluble organic molecules

• shuttles electrons + proteins

cytochrome C

small water soluble protein shuttles

The ETC creates a _______ ________across the inner membrane

proton gradient

which activated carrier molecule contributes to the proton gradient more?

NADH because its present from the 1st stage unlike FADH2 which enters at the 2nd stage.

what does the proton gradient do?

moves electrons from NADH and FADH2 by redox and moved protons from matrix to intermembrane.

oxygen is the…

final electron acceptor

what does water do in the ETC?

pulls out protons and decreases the amount of protons on the inside.

what powers the movement of protons?

Free energy (each molecule in the pathway is more electronegative than the previous one)