Cell Structure &functions Lec 9

Question 1

Energy in C-H bonds vs. C-O bonds

Answer 1

-Carbohydrates are used for structural support,protection and energy
-C-H bonds are stronger due to the bond length being shorter
-C-O bonds are longer due to the bond length being longer

Question 2

Redox (Oxidation vs. Reduction)

Answer 2

Oxidation:Loss of electrons
-During glycolysis, Glyceraldehyde-3P losses electrons in hydrogen and gains oxygen as part of phosphate
Reduction:Gain of electrons

Question 3

NAD+ vs. NADH

Answer 3

-Is a coenzyme that can transport electrons
-When an electron such as e- is transferred molecules pick up a hydrogen ion (H+ or proton)to balance the charge
-NAD is a nucleotide
-The coenzyme NAD+ is reduced which helps NADH gain 2 electrons

Question 4

Coenzymes

Answer 4

-Are non protein cofactors for reactions

Question 5

Describe the steps in the Glycosis

Answer 5

Step 1:Phosphorylation of glucose to glucose-6 phosphate. * This reaction requires energy, and so it is coupled to the hydrolysis of ATP to ADP and Pi.
Enzyme: hexokinase
-It has a low Km for glucose; thus, once glucose enters the cell, it gets phosphorylated.
* This step is irreversible. So, the glucose gets trapped inside the cell. (Glucose transporters transport only free glucose, not phosphorylated glucose.)

Step 2: Isomerization of glucose-6-phosphate to fructose 6- phosphate. The aldose sugar is converted into the keto isoform.
* Enzyme: phosphoglucomutase.
* This is a reversible reaction. The fructose-6-phosphate is quickly consumed, and the forward reaction is favored.

Step 3:Is another kinase reaction. Phosphorylation of the hydroxyl group on C1 forming fructose-1,6- bisphosphate.
* Enzyme: phosphofructokinase. This allosteric enzyme regulates the pace of glycolysis.
* Reaction is coupled to the hydrolysis of an ATP to ADP , and Pi.
* This is the second irreversible reaction of the glycolytic pathway.

Step 4: fructose-1,6-bisphosphate is split into 2 3-carbon molecules,
one aldehyde and one ketone: dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP).
* The enzyme is adolase.

Question 6

What is Fermentation

Answer 6

-Occurs in the cytosol without oxygen
-Converts pyruvate into lactate
-Converts NADH back to NAD+
-Glycosis stops without NAD+
-Commonly used in Stressed tissues like overused muscles
-Converts pyruvate into ethanol
-Produces carbon dioxide
-Commonly used to make beer and wine

Question 7

What is fermentation in yeast?

Answer 7

-Involvs metabolites in mutiple tissues
1)Dietary Glucose
2)Blood Glucaose -Liver Glucose-6P
3)Muscle Glucose-6P-Muscle Lactate
4)Muscle Glycogen
5)Liver Glycogen
6)Liver Glucose-6P
7)Liver Lactate-Blood lactate

Question 8

What is the process of Replenish

Answer 8

-Happens in NAD+ for further rounds of glycosis
-Are used in coenzymes to describe how NAD needs this action for metabolic pathways to continue

Question 9

Define Interconnected pathways

Answer 9

-A catalyization that happens in specific enzymes

Question 10

of ATP produced by aerobic respiration

Answer 10

-Glycolysis and fermentation do not require oxygen to produce a little energy in the cytosol(2ATP)

Question 11

Mitochondria

Answer 11

With oxygen there is :<32 ATP/Glucose
Without oxygen:There is 2ATP/Glucose
-Major energy source of eukaryotic cells
-Contains unique lipids called (Cardiolipin)
-Are derived from a symbotic prokaryote
-After the first organelles developed,a bacteria took up residence in a eukaryotic cell
-Some mitochondrial proteins are now encoded in the eukaryotic nuclear geonome
-Are more active

Question 12

What is a mitochondrial genome(mtDNA vs.Nuclear genome(DNA)

Answer 12

mtDNA
-After the first organelles developed,a bacteria took up residence in a eukaryotic cell

Nuclear genome(DNA)
-Some mitochondrial proteins are now encoded in the eukaryotic nuclear geonome

Question 13

Define Mitochondrial matrix

Answer 13

-Contains their own genome and ribosomes in the mitochondrial matrix
-Pyruvate travels through two transports to reach the mitochondrial matrix
-The matrix has a distinct chemical environment within mitochondria

Question 14

Define Outer vs. Inner Mitochondrial Membrane

Answer 14

-On the outside of the mitochondrial matrix
-Specific pyruvate transports (MPC)imports pyruvate across the inner mitochondrial membrane

Question 15

Define Intermembrane space

Answer 15

-Happens within the outer mitochondrial membrane of the porins and transfers into the intermembrane space
-The intermembrane space has similar ions to the cytosol
-The matrix has different ions than the intermembrane space
-The intermembrane space shares ions and molecules ithin the cytosol

Question 16

Define Cristae

Answer 16

-Wrapped in two membranes, the inner membrane has internal folds

Question 17

Define Symbiote

Answer 17

-An organism that is very closely associated with another,usually larger organisms

Question 18

Define Mitochondrial Fission vs. Fusion

Answer 18

Mitochondrial Fission:
-Mitochondria use dynamic-related proteins(Drp) to squeeze the organelle to promote fission
Mitochondrial Fusion:of both mitochondrial membranes is needed to connect the cristae membranes and share a common matrix
-The outer membranes fuse with the help of mitofusins (Mfn) The inner membranes fuse with the help of Opa proteins
*Mitochondria can grow and divide to meet the metabolic needs of a cell *

Question 19

Define Dynamin

Answer 19

Are large GTPases
Form of helix around membranes
Hydrolyze GTP to change conformation to thin membranes
Include membrane scission

Question 20

Define the mitochondrial divide

Answer 20

-The ER helps mitochondria divide
-The endoplasmic recticulum marks future sites of mitochondrial fission
-Drpl is recruited and constricts the mitochondrion
-The mitochondrion divides into two mitochondria

Question 21

Define Reactive Oxygen Species (ROS)

Answer 21

-Sperm mitochondria are damaged by ROS
-Damaged mitochondria are degraded via a processes called autophagy
-Only oocyte mitochondria are inherited by embryos

Question 22

Define porin

Answer 22

-Are large channels that allow molecules to diffuse across the outer mitochondrial membrane into the inter-membrane space

Question 23

Define a Beta-barrel

Answer 23

Are porins that are large with a large pore(<2nm) in the outer membrane
-Non-specific channel

Question 24

Define Mitochondrial Pyruvate Carrier

Answer 24

-Are a heterodimer with transmembrane domains in the inner membrane
-Has a specific transporter(Facilitated)

Question 25

· Specific vs. non-specific transport

Answer 25

Key Takeaways:Mitochondrial transport
-The mitochondrial outer membrane is generally permeable to small molecules via large porin channels
-The inter-membrane space has similar ions to the cytosol
-The mitochondrial inner membrane is a tightly controlled barrier with specific transporters fir each molecule
-The matrix has different ions than the inter-membrane space

Mitochondria:Key themes
-Redox reactions allow the exchange of energy in the form of electrons
-Mitochondria are key energetic organelles to a eukaryotic cell’s survival
-Mitochondria are subdivided into distinct compartments with different chemical compositions