First Examniation Cell Biology

Front 1

What is cell biology a combination of?

Back 1

3 life sciences:
-Cytology
-BioChemistry
-Genetics

Front 2

Who is Robert Hooke?

Back 2

1665- coined the them cell when he examined slices of cork(dead phlom)and observed honeycomb like compartments calling them cells

Front 3

Who is Van Leeuwenhoek?

Back 3

First to observe living cells in the 1670's
-observed blood cells and single cell organisms in pond water

Front 4

Which 3 scientits developed the cell theory

Back 4

Matthias Schleiden (botanist)
Thodore Schwann (zoologist)
Rudolf Virchow (pathologist)bacteria

Front 5

What does the cell theory state?

Back 5

1. All Living things are made of cells
2.The Cell is the basic unit of Life
3.All cells come from pre-existing cells
Meaning that ALL LIFE IS CELLULAR

Front 6

What are the Fundamental Properties of Cells?

Back 6

1.cells are Microscopic, aqueous compartments

2. All cells have a Plasma membrane

3.Obey the laws of chem and physics

4. use enzymes as catalysts

5. engage in energy transduction (sun-organic-energy)

6. are irritable: respond to their enviornment

7. Can reprduce themselves

8. use DNA as gentic material

9.Follow central dogma for gene expression (DNA-RNA-Protien)

Front 7

What are the 2 major cell types?

Back 7

Prokaryotic and Eukaryotic

Front 8

What are the basic charateristics of Prokaryotic cells

Back 8

Lack a true nucleus
Relatively small (1-5 microns)
Relatively Old (3.5 billion)
simple construction

Front 9

What is Prokaryotic cell construction like?

Back 9

One compartment
bounded by plasma membrane
bounded by a cell wall (peptidoglychan)
May have a capsule

Front 10

What does the Prokaryotic cell's cytoplasm consist of?

Back 10

NO organelles or cytoskeleton
DNA
-is one circular chromosome
- confined to an area "nucleoid"
Has many ribosomes around nucleoid

Front 11

What is an example of a Prokaryotic Cell?

Back 11

Bacteria --- E.COlI

Front 12

What are the basic charateristics of a Euckaryotic cell?

Back 12

True Nucleus
Relatively Large 10-50 micron
Relatively young-evloved from prokaryotic cells,1.5 billion

Complex construction

Front 13

What is the COnstruction of a
Eukaryotic cell?

Back 13

Subcellular compartments
-nucleus
-cytoplasm
each bounded by either a nuclear envelope or a cell membrane resepectively

Has organelles
Has Cytoskeleton
Rich in Ribosomes

Front 14

WHat is found in the Eukaryotic Nucleus?

Back 14

DNA - more than one linear chormosome

Front 15

what is found in the Eukaryotic cytoplasm?

Back 15

Organelles
Has a cytoskeleton
Rich in Ribosomes

Front 16

Name the Euckaryotic Organelles (Family of cell organelles)

Back 16

Endoplasmic Reticulum
-rough and smooth
Golgi Appartus
Mitochondria
Plastids - Chloroplast (plants only)
Peroxisomes
Vessicles
Vacuoles (small-animal, Large-Plant)

Front 17

What are the Non-membranous structures found in Eukaryotic Cell Cytoplam?

Back 17

Ribosomes
Cytoskeleton

Front 18

What are Ribosomes?

Back 18

Scaffolds on which protien synthesis takes place
Found in cytosol

Front 19

WHat is the Cytoskeleton?

Back 19

Fibrous protien filaments that provide mechanical support and produce mechanica force in the cell

Front 20

What is the plant cell composed of?

Back 20

All Subcellular compartments
-nucleus, cytoplasm
All Organelles
All Non-membranous sturctues
-including cell wall

Front 21

What does the Animal Cell Consist of?

Back 21

ALl Subcellular compartments
ALL Organelles except... plastids and large vacuole
All Non membranous sturctures except: Cell walls

Front 22

How many Eukaryotic cell groups are there? What are they?

Back 22

4.
Protists
Fungi
Plants
Animals

Front 23

How many Prokarotic Cell groups are there? what are they?

Back 23

2.
Eubacteria
Archebacteria

Front 24

Why do cells require a High surface area to volume ratio?

Back 24

B/C a cells volume represents the cells capacity to consume nutrients and produce wastes

while the cells surface area is the cells capacity to deliver nutrients to and remove wastes from its volume

Thus the surface area must be high enough to meet needs of a cells volume

Front 25

How do surface area and volume change as a cell gets larger?

Back 25

As a cell gets larger volume increases faster than surface area

surface area to volume ratio decreases thus smaller is better

Front 26

How do you increase surface area without increasing volume?

Back 26

Through the use of microvilli and surface folds

Front 27

What is Eubacteria

Back 27

present day bacteria including cynobacteria (blue-green algae)

Front 28

What is Archea?

Back 28

ancient/original form of bacteria divided into 3 maingroups:
1.methanobacteria
2.Halobacteia
3.Sulfabacteia

Front 29

Diffusion

Back 29

High-Low
rate varies inversly with size though can use cytoplasmic streaming (active transport)

Front 30

why do living systems engage in energy transduction?

Back 30

Living systems are highly ordered
reactions within system require energy
get energy from reactions that release energy

To obtain energy for reactions

Front 31

How do you determine which reactions release energy and or require it?

Back 31

Through the study of Thermodynamics

Front 32

What is biogenetics

Back 32

the application of thermodynamics to biological systems

Front 33

what is chemical equilibruim?

Back 33

estabilished when concentrations of each reactant and each product remains constant with time
thus the rate of the forward reaction is equal to the rate of the reverse reaction

Front 34

What is K ?

Back 34

equibrium constant
K=1 [p]=[r] At equilibrum
k>1 [p]>[r]far to right of center product side
k<1 [p]<[r] equilbrim is far to the left reactant side

Front 35

What is Free Energy (G)?

Back 35

-is the amount of energy available in a molecule that can be released to do work
-spontaneous chemical reactions release free energy to their enviornments as they proceed

Front 36

What are spontaneous reactions?

Back 36

reactions that proceed without out side intervention (w/o input of energy)
- loose free energy
- have a negative change G
- are exergonic

Front 37

what are charateristics of Non-spontaneous reactions?

Back 37

-move away from equilbrium
-are irreversable
-require energy input to start the reaction
-have a positve change G
-Are Endergonic

Front 38

How much free energy is lost/required in a spontaneous/nonspontaneous reaction?

Back 38

dependent on the Keq and concentrations of reactant and product

the furter away we get from equilibrium the greater the change G

Front 39

what are the 3 ways to calculate ∆G?

Back 39

Standard form
ambient form
generic form

Front 40

What is the Formula for the Standard Form of the ∆G?

Back 40

RT ln([p]/[r])- RT ln Keq
-where R= 1.98
-T=298 K
-P and r = 1.0M

comes to :-RTlnKeq

Front 41

What is the Formula for the Ambient Form for the ∆G?

Back 41

standard K and R
= 592cal/mol ln ([p]/[r])-592ln Keq
=RTln([p]/[r])+ (∆G standard)

Front 42

How do you interpret the ∆G?

Back 42

∆G<0 = neg, spontanous, reation quotient is < Keq'
The reaction is exergonic and releases energy, proceeds from Right to Left spontaneously

If ∆G > 0 = Positive
non spontanous, product favored (L-R),endergonic, REQUIRES ENERGY

If ∆G= 0 it is at equillibrium

Front 43

what 2 conditons must reactions satisfy to be effective with in the cell?

Back 43

High rate of the reaction
reaction rate must be capable of being regulated

Front 44

What is the primary function of enzymes

Back 44

increase the reate of chemical reactions

Front 45

What are enzymes?

Back 45

Biological catalysts- increase the rate of the reaction with out being consumed in it

Front 46

what are the 8 fundamental charateristics of enzymes?

Back 46

1. Enzymes accelerate the rate of chemical reactions
2. Enzymes do not alter the Keq or the ∆G of the reactions
3.Enzymes are not consumed in rxn
4. Enzymes are effective for a particular rxn or group of simal rxns (specific for substrate)
5. Are effective in small quantities
6.Most are protiens
7.affected by temp and PH
8.some require the used of coenzymes or proshtetic groups

Front 47

What does the amino acid structre consist of ?

Back 47

Center= Alpha carbon
Left= Amnio Group
Right= Hydorgen atom
Top= Carboxly group (o-C =o)
Bottome= Varriable R Group

Front 48

What is Zwitterions?

Back 48

When a free amno acid at neutral pH have a negative and positve charge, thus has an inoization at a neutral pH

Front 49

What is the steroisometeric form that protiens exist in?

Back 49

L form
-center carbon
left NH3+
Right; Hydrogen group
Bottom:Variable R group
Top:COO-

Front 50

What are the charateristics of the Nonpolar Amino Acids?

Back 50

Most Hydrophobic, least hydrophillic
R groups are nonpolar hydrocarbons

Front 51

Name the 9 Group A: Nonpolar Amnio Acids?

Back 51

Glycine: H
Alanine: CH3
Valine: CH-CH3-CH3
Leucine: CH2-CH-CH3-CH3
Isoleucine: H3C-CH-CH2-Ch3
Methoinine: CH2-CH2-S-Ch3
Phenylanine: CH2- Carbon group
Tryptophan-CH2-NH
Proline: H2C-CH2-CH2

Front 52

What are the Group B Amno Acids Charateristics?

Back 52

Polar, uncharged amnio acids
Moderately hydrophobic, Moderately hydrophilic

Front 53

What are the names of the Group B Charged amnio acids?

Back 53

Serine: CH2-OH
Threonine: CH-OH-CH3
Cysteine: CH2-SH
Tyrosine:CH2-6carbon-OH
Asparagine: CH2-C-NH2=O
Glutamine:CH2-CH2-C=O-NH2

Front 54

What are the Group C charged Amino Acids charateristics?

Back 54

Polar, charged
R groups are charged
poorly hydorphobic, very hydrophilic

Front 55

Name the Acidic Group C Amnio Acids

Back 55

Aspartate: CH2-C-O=O
Glutamate: CH2-CH2-C-O=O

Front 56

What are the Basic Group C Amino Acids?

Back 56

Lysine: Long chain of CH2 + NH3
Arginine long chain of CH2-NH-C=NH2

Front 57

What is Hydorphobicity?

Back 57

the realative degree to which a molecule is hydrophobic, Amino Acids are ranked according to the hydrophobicity scales

Front 58

What do hydorphobicity scales show?

Back 58

- the nonpolar amino acids= Most hydrophobic
- The Charged amino acids are the least hydophobic
- The polar, uncharged amino acids are moderately hydrophobic

Front 59

What are the two sturtural types of Protiens?

Back 59

Fibrous Proteins-very important,small fraction of cell
Globular Protiens- Most proteins in the cell are globular including enzymes

Front 60

What is the structure of Globular proteins?

Back 60

They have a hierarchical structure:
-Primary Structure
-Secondary Structure
-Tertiary Structure

It has a specific 3D shape called conformation which is achieved through a complex process of folding that takes place after synthesis

shape is held together by mostly non-covalent bonds and a few covalent

Front 61

what does the primary structure of a globular protein consit of?

Back 61

is the specific sequence of amino acids in that protein

This primary sturcture is very specific for a protein(determined by the sequence of nucleotide in the gene that codes for the protein
Adhacent amino acids are held together by a covalent bond called a peptide bond

Front 62

What is a peptide bond?

Back 62

is a condensation reaction (dehydration) reaction between the alpha carboxyl group of one amino acid and the alpha amnio groups loose their charge

Front 63

What is the size of an average protien?

Back 63

50-25,000 AA

Front 64

What does folding have to do with proteins?

Back 64

after the primary structure is synthesized, it carefully folds into a specific 3-d shape maintianed by molecular interactions among amnio acids, and polar and nonpolar R groups

Front 65

How is folding of proteins maintained?

Back 65

By molecular interaction among amnino acids which are located btwn N-H and C=O and
Non polar R groups interact with each other, Polar R groups interact with each other

Front 66

How many levels of folding exist in the primary sturcture?

Back 66

2- secondary struture and teritiar structure

Front 67

What are the 2 major secondary structures?

Back 67

alpha helix
beta sheet

Front 68

what is the alpah helix?

Back 68

multipule hydrogen bonds btwn the alpah N-H and alpha C=O groups of every peptide bond within the struture
-whether parts of the secondary struture become this depends on the sequence of amino acids

Front 69

Is there a limit o the alpha helix length?

Back 69

No practical limt

Front 70

What is the beta sheet?

Back 70

created through interactions of adjacent beta strands which is about 5-10 residues long and the sheets are pleated with alternating r groups in opp directions

Front 71

What is the tertiary structure of globular protiens?

Back 71

it is the final 3-D shape (conformation) of the protien
that comes about through the global folding of amino acid chains along with it seconday structures

Front 72

What does the tertiary structure consist of ?

Back 72

regions of high hydrophbicity = interior of the protein
Stabailized through several different types of molecular interactions between R groups

Front 73

what is the single most important driving force that determines the final specific 3D shape of a protien

Back 73

requirement that the interior
core of the globular protein be densely packed and very
hydrophobic.Regions of high hydrophobicity usually fold into the interior of the
protein.

Front 74

what forces stablize the teritiar structure?

Back 74

Intermolecular forces:
Noncovalent bonds among
R groups
• Hydrophobic interactions
• Ionic bonds
• Hydrogen bonds
– Covalent bonds among R
groups
• Disulfide bonds

Front 75

What about the quaternary structure?

Back 75

found only in complex protiens composed of more than one smaller protien subunit called multimeric subunits and each subunit has a complete sturctrue

4th is stablized by same bonds teritary sturture

Front 76

What is an active site?

Back 76

locus on the protein wehre the substrate binds

it is a crevice or pocket extending from the surface of the protein to the interior consiting of 15-30 amino acids R groups exposed on the surface of the crevice

Front 77

What are coenzymes and prosthetic groups?

Back 77

molecules that possess properties required by the enzyme to catalyze a partiular reaction but not possessed by the enzyme

Front 78

What do coenxymes and prosthetic groups consist of?

Back 78

they are always non-protein molecules, realatively small moleular weight, may be inorganic or organic

Front 79

what is the difference between coenzymes and protosthic groups?

Back 79

Prosthetic groups are tightly bound, functionally permanent parts of the enzyme

while conezymes are loosely bound and reverisbly bind to the enxyme during the reation and take part in some critical aspect of the enzymes function

Front 80

what is an example of a coenzyme?

Back 80

NAD, used in some biological oxidation reduction reactions

Front 81

what is an example of a prosthetic group?

Back 81

heme

Front 82

Why do reactions proceed so slowly?

Back 82

Reaction rate is dependant upon activaton energy, thus if the EA is High the reaction rate will be slow and if the EA is low then the reaction rate will be fast
thus the activation of cellular processes are suffently high so that the reaction proceeds slowly

Front 83

what is Activation Energy?

Back 83

is the minumum amount of energy needed to activate the reactants

Front 84

What is a Transistion State?

Back 84

an intermediate state between reatants and products

Front 85

HOw do you lower activation energy and why?

Back 85

To speed up reactions cells must lower the activation energy

to do so you can increase the temperature, and use catalysts (enzymes)

Front 86

How do enzymes lower activation energy?

Back 86

they lower activation energy by decreasing free energy of the transistion state and activation energy

Front 87

What is kinetics?

Back 87

is the study of the mechanism of a chemical reaction through the study of the rate law that governs the reaction

Front 88

What do rate laws do?

Back 88

Define the mechanism of the reaction

Front 89

What is the mechanism of a basic enzyme catalized reaction?

Back 89

Michaelis-Menten
It is a 2 step reaction:
[E]+[s]<-->[ES]-->[P]+[E]

E= free unbound enzyme
S= is unbound substrate
p= unbound prouduct
ES= is enzyme-substrate complex

reaction 1: substrate binding step
reaction 2: catalytic step

Thus the enzyme has an active site

Front 90

what were the 3 scientist asked to find the basic mechanism of an enzyme reation?

Back 90

L.Michaelis
M.L. Menten
V. Henri

Front 91

what happens at a realitivly low substrate level?

Back 91

there are more enzymes than substrate therefore there are more sites to bind if more substrate is added = as the substrate concentrtion increase the velocity increases
thus the hyperbolic curve continues upward

Front 92

what happens when the substrate concentration is equal to the enzyme concentration?

Back 92

the enzyme is completely saturated so velocity is saturated, there is no free active sites to bond to and increase the velocity thus it stays the same/constant

Front 93

what are the two models of substrate bonding?

Back 93

Lock and Key model
infuced fit model

Front 94

What does the lock and key model consist of?

Back 94

-Enzyme and Active Site have a rigid shape
-Enzyme and active site have one conformation
- substrate has a perfectly complementary/shape
-upon substrate binding there is no complementary change in the active site

Front 95

What does the induced fit model consist of?

Back 95

More accepted model
-enzyme and active sites are Not rigid structures
- Enzyme and active site have 2 basic conformations
1.when it is bound
2.when substrate is not bound
- Substrate has a near-complementary size/shape
- at binding the substrate interacts with a few critical R groups thus inducing a shape change that results in a perfect fit for the enzymes active site

Front 96

What are the two basic phases of catalysis?

Back 96

Substrate activation
product formation

Front 97

what does substrate activation consist of?

Back 97

period when the substrate reaches the transition state

Front 98

what are the 3 most common mechanisms of substrate acivation used in catalysis?

Back 98

-Substrate bond distortion: makes the bonds vunerable to catalytic attack
-change in the active site pH through proton exchange
-electron rearrangement and formation of temporary covalent bonds

Front 99

what is teh Vmax?

Back 99

it is a qualitative charaterization of Enzyme Function that measures the velocity of catalysis

It is directly dependant on the [E]

Front 100

what is the Km?

Back 100

It is the michaelis -Menton constant for the measure of the enzymes affinity for a substrate

Km=[S]1/2vmax

Front 101

what is substrare binding affinity

Back 101

how strongly a substrate binds to an acive site

a substrate meant for the active site is going to bind strongly to the active site

one that is not will form a weak bond

can be measured using Km

Front 102

What is the significance of Km in reguards to binding affinity?

Back 102

the lower the Km the higher the substrate binding affinity for that enzyme is thus a high specificty
and the less substrate is needed to create product

A High Km =
Lower binding affinity and a lower specificity

Front 103

what is the usefullness of Km?

Back 103

helps determine the specificity of the enzyme
helps identify the natural substrates
helps determine the approximate intercellular concentrations of the natural substrate which is approx to Km

Front 104

how can Km regulate rate the reaction?

Back 104

if intracellular concentration of substrate is = KM then the cell can regulare the Velocity of the reaction by simply regulating the concentration of the substrate

Front 105

what is the equation of the hyperbolic curve velocity vs. substrate concentration?

Back 105

Vi = (Vmax [S]) / (KM + [S])

Front 106

what are the 3 ways Cells can regulate the rate of an enzyme-catalyzed reaction?

Back 106

1. Regulating the [E]–because Velocity of the reaction is directly dependent on [E]
2. Regulating the [S] of the substrate – Assuming it is approx equal to KM.
3. Regulating the activity of the enzyme. The activity of many enzymes can be increased or decreased. increasing enzyme activity is known as “enzyme activation” or positive regulation
• Decreasing enzyme activity is known as “enzyme
inhibition or negative regulation

Front 107

what are the two major mechanisms for controlling enzyme activity?

Back 107

Allosteric regulation
covalent modification

Front 108

What is allosteric regulation?

Back 108

Allosteric regulation is the single most
important mechanism used by the cell to
control enzyme activity.
– Used to regulate a special class of enzymes called allosteric enzymes. done by binding to the allosteric site increasing or decreasing activity of the enzyme.

Front 109

What is the structure of an allosteric enzyme?

Back 109

It is a multimeric protien that have two basic subunits
- catolic subunit (C)
contains an active site
- regulatory subunits (R)
contains an allosteric site

Front 110

what are the 2 conformations of allosteric regulation?

Back 110

Allosteric enzymes have two
possible conformations:
- Active conformation with high substrate affinity
- Inactive conformation with low substrate affinity

Front 111

what is postive cooperativity?

Back 111

allosteric enzymes kinetics:
at a vey low substrate concentration an enzyme exhibits low affinity and thus low velocity

with addition of more substrate , the substate induces a greater binding affinity and thus greater velocity

At high substrate concentration there is saturation

Front 112

what is the effect of allosteric regulators on kinetics?

Back 112

– No change in Vmax/ do not effect the Vmax

1. Allosteric activators shift
the curve to the left decreaseing Km thus increasing substrate binding affinity as well as the velocity of the reaction

2. Inhibitors shift the curve to the right (increase the KM)decreasing substrate binding affinity and decreasing velocity

Front 113

what is allosteric inhibition?

Back 113

the most common form of allosteric regulation applied in the cell through feedback inhibition along the metabolic pathway

Front 114

what is feedback inhibition?

Back 114

the downstream product of a partiular reaction serves as an allosteric inhibitor of an upstream enzyme

Front 115

How does feedback inhibition work?

Back 115

The greater the activity of the pathway leads
to . . .
– the greater production of the final downstream product, which leads to . . .
– the increased inhibition of the upstream enzyme, which results in . . .
– a decrease in the activity of the pathway and a reduction in the synthesis of the downstream product.
• Purpose: control the concentration of the
product (prevent the toxic accumulation of
the product)
• Analogy: operation of a thermostat

Front 116

what is an example of feedback inhibition?

Back 116

Biosynthesis of Isoleucine through 5 reactions
Isoleucine is the downstream
product – it is an allosteric
inhibitor of threonine deaminase(an allosteric enzyme)
• As isoleucine is produced and accumulates, it allosterically inhibits threonine deaminase.

1. allosteric inhibitor binds to the allosteric site of the enzyme
2. that causes the active site to go through conformation change
3 change in the substrate binding affinity-- stabilizes the enzyme in its low affinity form resulting in no or little activuty

Front 117

what is covalent modification?

Back 117

A mechanism in which enzyme activity is regulated through the covaletn addition or removal of a functional group to or from a particular amino acid R group on the enzyme

Front 118

How is covalent modification different from feedback inhibition?

Back 118

– regulator molecule is a simple functional group
– site of binding is NOT a crevice or pocket (with
specificity), but rather a simple amino acid R group
exposed on the enzyme surface
– binding of the regulator to the enzyme is COVALENT
– binding reaction is enzyme-catalyzed
– Removal of the regulator requires breaking the covalent
bond
• Requires a different enzyme

Front 119

what are the three basic types of covalent modification?

Back 119

Protein Mehylation
Protien Acetylation
Protien Phosphoralation

Front 120

what are the basic features of protien phosporalation?

Back 120

the additon of a phospate group to an enzyme
- it is covalently linked/bonded to amnio acid groups
- The reaction is protien mediated
-the dephosphoralation reaction is enzyme mediated
- can result in the activation or inhibiton of and enzyme depending on the particular enzyme

Front 121

To which amino acid residues does the phosphate group attach during phosporalation?

Back 121

SERINE,THREONINE, or TYROSINE

Front 122

which protein mediates the phosphoralation reaction? The dephosphoralation reaction?

Back 122

Protien Kinase

Protien Phosphotase

Front 123

what are the 5 major protien kinase families?

Back 123

Receptor Tyrosine Kinases
Protein Kinase A
Protein Kinase C
CaM Kinases
Protein Kinase III

Front 124

what is an example of protien kinase A in action?

Back 124

Gycogenolosis

Front 125

what is glycogenolosis?

Back 125

the chemical breakdown of glycogen to glucose by the enzyme glycogen phosphorolase

Front 126

How does protien Kinase activate glycogenolosis?

Back 126

1.cyclic AMP acivates the allosteric enzyme protien kinase A
2.1st reaction: Activation of glycogen phosphorylase kinase
3 second reaction:Activation of glycogen phosphorylase

Front 127

How does the Activation of glycogen phosphorylase kinase occur?

Back 127

this is the first reaction in glycolosis...

Glycogen phosphoylase kinase is activated by Protien Kinase A with the additon of a phosphate group to the
hydroxl group of the protien

Front 128

How does the activation of glycogen phosphoralase occur?

Back 128

This is the second reaction in glycolosis...
Glycogen phosphoralayse kinase
activates glycogen phosphoralase b (inactive) with the addtion of a phospate group from ATP to the hydroxl group of the protien creating glyogen phosphoralse a which
catalyzes the break down of glycogen

Front 129

How does the Regulation of
Protein Kinase A by cAMP occur?

Back 129

1.cAMP activates protien kinase A by binding to the regulatory subunits
2.the binding of cAMP to the regulatory subunits causes the regulatory subunits to change conforamtion and detach
from the catolic subunits
3. once the catolic subunits are free they are activated and capable of phosphorylating target protiens in the cell

Front 130

How is glycogen broken down in the liver?

Back 130

1. Decrease in blood [glucose]
stimulates glucagon (hormone)
production
2. Glucagon binds to surface receptors on liver & sksletal muscle
3. Causes a rise in cAMP in the cell
4. Activates Protein Kinase A
5. Stimulates glycogen phosphorylase kinase
6. Stimulates glycogen phosphorylase
7. Accelerates glycogenolysis
8. Increase in blood [glucose]

Front 131

why are cells compartmentalized?

Back 131

activity can be controlled with in the compartments different opperations can be carried out and run at differnt levels of concentration

Front 132

what are the two catagories of biological membrane?

Back 132

– Plasma membrane
– Internal membrane

Front 133

what are the two common charateristics that all biological membranes share?

Back 133

- Same basic structure
– All are selectively
permeable
- lipids are amphathic : hydrophillic head, hydrophobic tail

Front 134

what is the fluid mosaic model?

Back 134

The model states that
biological membrane is composed of proteins embedded to various extents in a fluid lipid-bilayer.

found by First proposed by
Singer & Nicholson in 1972

Front 135

what is the average chemical composition of biological membrane?

Back 135

Average membrane 47protien and lipid 6carbon protien lipid ratio 1:00

Front 136

what is the sturture of a liposome and why are they formed?

Back 136

liposomes
• Structure of the lipid
membrane in a liposome:
a bilayer:
– hydrophobic tails come
together away from water
– Hydrophilic heads face
water

formed in the presence of water

Front 137

What types of lipids are there?

Back 137

Phospholipids
Sterols
glycolipids

Front 138

what are phospholipids?

Back 138

Lipids that contain phosphate groups
– 50 – 90% of the lipids in a membrane

Front 139

What are sterols?

Back 139

Lipids containing a 4-ring hydrocarbon
structure
- 5 – 45% of the lipids in a membrane

Front 140

What are glycolipds?

Back 140

Lipids with carbohydrate covalently
attached
– Less than 5% of lipids in a membrane

Front 141

What are the two types of membrane phospholipids?

Back 141

Phosphoglicerides
(Head) Chlorine-Phoshpate- (Tail)Glycerol- 2 fatty acids
Sphingolipids
chlorine-phospate-sphingosine- 1 fatty acid

Front 142

What are the 4 R grops?

Back 142

ethanolamine
choline
serine
inositol

Front 143

what does the sturctue of a sterol consist of?

Back 143

Hydrophobic tail
• 4-ring structure
– Hydrophilic head
• Single OH group
– The main sterol in
animal cell membranes
is cholesterol
– The main sterols in
plant cell membranes
are the phytosterols

Front 144

What doe the structure of a glycolipid consit of?

Back 144

– Most are derivatives of
sphingolipids
– Hydrophobic tail
• Sphingosine
• One fatty acid
– Hydrophilic head
• Six-carbon sugar

Front 145

What is bilayer fluidity and why is it important?

Back 145

bilayer fluidity: the ease with which the lipid molecules of a membrane move within the plane of the bilayer

Front 146

what are the 3 types of possilbe membrane lipid movements?

Back 146

Lateral diffusion: 1 particular lipid molecule can move laterally with in leaflet
– Rotational diffusion: roate along its access
– Transverse diffusion: moves out of it leaflet
• Aka “flip-flop”
• Extremely rare

Front 147

How can you measure lipid fluidity?

Back 147

Through the method of Fluorescence Recovery after Photobleaching.

label with florecent dye, hit with laser in one area to bleach it, watch for rate of diffusion of dye back into the spot

find that a Typical phospholipid molecule can travel a few microns in a
second or less.

Front 148

what are the factors that determine lipid fluidity in a bilayer?

Back 148

Temperature
Molecular characteristics of
the phosphoglycerides
– Fatty acid chain length
– # C=C double bonds in the fatty acid chain
• Concentration of sterols in the bilayer

Front 149

What is the effect of temperature on bilayer fluidity?

Back 149

generally as temperature increases bilayer fluidity increases because as you increase temp you are getting closer to the melting point of the bilayer

Front 150

what is the melting point of a bilayer also known as?

Back 150

The transition state (Tm)
when the bilayer undergoes a gel to liquid phase change

Front 151

What does Tm Measure?

Back 151

Tm Measures the bilayer fluidity
Rule:The lower the Tm , the
greater the bilayer fluidity.

Front 152

What is the Effect of F.A.Chain Length on the Tm and Bilayer Fluidity?

Back 152

Fatty acids are acids with a
hydrocarbon chain.
• In nature, fatty acid chain
lengths range from 10 – 20
carbons approx.
• Adding 2 carbons increases
Tm by 5 – 10 degrees C
• Membranes containing longer
chain fatty acids have higher
melting point

Front 153

Why do chain lengths decrease fluidity?

Back 153

The longer the hydrocarbon chain, the more hydrophobic
bonds. thus the more bonds that need to be broken = takes more energy (heat)increasing the temp and Tm

The longer the chain the more energy needed to break the hydrophobic bonds

Front 154

What does the effect of a carbon to carbon double bond have on Tm and bilayer fluidity?

Back 154

Each C=C creates a kink in the fatty acid chain, As the # of C=C double bonds increases, the melting
point of the fat (Tm)
decreases, and the fluidity
increases
-One C=C drops MP by 55 degrees C.

Front 155

what are fatty acids with no carbon to carbon bonds?

Back 155

Saturated fatty acids

Front 156

Why does the inclusion of C=C decrease Tm (increase fluidity)?

Back 156

because the kink separtates the chain decreasing bond strength because they are not so densly packed

Front 157

What effect does cholesteral have on membrane fluidity?

Back 157

Cholesterol moderates the
effect temperature has on the membrane.
– Cholesterol reduces membrane
fluidity at higher temps
•Due to rigidity of the cholesterol molecule.
– Cholesterol increases membrane fluidity at lower temperatures
• Cholesterol prevents close
packing of phospholipids as temp is decreased

Front 158

what is found in the extracellular leaflet?

Back 158

1. Phosphatidylcholine and sphingomyelin are more
concentrated in extracellular leaflet.
2. Glycolipids are absolutely restricted to the extracellular leaflet (never found in the cytosolic leaflet)

Front 159

What is found in the cytosolic leaflet?

Back 159

1. Phosphatidylserine and phosphatidylethanolamine are more concentrated in cytosolic leaflet.
2. Phosphatidylinositol is absolutely restricted to the cytosolic leaflet. (never found in the extracellular leaflet)

Front 160

What effect does cholesteral have on membrane fluidity?

Back 160

Cholesterol moderates the
effect temperature has on the membrane.
– Cholesterol reduces membrane
fluidity at higher temps
•Due to rigidity of the cholesterol molecule.
– Cholesterol increases membrane fluidity at lower temperatures
• Cholesterol prevents close
packing of phospholipids as temp is decreased

Front 161

what is found in the extracellular leaflet?

Back 161

1. Phosphatidylcholine and sphingomyelin are more
concentrated in extracellular leaflet.
2. Glycolipids are absolutely restricted to the extracellular leaflet (never found in the cytosolic leaflet)

Front 162

What is found in the cytosolic leaflet?

Back 162

1. Phosphatidylserine and phosphatidylethanolamine are more concentrated in cytosolic leaflet.
2. Phosphatidylinositol is absolutely restricted to the cytosolic leaflet. (never found in the extracellular leaflet)