CHAPTER 4: CELLULAR METABOLISM

CHAPTER 4:

CELLULAR

METABOLISM

BIO 137

HUMAN ANATOMY AND

PHYSIOLOGY I

MARY CATHERINE FLATH, Ph.D.

Copyright 2012 Dr. Mary Cat Flath

CHAPTER 4 TOPICS

DIVISIONS OF METABOLISM

ENZYMES

ATP

CELLULAR RESPIRATION

DNA REPLICATION

PROTEIN SYNTHESIS

MUTATIONS


Cellular Metabolism

Metabolism is the sum of all chemical reactions that

occur in the body

▪ Each reaction is catalyzed by a specific

enzyme

▪ The reactions typically occur in pathways

▪ Two types of metabolic reactions

Anabolism

• large macromolecules

(polymers) are made

• requires energy

Catabolism

• large macro

molecules (polymers)

are broken down

• releases energy

4-2


For each division of metabolism, you

should be able to:

Write a descriptive sentence about the process

Name at least two descriptive terms

State whether bonds are being made or broken

State how water is involved and name the

scientific term

State how energy is involved and name the

scientific term

Write an equation illustrating the process

Provide an example in human metabolism

Divisions of Metabolism



Anabolism

Anabolism is the building of polymers from monomers.

Anabolism involves constructive, synthesis reactions.

Anabolism requires cellular energy to build bonds between

monomers (Endergonic).

Bonds are built through Dehydration Synthesis

Examples (follow arrows to right):

▪ building a triglyceride from glycerol and fatty acids

▪ building glycogen from glucose molecules

4-3


Anabolism (follow arrows to right)

4-4


Catabolism

Catabolism breaks polymers into smaller monomers.

Catabolism involves destructive, digestive reactions.

Energy is released when bonds between monomers are

broken (i.e. Exergonic)

Water is used to break bonds: Hydrolysis

Examples include (follow arrows to left):

▪ Breaking a protein into amino acids

▪ Breaking DNA into nucleotides

4-5


Catabolism (follow arrows to left)

4-6


Control of Metabolic Reactions:

Enzyme Action Enzymes are biological, protein catalysts that increase the rate of

a chemical reaction without being consumed by the reaction.

• (They lower activation energy needed to start reactions).

• Enzymes are globular proteins with specific shapes

• • Enzymes are specific for their substrate (i.e. the substance

they act upon) • The enzyme’s active site fits with the substrate like a lock & key

4-7


Enzyme Substrate Interaction



Enzyme Action The active site on the enzyme may not be exposed and a cofactor

or coenzyme may be required.

Cofactors are ions of metals (Fe++, Cu++, Zn++)

Coenzymes are vitamins (primarily B vitamins)

4-7



Enzyme Action Enzyme names are often derived from the substrate they act on

▪ The root of the enzyme name comes from the substrate

▪ The enzyme name typically ends in the suffix –ase

▪ Examples include:

The enzyme lactase that breaks down the substrate lactose

The enzyme lipase that breaks down a (substrate) lipid.

The enzyme DNA Polymerase is used to build DNA from

nucleotide substrates.

▪ Enzymes are unchanged by the reaction they catalyze and are

recycled.

▪ Enzymes can be denatured in extreme conditions.

▪ Metabolic pathways involve several reactions in a row, each

requiring a different, specific enzyme.

4-7


Control of Metabolic Reactions

Metabolic pathways

• series of enzyme-controlled reactions

leading to formation of a product

• each new substrate is the product of the

previous reaction

4-8


Energy for Metabolic Reactions

Energy

• Energy is the ability to do work or change

something.

• Common forms include heat, light, sound,

electricity, mechanical energy, chemical energy

• Energy cannot be created or destroyed, but it

changes from one form to another.

• All metabolic reactions involve some form of

energy.

4-10


Energy for Metabolic Reactions

Release of chemical energy

Most metabolic processes depend on chemical

energy

Energy is held within the covalent bonds

between atoms (as potential energy).

When the bond breaks, free (kinetic) energy is

released.

Cellular respiration releases chemical energy from

nutrients and makes it available for cellular use.


ATP Molecules

• each ATP molecule has three parts

• an adenine molecule

• a ribose molecule

• three phosphate molecules in a chain

• third phosphate attached by high-energy bond

• when the bond is broken, energy is transferred

• when the bond is broken, ATP becomes ADP,

•but ADP can be recycled back to ATP, if a phosphate is

added back to ADP during catabolic reactions

4-12




CELLULAR RESPIRATION (CR) Cellular respiration is the way in which animal

cells use oxygen to release energy (ATP) from nutrients

CR reactions occur in two major series of reactions (with each requiring a specific enzyme): Anaerobic Steps do not require oxygen

Occur in cytoplasm

Glycolysis

Aerobic steps do require oxygen

Occur in mitochondrion

(Krebs cycle (citric acid cycle) and Electron transport chain [ETC])

OVERVIEW OF



OVERVIEW OF



COENZYMES REQUIRED FOR

CELLUAR REPSIRATION

NADH (NIACIN)

FADH2 (RIBOFLAVIN)


For each major series of reactions in

Cellular Respiration, you should be able

to:

State whether the reactions are aerobic

or anaerobic

Locate the reactions in the cell

Name starting products

Name end products

Including ATP


CELLULAR

RESPIRATION

ANAEROBIC

REACTIONS

AEROBIC

REACTIONS

Is oxygen

required?

Where do the

reactions occur

in the cell?

Starting

Products?

End-Products?


CELLULAR

RESPIRATION

ANAEROBIC

REACTIONS

AEROBIC

REACTIONS

Is oxygen

required?

NO YES

Where do the

reactions occur

in the cell?

CYTOPLASM

MITO-

CHONDRION

Starting

Products?

GLUCOSE

TWO PYRUVIC

ACIDS

End-Products? TWO PYRUVIC

ACIDS

2 ATP

36 ATP

WATER

CO2


ANAEROBIC GLYCOLYSIS:

(FERMENTATION)

If oxygen is not available, pyruvic

acid is fermented under anaerobic

conditions:

In animals, pyruvic acid is

converted to lactic acid

Accumulates and causes

muscle fatigue and soreness


ANAEROBIC GLYCOLYSIS:

(FERMENTATION)

Let’s review objectives 1-14


Regulation of Metabolic Pathways

• limited number of regulatory enzymes

• negative feedback whereby the end-product comes

back and inhibits the first enzyme in the

pathway

4-23

NUCLEIC ACIDS AND

PROTEIN SYNTHESIS


NUCLEIC ACIDS AND

PROTEIN SYNTHESIS

ENZYMES ARE PROTEINS THAT

REGULATE METABOLIC REACTIONS

CELLS MUST HAVE THE INFORMATION

FOR MAKING THESE SPECIAL PROTEINS

THAT INFORMATION IS CARRIED IN THE DNA

IN OUR CELLS

INFORMATION IS CARRIED BY GENES ON OUR

CHROMOSOMES

DNA DIRECTS PROTEIN SYNTHESIS

RNA ASSISTS DNA IN THAT EFFORT


GENETIC INFORMATION

DNA HOLDS THE GENETIC INFORMATION WHICH IS INHERITED FROM PARENTS TO OFFSPRING

DNA IS LOCATED IN NUCLEUS

DNA INSTRUCTS CELLS IN THE CONSTRUCTION OF PROTEINS

PROTEINS ARE SYNTHESIZED AT RIBOSOMES (RER OR IN CYTOPLASM)

THE PORTION OF A DNA MOLECULE THAT CODES FOR ONE PARTICULAR PROTEIN IS CALLED A GENE

ALL OF THE DNA IN A CELL CONSTITUTES ITS GENOME HUMAN GENOME PROJECT


HOW DOES DNA WHICH IS

CONFINED TO THE NUCLEUS,

DIRECT PROTEIN SYNTHESIS AT

RIBOSOMES?

WITH THE HELP OF RNA

NUCLEIC ACID

STRUCTURE

DEOXYRIBONUCLEIC ACID (DNA)

RIBONUCLEIC ACID (RNA)

DEOXYRIBONUCLEIC

ACID

DNA


DNA STRUCTURE

DNA IS COMPOSED

OF NUCLEOTIDES

EACH NUCLEOTIDE

IS COMPOSED OF:

SUGAR DEOXYRIBOSE

PHOSPHATE GROUP

NITROGEN BASE

PURINE

ADENINE (A)

GUANINE (G)

PYRIMIDINE

CYTOSINE (C)

THYMINE (T)

D


DNA STRUCTURE

EACH DNA STRAND

IS COMPOSED OF

ALTERNATING

DEOXYRIBOSE

SUGARS AND

PHOSPHATES

EACH DEOXYRIBOSE

SUGAR IS LINKED TO

ONE OF FOUR

BASES


DNA STRUCTURE

EACH DNA MOLECULE

CONSISTS OF TWO

STRANDS OF

NUCLEOTIDES

STRANDS ARE HELD

TOGETHER BY

HYDROGEN BONDS

BETWEEN

COMPLEMENTARY

BASES

A::T (2 H-bonds)

G:::C (3 H-bonds)



DNA STRUCTURE

THE DNA

MOLECULE IS

TWISTED INTO A

DOUBLE HELIX




SEM of chromosomes prior to cell

division

DNA REPLICATION


DNA Replication: Occurs in the nucleus

during interphase of cell cycle • DNA unwinds and hydrogen

bonds break between

complementary bases pairs

• DNA polymerase positions

DNA nucleotides with

exposed bases and

backbones of strands are

formed

• two identical DNA molecules

result

•Semi-conservative

replication

4-30

RIBONUCLEIC ACID

RNA


RNA STRUCTURE

RNA IS COMPOSED

OF NUCLEOTIDES

SUGAR IS RIBOSE

BASES:

A, URACIL (U)

C, G

PHOSPHATE

GROUP

R


RNA STRUCTURE

EACH RNA STRAND

IS COMPOSED OF A

BACKBONE OF

ALTERNATING

RIBOSE SUGARS

AND PHOSPHATES

EACH RIBOSE IS

BONDED TO A BASE

RNA IN SINGLE

STRANDED


TYPES OF RNA

MESSENGER RNA (mRNA)

Carries code for protein to be synthesized

from nucleus to ribosome

TRANSFER RNA (tRNA)

Carries appropriate amino acid to ribosome to

be incorporated into protein

RIBOSOMAL RNA (rRNA)

The RNA component of the ribosome (recall

that a ribosome is composed of RNA plus

protein)


DNA AND RNA COMPARISON

DNA RNA

PENTOSE

SUGAR

BASES

STRUCTURE


DNA AND RNA COMPARISON

DNA RNA

PENTOSE

SUGAR

DEOXYRIBOSE RIBOSE

BASES A, T, G, C A, U, G, C

STRUCTURE DOUBLE

STRANDED

SINGLE

STRANDED

PROTEIN SYNTHESIS


For each step in Protein Synthesis, you

should be able to:

Name the step

Give the location of the step in the cell

Name molecules involved in the

process

Name the overall result of each step


PROTEIN SYNTHESIS:

TWO MAJOR STEPS TRANSCRIPTION

OCCURS IN NUCLEUS

RNA POLYMERASE ALLOWS FOR THE MAKING OF

A STRAND OF MESSENGER RNA

mRNA IS COMPLEMENTARY TO THE DNA GENE (and

now carries code for protein to be synthesized)

TRANSLATION

OCCURS AT RIBOSOME

TRANSFER RNA BRINGS AMINO ACIDS TO

RIBOSOME

mRNA IS TRANSLATED INTO A PROTEIN


TRANSCRIPTION

OCCURS IN NUCLEUS

DNA UNWINDS AND UNZIPS (HYDROGEN BONDS ARE BROKEN)

RNA POLYMERASE POSITIONS RNA NUCLEOTIDES ALONG THE GENE AND BONDS BACKBONE TOGETHER FORMING A STRAND OF MESSENGER RNA

mRNA IS COMPLEMENTARY TO THE DNA GENE (and now carries code for protein to be synthesized)

IF GENE IS: TACGATTGCCAA

THEN mRNA is: AUGCUAACGGUU

THE mRNA IS READ IN THREE BASE CODONS

AUG CUA ACG GUU


Figure 04.22


TRANSLATION

mRNA IS TRANSLATED INTO A PROTEIN

OCCURS AT RIBOSOMES FREE IN CYTOPLASM

ON ROUGH ENDOPLASMIC RETICULUM

TRANSFER RNA BRINGS AMINO ACIDS TO RIBOSOME

tRNA HAS ANTICODON WHICH IS COMPLEMENTARY TO mRNA codon

IF mRNA CODON IS AUG, THEN tRNA ANTICODON IS UAC

TWO CODONS ARE READ IN RIBOSOME AT A TIME PEPTIDE BOND IS FORMED BETWEEN TWO AMINO ACIDS

RIBOSOME MOVES AND POSITIONS NEXT CODON

CODONS ARE READ UNTIL STOP CODON IS REACHED



should be able to:

Name the step



process


Protein Synthesis Overview

Step 1

_______________

_______________

_______________

_______________

_______________

_______________

_______________

_______________

Step 2

______________

______________

______________

______________

______________

______________

______________

______________



Step 1

TRANSCRIPTION

NUCLEUS

DNA IS COPIED

INTO A STRAND OF

MESSENGER RNA

(mRNA) BY RNA

POLYMERASE; RNA

NUCLEOTIDES

A STRAND OF

mRNA

Step 2

TRANSLATION

RIBOSOME (free or

on RER)

mRNA IS

TRANSLATED INTO

A PROTEIN;

TRANFER RNAs;

AMINO ACIDS

A PROTEIN




Protein Synthesis

4-28




PROTEIN SYNTHESIS WORKSHEET

GENE mRNA AMINO ACIDS

(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

T

T

G

C

A

A

T

C

G

A

T

T




(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

A

U

G

T

T

G

A

A

C

C

A

A

G

U

U

T

C

G

A

G

C

A

T

T

U

A

A





(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

A

U

G

MET (METHIONINE)

START

T

T

G

A

A

C

C

A

A

G

U

U

T

C

G

A

G

C

A

T

T

U

A

A





(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

A

U

G

MET (METHIONINE)

START

T

T

G

A

A

C

ASN (ASPARGINE)

C

A

A

G

U

U

T

C

G

A

G

C

A

T

T

U

A

A





(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

A

U

G

MET (METHIONINE)

START

T

T

G

A

A

C

ASN (ASPARGINE)

C

A

A

G

U

U

VAL (VALINE)

T

C

G

A

G

C

A

T

T

U

A

A





(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

A

U

G

MET (METHIONINE)

START

T

T

G

A

A

C

ASN (ASPARGINE)

C

A

A

G

U

U

VAL (VALINE)

T

C

G

A

G

C

SER (SERINE)

A

T

T

U

A

A





(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

A

U

G

MET (METHIONINE)

START

T

T

G

A

A

C

ASN (ASPARGINE)

C

A

A

G

U

U

VAL (VALINE)

T

C

G

A

G

C

SER (SERINE)

A

T

T

U

A

A

STOP




(PROTEIN)

tRNA anticodon

SEQUENCE

T

A

C

A

U

G

MET (METHIONINE)

START

U

A

C

T

T

G

A

A

C

ASN (ASPARGINE) U

U

G

C

A

A

G

U

U

VAL (VALINE) C

A

A

T

C

G

A

G

C

SER (SERINE) U

C

G

A

T

T

U

A

A

STOP A

U

U



should be able to:

Name the step



process



Step 1

_______________

_______________

_______________

_______________

_______________

_______________

_______________

_______________

Step 2

______________

______________

______________

______________

______________

______________

______________

______________



PROTEIN SYNTHESIS SUMMARY

TRANSCRIPTION NUCLEUS

RNA POLYMERASE

MESSENGER RNA IS MADE

COMPLEMETARY TO GENE

THREE BASE CODONS

TRANSLATION RIBOSOME

MESSENGER RNA IS TRANSLATED INTO A PROTEIN

TRANSFER RNA BRINGS AMINO ACID

ANTICODON

TWO CODONS READ AT ONE TIME

PEPTIDE BOND

STOP CODON ENDS TRANSLATION


MUTATIONS

CAUSED BY ERROR IN DNA CODE (GENE)

ARE CAUSED BY A VARIETY OF SOURCES

MUTATIONS IN GENES, CAUSE THE END-PRODUCT, THE PROTEIN TO BE ALTERED OR ABSENT

AN ENZYME MAY NOT BE MADE AT ALL

A PROTEIN MAY HAVE ALTERED FUNCTION

A PROTEIN MAY BE MADE IN EXCESS


Table 04.04


MUTATIONS IN GENES CAUSE THE END-

PRODUCT, PROTEIN TO BE ALTERED OR

ABSENT


CHILDHOOD STORAGE DISEASES

PKU


ALTERED CHLORIDE PUMP IN CYSTIC

FIBROSIS

ALTERED HEMOGLOBIN IN SICKLE CELL

ANEMIA

A PROTEIN MAY BE MADE IN EXCESS.

EXCESS GABA AND EPINEPHRINE IN EPILEPSY




Clinical Application

Phenylketonuria

PKU

• enzyme that breaks down the amino

acid phenylalanine is missing

• build up of phenylalanine causes

mental retardation

• treated by diets very low in

phenylalanine 4-32




A genetic order albinism, results in

lack of melanin in skin, hair, and irises


Fig. 4.26 STARTING MATERIALS

INTERMEDIATE #1

Enzyme #1

Enzyme #2

Enzyme #3

Enzyme #4

Enzyme #5

Enzyme #6

Enzyme #8

HEME

Enzyme #7

ALA dehydratase deficiency

acute intermittent porphyria

congenital erythropoietic

porphyria

porphyria cutanea tarda

coproporphyria

erythropoietic protoporphyria

porphyria variegata

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

INTERMEDIATE #2

INTERMEDIATE #3

INTERMEDIATE #4

INTERMEDIATE #5

INTERMEDIATE #6

INTERMEDIATE #7





ABSENT



PKU



FIBROSIS


ANEMIA










ABSENT



PKU



FIBROSIS


ANEMIA




CHAPTER 4 TOPICS DIVISIONS OF METABOLISM

Catabolism and Anabolism

ENZYMES

ATP

CELLULAR RESPIRATION Anaerobic reactions vs. Aerobic reactions

DNA REPLICATION

PROTEIN SYNTHESIS Transcription vs. Translation

MUTATIONS

Let’s review objectives 15-

26


Documents

CHAPTER 4: CELLULAR METABOLISM