Chapter 8 Introduction to Metabolism - Support Center ...facultyweb.wcjc.edu/users/kevind/Biology_Chapter_8_2014.pdf · • Defined as the sum total of the chemical reactions that

Biology – Kevin Dees

Chapter 8

Introduction to Metabolism


____________

• Defined as the sum total of the chemical

reactions that occur in a living thing.

Think of metabolism as a road map of

thousands of different chemical reactions

_____________ regulate metabolism

A B C D

ENZYME 1

ENZYME 3

ENZYME 2


There are two basic metabolic

processes

1. ___________________ pathways

– Degradation reactions

– breakdown large molecules into smaller

ones

– Releases energy

– i.e aerobic cellular respiration

C6H12O6 + O2 CO2 + H2O


There are two basic metabolic

processes

2. ________________ pathways

– Building reactions

– Form large molecules from smaller ones

– Consume energy

– i.e photosynthesis

CO2 + H2O C6H12O6 + O2


The key is understanding

ENERGY!!

• ________________ can be defined as the capacity to cause change – WORK!!!

• Energy is fundamental to all metabolic processes


• _______________________– “moving energy” – Energy associated with relative motion

– Heat is also kinetic energy

– Thermal energy

• ____________________– “stored energy” – energy because of location or structure

– Chemical energy can be potential energy because of the energy stored in chemical bonds



Energy changes forms!!!!

• The study of energy transformations is

known as _____________________

• There are two laws of thermodynamics

that govern energy transformations in

organisms and all other collections of

matter


The first law of thermodynamics (principle of conservation of energy)

• The amount of energy in the universe is ______________;

• energy can be transformed and transferred, but cannot be

created or destroyed.

– Plants converting light into sugar

– Food particles being converted into kinetic energy of movements of

animals


The second law of thermodynamics (principle of entropy)

• Every energy transformation or transfer

increases the entropy in the universe.

_____________ = measure of disorder

• As energy transformations or transfers

occur some energy is converted into an

unusable form

– Body heat



Cellular work

• There are three types of cellular work

– Mechanical work • motility

• Cilia beating; contraction of muscle cells

– Transport work • Active transport mechanisms

• Na-K pump

– Chemical work • Driving reactions to proceed

• Joining of amino acids to form polypeptides


In most cases, cells’ energy demands

needed to do work is ion the form of

• Adenosine triphosphate (ATP)


Energy is released why ATP is

hydrolyzed


How is this

energy used

by a cell?

• To perform the

three types of

cellular work

• A phosphate is

removed

• The recipient of

the phosphate is

said to be

phosphorylated


ATPs are used constantly by a cell

• You use about 45kg of ATP a day

• At any given instant there is <1 g present

in your cells

• Why???


Biological catalysts - enzymes

• Catalysts speed up reactions by lowering

activation energy

– The amount of energy needed to initiate a

reaction

• Enzymes are organic catalysts – proteins!!

– Typically end in –ase

– Enzymes regulate metabolism!!


Substrate specificity of enzymes

• Enzymes are very specific as regards the

reactions they participate in.

• In order for an enzyme to work, the reactants

(called substrates) bind to the enzyme forming

an enzyme-substrate complex

• The site on the enzyme where the substrates

bind is known as the active site

– Recall that proteins are large 3-D molecules and

shape plays a significant role in their function!!!



Substrate

Active site

Products


The enzymatic activity is affected

by the environment

– pH – most have optimal range

– Temperature – most have optimal range

– Cofactors – non-protein helpers

– Coenzymes – organic helpers – vitamins

– Inhibitors – compete for active sites with substrates

• Nerve gas – sarin – blocks actylcholinesterase - disrupts the nervous system

• Pesticides

• Penicillin

Chapter 8 Introduction to Metabolism - Support Center ...facultyweb.wcjc.edu/users/kevind/Biology_Chapter_8_2014.pdf · • Defined as the sum total of the chemical reactions that

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