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Learning objectives

  • Define and describe metabolism
  • Compare and contrast autotrophs and heterotrophs
  • Describe the importance of oxidation-reduction reactions in metabolism
  • Describe why ATP, FAD, NAD + , and NADP + are important in a cell
  • Identify the structure and structural components of an enzyme
  • Describe the differences between competitive and noncompetitive enzyme inhibitors

Part 1

Hannah is a 15-month-old girl from Washington state. She is spending the summer in Gambia, where her parents are working for a nongovernmental organization. About 3 weeks after her arrival in Gambia, Hannah’s appetite began to diminish and her parents noticed that she seemed unusually sluggish, fatigued, and confused. She also seemed very irritable when she was outdoors, especially during the day. When she began vomiting, her parents figured she had caught a 24-hour virus, but when her symptoms persisted, they took her to a clinic. The local physician noticed that Hannah’s reflexes seemed abnormally slow, and when he examined her eyes with a light, she seemed unusually light sensitive. She also seemed to be experiencing a stiff neck.

  • What are some possible causes of Hannah’s symptoms?

Jump to the next Clinical Focus box.

The term used to describe all of the chemical reactions inside a cell is metabolism ( [link] ). Cellular processes such as the building or breaking down of complex molecules occur through series of stepwise, interconnected chemical reactions called metabolic pathway s. Reactions that are spontaneous and release energy are exergonic reaction s, whereas endergonic reaction s require energy to proceed. The term anabolism refers to those endergonic metabolic pathways involved in biosynthesis , converting simple molecular building blocks into more complex molecules, and fueled by the use of cellular energy. Conversely, the term catabolism refers to exergonic pathways that break down complex molecules into simpler ones. Molecular energy stored in the bonds of complex molecules is released in catabolic pathways and harvested in such a way that it can be used to produce high-energy molecules, which are used to drive anabolic pathways. Thus, in terms of energy and molecules, cells are continually balancing catabolism with anabolism.

Diagram of metabolism. Catabolism: large molecules are broken down into small ones releasing energy. This is shown as a chain of 4 circles splitting into individual circles and Energy. The reverse process (using energy to connect the 4 circles) is anabolism. Anabolism: small molecules are assembled into larger ones, using energy.
Metabolism includes catabolism and anabolism. Anabolic pathways require energy to synthesize larger molecules. Catabolic pathways generate energy by breaking down larger molecules. Both types of pathways are required for maintaining the cell’s energy balance.

Classification by carbon and energy source

Organisms can be identified according to the source of carbon they use for metabolism as well as their energy source. The prefixes auto- (“self”) and hetero- (“other”) refer to the origins of the carbon sources various organisms can use. Organisms that convert inorganic carbon dioxide (CO 2 ) into organic carbon compounds are autotroph s . Plants and cyanobacteria are well-known examples of autotrophs. Conversely, heterotroph s rely on more complex organic carbon compounds as nutrients; these are provided to them initially by autotrophs. Many organisms, ranging from humans to many prokaryotes, including the well-studied Escherichia coli , are heterotrophic.

Questions & Answers

it could be hormonal in balanced kindly see a doctor thanks
Precious Reply
U mean u have never had Ur period before?
Tee Reply
pregnancy
Cerah Reply
how many months does you notice that problem
pavan Reply
I am 21 years old and I haven't seen my period,what could be the cause?
Faith Reply
Please what is the solution to the problem?
Faith
abnormal cytobacteria ukrine
dzaram Reply
my period dos'nt flow as normal Pls what could be the cause?
Chinelo Reply
No some are beneficial & others are pathogenic
Diuniceous Reply
are all bacteria dangerous
Lorretha Reply
What is a bacteria?
Nang Reply
PLEASE WHAT IS CULTURE ?
Emmanuella Reply
Which type of cytoskeletal fiber is important in the formation of the nuclear lamina?
shaletta Reply
Nice, explanation about Gram's bacterial differential procedure
surendra Reply
Beer, cheese, bread, are orange juice is not fermentation
shaletta Reply
describe gram staining
Aditi Reply
if I'm not mistaken(no googling) it's the testing of bacteria to see whether it is gram positive or negative... it is clinically useful because if you have a gram positive person you don't want to give them gram-negative medicine
Coach
it is a procedure in which we have know about bactrria either gram positive or gram negative after cultivation of bacteria on agat plates we put crystal voilet then iodine then de colorizer and then if not retain voilet colur so put safranin for gram negative bacterai in case of retaining voilet
badshah
Practice MCQ 5

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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