Bioenergetics and Digestion

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Bioenergetics and Digestion
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Bioenergetics of an animal the big picture

• Food fuel, carbon skeletons, essential
  nutrients
• ATP powers basal or resting metabolism, as well
  as activity, and temperature regulation
• Excess calories can be used for biosynthesis
• 85-90 of energy from food is lost as heat

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Do plants have digestive systems?

• Carnivorous plants in marshlands have primitive
  digestive systems
• Habitats with N-poor soils
• Adaptation occasionally feed on animals
• CH2O ? Photosynthesis
• N minerals ? insects, etc.

Images from wikipedia.org
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Evolution of digestion

• Different types depending on diet and lifestyle
• All must accomplish
• Ingestion
• Digestion
• Mechanical breakdown
• Chemical breakdown
• Absorption
• Elimination
• Digestion occurs in specialized compartments

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Digestion in lower forms

• Evolutionary perspective is manifested by the
  various digestive processes occurring from the
  most simple to the most complex forms.

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Intracellular digestion (1) (evolved in
single-celled protists, retained in simplest
animals)

• Protozoan
• Ex. Paramecium

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Intracellular digestion (2) (evolved in
single-celled protists, retained in simplest
animals)

• SPONGES

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Extracellular digestion (by fungi)

• Fungi

• Sedentary heterotrophs living in or on food
  supply
• Saprophytes/parasites
• No internal cavity ? release digestive enzymes

Image from http//www.aber.ac.uk/fungi/graffeg/dec
omp/digestion-by-hypha.jpg
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Extracellular digestion1. In animals with
incomplete digestive systems (1)

• Cnidarians
• Ex. Hydra

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Extracellular digestion 1. In animals with
incomplete digestive systems (2)

• Flatworms
• Ex. Planaria and tapeworms

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Extracellular digestion 2. In animals with
complete digestive systems (1)

• Earthworms

• 2o cm long with 100 segments
• 1st mouth
• Last anus
• Eats its way through soil

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Comparison of vertebrate digestive systems(More
specialized compartments)
Can you name the function of each specialized
compartment of the GI tract?
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Mammalian digestion (General plan)
Organs of the GI tract
Accessory digestive organs
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Comparison of mammalian digestive systems(Diet
plays an important role in the length and
structure)