1 Lecture #9 – Animal Nutrition and Digestion

2 Key Concepts: Animals are heterotrophic! Nutritional needs – what animals get from food Food processing The human digestive system

3 Critical Thinking Is this animal approaching the fruit or the flower??? Why???

4 Critical Thinking Is this animal approaching the fruit or the flower??? The flower!!! Why??? Butterflies pollinate while drinking nectar; frugivores eat fruits and distribute seeds!

5 Animals are always consumers Only photosynthesis can convert solar energy to usable chemical energy Plants store chemical energy Animals eat plants (or other animals) ….of course this is somewhat simplified…. but NO animals are autotrophic

6 Critical Thinking Why do we eat??? Specifically, what do we get from food???

7 Critical Thinking Why do we eat??? Specifically, what do we get from food??? Energy Carbon skeletons Essential nutrients  Amino acids  Fatty acids  Vitamins  Minerals

8 Why we eat – energy Animals generate ATP by aerobic respiration Main substrate is carbohydrates  Fats are also used  Proteins are used as a “last resort” Digestion converts consumed polymers to the monomers used in respiration

9 Diagram – bioenergetics and the fate of food Remember bioenergetics Managing the energy budget is essential to maintaining animal function ATP powers basal metabolism, other activities; maintains homeostasis; etc… Animals must eat to make ATP

10 Why we eat – carbon skeletons Animals need organic carbon scaffolds to build our own organic molecules – such as???

11 Why we eat – carbon skeletons Animals need organic carbon scaffolds to build our own organic molecules – such as carbohydrates, lipids, proteins and nucleic acids These are the 4 main categories of macromolecules common to all forms of life Animals can’t make organic molecules from CO 2

12 Why we eat – essential nutrients Molecules that animals cannot make at all  Do not have the right biosynthetic pathways Must be eaten in pre-assembled form Some common to all animals; some specialized  Essential amino acids  Essential fatty acids  Vitamins  Minerals

13 Essential Amino Acids Most animals use the same 20 amino acids to make what???

14 Essential Amino Acids Most animals use the same 20 amino acids to make proteins (including enzymes!) Most animals can only synthesize about half Remaining amino acids must be consumed  All animal proteins are complete – contain all the essential amino acids  All plant proteins are incomplete – missing some of the essential amino acids

15 Chart – essential amino acids; overlap between grains and legumes Human vegetarian diets must mix plant groups to obtain all essential amino acids Grains and legumes mixed provide all essential amino acids – cultural traditions prevent protein deficiencies

16 Essential Fatty Acids Some unsaturated fatty acids cannot be synthesized Most animals (especially humans!) get adequate essential fatty acids from their diet We use fatty acids for????

17 Essential Fatty Acids Some unsaturated fatty acids cannot be synthesized Most animals (especially humans!) get adequate essential fatty acids from their diet We use fatty acids for  Phospholipid membranes  Energy storage  Cushioning and insulation  Steroids and some hormones

18 Vitamins Organic molecules used in small quantities Water soluble vitamins usually function as coenzymes Fat soluble vitamins function in nutrient absorption, as antioxidants, etc.. Deficiencies are rare with an adequate, balanced diet

19 Critical Thinking Which category of vitamin is more likely to accumulate and become toxic – water soluble or fat soluble??? Why???

20 Critical Thinking Which category of vitamin is more likely to accumulate and become toxic – water soluble or fat soluble??? Why??? Water soluble vitamins dissolve in blood  Excesses are filtered and excreted in urine Fat soluble vitamins dissolve into our adipose tissue  Excesses are stored in fat and can become toxic

21 Table – essential vitamins; sources and functions Study table in text for a general under- standing

22 Minerals Inorganic elements  Some required in small amounts; some in larger  Requirements vary by taxon Many different functions  Some metabolic; some structural Know top 8 minerals and their main functions

23 Mineral Functions??? Calcium – Phosphorous – Sulfur – Potassium – Chlorine – Sodium – Magnesium – Iron –

24 Some Mineral Functions Calcium – bones and teeth; nerve and muscle fx. Phosphorous – bones and teeth; ATP; nucleic acids; membranes Sulfur – in some amino acids Potassium – pH and solute balance; nerve fx. Chlorine – pH and solute balance; nerve fx. Sodium – pH and solute balance; nerve fx. Magnesium – enzyme cofactor Iron – hemoglobin; e - carrier; enzyme cofactor

25 Diagram – food procession in a small mammal Food Processing Ingestion Digestion Absorption Elimination

26 Evolution of Compartmentalization Food digestion must be contained  Why??? Earliest containment structures are food vacuoles  Sponges digest entirely intra-cellularly Most animals digest at least partly outside the cells  Simplest body plans have a digestive sac with one opening  More complex animals have a digestive tube with an opening for ingestion and one for elimination

27 Evolution of Compartmentalization Food digestion must be contained  Avoids digestion of body cells and tissues Earliest containment structures are food vacuoles  Sponges digest entirely intra-cellularly Most animals digest at least partly outside the cells  Simplest body plans have a digestive sac with one opening  More complex animals have a digestive tube with an opening for ingestion and one for elimination

28 Evolution of Compartmentalization Food digestion must be contained  Avoids digestion of body cells and tissues Earliest containment structures are food vacuoles  Sponges digest entirely intra-cellularly Most animals digest at least partly outside the cells  Simplest body plans have a digestive sac with one opening  More complex animals have a digestive tube with an opening for ingestion and one for elimination

29 Diagram – sponges and their choanocytes Sponges digest food in vacuoles that fuse with lysosomes containing hydrolytic enzymes

30 Evolution of Compartmentalization Food digestion must be contained  Avoids digestion of body cells and tissues Earliest containment structures are food vacuoles  Sponges digest entirely intra-cellularly Most animals digest at least partly outside the cells  Simplest body plans have a digestive sac with one opening  More complex animals have a digestive tube with an opening for ingestion and one for elimination

31 Images – a jellyfish and a flatwormDiagram – two cell layers in cnidarians Jellies and flatworms start digestion in gastrovascular cavities; finish in food vacuoles

32 Jellies and flatworms start digestion in gastrovascular cavities; finish in food vacuoles Problem ???

33 Evolution of Compartmentalization Food digestion must be contained  Avoids digestion of body cells and tissues Earliest containment structures are food vacuoles  Sponges digest entirely intra-cellularly Most animals digest at least partly outside the cells  Simplest body plans have a digestive sac with one opening – single opening for incoming food and outgoing waste is inefficient – food and waste mix  More complex animals have a digestive tube with an opening for ingestion and one for elimination

Hands On Be sure to examine specimens and comment on structure-function relationships Be sure to examine Cnidarians at the aquarium and comment on structure- function relationships 34

35 Evolution of Compartmentalization Food digestion must be contained  Avoids digestion of body cells and tissues Earliest containment structures are food vacuoles  Sponges digest entirely intra-cellularly Most animals digest at least partly outside the cells  Simplest body plans have a digestive sac with one opening  More complex animals have a digestive tube with an opening for ingestion and one for elimination

36 Critical Thinking The 2-hole tube body plan processes food sequentially – no mixing of incoming food and outgoing waste Can you think of another advantage for the 2-hole tube plan???

37 Two hole tube digestive plan – essentially an open tube that passes through the body