Chapter 6: Nutrition

Introduction

NutritionProcess of an organism furnishing itself or being furnished with the essential materials needed for energy production, growth and reproduction secretion, storage and for the maintenance of the osmotic conditions and pH within its body

Can be categorized into:-1. Autotrophic nutrition2. Heterotrophic nutrition

Autotrophic Nutrition

PropertiesOrganic compounds are synthesized / manufactured from raw inorganic materials by the organisms

Organism, for example all green plants and some bacteria, in such nutrition – autotrophs

Methods of autotrophic nutrition:-1) Photosynthesis

a) Definition Process of synthesizing organic compounds using sunlight as the source of energy

b) Organism that carried out photosynthesis – photoautotrophi) All green plantsii) Algaeiii) Some bacteriaiv) Cyanobacteriav) Chlorobiumvi) Chromatium

c) Equation of photosynthesis process (optional)i) Carried out by (i), (ii), (iii), (iv) with the help of chlorophyll

(1) CO2+H 2O→(CH 2O)+O 2+H 2O(2)

6CO2+12H 2O→C6H 12O6+6O2+6H 2Oii) Carried out (v), (vi) with the help of bacteriochlorophyll

(1) CO2+2H 2S→(CH2O)+2 S+H 2O2) Chemosynthesis

a) DefinitionProcess of synthesizing organic compounds from carbon dioxide and water using energy supplied by chemical process that involve the oxidation of inorganic substances

b) Organisms that carried out chemosynthesis – chemoautotrophsc) Energy to drive the synthesis of organic compounds is obtained by

oxidizing inorganic chemicalsd) Examplesi) Lepothrix

(1) Fe2+¿→Fe3+¿+energy¿ ¿

ii) Thiobacillus

(1) S→SO42- + energy

iii) Nitrifying bacteria (1) Nitrosomonas – obtain their energy from the oxidation of

ammonia to nitrites (from decomposing plants and animals)

(a)

2NH3+3O2→2HNO2+2H 2O+energy(2) Nitrobacter – oxidizes nitrites to nitrates

(a) 2HNO2+O2→2HNO3+energyChemoautotrophs play important roles in biogeochemical cycles

Heterotrophic nutrition

DefinitionOrganisms are not able to synthesize organic compounds but obtain them from various sources

Organisms – heterotrophs

1) All animals2) Fungi3) Many bacteria4) Some protoctists

Types of heterotrophic nutrition1) Holozoic

a) Organismsi) Most animalsii) Insectivorous plants iii) Some protoctists

b) Holozoic characters of mammals i) Ingestion

Taking in of large, insoluble, complex food material consisting mostly of organic polymer molecule

ii) DigestionMechanical that breaks down large particles into smaller pieces and digested chemically by enzymes into small, simple soluble molecules

iii) AssimilationUse of the absorbed molecules in the body which includes releasing energy to carry out metabolism or synthesizing cellular structure

iv) EgestionElimination of undigested waste substances from the body

c) Division of Holozoic organismsi) Herbivores – eat plants

(1) Examples:-(a) Goats(b) Cows(c) Rabbits

ii) Carnivores – feed on other animals(1) Examples:-

(a) Tigers(b) Lions(c) Hawks

iii) Omnivores – feed on both plants and animals(1) Examples:-

(a) Humans(b) Bears

iv) Detritivores – feed on dead and decaying detritus (1) Examples:-

(a) Earthworms(b) Centipedes (c) Woodlice

v) Insectivorous plants – plants that are able to trap insects and digest them (1) Examples:-

(a) Pitcher plants, Nepenthes(b) Sundews, Drosera(c) Venus fly traps, Dionaea muscipula

d) Main groups of Holozoic organismsi) Microphagus feeders

(1) Take in very small particles(2) Examples

(a) Unicellular organisms(i) Amoeba(ii) Paramecium

(b) Multicellular aquatic organisms(i) Daphnia(ii) Gastropods

ii) Liquid feeders(1) Take in liquid food or food with very soft tissues(2) Examples

(a) Aphids(b) Bees(c) Flies(d) Mosquitoes

iii) Macrophagus feeders(1) Take in relatively large particles(2) Examples

(a) Bigger animals (of the most)(b) Fish(c) Birds(d) Reptiles(e) Mammals

e) Human digestive system

Biology Notes

Chapter 6: Nutrition

i) Stages in human digestive system(1) Ingestion

Taking food into the body(2) Physical digestion – Peristalsis

Movement of food along the alimentary canal by muscular contraction and relaxation

(3) Chemical digestion – Digestion (a) Complex food molecule is broken into simple

molecules that can be absorbed during hydrolysis by digestive enzymes, which are secreted by glands outside the food canal

(b) Division of groups for different digestive enzymes(i) Carbohydrases

Act on carbohydrates and break them up into simple molecules

(ii) LipasesAct on fats and break them up into glycerol and fatty acids

(iii) ProteasesAct on proteins and break them up into amino acids

(4) Absorption(a) Absorption of hexose sugars in most animals occurs

through the intestinal walls(b) Modifications of the intestinal wall to facilitate the

absorption of the products of digestion(i) Long intestine(ii) Thousands of villi on the surface of walls (iii) Thousands of microvilli on each epithelial cell

of intestinal surface(c) Small intestine has a blood capillary system that is

extensive so that the products of digestion can be transported quickly from the absorption site to the liver through hepatic portal vein

(d) Absorption through active transport occurs against the concentration gradient(i) Glucose(ii) Fructose(iii) Galactose

(e) Fatty acids and glycerol are absorbed by the epithelial cells and from there they enter the blood capillaries and go directly into the general blood system(i) Fat droplets enter the villi through pinocytosis

and then go into the lacteals and finally into the lymphatic system

(ii) Proteins in the lymphatic ducts are deposited on the fat molecules to form lipoproteins

(f) Absorption of water into blood capillaries occurs in the large intestine through osmosis(i) Contents of large intestine are hypotonic

compared to the contents of the blood capillaries of the villi in the large intestine

(5) Assimilation(a) Process of combining the simple products of digestion

or nutrients in an animal to make complex compounds(b) Most of the simple sugars change into glycogen for

storage in the liver and muscles and the rest are circulated throughout the body for cellular respiration

(c) Excess glycogen is changed into lipids, which are then stored at several storage sites

(d) Glycogen and fatty acids are taken to the lipid storage sites in the form of lipid droplets and phospholipids(i) Kept in

1. Adipose tissues beneath the skin2. Around the heart3. Kidney4. Mesentery tissues

(e) Phospholipids are used in the formation of plasma membrane and nuclear membrane(i) When they are needed by cells, they are

removed from storage and brought to the liver to be used to form cell components or to produce energy through cellular respiration

(f) Amino acid, which are needed for growth, tissue reproduction and secretory activities, are distributed throughout the body by circulatory system from liver(i) Excess amino aids are metabolized through

deamination to form urea, uric acid, or other nitrogenous excretory products

(ii) Some of the amino acids are transaminated to form other amino acids

(g) Some vitamins can be stored in the liver(i) Example:

1. Vitamin A, D, K and B12(h) Other vitamins if found in excess will be metabolized

by the liver and filtered out of the blood by the kidneys

(6) Egestion(a) Once absorption through the ileum is completed,

whatever left is the remains of undigested food – cellulose, secretions from the intestines and other organs and plenty of water

(b) When the undigested food passes through the colon, water is reabsorbed and undigested food becomes more compact

(c) When it reaches the rectum, it becomes faeces and egested by the constriction of the muscles of the rectum(i) Composition and quality of the faeces differ

according to the dietii) Functions of general structure

(1) Teeth (a) Breakdown of large food particles into smaller pieces(b) Known as mechanical digestion

(2) Salivary gland(a) Secretes saliva

(3) Epiglottis(a) Closes over the glottis during swallowing of food

(4) Esophagus(a) Peristalsis moves food from pharynx to stomach

(5) Liver(a) Produces bile

Biology Notes

Chapter 6: Nutrition

(6) Gall bladder(a) Stores bile

(7) Stomach(a) Secretes gastric juice

(8) Duodenum(a) Secretes intestinal juice, receives bile from liver and

pancreatic juice from pancreas(9) Pancreas

(a) Secretes pancreatic juice(10) Ileum

(a) Completion of digestion and absorption of digested food

(11) Colon(a) Absorption of water, mineral salts, vitamin K and folic

acid produced by E.coli and also absorbed (12) Rectum

(a) Temporary storage of faeces(13) Anus

(a) Undigested food is egested

Sites of Production

pH Secretion Enzyme Substrate Products

Mouth 6.5 – 7.5 Saliva Salivary amylase

Starch Maltose

Stomach 2.0 Gastric juice Rennin Milk protein caseinogem

Casein

Pepsin Proteins PolypeptidesLiver 7.0 Bile Bile salts to emulsify fats into small droplets

Pancreatic juice

Pancreatic amylase

Starch Maltose

Lipase Lipids Fatty acidsGlycerol

Trypsin Proteins PolypeptidesChrymotrypsin Proteins Peptides Carboxy-peptidase

Carboxyl end of polypeptide

Amino acids

Nuclease Nucleic acids NucleotidesVilli of small intestine

8.5 (border)

Brush border of epithelial cells

Enterokinase Trypsinogen (inactive)

Trypsin (inactive)

Maltase Maltose Glucose + glucose

Sucrose Sucrose Glucose + fructose

Lactase Lactose Glucose + Galactose

Amino peptidase

Amino end of polypeptides

Amino acids

Peptidase DipeptidesNucleotidase Nucleotides Pentose

sugarsPhosphatesNitrogenous organic base

2) Saprophytic a) Organisms that feed on dead and decaying organic molecules, which

can’t synthesize their own organic moleculesb) Enzymes are secreted by extracellular digestion and absorbed the

products of digestion through the cell surfacei) Complex food are hydrolyzed into glucose, amino acids, fatty acids

and glycerol for absorptionc) They act as decomposers whereby organic molecules of dead organisms

and their waste products are broken down and the component chemical elements are eventually released for reuse by autotroph

d) Examples:-i) Mucor

ii) Rhizopus

iii) Saccharomyces – yeastiv) Mushroomv) Clostridium botulinun

(1) Produce exotoxin botulin which decays food that will cause food poisoning in man

3) Symbiotic a) Definition

Close or permanent association between 2 or more organisms of different species

b) May or may not be beneficial to the symbiontsc) Some relationships are obligatory, where 1 or both the organisms can’t

survive at the same time d) Common types

i) Parasitism(1) Parasite obtains its food from host

(a) It absorb the following which may harm the host(i) Blood(ii) Plant sap(iii) Digested food(iv) Tissues

(b) Well adapted to their host and don’t cause great harm(i) Enables them to have larger number of hosts

and to spread more widely(2) Division of groups

(a) Endoparasites – live within a host (i) Usually bathed in nutrients and absorbed the

already digested food by the host1. Examples

a. Liver flukesb. Taenia, tapeworms

Biology Notes

Chapter 6: Nutrition

c. Potato fungusd. Phythophthora infestans

(b) Ectoparasites – live on the surface of host(i) Attack the surface of their living host and suck

up juices from their bodies1. Examples

a. Ticksb. Fleasc. Leeches

(c) Obligate parasites(i) Unable to survive and reproduce in the absence

of a host1. Examples

a. Tapewormb. Phythophthora infestans

(d) Facultative parasites(i) Can live independently in the absence of a host(ii) Have the opportunity to be parasitic if the

opportunity arises(iii) Example

1. Armillaria mellea, bootlace fungus(e) Adaptation

(i) Have special method of entry into the body of the host1. Locomotory structures are generally

reduced or absent(ii) Have structures that anchor them onto their host(iii) Have lost organ systems and function that are

no longer needed(iv) Protect themselves against the internal defenses

of their host(v) Have complex life cycles(vi) Have a high reproductive output

ii) Commensalism(1) Definition

Close association between commensal derives benefits from the association but the host in unaffected

(2) Examples:-(a) Epiphytic orchids and ferns – on the trunk and

branches

(b) Remora fish and shark

iii) Mutualism(1) Definition

Close association between 2 different living species where both are benefited

(2) Examples(a) Rhizobium and host plant(b) Lichen and fungal cells(c) Lichen and algal cells(d) Mycorrhiza and fungus(e) Mycorrhiza and plant root(f) Protozoa and termites

Biology Notes

Tapeworm Scolex @ Head