Nutrition Summary

Maris Stella High School GCE O Level Biology Revision Summary

Nutrition

Class Components Carbohydrates Monosaccharides (simple (contain sugars) C, H, O) (H: O ratio = 2:1)

Disaccharides (Complex sugars) o

Formed when 2 simple sugars combine with elimination of a water molecule

Name: ___________________ Class (Index No.): ____ ( ) Date:_____________

Sources Examples: o Glucose o Fructose o Galactose o All are Reducing sugars (sweet fruits & honeys)

Examples: o Maltose (Reducing) = Glucose + Glucose o

Importance o Main source of energy o To form supporting structures (eg. Cellulose cell wall in plts) o Converted to other organic compounds eg. Fats & amino acids o For formation of nucleic acids (DNA)

Lactose (Reducing) = Glucose + Galactose

Sucrose (non-reducing) = Glucose + Fructose Examples: o Starch (green plts) o Glycogen (animals) o Cellulose (plants) •

Polysaccharides (Macromolecules) o

Class Fats (contain C, H, O), but less O compared to Carbohydrates

Made up of thousands of simple sugar units (glucose)

Components Fats: solid at r.t.p Oils: liquid at r.t.p Fats = Fatty acids + Glycerol

In each, the glucose is linked differently Sources o Meat, Milk, lard, butter, egg yolk (from animals) o Oils in nuts and seeds (from plants) o

(H:O > 2:1) Proteins (contain C, H, O, N)

Made up of amino acids

o

Each protein is unique may contain some or all of the amino acid molecules  the way each a.a is arranged determines what type of protein it is

o

Lean meat, fish, eggs, milk, cheese (from animals) Beans & Cereals (from plants)

Importance o As a source of energy o To form part of the cell membrane o As solvents for fatsoluble vitamins and some hormones o As an insulator to prevent excessive heat loss from skin o For growth & repair of worn-out parts, new protoplasm o Source of energy o For producing enzymes, hormones, antibody, haemoglobin, etc

Absorption Process Water & mineral salts

Simple sugars + mineral salts + vitamins + amino acids

Absorbed by

Fatty acids

Glycerol

Pass through villi

React with bile salts

Large intestine

Blood capillaries

Other parts of body

Form

Soluble soaps

Diffuse into villi epithelium Soluble soaps + glycerol --> small fat globules Absorbed by lymphatic capillaries

Assimilation Simple sugars + amino acids Hepatic portal vein

In Liver Excess glucose --> glycogen Excess amino acids --> urea

Hepatic vein

Distributed round body & used

Remaining

Simple sugars

Amino acids

Tissue respiration

Growth & repair of worn-out body parts Used as building blocks of enzymes and hormones

Fats Fats

Enter

Lymphatic capillaries

Excess fats

Fats + Lymph

Glucose insufficient

Stored in adipose tissues • Fat storage • Insulation

Form

Chyle

Fats transported to liver --> converted to oxidizable forms

Transported in Lymph vessels

Functions of Liver

Bile production  stored in gall bladder

Physical Digestion

Liver

Release Hb back to

Assimilation

Deamination of excess amino acids  urea Regulation of blood glucose level

Breakdown of RBC in spleen Protein synthesis Detoxification

Otherwise

Excessive alcohol consumption leads to

Eg. Breakdown of alcohol  acetaldehyde (harmless)

Fasting (glucagon converts)

Glycogen  Glucose  enter into bloodstream

After heavy meal insulin converts

Glucose  Glycogen  stored

Stimulate HCl (acidic) secretion in the stomach

Liver cirrhosis  liver cells killed  replaced with fibrous tissue  liver failure

Intake of CO2 and H2O by plants for photosynthesis 
 
 
 
 
 
 
 
 


Raw materials (H2O + CO2) Entry of H2O + mineral salts

Entry of CO2 Light

Veins in leaf

CO2 in leaf < CO2 in atm

Form

Diffusion gradient forms Atm CO2  stomata  intercellular air spaces CO2  dissolves in thin film of H2O on surface of mesophyll cells

Dissolved CO2  diffuses into cells

Fine branches ending among mesophyll cells Contains

Xylem

Phloem

Transport H2O + mineral salts soil  root  leaf via mesophyll of leaf

Diffuse from cell to cell

Structure

Adaptation

Large surface area Thin Lamina

Absorb maximum light energy • Diffusion distance reduced to allow CO2 to reach inner cells rapidly. • Enables sunlight to reach all mesophyll cells. Chlorophyll absorbs and converts light energy to chemical energy used to manufacture sugars. More light energy can be absorbed near leaf surface. Allows rapid diffusion of CO2 to mesophyll cells. Open in sunlight, allowing CO2 to diffuse in and O2 to diffuse out of leaf. Xylem • Transports water and mineral salts to mesophyll cells Phloem • Transports sugars away from leaf Holds leaf in position to absorb maximum light energy

Chloroplasts found in all mesophyll cells More chloroplasts in upper palisade tissue Inter-connecting system of air spaces in mesophyll Stomata present in epidermal layers Veins (vascular bundles) containing xylem and phloem

Petiole (Leaf stalk)