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Maris Stella High School Name: ___________________GCE O Level Biology Class (Index No.): ____ ( )Revision Summary Date:_____________

Class Components Sources Importance

Monosaccharides (simplesugars)

Examples:o Glucoseo Fructoseo Galactoseo All are Reducing

sugars (sweet fruits &honeys)

Disaccharides (Complexsugars)

o Formed when 2 simplesugars combine withelimination of a watermolecule

Examples:o Maltose (Reducing) =

Glucose + Glucose

o Lactose (Reducing) =Glucose + Galactose

Sucrose (non-reducing) =Glucose + Fructose

Carbohydrates(containC, H, O)

(H: O ratio =2:1)

Polysaccharides(Macromolecules)

o Made up of thousandsof simple sugar units

(glucose)

Examples:o Starch (green plts)o Glycogen (animals)o Cellulose (plants)

o In each, the glucose islinked differently

o Main source ofenergy

o To form supportingstructures (eg.Cellulose cell wallin plts)

o Converted to otherorganic compoundseg. Fats & aminoacids

o For formation ofnucleic acids (DNA)

Class Components Sources Importance

Fats(containC, H, O), butlessOcompared toCarbohydrates

(H:O > 2:1)

Fats: solid at r.t.pOils: liquid at r.t.p

Fats = Fatty acids +Glycerol

o Meat, Milk, lard, butter, eggyolk (from animals)

o Oils in nuts and seeds(from plants)

o As a source of energyo To form part of the cell

membraneo As solvents for fat-

soluble vitamins andsome hormones

o As an insulator toprevent excessive heatloss from skin

Proteins(containC, H, O, N)

Made up of amino acids

Each protein is uniquemay contain some or all ofthe amino acid molecules the way each a.a isarranged determines whattype of protein it is

o Lean meat, fish, eggs, milk,cheese (from animals)

o Beans & Cereals (fromplants)

o For growth & repair ofworn-out parts, newprotoplasm

o Source of energyo For producing

enzymes, hormones,antibody, haemoglobin,etc

Nutr i t ion

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Absorption Process

Assimilation

Water&

mineral

salts

Absorbed

by

Large

intestine

Simple sugars + mineral salts +

vitamins + amino acids

Pass through

villi

Blood capillaries

Other parts of body

Fatty acids Glycerol

React with bile salts

Soluble soaps

Form

Diffuse into villi epithelium

Soluble soaps + glycerol --> small fat globules

Absorbed by lymphatic capillaries

Simple sugars + amino acids

Hepatic portal

vein

In LiverExcess glucose --> glycogen

Excess amino acids --> urea

Remaining

Hepatic vein Distributed round body & used

Simple sugars Amino acids

Tissue respiration Growth & repair of

worn-out body parts

Used as building

blocks of enzymesand hormones

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Functions of Liver

Fats

Enter

Lymphatic capillaries

Fats

Excess fats Glucose insufficient

Stored in adipose tissues Fat storage Insulation

Fats transported toliver --> convertedto oxidizable forms

Fats + Lymph

Form

Chyle

Transported in Lymph

vessels

Liver

PhysicalDigestion

Bile production stored ingall bladder

Assimilation

Regulation of blood

glucose level

Deamination of excess aminoacids urea

Fasting (glucagon

converts)

Glycogen Glucose enter into

bloodstream

Glucose Glycogen stored

Breakdown of

RBC in spleen

Release Hb

back to

Protein synthesis

Detoxification Eg. Breakdownof alcohol

acetaldehyde

(harmless)

Excessivealcohol

consumption

leads toLiver cirrhosis liver cells killed

replaced with fibrous tissue liver failure

Otherwise

After heavy meal

insulin converts

Stimulate HCl (acidic) secretion in the stomach

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Intake of CO2 and H2O by plants for photosynthesis

Structure Adaptation

Large surface area Absorb maximum light energyThin Lamina Diffusion distance reduced to allow CO2to reach inner cells rapidly.

Enables sunlight to reach all mesophyllcells.

Chloroplasts found in allmesophyll cells

Chlorophyll absorbs and converts light energyto chemical energy used to manufacturesugars.

More chloroplasts in upperpalisade tissue

More light energy can be absorbed near leafsurface.

Inter-connecting system of air

spaces in mesophyll

Allows rapid diffusion of CO2 to mesophyll

cells.Stomata present in epidermallayers

Open in sunlight, allowing CO2 to diffuse inand O2 to diffuse out of leaf.

Veins (vascular bundles)containing xylem and phloem

Xylem Transports water and mineral salts to

mesophyll cellsPhloem

Transports sugars away from leaf

Petiole (Leaf stalk) Holds leaf in position to absorb maximum lightenergy

Raw materials (H2O + CO2)

Entry of CO2Entry of H2O +

mineral salts

Light

CO2 in leaf < CO2 in atm

Diffusion gradient forms

Atm CO2 stomata intercellular air

CO2 dissolves in thin film ofH2O on surface of mesophyll cells

Dissolved CO2 diffuses into cells

Veins in leaf

Fine branches ending amongmesophyll cells

Form

Contains

Xylem Phloem

Transport H2O + mineral saltssoil root leaf

Diffuse from cell to cell

via mesophyll of leaf