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Class notes Biology
- Course
- Biology
- Institution
- 12th Grade
Biology 12 notes showing summaries and an easier way of understanding major lessons in this subject.
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Carbohydrates- Most abundant macromolecule
- Made by autotrophs (producers) via Photosynthesis
- Composed of Carbon, Hydrogen, and Oxygen
- Mainly starches and sugars
Their primary functions are:
1) Initial and main fuel in cellular respiration
2) Structural building block of cells and cell components (think cellulose,
chitin)
3) Cell surface markers or receptors used in cell-cell communication and
identification
• carb residues can be bonded to both the lipid and the protein
membrane components forming glycolipids and glycoproteins
In chemical terms a carbohydrate is a substance composed of carbon, hydrogen
and oxygen atoms, that tend to be in a 1:2:1 ratio.
FOUR MAIN TYPES (SUBCLASSES) OF CARBOHYDRATES
a) Monosaccharides – single monomer
b) Disaccharides – 2 monomers
c) Oligiosaccharides – 3-5 monomers
d) Polysaccharides – 5+ monomers
“Saccharide” means sugar
Mono means one
Di means two
Poly means many…
Monosaccharides
- Simplest sugars
- Monomer units of all other carbohydrates when they are linked
- Contain multiple functional groups (hydroxyl/carbonyl) which makes them
POLAR and many dissolve in water.
Monomers, with major biological significance, are those containing either 5
carbons (pentoses) or 6 carbons (hexoses). Pentoses of biological importance
include ribose and deoxyribose which are the sugar components of nucleic acids.
These hexoses (6 carbon) are
the foundational building
blocks of all other
carbohydrates (glycogen,
starch, cellulose). These three
are ISOMERS, they have the
same chemical formulas but are
arranged differently in terms of
their 3D shape, and
arrangement of hydrogen
atoms and hydroxyl groups.
Linear chain: monosaccharides are in the anhydrous state (without water)
Ring structure: monosaccharides with water or are in water state
1-4 linkage: Monosaccharides (single sugars) can be linked via condensation
reactions to form bigger sugars. These reactions generally occur between the
first carbon of the first monosaccharide and the fourth carbon of the second
monosaccharide.
, Disaccharides and Oligiosaccharides …
- They contain 2 or 3-5 monosaccharides linked via glycosidic or ether
linkages.
- Used as fuel for cell
There are 3 bio significant disaccharides:
1.maltose (found in grains) – 1-4 linkage glucose to glucose
2.lactose (dairy sugar)– 1-4 linkage glucose to galactose
3.sucrose (table sugar) – 1-2 linkage glucose to fructose
Polysaccharides
- many (hundreds to thousands) of monosaccharides are joined together
through multiple condensation reactions
- usually either 1-4 or 1-6 glycosidic linkages.
THREE MAIN POLYSACCHARIDES: All three of these are polymers
of glucose. However, the different ways the glucose molecules
are linked gives them different 3D shape, which is reflected in
their functions.
1. Glycogen - found in humans/animals and are made of
Alpha Glucose in 1-6 linkage (easier to break down)
2. Starch - found in plants and are made of Alpha glucose
in 1-4 linkage
3. Cellulose - made of Beta Glucose in 1-4 linkage and
cannot be digested
Their cellular role is to either serve as:
1. An energy storage molecule (i.e. glycogen in animal cells and
starch in plant cells) that can be broken down into glucose
2) Provide structural support (i.e. cellulose as primary
component in cell walls of plants vs chitin which is a structural
component in the cell walls of fungi or exoskeleton of
crustaceans).
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