Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Carbohydrates and lipids

Topic 2
...
3

Biology SL

Cellulose
➢ Major component of plant cell wall
➢ Helps give rigidity and support to plant parts, such as roots, stems and leaves
➢ Long chains of glucose that are hydrogen bonded to each other
➢ Few animals can digest it
○

In symbiosis with a bacterium that breaks down cellulose

➢ Holds a lot of energy
Starch
➢ Organic products of photosynthesis are stored in plants as starch
○

As starch granules in chloroplasts

○

In plant storage areas, such as roots or root structures

➢ Amylopectin is branched and humans cannot digest it
➢ Amylose is the only one of the 3 polysaccharides mentioned that is linear and
humans can digest it
Glycogen
➢ Animals store excess glucose as glycogen
○

In the liver and muscle cells

➢ Structure similar to amylopectin, but it is built in a way so humans can break it
down
Fatty acids
➢ All fatty acids have similar molecular structure, but they are not identical
○

Have a carboxyl group (-COOH)

○

Have a methyl group (CH3-)
■

○

At the opposite side on the carboxyl group

Chain of hydrocarbons in between
■

Between 11 and 23 carbons long
●

The carbons of the carboxyl and methyl groups not included

➢ Fatty acids and glycerol are building blocks of lipids
➢ Depending on the fatty acids, we get different lipid properties
➢ Fatty acids can either be saturated or unsaturated
○

Unsaturated fatty acids can either be monounsaturated or polyunsaturated

➢ Fatty acids can be turned into ATP in the cell respiration
○

Stored as triglycerides in adipose cells
2

Carbohydrates and lipids
○

Topic 2
...
3

Biology SL

Hydrogenation
➢ In heavily processed foods, polyunsaturated fat are often hydrogenated or partially
hydrogenated
○

The double bonds are eliminated or partially eliminated by adding hydrogen
atoms

○

This straightens out the natural bent shape of the unsaturated fatty acids

➢ The naturally curved fatty acids are called cis
➢ The hydrogenated ones are called trans lipids
○

Result of chemical transformation

○

Still have one or more double bonds

➢ Cis fatts have bendings on the same side of the molecule and trans have on
different
➢ One category of cis fatty acids is called omega-3
○

The name comes from the fact that the first carbon double bond is found in
the molecule at the third carbon atom counting backwards from the omega
end

○

Fish are good source of omega-3 fats

Triglyceride lipids
➢ Made up of glycerol and 3 fatty acids
➢ They vary greatly from each other, including their relative healthiness
➢ The identity/characteristics of the 3 fatty acids in each triglyceride will determine
the overall characteristics of the fat or oil
○

Fat = animals

○

Oil = plants

➢ When triglycerides are needed, they are hydrolysed into 2 carbon segments that
enter into cell respiration at a moment which is efficient for the production of ATP
○

Triglycerides -> hydrolysis -> 2C -> cell respiration -> ATP

➢ They are insoluble in water, so they do not disturb the osmotic balance of the
solutions
○

Insoluble in the cytoplasm, blood plasma and extracellular fluid

○

If they were soluble in water, glucose would attract water and the cell would
swell extremely
■

This would happen, due to hypotonic fluids

4



---