IB Biology Unit 2.3

cellulose microfibrils

- individual strands together form bundles with hydrogen bonds which link the cellulose molecules together - Microfibrils have very high tensile strength which prevents plant cells from bursting (even when water enters the cell by osmosis)

formation of starch

- made by linking alpha glucose molecules together, formed by a condensation reaction between the carbon 1 and carbon 4 on the next alpha glucose molecule - Results in a glycosidic bond joining the 2 glucose molecules and a molecule of water is lost.

Condensation reaction

- the joining of subunits together - Monosaccharides are joined together to form disaccharides or polysaccharides by a condensation reaction.

what would happen if glucose was stored as glucose in plants?

it would cause too much water movement in and out of the cell (by osmosis) because glucose is soluble and would upset the osmotic balance

What are Triglycerides?

one of the main group of lipids (there are many)

disaccharide

structure: 2 single monosaccharides linked together examples: Glucose + glucose = maltose Glucose + fructose = sucrose Glucose + galactose = lactose

polysaccharide

structure: Many monosaccharides linked together examples: Starch, glycogen, cellulose (all made from glucose linked together in different ways)

Monosaccharide

structure: Single sugar unit examples: Glucose, fructose and ribose

Glycosidic bond

the bond that chemically joins the 2 monosaccharides together

Advantages of storing glycogen

Short term energy: Broken down rapidly and transported in the blood to where it is needed. Used in either aerobic or anaerobic respiration

disadvantages of storing glycogen

Short term storage

Extra glucose molecules can be easily added or removed to/from both starch and glycogen

- Can be done at both ends of an unbranched molecule or at any of the ends in a branched molecule. - Both starch and glucose do not have a fixed size and the number of glucose molecules that they contain can be increased or decreased.

structure of cellulose

- Cellulose is an unbranched chain of glucose molecules the individual chains get together to form bundles with hydrogen bonds which link the cellulose molecules together.

formation of cellulose

- Condensation reactions link carbon 1 to carbon 4 on the next beta glucose molecule - Results in a glycosidic bond joining the 2 glucose molecules and a molecule of water is lost. - - Each beta glucose added to the chain has to be positioned at 180 degrees because the -OH (hydroxyl) groups need to be positioned next to each other to form H20.

gylcogen

- Stored in the liver and some muscles in humans - similar to branched form of starch (amylopectin) but has more branching which makes the molecule more compact. - Function: store energy in the form of glucose

Starch is made up of two different molecules

- amylose and amylopectin - Amylose is unbranched and forms a helical shape whereas amylopectin is branched and forms a more globular shape.

cellulose

- found in plant, used for making cell walls - made from beta glucose joined together

Starch

- found in plants, plants store glucose as starch - alpha glucose - It is hydrophilic but too large to be soluble in water - Insoluble - allows plants to store glucose as starch and has no effect on water movement in and out of the cell

There are 2 types of glucose

Alpha and beta

Evaluate the use of animals in researching health claims

Animals are used to research health claims as it would be impossible to restrict/ control what people eat for their whole life yet the results might not be applicable to humans as we a different animals

Explain the advantage of glycogen being highly branched.

Extra glucose molecules can be easily added or removed to/from both starch and

Describe the formation of maltose

Glucose and galactose join to form lactose (a disaccharide) which involves the loss of -OH from one molecule and -H from another molecule which forms H2O.

Saturated fatty acid

If all carbons in the hydrocarbon chain are linked by single bonds

cis-fatty acid

If the hydrogen atoms are on the same side of the carbon atoms

trans-fatty acid.

If the hydrogens are on opposite sides of the carbon compounds

Polyunsaturated fatty acid:

If there is more than one double bond present in the hydrocarbon chain

Monounsaturated fatty acid

If there is one double bond present in the hydrocarbon chain

Describe the difference between 'implications' and 'limitations' of research.

Implications are referring to the results and how they support claims while limitations is questioning the method of research/experimentation to see if the conclusion is accurate.

Explain the importance of glucose being easily removed and glycogen storages

It can be done at both ends of an unbranched molecule or at any of the ends in a branched molecule.

Describe the formation of a triglyceride molecule in detail

It is formed from 1 glycerol and 3 fatty acids by condensation reactions. The 3 reactions produce 3 molecules of water. The bond between each fatty acid to the glycerol molecule is the ester bonds.

Why cant humans store glucose as glucose>

It would cause water to move into cells by osmosis (cells would burst) because glucose is soluble but glycogen is insoluble.

Explain why lipids are a more suitable store of energy compared to carbohydrates for long-term energy storage.

One gram of fat releases twice as much energy during cell respiration, thus, we can store large amounts of fat. Also, lipids are poor conductors of heat, therefore, they insulate us. Lastly, fat is liquid at body temperature and can act as a shock absorber.

disadvantages of storing fat

Only used in aerobic respiration Takes time to become available.

Outline the evidence for trans fats causing CHD

Patients who died from CHD, fatty deposits in the diseased arteries have been found to contain high concentrations of trans-fats.

Outline how epidemiological studies aid the research of health claims

Statistical analysis can be carried out on the results to see if there is a pattern between what people eat and their health, particularly diseases.

Explain the reasoning behind the difference in melting points of cis and trans fatty acids

The bend in cis-fatty acids makes the fatty acids less good at packing together in regular arrays, meaning they have a lower melting point than saturated fatty acids and trans-fatty acids.

Describe the difference between alpha glucose and a beta glucose molecule.

The main difference is the position of the -OH group (hydroxyl group) - in alpha glucose the -OH group is below carbon 1 - in beta glucose the -OH group is above carbon 1 - this determines the polysaccharide made

BMI

To calculate you need to know the person's mass in kilograms and their height in meters

Advantages of storing fat

Twice as much energy with half of body mass Mass: When we store fat they form pure fat droplets (No water) Lipids are poor conductors of heat - they insulate us. Protection: fat is liquid at body temperature so it acts as a shock absorber