1Triglycerides are a type of lipid found in milk
Describe the structure of a triglyceride molecule (3)
(one) glycerol / glyceride;
3 fatty acids;
ester bond (between glycerol and fatty acid)
2State three roles of lipids in living organisms (3)
(thermal) insulation;
energy, store / source / release;
protection;
membranes / phospholipid bilayer / control entry and exit into cells;
(steroid) hormones / named steroid hormone;
buoyancy;
waterproofing;
source of water (from respiration);
(electrical insulation) in myelin / around neurones / around axons / around dendrons;
aid, absorption / storage / production, of, fat soluble / A / D / E / K, vitamins
3Human populations with diets high in animal fats have a lower life expectancy than those with diets high in vegetable oils
Suggest one difference between lipids from animals and those from plants (1)
saturated;
(fatty acids have) no / fewer, double bonds;
solid at room temperature;
4Milk is considered to be a compete food containing most of the components of a balanced diet
A student carried out a series of food tests on a sample of milk. The student’s observations and conclusions are shown in (table 1.1)
Complete (table 1.1) by:
- naming the molecule being tested for
- stating whether this molecule is present or absent
The first row has been completed for you
(refer to table 1.1) (3)
- REDUCING sugar / lactose / glucose / galactose / monosaccharides (present);
- protein / named milk protein (present);
- starch / amylose (absent);
5Milk is considered to be a compete food containing most of the components of a balanced diet
A student carried out a series of food tests on a sample of milk. The student’s observations and conclusions are shown in (table 1.1)
Although the student entered ‘present’ for lipid in the first row of the table, he was unsure whether the result was correct
Suggest why the student was unsure if the positive result for the lipid was correct for the milk sample (1)
milk is already, cloudy / an emulsion / white;
6(fig 2.1) represents a water molecule
Water molecules are polar. As a result, they attract each other.
Draw a second water molecule on (fig 2.1)
Your drawing should show:
- the bond(s) between the two molecules
- the name of the bond
- the charges on each atom
(3)
refer to ms cell structure 3 q 3a. fig (2.1)
7Ponds provide a very stable environment for aquatic organisms
Three properties of water that contribute to this stability are as follows:
- the density of water decreases as the temperature falls below 4 degrees Celsius so ice floats on the top of the pond
- it acts as a solvent for ions such as nitrates (NO3-)
- a large quantity of energy is required to raise the temperature of water by 1 degree Celsius
Explain how these properties help organisms survive in the pond
In your answer you should make clear links between the behaviour of the water molecules and the survival of the organisms (8)
ice floats:
- P1 (ice less dense because) molecules spread out;
- P2 molecules form, crystal structure / lattice;
- P3 ice forms insulating layer / clearly described;
- P4 water (below ice), does not freeze / still liquid / remains water / kept at higher temperature;
- S1 organisms do not freeze;
- S2 animals / organisms, can still, swim / move;
- S3 allows, currents / nutrients, to circulate;
solubility:
- P5 ions / named ion, polar / charged;
- P6 ions / named ion, attracted to / bind to / interact with, water;
- S4 (named) organisms / plants / animals, uptake / minerals/ named minerals / nutrients;
- S5 correct use of named, mineral / nutrient, in organisms; (eg nitrates for amino acids / protein / nucleic acid, phosphate for ATP / phospholipids / plasma membrane, magnesium for chlorophyll )
temperature stability:
- P7 many / stable, (hydrogen) bonds between molecules;
- P8 a lot of energy to, force apart molecules / break bonds;
- P9 high (specific) HEAT CAPACITY;
- S6 temperature does not change much / small variation in temperature;
- S7 effect of temperature on, enzymes / metabolic rate;
- S8 gases remain soluble;
H award once in any section
- hydrogen bonds;
QWC- award if you see a P mark AND an S mark within the same section (1)
8Water is important in many biological reactions
Complete Table 2.1 by writing an appropriate term next to each description (2)
Table 2.1
description, term
the type of reaction that occurs when water is added to break a bond in a molecule, ___
the phosphate group of a phospholipid that readily attracts water molecules, ___
hydrolysis / hydrolytic;
hydrophilic*;
94A. Amino acids are the basic building blocks for proteins. fig (4.1) shows the amino acid cysteine
Complete the table by selecting the letter J, K, L or M, that represents the following groups in cysteine:
group letter
carboxyl
R group
Amine group
L;
M;
J;
10Amino acids are the basic building blocks for proteins. fig (4.1) shows the amino acid cysteine.
The primary structure of a protein consists of a chain of amino acids.
Describe how a second amino acid would bond to cysteine in forming the primary structure of a protein (3)
- peptide bond;
- between, amine group (of one amino acid) and carboxyl group (of another);
- H (from amine group) combines with OH (from carboxyl group);
- condensation reaction OR water, lost / eliminated / produced / created;
- covalent;
11Amino acids are the basic building blocks for proteins. fig (4.1) shows the amino acid cysteine.
Each amino acid has a different R group
Describe how these R groups can interact to determine the tertiary structure of a protein (4)
- some R groups, attract / repel;
- DIsulfide, bridges / bond;
- between, cysteine / SH / S (atoms);
- hydrogen / H, bonds;
- Ionic bonds between, oppositely charged / + and -, R groups;
- hydrophilic R groups, on outside of molecule / in contact with water (molecules);
- hydrophobic R groups, on inside of molecule / shielded from water (molecules);
12(fig 4.2) shows the structure of two polymers, glycogen and collagen, that are found in mammals
Complete the table below to give three differences between the structure of glycogen and collagen (3)
glycogen:
- carbohydrate/ polysaccharide
- (alpha) glucose (units)
- identical units
- glycosidic, bonds / links
- branched
- non-helical
- one chain (per molecule)
- no cross-links
- contains CHO
collagen:
- protein / polypeptide
- amino acid (units)
- different amino acid units
- peptide, bonds / (links)*
- unbranched / linear
-
- three chains per molecule
- cross links (between chains)
- contains C H O N
13Collagen is found in the ligaments which hold bones together as joints
State two properties of collagen that makes it suitable for this purpose (2)
- (high tensile) strength / strong
- does not stretch / is not elastic
- insoluble ;
- flexible;