5.7 understand the role of bacteria (Lactobacillus) in the production of yoghurt

Yeast makes bread, beer

Lactobacillus makes bacteria, yoghurt

Fermentation in Lactobacillus

Lactose —> lactic acid

Step 1

Sterilisation can happen if heated as well as using anti-bacteria. It removes the microbe which reduces contamination so we do not get infected.

Step 2

Pasteurisation kills the bacteria which reduces contamination so we do not get infected. Also, this makes sure that the right product is produced.

Step 3

Lactobacillus undergoes fermentation. pH lowers which denatures the protein

This is a triple science, paper 2 fact

3.11 understand how the developing embryo is protected by amniotic fluid

• Once an ovum is fertilized, it develops into an embryo, which will implant into a uterus. At this point, an amnion membrane forms. The amnion membrane is full of amniotic fluid which surrounds the embryo, protecting it from knocks and bumps
• The fluid at the start is composed of 98% water, 2% salt from foetus. Generally as the pregnancy continues, the composition will be changed to include urine and antibodies

Other functions of amniotic fluid:  (Amniotic fluid doesn’t just protect, it develops the foetus)

• Breathe (to develop lungs)
• Move (to develop muscles and bones)
• Swallow (to develop a digestive system)
• to keep warm
• separate fingers and toes

This is a paper 2, triple science fact.

3.10 describe the role of the placenta in the nutrition of the developing embryo

Placenta does 3 things:

• Attaches foetus
• Removes waste
• Supplies nutrients

The difference in levels is the concentration gradient – this difference allows diffusion to happen.
Nutrients and waste products are free to diffuse from one blood supply to another, but maternal and foetal blood never mixes.

Adaptations of the Placenta –

• The exchange of waste and nutrients happen because of the difference (concentration gradient) of the two substances.
• These substances diffuse across the villi of the placenta
• Villi have large surface area  for more area for diffusion and is very close to the bloodstream
• 

 

This is a paper 2, triple science fact

 

2.89 describe the role of the skin in temperature regulation, with reference to sweating, vasoconstriction and vasodilation

When too cold (and need to warm) – VASOCONSTRICTION

• Blood vessels near the surface of the skin constrict (tighten)
• This is so that less heat can be transferred from the blood to surroundings
• Shiver to generate heat
• Little sweat is produced, as sweat cools you
• Body hairs stand on end (perpendicular to your skin) – traps a layer of air which will act as an insulator.

 

When too hot (and need to cool) – VASODILATION

• Blood vessels near the surface of the skin dilate (widen)
• This is so that more blood can flow near the surface, allowing more heat to radiate into the surroundings
• You produce sweat, and as it evaporates heat transfers from your skin to your surroundings.
• Hairs lie flat to avoid trapping air for insulation

This a paper 2, triple science fact.

2.88 understand the function of the eye in focusing near and distant objects, and in responding to changes in light intensity

• Near objects – ciliary muscle contracts, slackening the suspensory ligament making the lense ‘fat’
• Distant objects – ciliary muscles relax, tensing the suspensory ligaments, making the lense ‘thin’
• Bright light – circular muscles contract, iris gets bigger so the pupil gets smaller. Less light gets into the eye
• Dark light – radial muscles contract, iris gets smaller, pupils get bigger, more light gets into the eye.

This is a paper 2, triple science fact.

 

1.45 explain how the uses of diamond and graphite depend on their structures, limited to graphite as a lubricant and diamond in cutting.

Diamond

• Cutting tool because of it’s rigid, trigonal structure and tight bonds

Graphite

• Lubricant, because the graphite in the atoms form layers and layers are able to slide over each other
• This makes the object slippery, a great lubricant.

This is a paper 2, triple science fact.

1.44 draw diagrams representing the positions of the atoms in diamond and graphite

Diamond

• Allotrope of carbon
• Electric configuration: 2.4
• Melting point: 355°c
• Diamonds have no free electrons to carry electrical current

Graphite

• Allotrope of carbon
• Melting point: 3457°c
• The only non metal that conducts electricity
• The layers allow the electrons to slip easily across each other, the electrons are free to conduct electricity

This is a paper 2, triple science fact.

1.37 draw a diagram to represent the positions of the ions in a crystal of sodium chloride.

PC: BBC

This is a paper 2, triple science fact

1.36 describe an ionic crystal as a giant three-dimensional lattice structure held together by the attraction between oppositely charged ions

• Ionic crystals are 3D lattice structures held together by electrostaticity.
• Key term: electrostaticity / electrostatic force is the force/act of attraction/repulsion in molecules
• This is present in ionic compounds as the ions are strongly attracted to each other
• Ions are of alternating positive and negative. Their opposing charges hold the structure together.

 

this is a paper 2, triple science fact.

1.35 understand the relationship between ionic charge and the melting point and boiling point of an ionic compound

• The higher the charge of the ions, the higher the melting points

This is a paper 2, triple science fact.