Biology Unit 5.1: Transport In Plants

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Unit 5.1: Transport In Plants

1. State the functions of xylem and phloem.

Xylem: specialised tissue in plants that transports water and inorganic ions from the root up to all the other parts of the plant

Phloem: specialised tissue in plants that transports food nutrients (e.g. glucose) from the leaves to other parts of the plant.

2. Identify the positions of xylem and phloem tissue.

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3. Identify root hair cells, as seen under the light microscope, and state their functions.

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Root hair cells are found at the end of young roots, their function is to help the plant absorb water and mineral ions from the soil via osmosis. They have large surface areas so they can maximise absorption. 

4. Relate the structure and functions of root hairs to their surface area and to water and ion uptake.

As said above, root hairs have large surface areas for absorption of water and ions. The cell membrane is semi-permeable so only minerals and water can go through, but not necessarily go back out.

5. State the pathway taken by water through root, stem and leaf (root hair, root cortex cells, xylem, mesophyll cells).

1. There is a high concentration of salts in the cell sap of the root hair, but a low concentration in the soil.
2. By osmosis, water passes into the root hair from the soil.
3. The cell sap is now diluted by the water. Next to the root hair is the cells of the cortex. Osmosis occurs through the cells until the water reaches the xylem.
4. The xylem vessel transports the water up the xylem tube from root to stem through a process called capillary action*.
*capillary action = cohesion of hydrogen bonding and adhesion to cell wall --> this pulls up everything against the force of gravity
5. The water leaves the xylem and is absorbed by the cells in the leaves.

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6. Investigate, using a suitable stain, the pathway of water through the aboveground parts of a plant.

7. Define transpiration as evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, through the stomata.

So water is pulled up form the xylem, and is used for photosynthesis. Transpiration is when water evaporates from the leaves into the air. When the water has evaporated, more is needed to continue photosynthesis. The transpiration stream is the stream of water that is pulled up from the roots to the leaves, similar to how a drink is sucked up a straw.

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8. Describe how water vapour loss is related to cell surfaces, air spaces and stomata.

Water in the mesophyll cells forms a layer on the surface of the cell. The water evaporates into the air spaces between the spongey cells. A high concentration of water is in the cells, so water diffuses out of the leaf through the stomata. The water lost is replaced by water from the xylem.

9. Describe the effects of variation of temperature, humidity and light intensity on transpiration rate.

temperature: the higher the temperature, the faster the rate of transpiration
humidity: the higher the humidity, the slower the transpiration --> this is because there is a lot of moisture in the air
wind speed: transpiration increases as wind speed increases
light intensity: the more light, the faster the transpiration --> this is because the stomata open in light for photosynthesis
water supply: the less the water, the slower the transpiration --> when there is less water, the stomata close up to conserve water

10. Explain the mechanism of water uptake and movement in terms of transpiration producing a tension (‘pull’) from above, creating a water potential gradient in the xylem, drawing cohesive water molecules up the plant.

Once water enters the xylem tubes in the roots, it flows to the stem, then the leaves. This flow is called the transpiration stream. The columns of water in the xylem tubes are prevented form breaking by strong cohesive forces between the water molecules.

11. Define translocation in terms of the movement of sucrose and amino acids in phloem; from regions of production to regions of storage OR to regions of utilisation in respiration or growth.

Translocation is the movement of manufactured food through the phloem tissue. Food in manufactured in the leaves. In younger plants, food is distributed to areas of growth while in older plants, it is transported to areas for storage e.g. roots in a potato plant. In all plants, food needs to be transported to the cells for respiration.

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Biology Unit 9.1+2: Chromosomes and Genes, Cell Division

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9.1: Chromosomes and Genes

1. Define inheritance as the transmission of genetic information from generation to generation.

Well, there you go! But here's a little more detail: inheritance is how parents pass on their characteristics to their children or offspring.

2. Define the terms chromosome, gene, and allele.

Chromosome: A thread of DNA, made up of a string of genes.

Gene: A length of DNA that is the unit of heredity and codes for a specific protein. A gene may be copied and passed on to the next generation. 

Allele: Any of two or more alternative forms of a gene.

3. Define the terms haploid nucleus and diploid nucleus.

Haploid nucleus: a nucleus containing a single set of unpaired chromosomes.

Diploid nucleus: A nucleus containing two sets of chromosomes.

A set is 23 single chromosomes, meaning a haploid nucleus has 23 chromosomes while a diploid nucleus has 46 (who pairs of 23). Body cells (somatic cells) are known as diploid nucleuses, while male and female gametes are haploid nucleuses. 

When an egg and sperm fuse in the process of fertilisation, the 23 chromosomes from the egg and the 23 chromosomes from the sperm add up together in the zygote, returning the chromosome number to 46. (Each gamete is a h______ n______; the zygote is a d______ n______)

Think about it this way:
Haploid sounds like half;
Diploid means 'double' or 'two'

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4. Describe the inheritance of sex in humans (XX and XY chromosomes)

All eggs contain an X chromosome while sperm contain either X or Y chromosomes. When the X egg is fertilised with an X sperm, the XX chromosome makeup makes a girl. When the X egg is fertilised with a Y sperm, the XY chromosome makeup makes a boy. Therefore the baby has a 50/50 chance of being a girl or boy, and it is the sperm that determines the baby's gender. 

9.2: Cell Division

1. Define mitosis

Mitosis: nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes.

Mitosis begins with a single cell, so it contains 46 chromosomes (23 pairs). This is known as the diploid parent cell. The cell makes a copy of each chromosome, resulting in 92 chromosomes. It then divides itself in half, forming two new cells that each contain a full set of chromosomes and are identical to the parent cell. They are known as the daughter diploid cells.

Gotta love that comic sans!

What type of cells go through mitosis? Body cells! The daughter cells end up with a full set of chromosomes, and we know that body cells are diploid nucleuses.


2. Sate the role of mitosis in growth, repair of damaged tissues, replacement of worn out cells and asexual reproduction.

As said above, mitosis is used to provide body cells that replace old or dead ones. It is also used for asexual reproduction, as asexual reproduction produces a clone of the parent with the exact same genetic makeup.


3. Define meiosis

Meiosis: reduction division in which the chromosome number is halved from diploid to haploid.

Meiosis is similar to mitosis. The process is the same until the end; the two daughter cells split in half again, resulting in four cells that contain 23 chromosomes each.

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4. State that gametes are the result of meiosis.

Gametes are the result of meiosis. *Heh* We know that gametes contain 23 chromosomes each, and meiosis results in four cells that contain 23 chromosomes each. It adds up!

5. State that meiosis results in genetic variation so the cells produced are not all genetically identical.

To form a zygote, you need an egg and sperm. Both of these gametes contain different genetic information, so through meiosis genetic information is shared and split between the cells. This results in genetic variation, where cells don't all contain the same genetic information.

This can be beneficial as if the parent has a disease, it could potentially be passed down to the child; genetic variation makes it so that the disease has a chance of not being passed.

Chemistry Unit 8: Acids, Bases and Salts

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Unit 8.1 The characteristic properties of acids and bases

Before I start going into the syllabus, let's define acids and bases clearly!

Acids: a substance that dissolves in water to produce hydrogen

Base: a substance that neutralises an acid

A lot of the time, you'll hear the word alkali. An alkali is a type of base that can dissolve in water. An alkali is a base, but a base is not an alkali.

1. Describe neutrality and relative acidity and alkalinity in terms of pH (whole numbers only) measured using full-range indicator and litmus.

When talking about pH, you've got the whole pH scale in mind, where you identify the pH according to a certain colour. You can use litmus paper or universal indicator (UI) to check a substance's pH. 

Neutral: pH 7, turns UI green, turns litmus paper purple

Acid: low pH (less than 7), turns UI red-yellow, turns litmus paper red

Alkali: high pH (greater than 7), turns UI blue-purple, turns litmus paper blue

Below is an image displaying the different colours universal indicator turns according to pH levels, and also what substances are of that pH level.

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2. Describe the characteristic reactions between acids and metals, bases (including alkalis) and carbonates.

Here is a handy-dandy four-step system to this:

● acid + alkali --> salt + water

● acid + metal --> salt + hydrogen

● acid + carbonate --> salt + water + carbon dioxide

● acid + oxides (bases) --> salt + water

3. Describe and explain the importance of controlling acidity in the environment (air, water and soil)

Soil: Soil is used to grow crops, so it is important for it to be neutral. If it happens to be too alkaline or acidic, the crops tend to grow poorly. Acidity is usually the problem for soil, so a base can help neutralise it. Bases include limestone, slaked lime, or quick lime (more on that later!).

Water: Factory waste is often acidic, and it can leak into water. To prevent this from happening, it needs to be neutralised. Again, slaked lime is used for this. 

Air: Burning fossil fuels releases gases into the air, such as nitrogen oxides and sulphur dioxide. They react with water and air, leading to acid rain. As you can tell by the name, it's not that great; it causes buildings to erode and will negatively affect soil and water. 

Unit 8.2 Types of oxides

1. Classify oxides as either acidic or basic, related to metallic and non-metallic character of the other element.

First, let's define oxide: it is a compound made up of oxygen and another element. Next, acidic oxide: a compound of oxygen and a non-metal, most commonly a gas. Lastly, basic oxide: a compound of oxygen and a metal.

Here are some examples of each type of oxide:
acidic oxide: sulphuric acid (H2SO4), nitric acid (HNO3)
basic oxide: sodium hydroxide (NaOH), copper oxide (CuO)

So now that you know what the different oxides are, it's easier to classify them into groups. 

Acidic oxides:
● react with water to give and acid
i.e carbon dioxide + water --> carbonic acid
     CO2 + H2O --> H2CO3
● react with bases to form a salt
i.e. sulphuric acid + copper oxide --> copper sulphate + water
     H2SO4 + CuO --> CuSO4 + H2O

Basic oxides:
● react with acids to form a salt and water
i.e. copper oxide + hydrochloric acid --> copper chloride + water

     CuO + 2HCl --> CuCl2 + H2O


2. Further classify some oxides as neutral, given relevant information.

Some oxides are neither basic or acidic, so they are neutral oxides. They don't react with acids or bases either. Examples of neutral oxides include nitrous oxide (N2O) and carbon monoxide (CO). 




Unit 8.3 Preparation of salts

1. Describe the preparation, separation and purification of salts using techniques selected from section C2.1 and the reactions specified in C8.1.

Preparing the salt:
1. Add an excess of your carbonate to your acid
2. Test the pH with U.I. paper to check if the solution is neutral
3. Filter the solution to get rid of the excess carbonate
4. Heat the liquid until most of it has evaporated and you are left with salt crystals

Separating the salt:
Let's say we have a mixture of salt and pebbles
1. Add water to your mixture so the salt dissolves
2. Filter the mixture
3. Evaporate the liquid

Purifying the salt:
If it's an insoluble salt: filtration
If it's a soluble salt: distillation

2. Suggest a method of making a given salt from suitable starting materials, given appropriate information. 

Remember that handy-dandy four-step system from above? Here, it comes to use.

Acid + alkali --> salt + water
Hydrochloric acid + sodium hydroxide --> sodium chloride + water
HCl + NaOH --> NaCl + H2O
1. Add 30cm2 of sodium hydroxide to a flask
2. Add two drops of the indicator phenolphthalein 
3. Add the hydrochloric acid to the flask
4. The solution will turn colourless when neutralised
5. Heat the solution to evaporate the liquid and obtain the salt

Acid + metal --> salt + hydrogen
Sulphuric acid + zinc --> zinc sulphate + hydrogen
H2SO4 + Zn --> ZnSO4 + H2
1. Add zinc to a flask of the acid
2. When the zinc dissolves, hydrogen bubbles will appear
3. Filter the solution to remove the excess zinc
4. Heat the solution to evaporate the liquid and obtain the salt

Acid + base --> salt + water
Sulphuric acid + iron(II) oxide --> iron sulphate + water
H2SO4 + FeO --> FeSO4 --> H2O
1. Add and excess of iron oxide to the sulphuric acid
2. Filter the solution to remove the excess iron oxide
3. Heat the solution to evaporate the liquid and obtain the salt




Unit 8.4 Identification of ions and gases

1. Use the following tests to identify aqueous cations, anions, and gases.

Aqueous cations:
● ammonium
● copper(II)
● iron(II)
● iron(III)
● zinc 

Cation	Test	What happens if cation is present?
Ammonium	Add dilute sodium hydroxide, warm up	Ammonia gas is released, damp red litmus paper turns blue
Copper(II)	Add dilute sodium hydroxide or ammonia solution	A blue precipitate forms
Iron(II)	Add dilute sodium hydroxide or ammonia solution	A pale green precipitate forms
Iron(III)	Add dilute sodium hydroxide or ammonia solution	A red-brown precipitate forms
Zinc	Add dilute sodium hydroxide or ammonia solution	A white precipitate forms

Anions:

● carbonate

● chloride

● nitrate

● sulphate

Anion	Test	What happens if anion is present?
Carbonate	Add dilute hydrochloric acid	Bubbles that give off gas turn limewater a milky-white
Chloride	Add the same volume of nitric acid as chloride, add aqueous silver nitrate	A white precipitate forms
Nitrate	Add sodium hydroxide, then aluminium	Ammonia gas will be given off
Zinc	Add dilute sodium hydroxide or ammonia solution	A white precipitate forms

Gases:

● ammonia

● carbon dioxide

● chlorine

● hydrogen

● oxygen

Anion	Test	What happens if gas is present?
Ammonia	Damp red litmus paper	Paper turns blue
Carbon dioxide	Limewater	Limewater turns milky-white
Chlorine	Damp blue litmus paper	Paper turns white
Hydrogen	Lighted splint	A loud POP
Oxygen	Glowing splint	Splint relights