Life and Cells
Nucleus - Has genetic material, and controls the cell.
Cytoplasm - Gel like substnace where chemical reactions happen. Contains enzymes.
Cell Membrane - A shell for the cell, controls what enters and exits.
Mitochondria - Reactions for respiration take place here.
Ribosomes - Proteins are made here.
All of the above plus:
Cell Wall - Made of cellulose. Supprots and strengthens the cell.
Permanent Vacuole - Contains cell sap - a weak solution of sugar and salts.
Chloroplasts - Photosynthesis occours here, it contains chlorophyll.
Carbon Dioxide + Water ---------------> Glucose + Oxygen
4 things needed for photosynthesis
Light - from the sun
Chlorophyll - a green substance found in chloroplasts
Carbon Dioxide - diffuses into the leaf from the air
Water - comes from the soil, and along the plant and into the leaf veins
The rate is limited by:
For light and CO2, it is only limited when too low, but for temperature, it is limited when low and when high, as when it is high, it will kill of enzymes.
The best way to meet the best conditions is by using a green house. It can keep it hot inside, but also have heaters on, that produce CO2. Lights can also be used.
How Plants use Glucose, Minerals for Plants
Fruits, Cell Walls, Proteins
Plants need minerals to grow and survive...
Needed to make amino acids, which are used to make proteins
Lack of this means less growth, never reaching full height (protein is needed for growth).
Makes chlorophyll, needed for photosynthesis
Lack of this means leaves turn yellow, because chlorophyll is yellow.
Monoculture is when the same plant is grown many times is in the same place. Because they will need the same minerals, the plants may not get them, as they will have been used up by previous generations. This will reduce yield, unless fertilizers are used to give minerals to the soil.
Biomass - The mass of the living material at each stage of the food chain.
Energy is is lost in the food chain by:
Using it for photosynthesis
Elements are cycled back to the start of the food chain by decay
Dead animals or waste is broken down by microorganisms.
They work best in warm, moist conditions, when lots of oxygen is available.
The important elements are recylced, and put back into the soil, ready to be picked up by plants.
The efficiency of food production can be improved by:
Reducing the number of stages in the food chain - less energy lost by respiration etc.
Restrict energy lost by farm animals - heat loss can be reduced by placing them close.
Diseases can be spread in crowded conditions, it can also be cruel.
Enzymes need the right temperature and pH to function properly. pH is often optimum at neutral, however some enzymes require acidic or alkaline conditions to function in a specific area. For example, pepsin, in the stomach works best at pH2, because it is very acidic.
Enzymes sythesise amino acids, and also catalyse protein sythesis by joining them together.
Respiration is the process of releasing energy from glucose, which goes on in every cell.
Aerobic respiration is with using oxygen, functions better than when without (anerobic).
Aerobic respiration: Glucose + oxygen --> Carbon dioxide + water + energy
Respiration releases energy for:
To build up larger molecules from smaller (like protein from amino acids).
In aminals to allow the muscles to contract (which in turn allows them move about).
In mamals and birds the energy is used to keep their body temperature steady.
In plants, to build sugars, nitrates and other nutrientrs into amino acids, which are then built up into proteins.
Enzymes in Digestion
Digestive enzymes break down big molecules into smaller ones
Amylase converts starch into simple sugars
Starch --Amylase--> Maltose (And other simple sugars)
Amylase is made in: Salivary glands, Pancreas, Small intestine
Protease converts proteins into amino acids
Proteins --Protease--> Amino Acids
Protease is amde in: Stomach, Pancreas, Small intestine
Lipase converts fats into glycerol and fatty acids
Fat --Lipase--> Glycerol and Fatty Acids
Lipase is made in: Pancreas, Small intestine
Bile neutralises the stomach acid and emulsifies fats
Hydrochloric acid makes the pH in the small intestine too acidic for the enzymes in there. Bile changes the pH to alkaline, so the enzymes can work best.
It also breaks fats down to tiny droplets, giving a larger surface area for lipase to work on.
The Digestive System
Salivary Glands - Produces amylase in the saliva.
Liver - Bile is produced here.
Stomach - Pummels food with muscular walls. Produces protease (pepsin).
Produces hydrochloric acid: to kill bacteria and to get the right pH for protease.
Gall Bladder - Bile is stored here before it is released into the small intestine.
Pancreas - Produces protease, amylase and lipase. Releases them into small intestine.
Small Intestine - Produces protease, amylase and lipase to complete digestion. Food is also absorbed here into the body.
Large Intestine - Where excess water is absorbed from food.
Rectum - Faeces (indigestible food) stored here, and then leave through the anus.
Uses of Enzymes out of the Body
Some microorganisms produce enzymes that pass out of their cells to help outside. these enzymes have many uses in home and in industry.
Biological Detergents - Mainly protease and lipase, used in washing powder, helps remove stains.
Used to Change Foods - Pre digested baby food so it is easier to digest. Starch syrup can be turned into sugar syrup using carbohydrase. Glucose syrup to fructose syrup using isomerase. Fructose is sweater, can use less of it.
Used in the Industry - Substnaces are continually run over enzymes, they must be stopped from washing away.
- Only catalyse a specific reaction.
- Means that there is less need for higher temperature and pressure to speed up a reaction, menaing that cost is lowered and energy is saved.
- Enzymes don't get used up, so they can be used a lot after bought.
- Biodegradeable, so cause less environmental pollution.
- Some people are alllergic to these enzymes, for example, in biological washing powder.
- The conditions that they work in must be tightly controlled, as they can be denatured at too high of a temperature, and they are unefficient with changes in pH and temperature. They can also be poisoned.
- Contamination of the enzyme with other substances can affect reactions.
Homeostasis is the maintenance of a constant internal environment.
Six main things that need to be controlled:
Body temperature, Water content, Ion content, Blood sugar level,
Removal of CO2, Removal of Urea.
- Hairs lie flat
- Sweat is produced in sweat glands, which evapourates and removes heat.
- Blood vessels supplying the skin dilate, more blood flows close to the surface, its heat is lost to the environment.
- Hairs stnad up to trap insulating layer of air.
- No sweat is produced.
- Blood vessels supplying skin capillaries constrict to close off the skin's blood supply.
- Shivering (muscles contracting automatically) requires respiration, releases some energy as heat.
The Kidneys and Homeostasis
Kidneys act as filters to clean the blood
Removing Urea from the blood
Because protein cant be stored in the body, excess amino acids are converted into carbohydrates and fats which can be stored. Urea is a poisonous waste product, and so is released from the liver and into the bloodstream, which is then filtered out by the kidneys and excreted in urine.
Adjustment of Ion content in the blood
Having the wrong amount of ion content can mean that too much or too little water is drawn into cells by osmosis. Excess is removed by kidneys. Some ions are also lost in sweat.
Adjustment of Water content
Water is lost by: Urination, sweating, breathing out.
Water balance is between: Liquids consumed, amount sweated out, amount excreted by kidneys in urine. The body must always balance water coming in with water going out.
Cold day = less sweat = more urine (pale and dilute)
Hot day = more sweat = less urine (dark and concentrated) /// More water lost must be replaced to restore the balance.
Controlling Blood Sugar
Insulin controls blood sugar levels:
Blood glucose level is too high = insulin added
When there is too much glucose in the blood, insulin is secreted by the pancreas. When the blood flows to the liver, the insulin enters and tells it to remove glucose from the blood.
Blood glucose level is too low = insulin not added
When insulin is not added, the liver will automatically release glucose into the blood.
Diabetes type 1 is when the pancreas stops making insulin
This menas that the liver will constantly release glucose into the blood, and menas death.
1 - Avoid foods rich in carbohydrates with lots of glucose in. Also, take exercise to use up extra glucose in the blood.
2 - Inject insulin into the blood at mealtimes, which causes the added glucose to be removed quickly. If they dont eat after injecting insulin, their blood sugar could drop lots.
A glucose monitoring device allows diabetics to check their blood sugar level.
Insulin and Diabetes
In the 19th century, scientists removed pancreases from dogs. The dogs became diabetic. In the 1920s, Banting and Best managed to isolate insulin.
They removed a healthy pancreas from a dog, and injected parts of it into diabetic dogs. The dogs blood sugar levels fell dramatically. This shows the pancreas extract caused a temporary decrease in blood sugar level. They then isolated insulin from the extract.
Banting and Best then injected insulin into diabetic humans, and it worked. Insulin was mass produced. Diabetics can inject insulin 2-4 times a day. Initally pancreases from pigs and cows were used. In the 80s human insulin made by genetic engineering was made. They didnt cause adverse reactions that animal one did.
Diabetics can also have a pancreas transplant. However your body can reject the tissue. You can also implant just the cells that produce the insulin.
Chromosomes are really long molecules of DNA
DNA stands for deoxyribose nucleic acid.
It contains all the instructions to put an organism together and to make it work.
Its found in the nucleus of all cells, in rally long molecules called chromosomes.
A gene codes for a specifc protein
A gene is a section of DNA. It contains the instructions to make a specific protein.
Only 20 amino acids are used, but they make up thousands of different proteins.
Genes simply tell cells in what order to put the amino acids together.
DNA also determines what proteins the cell produces eg. haemoglobin, keratin.
That in turn determines what type of cell it is, eg. red blood cell.
Everyone has unique DNA (except clones and identical twins)
Cell Division - Mitosis
Mitosis makes new cells for growth and repair
Body cells normally have two copies of each chromosome - oe from the organism's 'mother' and one form the 'father'.
A human cell has 23 pairs of chromosomes.
When a body cell divdes it needs to make new cells identical to the original cell - with the same number of chromosomes.
This type of cell division is called mitosis. It's used when plants and animals want to grow or to replace cells that have been damaged.
Mitosis is when a cell reproduces itself by splitting to form two identical offspring
If the cell gets a signal to divide, it needs to duplicate its DNA - so there's one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each 'arm' of the chromosome is an exact duplicate of the other.
The chromosomes then line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell.
Membranes form around each of the sets of chromosomes. These become the nuclei.
Lastly, the cytoplasm divides.
Asexual reproduction also uses mitosis
Cell Division - Meiosis
Gametes have half the usual number of chromosomes
During sexual reproduction, two cells called gametes combine to form a new individual.
Gametes only have one copy of each chromosome. They are then combined.
Human body cells have 46 chromosomes, and the gametes have 23 each.
Meiosis involves two divisions
Meiosis produces cells which half the normal number of chromosomes
As with mitosis, before the cells start to divide, it duplicates its DNA - one arm of each chromosome is an exact copy of the other arm.
In the first division in meiosis the chromosome pairs line up in the centre of the cell.
The pairs are then pulled apart, so each new cell only has one copy of each chromosome. Some of the father's chromosomes and some of the mother's chromosomes go into each new cell.
Each new cell will have a mixture of the mother's and father's chromosomes. Mixing up the genes in this way creates variation. This is a huge advantage of sexual reproduction.
In the second division the chromosomes line up again in the centre of the cell. Its a lot like mitosis. The arms of the chromosomes are pulled apart.
You get four gametes each with only a single set of chromosomes in it.
After two gametes join at fertilisation, the cell grows repeatedly dividing by mitosis.
Embryonic stem cells can turn into any typeof cell
- Differentiation is the process by which a cell changes to become specialised for its job. In most animal cells, this is lost at an early stage, lots of plant cells dont ever lose this ability.
- Adults also have stem cells, but they're only found in certain places, like bone marrow. These aren't as versatile as embryonic stem cells - they can't turn into to any cell type, only certain ones.
Stem cells may be able to cure many diseases
- Medicine uses adult stem cells to cure disease.
- Scientists can also extract stem cells from very early human embryos and grow them.
- To get cultures of one specific type of cell, researchers try to control the differentiation of the stem cells by changing the environment they're growing in. So far, it's still a bit hit and miss - lots more research is needed.
X and Y Chromosomes and The Work of Mendel
Your chromosomes control whether you're male or female
There are 23 matched pairs of chromosomes in every human body cell. The 23rd pair are labelled ** or XY. They're two chromosomes that decide if you are male or female.
All men have an X and a Y Chromosome: XY --- The Y chromosome causes males.
All women have two X chromosomes: ** --- The ** chromosome causes females.
Mendel did genetic experiments with pea plants
- He was a monk, and on his garden plot at the monestrary, he noted how characteristics in plants were passed on from generations. The results of his research were published in 1866 and eventually became the foundation of modern genetics.
- Mendel shown the height charatceristic in pea plants was determined by seperately inherited 'herditary units' passed on from parents. The ratios of tall and dwarf plants in the offsring showed the unit for tall plants, T, was dominant over the unit for dwarf plants, t.
Mendel reached these conclusions:
- Charatceristics in plants were determined by 'herditary units' (now known as alleles).
- Herditary units are passed on from both parents, one unit for each parent.
- Herditary units can be dominant or recessive - if an it has both, dominant is used.
Genetic Diagrams and Disorders
Alleles - Different versions of the same gene (2 per gene).
Gene - Part of a chromosome, determines characteristics.
Chromosomes - Long strings of genes.
Most of the time you will have two copies of each gene - one from each parent.
If they're different alleles, the dominant will be expressed by the organisim.
Cystic Fibrosis is caused by a recessive allele
- It results in the body producing a lot of thick mucus in the air passages of the pancreas.
- Becuase it is recessive, people with only one copy of the allele wont have the disorder - they are carriers.
- For a child to have the disorder, both parents must be carriers or sufferers.
Huntington's is caused by a dominant allele
- It is a genetic disorder of the nervous system that results in shaking, eratic body movements and eventually severe mental deterioration.
- The carrier parent will be a sufferer too since the allele is dominant, but the symptons don't start to appear until about 40. The allele may have been passed on to children.
Embryos can be screened for genetic disorders
- During in vitro fertilisation (IVF) embryos are fertilised in a lab, and them implanted into the mother's womb. More than one egg is fertilised, so there is a better chance of success.
- Before being implanted, cells can be removed from each embryo to analyse its genes.
- Embryos with good genes would be implanted, the others a destroyed.