Biology - Unit 2

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• Cells make up tissue, which makes up an organ which makes up an organ system.

1. Properties of a cell

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   • all cells have a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. plant cells have all that plus a cell wall, vacuole and chloroplasts.
2. specialised cells

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   • palisade leaf cells- photosynthesis guard cells- open and closered blood cells- carry oxygensperm and egg cells- reproduce
3. Stem cells

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   • embryonic stem cells are celss that can turn into any type of cell. stem cells are undifferentiated cells, meaning they have not been allocated a specialisation. as they have the potential to turn into any cell they want meaning they have the potential to cure many things.
   1. Medical potential

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      • stem cells from bone marrow are already used to creat new blood cells when people have blood diseases but because of controversy the far more versatile embryonic stem cells are not widely used even though they could be used to create glands and heart tissue even nerve cells for spinal injuries and paralysis.
      1. Opposition

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         • Many people are against it as it is the potential of human life.  people believe that it is not sustainable and that scientists should focus on curing a disease than individual patients.
4. Cell division
   1. mitosis

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      • Mitosis takes place with every cell to create new cells in order to grow or repair.1)The 46 chromosomes in a cell duplicate to form 46 chromosomes which each consists of 2 chromatids bound by a centromere. 2)The chromosomes move to the centre of the cell, the 2 chromatids of each chromosome split at the centromere, creating 92 chromosomes. 46 chromosomes go to either side of the cell.  3The cell splits creating 2 cells each with 46 chromosomes, they are both identical to the original cell.
   2. Meiosis

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      • meiosis is cell division used in reproduction, it creates 4 daughter cells that each have 23 chromosomes. 1) 23 chromosomes from each parent combine to make a cell with 46 chromosomes. 2)These 46 chromosones duplicate to form 46 chromosomes that consist of 2 sister chromatids bound with a centromere. 3)The chromosomes pair with another chromosome from the other parent to form 23  homologous pairs, each homologous pair consists of 2 chromosomes (each are 2 sister chromatids)4)These 23 homologous pairs line up and exchange genetic material.5)These 23 homologous pairs split in the cell and form 46 chromosomes which have a mix of genetic material, half at each side of the cells.6)The cell splits and forms two cells with 23 chromosomes with a mix of genes.27)In each cell, the centromeres connecting the chromatids of the 23 chromosomes split producing 46 chromosomes at either side of the cell. 8)Both cell splits producing, in total, 4 daughter cells with 23 chromosomes each.

1. Plant structure

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   • plants have tissues and organs too.
2. Photosynthesis

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   • Carbon dioxide + water => glucose + oxygen (must have sunlight and chlorophyll) To create glucose for cellular respiiration, Oxygen is the bi-product.
   1. Limiting factors

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      • factors- sunlight, water and carbon dioxide. sunlight and heat- optimum temp 35" too hot- the enzymes, chloroplasts, get denatured and cannot aid the reaction. too cold- the reactants dont have enough energy so the reaction is very slow.                                                                                                                                                                              
   2. CARBON DIOXIDE + WATER -> GLUCOSE + OXYGEN
3. How plants use glucose

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   • -Respiration -Making:  -Cell walls-Proteins-Stored as glucose to be used in the winter when photosynthesis cannot take place.

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• The distribution of an organism depends on environmental factors, such as: temp, water, oxygen, carbon dioxide, nutrients, light.

1. Always consider reliability and validity

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• exercise increases the heart rate.

1. muscles

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   • Muscle cells use oxygen to release energy from glucose. this creates carbon dioxide which needs to be carried out in the blood, meaning heart rate increased.
   1. glucose

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      • glucose, from sugars, is needed for the muscle cells to create energy. glucose is stored as glycogen which is stored in the liver, but each muscle has its own store. when a muscle needs more glucose it releases the hormone glucagon because the GLUCose is All  GONe.

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• Genetic disorders are caused by dominant or recessive allelles. genetic screenings can detect genetic disorders but there are many argumants for and against this.

1. genetic screening
   1. For

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      • it will stop suffering there are limits- laws prevent things from going "TOO" far during IVF most embryos are destroyed anyway treating disorders will cost more money in the long run.
   2. Against

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      • its very subjective as people can basically decide every characteristic they want in a child- not natural rejected embryos are destroyed it implies that people with genetic problems are undesirable its expensive.

1. Extinction

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   • extinction happens when a species cant evolve quick enough to survive-  the changing environment predators disease competition for food or because of a catastrophic event that wipes out an entire species.      
2. Speciation

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   • speciation is when a population of a certain species evolve separately to the rest because of environment, predators.. and create an entirely new species.
3. what makes it a new species?

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   • a specie is a group of similar organisms that can breed to crete fertile offspring. when something evolves and can no longer breedto produce fertile offspring speciation has taken place and that is a new specie.

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• Fossils are the remains of plants and animals. as teeth, bones, shell... eventually decay they are replaced by minerals, the actual fossil, which is shaped like the original "hard part" when things are preserved I clay and soft things it will decay and the clay will harden leaving a cast. amber- in amber there is no oxygen or moisture so things cant decay meaning when it solidified anything inside is fully formed.

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• every cell has 46 chromosomes, 22 matched pairs and 1 either XX or XY pair(XX female XY male)

1. Sperm and eggs

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   • sperm cells are either X or Y (50/50) and eggs are always X.

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• deoxyribonucleic acid makes up chromosomes

1. Genes

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   • Genes are found in DNA, they contain the instructions to create a specific protein, this is done by stringing together the 20 different amino acids in different orders.
   1. Cells create protein, depending on the DNA and genes

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• natural catalysts speed up reactions, they are not used up in the reaction. they can split or create substances and are usually only shaped so that 1 reaction can take place using that catalyst.

1. Enzymes in digestion

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   • the process of digestion depends entirely on enzymes to break down large jmolecules nto smaller ones.
   1. Lipase

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      • lipase converts lipids into glycerol and fatty acids. it is created in the pancreas and small intestine.
   2. Amylase

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      • amylase is one of the main enzyme involved in digestion it converts starch into sugars, it is produced in pancreas, small intestite and as salivar.
   3. protease

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      • protease converts protein into amino acids.it is produced in the stomach, pancreas and small intestine. 
   4. Bile

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      • Bile is produced in the liver and is an alkaline that neutralizes the stomach acids so that enzymes can work efficiently. it also breaks down fat so that lipase can break it convert it easier (larger surface area).
2. Enzymes in respiration
   1. Aerobic

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      • Respiration using oxygen. its always happening in order to maintain body heat, contract muscles.
      1. GLUCOSE + OXYGEN => CARBON DIOXIDE + WATER + ENERGY
   2. Aenerobic

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      • used when the body dosent have enough oxygen for aerobic, basically a backup. it gives a short burst of energy
      1. Oxygen debt

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         • when your body cant keep up with the demand for oxygen to create energy you use anaerobic and get an oxygen debt. you will need oxygen,this will oxidise all of the harmful lactic acid produced into carbon dioxide and water.
      2. GLUCOSE => ENERGY + LACTIC ACID
3. NATURAL PROTEIN CATALYST

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   • in the human body an enzymes optimum catalysing temperature is 37" (body temp) optimum ph is usually neutral (7)
4. Uses for enzymes

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   • the digesting enzymes are used in detergents to break down stains. they're used in baby foods to basically pre-digest the food.
   1. Industry

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      • used to speed up reactions advantages- they're specific energy saving as there is no need for pressurising machines and high temperatures. long term cheaper as its only the initial cost. environmentally friendly.    
      1. advantages
      2. disadvantages

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         • allergies to enzymes very susceptible to being denatured from a small increase in temp and contamination in an industrial environment. expensive to produce  

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• the net movement of particles through a partially permeable membrane along a concentration gradient.