Biology F211 Unit 1

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  • Created by: EmilyA-J
  • Created on: 10-04-14 10:26
What is the formula to work out magnification?
Magnification= Image size/Actual size.
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Why was the light microscope developed?
To produce enlarged and more detailed images of cells.
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What does the term Resolution refer to?
The ability to distinguish two separate points as distinct from each other.
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What is the resolution of a light microscope?
200nm or 0.2μm
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What lenses does a light microscope have?
Condenser lens, objective lens and an eyepiece lens.
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What magnifications are light microscopes capable of?
x40 x100 x400 x1000 or with a x15 microscope lens x60 x150 x600 x1500.
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What is the formula for overall magnification?
overall magnification = objective lens magnification x eyepiece lens magnification.
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Staining...
Cloured stains are chemicals that bind to chemicals on or in the specimen, this allows the specimen to be seen.
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Sectioning...
Secimens are embedded in wax – thin sections are then cut out without distorting the specimen – this is especially useful for making sections of soft tissue, such as brain.
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Transmission Electron Microscope (TEM)...
The electron beam passes through a very thin prepared sample, and the electrons pass through denser parts less easily, giving some contrast in the final 2D image produced. Maximum possible magnification of x500,000.
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Scanning Electron Microscope (SEM)...
The electrom beam is directed onto a sample. The electrons don’t pass through the specimen, they bounce off, producing a final 3D image view of the surface of the sample. Maximum possible magnification of x100,000.
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Advantages of electron microscopes...
REsolution or 0.1nm, 2000x more than a light microscope. Porduces detailed images of structures inside a cell. SEM produces a 3D image which a light microscope doesn't.
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Disadvantages of electron microscopes...
Sample has to be placed inside a vacuum as the electron beams are deflected by air molecules. They are extreemly expensive. Alot of training and high skill is required to use one.
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Why are some images in colour?
False colour is put on afterwards as the image when produced is always grayscale.
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What name describes the structures within a cell?
Organelles, whihc make up the cells ultrastructure.
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When the structures within a cell work together what is it called?
Division of labour.
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Cells contain a network of fibres made up of?
Protein, keeping the cells shape stable by providing an inernal framework known as the cytoskeleton.
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What is the name of fibres that are able to move against each other?
Actin filaments.
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What are microtubles?
These are cylinders about 25nm in diameter made of a protein called tubulin, and may be used to move a microorganism through a liquid or to waft a liquid past a cell.
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Undulipodia and Cilia...
Structurally, flagella of eukaryotes (undulipodia) and cilia are the same. Each one is made up of a cylinder with nine microtubules arranged in a circle and two microtubules in a central bundle. Undulipodia are longer than cilla.
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What ensures that undulipodia and cillia can move?
ATP (Adenosine triphosphate). Microtubles use this.
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Vesicles and vacuoles...
Vesicles- Membrane bound sac found in cells. Used to transport substances around the cell. Vacuoles- maintains cell stability, filled with water and solutes so that it pushes the cytoplasm aginst the cell wall making the cell turgid.
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What are on the outside of the plant cell plasma membranes and what is it made of?
Plant cell walls, these are made of cellulose which helps support the cell and the whole plant.
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The nucleus...
Houses nearly all the cells genetic material. Largest organelle. Surrounded by a nuclear envelope. Darkened patchs known as chromatin. Nuceloulus inside and the nuclear envelope has nuclear pore to allow mRNA out of the organelle.
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Rough Endoplasmic Reticulum (Rough ER)...
Consists of membrane- bound flattened sacs called cisternae. Transports proteins made on the attached ribosomes.
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Smooth Endoplasmic Reticulum (Smooth ER)...
Consists of membrane- bound flattened sacs called cisternae. Involved in making lipids that the cell needs. DOES NOT HAVE RIBOSOMES!
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Golgi Apparatus...
A stack of membrane-bound flattened sacs. Recieves proteins from the ER and modifys them. It may add sugar molecules to them. The golgi then packs the modified proteins into vesicles so they can be transported.
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Mitochondria...
Spherical or sausage shaped. Inner membrane is highly folded. Site where ATP is produced
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Chloroplasts...
Only found in plant cells. Site of photosynthesis.
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Lysosomes...
Spherical sacs surrounded by a single membrane. Contain powerful digestive enzymes. Their role is to break down materials.
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Ribosomes..
NO MEMBRANE! Tiny organelles. Some in cytoplasm others on ER.Site of protein synthesis.
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Centrioles...
NO MEMBRANE! Take part in cell division. form fibres knwon as spindle which move chromosomes during nuclear division.
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Eukaryotic cells are/have?
Have a nucleus. Contain organelles.
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Prokaryotic cells are/have?
BACTERIA. Much smaller than eukaryotes.No membrane bound organelles. They have a cell wall. Smaller ribosomes than eukaryotes. Single loop of DNA in cytoplasm (Plasmids). No membrane round DNA. Area around DNA is called the nucleoid.
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Prokaryotic cells are/have? Continued...
ATP production on cell surface of mesosomes. Have flagella like udulipodi but have a different internal structure to them.
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Prokaryote and diseases...
Some are resistant to antibotics (MRSA) They pass the resitance between cells epecially to daughter cells during binary fission.
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Prokaryotes that help...
Cheese and yoghurt production, mamalian intestines- help with vitamin K production and help digest some foods. Skin is covered in 'normal flora' of bacteria preventing harmful microorganisms entry into our body. Sewage treatment.
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What is a phospholipid bilayer?
The basic structural component of plasma membranes (cell surface membranes). It consitats of two layers of phospholipid molecules. Proteins are embedded in this layer.
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5 roles of membranes...
1. Separating cell contents from outside environment. 2. separting cell contents from cytoplasm. 3. Cell regonition and signalling. 4. Holding the components of some metabolic pathways in place.5.Regulating transport of materials into or out of cell.
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The phosphate 'head' is?
Hydrophillic- Water loving.
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The phosphate 'tails' are? (Two fatty acid tails)
Hydrophobic- Water hating.
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If phosphilipid molecules are completely surrounded by water what can form?
A bilayer.
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What does this phospholipid 'barrier' help do?
Separate cell contents from the outside world.
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Why are all membranes permeable to water?
Water molecules can diffuse throught the lipid bilayer. Protein channels such as aquaporins allow water molecules to pass through them making them even more permeable.
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What does the term fluid mosaic mean?
Refers to the model of a cell membrane structure. The lipid molcules give fluidity and proteins in the membrane give it a mosaic (patchwork) appearance. The molecules can move about.
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What are the main features of the fluid mosaic model?
A bilayer of phospholipid molecules. Protein molecules floating in the phospholipid bilayer, some freely, some bound to other components. Some extrinsic proteins partially embedded in the bilayer, other intrinsic proteins spanning the bilayer.
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Glycolipids and glycoproteins...
Some of the proteins in the bilayer have small carbohydrate part attached to them. Where phosopholipid molecule have a carbohydrate part attached they are glycolipids, where protein molecules have carbohydrate parts attached they are glycoproteins.
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Name three things that glycoproteins do?
They are receptors for cell signalling and inding site for drugs.
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What gives the membrane stability and fluidity and why?
Cholesterol- gives the membranes of some eukaryotic cells mechanical stabilty. The steroid molecule fits between fatty acid tails and helps make the barrier more complete, so things like water molcules and ions can't pass easily through the membrane.
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What two things are the membrane transport functions?
Channel proteins- Allow the movement of some substances across the membrane. And Carrier proteins- Activly move some substances across the membrane.
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What two things are involved in cell recognition and communication?
Receptor sites- come allow hormones to bind with the cell so that a cell 'response' can be carried out. And glycoproteins and glycolipids.
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What components help with metabolic processes in the cell membrane?
Enzymes and coenzymes- Some reactions in photosynthesis take place in membranes inside chloroplasts. Some stages of respiration take place in membranes of mitochondria. Enzymes and coenzymes may be bound to these membranes.
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How does temperature affect the membranes?
Increasing temperature gives molecules more kinetic energy, so they move faster. This increased movement of phospholipids and other components makes membranes leaky, whic allows substances that wouold not normally do so to enter or leave the cell.
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Give an example of an experiment showing a leaky membrane.
Beetroot experiment.
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What does the term cell signalling mean?
Cells commmunicate with one another by signals.
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What happens when a cell sends out signals?
Receptors on cell surfaces pick up the signal, these receptors are usually protein molecules or modified protein molecules. Internal and external signalling allows the cells to communicate and leads to the survival of the whole organism.
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communication between cells is usually by chemical messengers known as?
Hormones, the hormones are sent to target cells where they send the message to that cell.
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Insulin recptors...
Hormone receptor- Insulin is released from special cells (beta cells) in response to increased blood sugar levels.
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How do medicinal drugs interfer with the receptors?
A number of medicinal drugs that have been developed are complementary to the shape of a type of receptor molecule. Such drugs are intended to block recptors. Beta -blockers are used to prevent heart muscle from increasing the heart rate.
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Ho do viruses hijack receptors?
Viruses enter cells by binding wit recptors on the cell's plasma membrane that normally bind to the host's signalling molecules. HIV can infect humans because it can enter the cells of the immmune system. Its shape fits into one of the receptors.
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Diffusion...
The movement of molecules from a region of high concentration of that molecule to a region of lower concentration of that molecule down a concentration gradient.
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Each molecule diffuses _______its concentration gradient?
Down.
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What happens to the molecules after diffusion has taken place?
Molecules are distributed evenly. This does not mean their movement stops as the moleclues continue to move around. This means the molecules have reached ite equilibrium.
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What sort of process is diffusion?
Passive process.
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What 6 things is the rate of diffusion affected by?
Temperature, Concentration radient, Stirring/moving, surface area, distance/ thickness and size of molecules.
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Why can oxygen and carbon dioxide molecule pass through the bilayer?
Beacuse they are small enough to.
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How are larger molecules 'carried' across?
Two types of protein molecule are involved in allowing such substances to pass htrough the membranes.Because these proteins allows substances to pass through the membrane, the diffusion of these molecules and ions is known as facillitated diffusion.
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What are the two proteins types in facillitated diffusion?
Channel proteins- Form pores in the membrane, which are often shaped to allow only one type of ion through, many are also 'gated' meaning they can be opened or closed.
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What are the two proteins types in facillitated diffusion? continued..
Carrier proteins- Shaped so that a specific molecule can fit into them at the membrane surface, when the specific molecule fits, the protein changes shape to allow the molcule through to the other side of the membrane.
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What does the term active transport mean?
Refers to the movement of molecules or ions across membranes, which uses ATP to drive protein 'pumps' within the membrane.
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Carrrier proteins- protein pumps...
Carry larger or charged molecules and ions through membranes. Carry specific molecules one way across a membrane.Use metabolic energy in the form of ATP.Carry molecules in the opposite direction to the CG. Much faster than diffusion.
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How does the carrier protein ensure one way flow only?
Shape change means that the specific molecule to be transported fits into the carrier protein on one side of the membrane only.
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Example of active transport- calcium ion movement.
Muscle fibres can only contract if calcium ions are present. When a muscle is stimulated to contract, calcium ions are released. When the msucle needs to relax again the calcium ions are pumped rapidly back to the stores.
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Exocytosis...
Involves moving material out of a cell. Used in bulk transport.
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Endocytosis...
Involved bringing material inot a cell. Used in bulk transport.
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Endo? Exo? Phago? Pino?
Endo=Inwards Exo=Outwards Phago= Solid Pino= Liquid.
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Osmosis in the terms of the bilayer?
Down a water potential gradient through bilayer or protein pores.
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What is a solute?
A substance that can dissolve.
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What is a solvent?
The liquid a solute dissolves in.
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What is a solution?
A solute and solvent together.
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What is water potential?
A meausure of the tendancy of water molecules to diffuse from one place to another.
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Water always moves from a region of ______ water potential to a region of ______ water potential.
High to Low.
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What has the highest water potential?
Pure water.
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What does the term osmosis mean?
The movement of water molecules from a region of higher water molecules to region of lower water potential across a partially permeable membrane.
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Water potential of cells is ________than that of pure water.
Lower.
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What is water potential measure in?
KiloPascals (kPa)
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The highest water potential figure is?
0kPa
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When a cell has a lot of water in it and it is about to burst or has burst it is called?
Plant cell- Turgid / Animal cell- Haemolysed.
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When a cell has little or no water in it, it is called?
Plant cell- Plasmolysed / Animal cell- Crenated.
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Where do new daughter cells form from?
Parent cells.
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The molecules of DNA that make up each chromosome are wrapped around proteins called?
Histones.
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What must happen before the cell can divide into two new daughter cells?
DNA of each chromosome replicated. They are held at the central point in the cell called the centromere.
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What is the order of the cell cycle?
I Poo Most After Thai Curry! Interphase Prophase Metaphase Anaphase Telophase Cytokinesis.
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What happens at Interphase, Mitosis and Cytokinesis?
I- DNA replicates in this stage. M- The nucleus divides and chromatid separate. C- The cyt9oplasm divides or cleaves. Growth phase- each new cell grows to full size.
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What is mitosis?
The process of nuclear division where two geneticlally identical nuclei are formed from one parent cell.
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What four reasons are there for making new cells?
Asexual reproduction, Growth, Repair, Replacement.
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What are the four stages of mitosis?
Prophase, Metaphase, Anaphase, Telophase.
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What happens during Prophase?
Replicated chromosomes supercoil (Shorten and thicken)
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What happens at Metaphase?
Replicated chromosmoes line up down the middle of the cell.
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What happens at Anaphase?
The replicas of each chromosome are pulled apart from each other towards opposite poles of the cell.
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What happens at Telophase?
Two new nuclei are formed.
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What happens at Interphase?
Growth- Each chromosome duplicates.
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CAn mistosis and cytokinesis happen anywhere at anytime?
In animals it can happen in most cells whereas plants can only do this in their meristem cells.
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What are clones?
Genetically identical cells or organisms derived from one parent.
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Which 3 cells after cell division are identical?
Parent cell and two daughter cells.
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Stawberry plant runners and potatoe tubers are a form of asexual reproduction known as?
Vegetative propagation.
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Stem cells can be described as?
Omnipotent or totipotent.
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Where can stem cells be found in humans?
Bone marrow, Blood/bone cells, Embryo.
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What cells are like stem cells but in plants?
Meristem cells.
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What is cytokinesis?
It 'nips' in the cell membrane and cytoplasm along what is termed a cleavage furrow.
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What is genetic information also known as?
Genome.
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Sex cells are known as?
Gametes.
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When two gametes fuse together your produce a?
zygote- Egg and Sperm cell together.
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What is the name for the type of cell division that produces a gamete called?
Meiosis.
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Normal adult cells of most eukaryotes contain two sets of chromosomes making them?
Diploid.- Their genome consists of pairs of homologous chromosomes.
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During meiosis how many of the pair goes inot each daughter cell?
one of the homologous pair.
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The daughter cells are now?
Haploid- Each daughter cell contains only one set of chromosomes.
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Are the haploid cells genetically identical?
No, because each pair of homologous chromosomes separates into haploid cells independantly of all other.
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The haploid daughter cells produced will differ because they contain the particular________ of each gene found on the member of the homologou pairs they recieve.
Alleles.
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How does meiosis differ from mitiosis?
It produces cells containing half the number of chromosomes. It produces cells that are geneticlly different from each other, and from the parent cell.
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What does the term differentiation mean?
Refers to the changes occurring in cells of a multicellular organism so that each different type of cell becomes specialised to perform a specific fuction.
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single celled organisms have a _______ surface area to volume ratio.
Large.
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Multicellular organisms have a _______ surface area to volume ratio meaning?
Small. They need specialised cells to form tissues and organs and to carry out particular functions.
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What happens when a cell becomes specialised?
It performs a specific role or function within the cell.
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How do cells differentiate?
Chnages to the number of a particular organelle, changes to the shape of the cell and changes to some of the contents of the cell.
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What are Erythrocytes?
Red blood cells.
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What are Neutrophils?
A type of white blood cell.
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All blood cells are produced from?
Undifferentiated stem cells in the bone marrow.- They lose their nucleus, mitochondria, golgi and rought E. They are packed full of the protein Haemoglobin. The shape of the cells change so that they become biconcave discs.
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Neutrophils- White blood cell...
Keep their nucleus.Lots of lysosomes produced.
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Tissues...
collection of cells that are similar to each other and performa a common function. E.g xylem, phloem in plants, epithelial and nervous tissues in animals.
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Organs...
A collection of tissues working together to perform a particular function. E.g Leaves in plants and Liver in animals.
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Organ systems...
Made up of a number of organs working together to perform an overall life function. E.g Excretory system and reproductive system.
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What are the two transport tissues in plants?
Xylem and Phloem.
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Where do xylem and phloem come from?
Dividing meristem cells such as cambium.
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Xylem...
Consists of xylem vessels with parenchyma cells and fibres. Meristem cells produce small cells that elongate. Their walls become reinforced and waterproofed by ligin.
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Phloem...
Consists of sieve tubes and companion cells. The meristem tissue produces cells that elongate and line up end to end to form a long tube. They form sieve plates between the cells. The sieve plates allow the movement up or down the tubes.
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What are the four main catagories of animal tissues?
Epithelial tissue, Connective tissue, Muscle tissue and Nervous tissue.
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What is squamous epithelial tissue?
Made up of flattened cells whihc are very thin. They have a smooth surface. Lining tubes such as blood vessels where fluids can easliy pass over them, also found in alveloi and provides a short diffusion distance. Made of collagen and glycoproteins.
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What is cilliated epithelial tissue?
Made up of collumn shaped cells, found on the inner surface of tubes for example, trachea, bronchi and bronchioles. The surface of it is covered in cillia that waft mucus up and out of breathing tract or out of the system.
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What is needed for photosynthesis?
Light, Supply of water, Supply of Carbon dioxide, presence of chlorphyll.
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How is the leaf adapted for photosynthesis?
Transparent upper surface layer, palisade layer contains lots of long thin tightly packed chloroplasts that contain chlorophyll. Lots of air spaces in spongy mesophyll layer.Stomata present. Leaf vein system.
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Guard cells...
Specialised cells that appaer on the lower epidermis. They contain chloroplasts. When water is moved into these cells they become turgid. The two guard cells bulge at both ends so a pore opens between them. This pore is known as the stoma.
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