Biology - Module 2
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Biology - Module 2 - Leaderboard
Biology - Module 2 - Details
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154 questions
| 🇬🇧 | 🇬🇧 |
| Define cell cycle | The process that all body cells in multicellular organisms use to grow and divide |
| Explain the cell cycle process | Interphase, subdivided into 3 growth stages: - gap phase 1 (G1) = cell grows and new organelles and proteins are made - synthesis (S) = cell replicates its DNA ready to divide by mitosis - gap phase 2 (G2) = cell keeps growing and proteins needed for cell division are made - M phase = mitosis and cytokinesis |
| How is the cell cycle regulated | - G1 checkpoint = the cell checks that the chemicals needed for the replication are present and for any damage to the DNA before entering the S-phase - G2 checkpoint = the cell checks whether all the DNA has been replicated without and damage. If it has, the cell can't enter mitosis -Metaphase checkpoint = the cell checks that all the chromosomes are attached to the spindle before mitosis can continue |
| What are the main stages of mitosis | Interphase, prophase, metaphase, anaphase and telophase |
| Describe interphase | - Cell carries out normal function, but also prepares to divide. - The cell's DNA is unravelled and replicated, to double it's genetic content - organelles also replicate - ATP content increases |
| Describe prophase | - chromosomes condense - tiny bundles of protein called centrioles start moving to opposite ends of the cell, forming a network of protein fibres across it called the spindle - the nuclear envelope breaks down and chromosomes lie free in the cytoplasm |
| Describe metaphase | - the chromosomes line up along the equator of the cell and become attached to the spindle by their centromere - at the metaphase checkpoint, the cell checks that all the chromosomes are attached to the spindle before mitosis can continue |
| Describe anaphase | - the centromeres divide, separating each pair of sister chromatid - the spindles contract, pulling chromatids to opposite poles of the cell |
| Describe telophase | - the chromatids reach the opposite poles of the spindle - they uncoil and become long and thin and are called chromosomes again - a nucleus envelope forms around each group of chromosomes, so there are now 2 nuclei - 2 genetically identical cells are produced |
| What is meiosis | It is a type of cell division that happens in the reproductive organs to produce gametes |
| Define gametes | Haploid sex cells produced by meiosis in organisms that reproduce sexually (sperm and eggs) |
| Define somatic cell | Any cell of a living organism but reproductive cells |
| Define zygote | The diploid cell produced by fertilisation (fertilised eggs) |
| What is a homologous chromosome | Pairs of matching chromosomes |
| Difference between haploid and diploid cells | Haploid = half the normal chromosomes number Diploid = normal number of chromosomes |
| What is the importance od meiosis | Produces genetic variation during sexual reproduction by independent assortment and crossing over. |
| What are the main stages of meisos | Interphase, prophase 1, metaphase 1, anaphase 1, telophase 1, prophase II, metaphase II, anaphase II, telophase II |
| Describe interphase | - Cell's DNA unravels and replicates to produce double armed chromosomes called sister chromatids |
| Describe prophase 1 | - Chromosomes condense - homologous chromosomes pair up and crossing over occurs - centrioles move to opposite poles of the cell forming spindle - nuclear envelope breaks down |
| Describe metaphase 1 | - homologous pairs line up across the equator of the cell and attach to the spindle by their centromeres |
| Describe anaphase 1 | - spindles contract, pulling pairs apart |
| Describe telophase 1 | - a nuclear envelope forms around each group of chromosomes - cytokinesis occurs and 2 haploid daughter cells are produced |
| Describe prophase II | - chromosomes condense - nuclear envelop breaks and spindle forms |
| Describe metaphase II | - chromosomes line up at the equator - independent assortment occurs |
| Describe anaphase II | - sister chromatids are separated randomly |
| Describe telophase II | - chromatids assemble at poles - cytokinesis occurs - 4 daughter haploid cells are produced |
| Define bivalent | Homologous chromatids referred to after crossing over |
| Explain crossing over | - occurs during prophase 1 - homologous pairs of chromosomes come together and pair up - the chromatids twist around each other and bits of the chromatids swap over |
| How does crossing over create variation | The chromatids still contain the same genes but now have different combinations of alleles |
| Explain independent assortment | - Of chromosomes happen during metaphase 1 - Of chromatids happen during metaphase II - homologous pairs line up and are separated. It's completely random which chromosome or chromatid from each pair end up in the daughter cells |
| How does independent assortment create variation | The 4 daughter cells produced have completely different combinations of those maternal and paternal chromosomes. |
| Define stem cells | Unspecialised cells, that can develop into different types of cells |
| Define differentiation | The process by which a cell becomes specialised for its job |
| Where can you find adult stem cells | - in the bone marrow - here they divide and differentiate to replace worn out blood cells (erythrocytes and neutrophils) |
| What can you find in embryos | Stem cells that can develop into any type of human cell |
| What do adult stem cells do | They replace damaged cells |
| Where can you find stem cells in plants | In the meristems, where they divide and differentiate into xylem vessels and phloem sieve tubes. |
| How can stem cells be used to cure diseases such as Parkinson's | - the disease causes the loss of a particular type of nerve cell found in the brain - these cells release a chemical called dopamine, which is needed to control movement - transplanted stem cells may help to regenerate the dopamine producing cells |
| What are erythrocytes | - they are red blood cells that carry oxygen in the blood - they have a biconcave disc shape which provides a large surface area for gas exchange - they have no nucleus so there's more room for haemoglobin |
| What are neutrophils | - a type of white blood cell - their flexible shape allows them to engulf foreign particles or pathogens - their cytoplasm contains many lysosomes to break down engulfed particles |
| What are epithelial cells | - cells that cover the surface of organs - the cells are joined by interlinkingg cell membranes and a membrane at their base |
| What are sperm cells | - male sex cells - they have a flagellum so they can swim to the egg - they have lots of mitochondria to provide energy to swim - the acrosome contains digestive enzymes to enable the sperm to penetrate the surface of the egg |
| What are palisade cells | - cells in the leaves - does most of the photosynthesis - they contain many chloroplasts, so they can absorb a lot of sunlight - the walls are thin, so carbon dioxide can easily diffuse into the cell |
| What are guard cells | - cells found in pairs, with a gap between them to form a stomata |
| Define tissues | A group of cells that are specialised to work together to carry out a particular function |
| How are erythrocytes specialised for their function | The function is to carry oxygen in the blood. - they have a biconcave disc shape providing them with a large surface area for gas exchange - they have no nucleus allowing them to have more room for haemoglobin |
| How are neutrophils specialised for their function | The function is to defend the body against disease - has a flexible shape allowing them to engulf foreign particles or pathogens - have many lysosomes in their cytoplasm containing digestive enzymes to break down and engulf the particles |
| How is sperm specialised for their function | The function is to fertilise eggs - has lots of mitochondria so that they have more energy - acrosomes contains enzymes for quicker digestion to penetrate egg |
| How are palisades specialised for their function | The function is photosynthesis - contains many chloroplast that absorbs light - the walls are thin for quicker diffusion or CO2 into cells |
| How are root hairs specialised for their function | The function is to absorb water and mineral ions from the soil - they have a large surface area for absorption - thin, permeable cell wall for easier entry of ions - cytoplasm contains extra mitochondria providing more energy for active transport |
| How are guard cells specialised for their function | They are used for gas exchange for photosynthesis |
| Define organ | A group of different tissues that work together to perform a particular function |
| Give examples of some organs | - lungs - leaf |
| Define organ system | Organs that work together for a particular system |
| How does hydrogen bonding occur between water molecules | Due to the polar water molecules interacting with each other. Oxygen is more negative and hydrogen is more positive. The more negative oxygen is attracted to the more hydrogen atom in the other molecules, vice versa, therefore creating a hydrogen bond |
| What are polar molecules | Uneven distribution of electrons |
| Explain the thermal stability of water | - Water molecules have a high heat capacity due to the hydrogen bonds. - Many hydrogen bonds between molecules = more energy needed to break bonds - therefore, the temperature remains constant |
| Explain why ice is less dense | - As the water cools and freezes, hydrogen bonds fix the positions of the polar molecules slightly further apart than the average distance in a liquid state. - therefore, water underneath stays liquid - insulates the water underneath from the outside temperatures - organisms are still able to move and allows nutrients to circulate |
| Explain how water is cohesive | Moves as one mass as molecules are attracted to each-other, therefore surface tension happens |
| Explain how water is a solvent | - As water molecules are polar, ions are able to interact with the water molecules - this provides organisms with minerals and nutrients for growth |
| What are carbohydrates | Molecules that only contain the elements carbon, hydrogen and oxygen. |
| What is starch | - the main energy storage material in plants - insolube - amylose - amylopectin |
| Describe amylose | - a long, unbranched chain of alpha glucose - the angle of the glycosidic bonds give it a coiled structure - this makes it compact - good for storage as you can fit more in to a small space |
| Describe amylopectin | - a long branched chain of alpha glucose - branches allow the enzymes to breakdown the molecule to get at the glycosidic bond easily, so glucose can be released quickly |
| What is glycogen | - the main energy storage in animals - a long chain of alpha glucose with a lot more side branches - stored glucose can be hydrolysed quickly - very compact |
| What is cellulose | - major component of cell walls in plants - made of long unbranched chains of beta glucose that bond forming a straight cellulose chain - forms microfibrils used for strucural support in plants |
| What components are lipids made of | Carbon, hydrogen and oxygen. |
| What is the structure of a Triglyceride | 3 fatty acid molecules that have long tails that are hydrophibic and a head made of glycerol that is hydrophilic. |
| What is the ester bond | Formed between each fatty acid and the glycerol molecule, [C-O-C]. |
| Define saturated | No double bonds present. |
| Define unsaturated | At least on double bond present. |
| What are proteins | They are made of long chains of amino acid. Therefore are composed of carbon, hydrogen, oxygen and nitrogen. |
| What are amino acids made of | - Amine group (NH2) - Carboxyl group ( COOH) - variable group (R) |
| Define dipeptide | Bond formed when 2 amino acids join together |
| Define polypeptide | Bond formed when more than 2 amino acids join together |
| Explain condensation reaction of polypeptides | - the carbon of one of the amino acids join withs with the nitrogen of another amino acid forming a peptide bond - a water molecule is produced aswell |
| Define primary structure | - The sequence of amino acids in the polypeptide chain. - held together by peptide bonds |
| Define secondary structure | Hydrogen bonds form between nearby amino acids in the chain. This makes it coil into an alpha helix or fold into a beta pleated sheet. |
| Define tertiary structure | Chain of amino acids are coiled and folded even further. More bonds form between different parts of the polypeptide chains. |
| Define quaternary structure | Proteins made of several different polypeptide chains held together by bonds. |
| What are the different types of bonds formed | - ionic bonds - disulphide bonds - hydrogen bonds - london forces |
| What are gobular proteins | - round and compact - soluble, so they're easily transported in fluids |
| Examples of gobular proteins | - Haemoglobin - Insulin - Amylase |
| Describe haemoglobin | - globular protein that carries oxygen around the body in red blood cells - conjugated protein - has a prosthetic group called haem, which contains iron which oxygen binds to. - consists of 4 polypeptide chains |
| Define conjugated protein | A protein that has a non-protein group attached, also known as prosthetic group. |
| Describe insulin | - hormone secreted by the pancreas - helps regulate blood glucose level - consists of 2 polypeptide chains held together by disulphide bonds. |
| Describe amylase | - an enzyme hat catalyses the breakdown of starch in the digestive system - made of a single chain of amino acid |
| What are fibrous proteins | - tough and rope shaped - insolube - structural proteins |
| Examples of fribrous proteins | - collagen - keratin - elastin |
| Desrcibe collagen | - found in animal connective tissue such as bone, skin and muscle - very strong |
| What is meant by partially permeable membrane? | Allows substances through but not all |
| How can substances move across a membrane? | Through diffusion, osmosis, active transport |
| When is the term plasma membrane used? | When talking about the membrane on the outside of a cell |
| Outline the importance of the plasma membrane | Acts as a barrier between the cells and its environment and controls which substances enter and leave the cell. |
| Outline the key roles for membranes within cells with examples | - membrane around organelles divides the cell into different compartments. |
| Role of cholesterol | - gives membrane stability - they bind to the hydrophobic tails of the phospholipids, causing them to pack more closely together making the membrane less fluid and more rigid - creates a barrier to polar substances moving through the membrane due to hydrophobic parts |
| Role of protein channel | - allows small, charged particles through |
| Role of carrier proteins | -transports larger molecules and charged particles across the membrane by active transport and facilitated diffusion |
| Role of proteins | - acts as receptors for molecules (hormones) in cell signaling - when a molecule binds to a protein, a chemical reaction is triggered inside the cell |
| Role of glyco-lipids and glycoproteins | -stabilizes the membrane by forming hydrogen bonds with the surrounding water molecules - also acts as a receptor for messenger molecules in cell signaling - are sites where drugs, hormones, and antibodies bind |