Download • What is a cell? The smallest unit of a living thing. A cell is

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What is a cell? The smallest unit of a living thing. A cell is the smallest possible organism. It is composed of a cell membrane within which there is a liquid, jelly-­‐like substance called the cytoplasm. The cell will also contain genetic material, ribosomes and the capacity to create energy using cellular respiration (along with other metabolic processes, which are various chemical reactions required to sustain life). •
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All cells will have the following structures: a cell membrane, genetic material (DNA and/or RNA) and ribosomes. Also, cytoplasm. An animal cell that does not have one of these structures is red blood cells. These do not have any genetic material. Therefore they have a very short life-­‐span and need to be replaced continuously. 2. a) partially (selectively) permeable = cell membrane, nuclear membrane b) jelly-­‐like and contains organelles = cytoplasm c) contains chromosomes made of DNA = nucleus d) made of cellulose = cell wall e) filled with fluid and helps support plants = vacuole (helps create turgidity) f) where most of the cell’s chemical reactions take place = cytoplasm g) controls the activities of the cell = genetic material (DNA and/or RNA), the nucleus h) carries out photosynthesis = chloroplasts (containing chlorophyll) i) carries out [cellular] respiration = mitochondria j) controls the passage of substances into / out of the cell = cell membrane k) contains the pigment chlorophyll = chloroplast l) passes information from parent to daughter cells when the cell divides = genetic material (DNA or RNA) •
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Cells have compartments inside them (organelles) when they are eukaryotic cells. Their function is specific for each organelle, allowing specific jobs to be carried out efficiently in each organelle. Organelles allow for a greater diversity of cell types because the cell can become very organised. Diffusion = the movement of a substance from an area of high concentration to an area of low concentration. The process occurs by the molecules of the substance moving further apart from each other, until they are all at equal distance from each other (at equilibrium). Oxygen diffuses through the cell membrane to get into the cell. The net movement of water would be INTO the cell. The concentration of water is 100% outside the cell but inside the cell there is a lower concentration of water. Therefore, because of the concentration gradient, the water will move across the cell membrane through the process called osmosis. The cell has a cell wall, so the cell cannot break open (lysis) with the increasing turgidity. The cell wall will hold the shape of the cell, and the turgidity will increase as more water enters the cell. Plant cell Animal cells HAVE a cell wall DO NOT HAVE a cell wall OFTEN have a large, permanent sap vacuole Vacuoles, if present, are small and temporary OFTEN contain chloroplasts NEVER contain chloroplast OFTEN contain starch granules NEVER contain starch granules •
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Cell C is a plant cell The cell has a cell wall and is a rectangular-­‐like shape (with elongated side) •
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All four cells have a cell membrane, a nucleus and cytoplasm The red blood cell will increase in size because water will move across its cell membrane, via osmosis. Eventually, the cell will become too full and will break open (lysed). This will happen because the cell is in an hypotonic environment, where the concentration of water outside the cell is higher compared to inside the cell. Lysis = cell membrane breaks open because of a hypotonic environment. stages of body cell division, in order: B ! E! C ! A ! D The number of chromosomes in a fruit fly cell = 8 (diploid) The number of chromosomes in a fruit fly gamete cell = 4 (haploid) DNA Questions: ALL true except “Chromosomes are coiled strands of DNA and glucose” = not true (does not have glucose with the DNA) the coiled shape of a DNA molecule is called double helix G – C A – T C – G T – A What is the cell theory? This includes three facts that describe all cells: -­‐ cells are the smallest unit of a living thing -­‐ all living things are made of cells -­‐ all cells come from other cells Compare and contrast eukaryotic & prokaryotic cells (similarlties & differences) Type of cell Eukaryotic Prokaryotic Differences -­‐ Contain membrane-­‐bound -­‐ do not contain a nucleus or any organelles (eg. Nucleus, membrane-­‐bound organelles mitochondria, etc) -­‐ smaller size -­‐ Larger size -­‐ reproduce only via mitosis -­‐ Reproduce via meiosis and/or -­‐ examples: bacteria, algae, mitosis archaea -­‐ Examples: plant cells, animal cells, fungi cells Similarities -­‐ Both contain genetic material (DNA and/or RNA) -­‐ Both have a cell membrane -­‐ Both have ribosomes -­‐ Both have cytoplasm •
What are examples of cell organelles, what are their functions? Cell wall Rigid & strong outer layer, Made of cellulose Provides support (to grow tall) and protection Cell membrane nucleus ribosomes mitochondria chloroplast Cilia & flagellum •
Allows H2O, O2, CO2 to diffuse in & out of cell A flexble, dynamic bilayer of phopholipids (mosaic pattern with choloesterol & proteins) Selectively permeable: Controls movement of substances in/out of the cell Provides support, protection: forms a barrier between the cell and its environment Maintains homeostasis Present in all cells Holds the DNA (only present in eukaryotic cells) Controls the cells activties Contains the hereditary material of the cell (chromosomes) Either attached to endoplasmic reticulum or floating freely in cytoplasm Made of RNA and protein (not a membrane-­‐bound organelle): present in all cells Synthesizes proteins (builds proteins) Has a double membrane Is the location of cellular respiration: breaks down glucose molecules to release energy Only present in eukaryotic cells Has a double membrane Contains a green pigment, called chlorophyll Is the location of photosynthesis: uses light energy to make glucose Only present in eukaryotic cells Projections from the outside of the cell that allow the cell to move (swim) or move substances past itself Compare and contrast cellular respiration & photosynthesis NB: autotroph = an organism that uses phtosynthesis to make its own food. Heterotroph = an organism that cannotmake its own food and so consumes other organic material for nutrients. Metabolic process differences similarities Cellular respiration why To produce energy. Energy needed for all cellular processes such as growing, moving, reproduction, etc how Oxygen & glucose react together to produce carbon dioxide and water. This chemical reaction also produces energy, in the form of ATP (adenine triphosphate). where Occurs in all cells. In eukaryotes: mitochondria In prokaryotes: cytoplasm needs Oxygen & glucose makes Carbon dioxide, water & energy what A chemical reaction photosynthesis To produce glucose. Glucose is used by the plant to make energy (in cellular respiration). Extra glucose made is stored as starch. Carbon dioxde and water react together to produce glucose and oxygen. This reaction takes place only in the presence of light energy and chlorophyll. Occurs only in autotrophs (eg. plants & algae) In eukayotes: chloroplasts In prokaryotes: cytoplasm Carbon dioxide, water, light energy & chlorophyll Oxygen & glucose Figure 1. Shelled amoeba cell (Amoeba Arcella) (Magnification = x200) Table 1. Data for calculation Magnification Diameter of the field of view (mm) X40 5 X200 1 X1000 0.2 Question – calculating size of specimen Use the data table to help answer this question. Calculate the approximate size of the Amoeba Arcella cell in µm (Figure 1). Show all mathematical working. Remember 1mm = 1000 µm ANSWER Number of specimens that fit across the diameter of the field of view = 1.5 specimens Diameter of field of view at x200magnification = 1mm = 1000 µm Size of specimen = 1000 µm / 1.5 specimens = 666.67 µm •
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What is the difference between a “common name” and a “scietific name”? Common name = the name of an organism in the local language. There are often several different common names for one species. This name often describes one of its main features, eg. Blackbird Scientific name = the name of an organism in Latin, assigned by a Taxonomist. One species only has one scientific name. It is made of the Genus and Species name. This name often describes one of its main features. What is an organic molecule? Examples? Features of each? An organic molecule is a large molecule (a macromolecule) which has a “backbone” on carbon atoms, and is primarily made of carbon, hydrogen and oxygen atoms. These molecules are made by organisms. There are four types: carbohydrates (eg. Sugars and starch), proteins, lipids and nucleic acids. What are the stages of mitosis? IPMAT = Interphase, Prophase, Metaphase, Anaphase, Telophase You should be able to identify what each stage looks like, but you will not need to draw these in the exam. •
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Explain the complementary rule (in DNA replication) This is the rule that determines which nitrogenous base pairs can join together: Adenine bonds to thyamine, Guanine bonds to cytocine. This rule is what allows DNA to replicate itself so that the two copies produced are exact copies of each other. Use a diagram: What is an adaptation? A characteristic of an organism which allows the organism to survive in its environment. The characteristic can be physical or behavioural. Explain how an adaptation helps an organism survive – use an example to help explain Physical adaptation = camouflage: the colour of the organism is the same as its environment. This allows prey organisms to hie from their predators, and so avoid being killed (therefore survive). Predator organisms which are camouflaged are able to hide from their prey, they either lie-­‐and-­‐wait for their prey to come close and then surprise attack or they quietly / quickly approach their prey without being seen and attack their prey. This allows them to survive because they are able to successful get food