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A level Biology Cells
Terms in this set (27)
• Nuclear Membrane
• Golgi Apparatus
• Golgi Vesicles
• Cell membrane
• Smooth Endoplasmic Reticulum
• Rough Endoplasmic Reticulum
State all the organells in a Eukaryotic cells
• Nucleous - small spherical region, manufactures ribosomal RNA and ribosomes.
• Nucleoplasm - Glandular jelly like material
• Nucleus - production of mRNA and tRNA take place here, retain genetic material as DNA
• Nuclear Membrane - Double membrane structure, outer membrane continuous with Endoplasmic reticulum, has ribosomes on its surface this is Rough Endoplasmic reticulum, has nuclear pores; allows passage of large molecules like mRNA, each are 40-100 micrometers.
State a description for Nucleous, Nuclear Membrane, Nucleoplasm, Nucleus.
• Sperm cell - fuse with the egg cell and complete fertilisation
• Oval head - has 2.5 to 3.5um, well developed acrosome that covers 40-70% of oval head. Slim Middle section
• Streamlined Body - allows sperm cell to move rapidly.
• Tightly packed Mitochondria - Middle price carries 70 mitochondria, discarded when sperm cell penetrates egg cell.
• Acrosome - Plays important role in identifying female gamete, contains lysosomal enzymes which degrade thick membrane of egg. Helps to promote fertilisation.
Describe how sperm cells are adapted for their function. State their function.
• Palisade Mesophyll - absorbs light efficiently
• Packed with chloroplast
• Column shaped and arranged closely
• Found at surface of leaf, moved around by proteins to maximise light absorption
• Large Vacuole - restricts chloroplast to layer of outside allows to reach light more easily.
Describe how palisade mesophyll is adapted for its function and state their function.
• No true nucleus, DNA not associated with proteins.
• DNA found in circular strands called plasmids.
• No chloroplast, ribosomes are smaller (70S).
• Cell wall made from murein (peptidoglycan).
• No membrane bound organelles.
• Have a capsule.
• Distinct nucleus with nuclear envelope.
• DNA associated with proteins called histones.
• Chloroplast found in plants and algae.
• Cell walls in plant made from cellulose, cell was all in fungi made from Chitin.
• Ribosomes are larger (80S).
• No plasmids, DNA is linear.
• Membrane bound organelles.
• No capsule.
State the differences between Prokaryotic cells and Eukaryotic cells.
Neurons - carries electrical impulses from part of of the body to another.
• Long fibre called axon which carries messages up and down the body over long distances.
• Axon is insulated by a fatty sheath called myelin which increases the speed of the nerve impulse.
• End of neuron there are tiny branches called dendrons which branch even further into dendrites which receive incoming nerve impulses from other neurons.
State the function of neurons with its characteristics.
• Formed by the Golgi apparatus, contains lysozyme and digest worn out organelles so useful chemical can be reused, carries out autolysis which is the break down of dead cells.
State the function of lysosome and its features.
• Has an outer and inner membrane, inner membrane folds inwards forming cristae and has a large surface area.
• Synthesises proteins and is composed of a small and large subunits.
• Ribosomes (80S) - Found in eukaryotic cells.
• Ribosomes (70) - Found in prokaryotic cells, chloroplast and mitochondria.
State a description for Mitochondria and Ribosomes with their features.
• Similar to SER, has a compact form with flattened membrane sacs called cristernae, has small hollow structures called vesicles which moves to the cell membrane and fuses to release its content. Modifies proteins and lipids, produces secretary enzymes and forms lysosomes.
• Envelope by a selective double membrane, has Grana stacks disc, each individual disc is called a thylakoid (containing chlorophyll) and has a large surface area. Stroma fluid filled matrix with enzymes and starch grains.
• Light absorption takes place in Grana as well as the first stage of photosynthesis. Second stage takes place in Stroma.
State a description for Chloroplast and Golgi Apparatus with their features.
• Sheet like membrane, continuous with outer nuclear membrane and enclosed network of tubules and flattened sacs called cristernae.
• Consists of microfibrils, provides mechanical strength and allows passage of water.
• Algae cell walls composed of cellulose and glycoproteins.
• Fungal cell walls composed of chitin (nitrogen containing polysaccharide), glycoproteins and glycan.
• Prevents cell from bursting under pressure of osmotic water entry.
State a description of Endoplasmic Reticulum and Cell wall with its features.
• Stores cell sap, waste products, nutrients and food.
• Membrane surrounding vacuole is called tonoplast.
• Composed of a phospholipid bilayer, proteins found on inner and upper surface.
State a description of Vacuole and Cell membrane with their features.
• Cell fractionation - breaking down of cells.
• Ultracentrifugation - separating organelles.
• Cell fractionation and ultracentrifugation used to study structure of cells.
State a definition for cell fractionation and ultracentrifugation. State what they are used for.
• Sample needs to be homogenised, breaking down of cells, ways include using pestle and mortar, electric blender.
• Mixture needs to be centrifugated, at different speeds due to diff densities of organelles.
• Homogenate filtered to remove bits of cells not broken down properly.
Describe the process carried out to study cells through cell fractionation and ultracentrifugation.
• Buffer solution - keep pH constant and prevent proteins from denaturing.
• Isotonic - prevent any osmotic entry of water.
• Temperature - cooled to prevent any enzyme activity.
State the conditions that must be constant with a description for each during cell fractionation and ultracentrifugation.
• Supernatant - fluid left at the top of tube after it has been spun in centrifugate.
• Pellet - organelles that fall down bottom of tube.
State the two things left after the mixture has been centrifugated with a description for each.
• Low speed - Nucleus.
• Medium speed - mitochondria, lysosomes.
• High speed - microsomes, other small vesicles.
• Very high speed - ribosomes, viruses, large macromolecules.
State the different speeds the mixture can be centrifugated with the organelles left in each speed.
• Shows coloured images.
• Has max magnification of X1500.
• Max resolution of 0.2um.
• Specimen thinly cut for light to pass through it.
• Max resolution of 0.0002um.
• Max Magnification of X 1'500'000.
• Images are black and white, computer adds colour to image
• Wavelength of electron are smaller, pass between two points that are closer together.
State the general features of Light microscopes and Electron Microscopes.
Light Microscopes Advantages:
• Shows coloured images.
• Cheaper to get.
• Used for living and non living specimens.
Light Microscopes Disadvantages:
• Not able to distinguish two points closer than half wavelength of visible light.
• Max resolution of 0.2um.
• Max magnification of X1500.
Electron Microscopes Advantages:
• Max magnification of X 1'500'000.
• Max resolution of 0.0002um.
Electron Microscopes Disadvantages:
• Images are in black and white.
• Expensive to get.
• Only used for non living specimens.
State the advantages and disadvantages of Light and Electron microscopes.
Transmission Electron Microscopes:
• Electrons passes through the specimen, denser parts absorb more electrons, images shown darker.
• Specimen has to be thinly cut, occurs in a vacuum, useful to view organelles.
Scanning Electron Microscopes:
• Beam of electrons passes over the surface of specimen.
• Used for thick specimens.
• Poorer resolution.
• Produces 3D images.
State the features of Transmission Electron Microscopes and Scanning Electron Microscopes.
• Magnification - Refers to microscopes power to show an objects apparent size.
• Resolution - Minimum distance apart that two objects can be in order for them to appear as separate objects.
State a definition for Magnification and Resolution in biology terms.
• Pipette a drop of water onto the slide.
• Separate one of thin layers of onion.
• Peel off a thin layer of epidermis tissue from the inner surface.
• Use forceps to put the thin layer onto the slide.
• Make sure that the onion layer is flat on the slide.
• Place two drops of iodine solution on the onion layer.
• Carefully cover slip the slide avoiding air bubbles forming.
• Place the slide onto the microscope stage.
Describe how a microscopic slide can be made.
Mitosis Key features:
• Occurs in eukaryotic cell, controlled by molecules called cyclins.
• Forms two daughter cells with the exact same copy of DNA
State the key features of Mitosis.
• Asexual Reproduction.
State the uses of Mitosis.
Structure of Chromosomes:
• Two sister chromatids held together by a centromere.
• Have the same characteristics; shape, size and order.
• Pair of chromosomes is called Homologous Chromosomes.
Describe the structure of chromosomes.
• Chromatid - identical copy of a chromosome held together by a centromere forming two sister chromatids.
• Sister chromatids - two copies of a chromosome held together by a centromere.
State a definition for chromatid and Sister chromatids.
State the phases of mitosis in order.
• Interphase - Cell isn't divided, still does normal functions.
- Gap phase 1 - Cell grows, new organelles and proteins are made.
- Synthesis - cell replicates DNA
- Gap phase 2 - cell keeps growing, proteins needs for cell division are made.
• Prophase - chromosomes condense, become thicker and sister chromatids become visible. Spindles develop, centrioles move to opposite ends of the cell. Nuclear membrane and nucleolus disappears.
• Metaphase - chromosomes line up in the middle of the equator (middle of the cell). Spindles are attached to the centromeres of the chromosomes and are also attached to the centrioles at each end of the cell.
• Anaphase - centromeres are divided separating sister chromatids. Spindles contract pulling the chromatids to opposite ends of the cell. Chromatids appear as a V shape. Energy to do this process is provided by the mitochondria.
• Telophase - Chromatids reach at each end of the spindle. Chromatids uncoil, become longer and thinner known as chromosomes. Nuclear membrane and nucleolus reform around each group of chromosomes forming two nuclei.
• Cytokinesis - cytoplasm divides and forms two genetically identical daughter cells.
- Animal cells - cells pinch themselves into two.
- Plant cells - new membrane is formed
Describe the whole process of mitosis with a description of each phase.
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