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| Question | Answer |
| What does the Cell Theory state | -All living things consist of cells - New cells are only formed by division of pre-existing cells - Cells contain info that acts as instructions for growth ( info can be passed on to new cells) |
| What types of microscopes have been developed to help scientists study cells | - Electron - Light |
| Magnification is | Degree to which an image is enlarged from actual size |
| Resolution | Degree to which we can distinguish between two points that are close together |
| How do light microscopes work | Uses number of lenses to produce image that can be directly viewed at eyepieces Light - Bulb under stage - Through condenser lens - Through specimen - Light beam focused through objective lens - Through eyepiece lens - Image magnified |
| Light microscope advantages | - Can view a wide range of specimens - Less expensive - Easier preparation methods - Used widely in labs - Can view living specimens |
| Light microscope disadvantages | - Low magnification ( x 1500 ) & resolution - Don't produce detailed or 3D images of organelles within cells - Can't reveal contours and cellular/ tissue arrangements like SEM |
| Staining | - Colored stains are chemicals that bind to chemicals on or in a specimen - Allows stains to be seen - Some stains bind to specific cell structures |
| Sectioning | - Specimens embedded in wax and thin sections are then cut without distorting structure |
| Equations for magnifiction | |
| Electron microscopes key points | - Generate a beam of electrons that has a shorter wavelength than light - Can distinguish between objects 0.2nm apart - Use magnets instead of light - Electrons not visible to human eye |
| Transmission electron microscope (TEM) | Electron beam passes through thin prepared sample, produces 2D image and has a mag of around x 500 000 |
| Scanning electron microscope | Electorn beam directed onto sample, electrons bounce off sample, 3D image produced and has a mag of about x 100 000 |
| Resolution of light and electron microscopes | Light - 200nm Electron - 0.2nm |
| Advantages of electron microscopes | - Higher resolution - Can produced detailed images of organelles - SEM produces 3D images revealing contours and tissue/ cellular arrangements |
| Disadvantages of electron microscopes | - Samples have to be placed in a vacuum a electron beams are deflected by air molecules - Expensive - Requires high degree of skill and training |
| How is a thin section of liver tissue prepared | Fix specimen in ghlutaraldehye to make tissue firm - dehydrate to replace water with ethanol - embed dehydrated tissue in solid resin - cut thin slices using diamond knife- stain using lead salts- electrons scatter differently (contrast) - mount on copper grid - place specimen in vacuum in microscope |
| What are colored electron micrographs | Electron micrographs are colored using specialized computer software ( false-color ) |
| 2 | 2 |
| What are the seven characteristics of all living things | Movement Respiration Sensitivity Growth Reproduction Excretion Nutrition |
| What type of microscope can be used to identify organelles in cells | Electron |
| What does the term 'Ultra structure' refer to | The detail of the inside of cells |
| What does the term 'Division of labour' refer to | Specific organelles having specific roles within a cell |
| What is the Cytoskeleton | Network of protein fibers within cells |
| What is the role of the Cytoskeleton | - Fibres keep cells shape stable - Move some organelles around the cell - Cause movement seen in some white blood cells |
| Types of protein fibres | - Actin filaments - Microtubles |
| What protein are Microtubules made of | Tubulin |
| What are the functions of microtubles | - Move microorganisms through liquid/ or waft liquid past cell - Move organelles and other cell contents along fibres (e.g. chromosomes during mitosis) = 'Microtubule Motors' |
| What are Cilia and Flagella | Hair- like extensions that stick out from cell surface - Made up of a cylinder (containing nine microtubles in a circle, with two in the middle) |
| What is the difference between Flagella and Cilia | Flagella is longer and usually has a tail for eased movement |
| How frequent are they on Cells | Flagella - ones or twos Cilia - Numerous ( in large numbers ) |
| Which is found on Bacteria | Flagella |
| What are vesicles and their role | Membrane bound sacs Carry many different substances around cells |
| How do Vacuoles maintain cell stability in plants | They are filled with water making them turgid so it pushes cytoplasm against cell wall |
| Where are plant cell walls found and what are they made of | Plants have cellulose cell walls found on outside of plasma membrane |
| Structure of Nucleus | Largest organelle Has nuclear envelope, pores and a nucleolus |
| Function of Nucleus | Houses cells genetic material Chromatin consists of DNA and proteins Has instructions for making proteins |
| Structure of Endoplasmic Recticulum (ER) | Series of flattened membrane bound sacks |
| Types of ER and Functions | 1) Rough ER - Transports ans synthesis' proteins ( Studded with ribosomes ) 2) Smooth ER - Synthesis' lipids |
| Structure of Golgi Apparatus | Stack of membrane bound flattened sacks |
| Function of Golgi Apparatus | Modifies and packages proteins |
| Structure of Mitochondria | Spherical/ sausage-shaped Double membrane, central matrix and cristae in inner membrane |
| Function of Mitochondria | Produce ATP, during respiration |
| Structure of Chloroplast | |
| Function of Chloroplasts | Site of photosynthesis in plant cells |
| Structure of Lysosomes | Spherical sacs surronded by single membrane |
| Structure of Ribosomes | Tiny organelles Free floating in cytoplasm or attached to Rough ER |
| Function of Ribosomes | Site of protein synthesis |
| Structure of Centrioles | Small tubes of protein fibres ( microtubules ) |
| Function of Centrioles | Form spindle during cell division |
| How do organelles work together in Protein synthesis | 1) Nucleus copies instructions onto mRNA molecule 2) Molecule leaves through nuclear pore 3)Attaches to a ribosome, instructions read and protein assembles 4) Pinched off in vesicle 5)Transported to Golgi Apparatus 6) Modified and then packaged into vesicles 7) Moved to CSM then secreted |
| Features of Eukaryotes | Have a true nucleus Each organelle performs specific role Larger Have mitochondria |
| Features of Prokaryotes | No true nucleus Bacteria Smaller No membrane bound organelles Single loop of DNA in cytoplasm Have flagella Peptidoglycan cell wall |
| Examples of useful Prokaryotes ( Bacteria ) | - Food industry ( yogurt, cheese ) - On skin to prevent harmful microorganisms getting into body - Digest/ respire dead or waste material ( useful for sewage treatment and natural recycling ) |
| Why are some bacterial cells well known | Due to the diseases they cause |
| What can some bacterial strains become resistant to | Antibiotics |
| 3 | 3 |
| What are the major roles of membranes | - Separate cell contents from outside environment or cytoplasm - Cell recognition and signaling - Regulate material transportation into/ out of cells - Hold components of some metabolic pathways in place |
| The phosphate head is | Hydrophilic |
| The fatty acid tails of a phospholipid are | Hydrophobic |
| Why are the tails hydrophobic and heads hydrophilic | Due to the distribution of charges across the molecule |
| Why can't oil and water mix | As their molecules have charges that are distributed evenly across them (oil), repel water molecules |
| What happens when phospholipids are mixed with water | Form a layer on water surface - Heads stick into water - Tails stick up out of water |
| When can a bilayer form | When phospholipid molecules are completely surrounded by water |
| What does bilayer look like | insert |
| Phospholipids aren't bonded together, how is the bilayer kept stable | Hyrophilic heads cant easily pass through hydrophobic region in middle of bilayer |
| All biological membranes have | A phospholipid bilayer |
| Why is the hydrophobic layer necessary | Creates a barrier to many molecules Separates cell contents from outside world |
| What type of microscope can be used to see membranes | Electron |
| Examples of differentiation in cell membranes | 1) Plasma membrane - contain receptors to detect molecules that regulate growth 2) Muscle cells - large number of channels, allow rapid glucose uptake (energy for contractions) |
| Why are all membranes permeable to water | Water molecules can diffuse through lipid bilayer |
| Why are membranes with aquaporins more permeable | They are protein channels that allow water through them |
| What are partially permeable membranes | Membranes that allow water and some solutes through |
| What does the term Fluid mosaic refer to | Molecular arrangement in membranes |
| Features of Fluid mosaic model | - Phospholipid bilayer (basic structure) - Protein molecules (floating in bilayer, free floating or bound to components) - Extrinsic proteins (partially embedded in bilayer) - Intrinsic proteins (completely span bilayer) |
| Phospholipid molecule + Carbohydrate part | Glycolipid |
| Protein molecule + Carbohydrate part | Glycoprotein |
| Role of cholestrol in membranes | - Mechanical stability Found between fatty acid tails to complete barrier |
| Role of channel proteins | - Allow movement of some substances across membrane (e.g. large hydrophilicmolecules/ions - go directly through cell using channel) |
| Role of carrier proteins | Actively move substances across membrane |
| Receptor sites... | - Allow specific (matching) hormones to bind with cells to carry out responses (e.g. allow drugs to bind, affecting cell metabolism) |
| How are glycoproteins and glycolipids involved in cell signalling | - Allow recognition by immune system - Components of some hormones |
| Advantage of enzymes/coenzymes on membranes | Speed up metabolic reactions |
| Temperature effect on membrane = | Increased Kinetic energy, move faster |
| Disadvantage of increased membrane movement, as a result of increasing temperature | Membranes become leaky Allows substances that wouldn't normally, enter or leave cell |
| How could an animal living in hot conditions become adapted to maintain membrane stability | Increase cholesterol content |
| What are receptors | Surface sensors, receive signals Usually protein molecules |
| Communication in multicellular organism cells are often mediated by... | Hormones |
| What are hormones | Chemical messengers within organism Produced by specific tissues |
| What is a target cell | Any cell with receptor for hormone molecule |
| Why do hormone molecules and receptors on target csm bind | Complementary shapes |
| Binding results in a ... | Particular response |
| Outline Insulin receptors and their function | - Hormone receptor - Released from beta-cells in Pancreas - Response to incresed blood suger levels - Muscle/liver cells - Insulin + its receptor = internal response in muscles, more glucose channels, more uptake so less glucose in blood |
| How are medicinal drugs able to interfere with receptors and why | - Complementary shape - Block certain receptors (e.g. beta blocker prevent heart muscle from increasing heart rate in individuals where it would be harmful) |
| How can viruses enter cells | Hijack receptors Bind with receptors on CSM that normally bind to hosts signalling molecules (e.g.HIV) |
| 4 | 4 |
| Why do cells need a supply of O2 and other nutrient molecules | To survive O2 for aerobic respiration |
| What is the name given to reactions in living cells | Metabolism |
| What does metabolism generate | Waste products that must be removed from cell across a membrane |
| What are the passive transport processes | Diffusion Faciliated diffusion Osmosis |
| What are the active transport processes | Active transport Endocytosis Exocytosis |
| What is diffusion | The net movement of substances from a region of higher concentration to lower concentration, down concentration gradient |
| What type of energy is used in diffusion for movement | Kinetic energy |
| What is equilibrium | A state in which there is no overall movement of molecules in one direction (no net movement) |
| Factors that affect rate of diffusion | Temperature (increasing means more kinetic energy) Molecules size (smaller molecules diffuse quicker) Distance (shorter diffusion distance necessary, thick membranes slow down diffusion) Concentration gradient (more molecules on one side- increased diffusion) |
| Why can steroid hormones able to diffuse through cell membranes | They are lipid based |
| Why can h20, co2 and o2 molecules pass through the bilayer | Molecules are small |
| Type of diffusion in which large or charged molecules can pass through bilayer | Facilitated diffusion |
| Channel proteins | Form pores in membrane Only allow one type of ion through Gated (sodium, calcium ions) |
| Carrier proteins | Shaped Allow specific molecule to fit into them at membrane surface Changes shape to allow molecule through to other side (e.g. glucose, amino acids) |
| How do membranes have some control over types of substances that pass in or out | Different membranes can have different carrier and channel proteins |
| Active transport | The movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by carrier proteins and requiring energy (to change shape) Against concentration gradient Faster than diffusion One way across membrane |
| How is one-way flow ensured | After molecule passes through ATP energy changes proteins shape so molecule can no longer re-enter (will no longer fit through) |
| Types of bulk transport | Endocytosis Exocytosis |
| Endocytosis | Bringing large amounts of material into cell |
| Exocytosis | Moving large amounts of material out of cell |
| Example of bulk transport | 1) Hormones Pancreatic cells make insulin in large quantities Golgi apparatus modifies and packages insulin into vesicles Vesicles fuse w/ outer membrane , insulin released into blood |
| Endo - Phago - Exo - Pino - | Inwards Solid material Outwards Liquid material |
| Solute + Solvent | Solution |
| Water potential | Measure of the tendency of water molecules to diffuse from one place to another |
| How does water always move | From a region of high water potential to a region of lower water potential Region of high concentration of 'free' water molecules to a region of lower concnetration |
| Osmosis is.. | Special kind of diffusion Movement of water molecules across partially permeable membrane Region of higher WP to regiom of lower WP |
| When does the net movement of molecules occur | WP same on both sides of membrane |
| Why is the WP lower in cells that in pure water | Sugars, salts and other substances are dissolved in the cytoplasm |
| What happens when cells are placed in solutions with high WP | Water will move in by osmosis Cell will swell Animal cells - Membrane will eventually burst Plant cells - Cytoplasm swells (turgid) Vacuole pushes against cell wall osmosis stops |
| What happens when cells are placed in solutions with low WP | Water moves out of cell by osmosis Cell shrinks Animal cells - Cell contents shrink membrane will wrinkle up Plant cells - Cytoplasm and vacuole shrink as they lose water Cell membrane pulls away from cell wall (plasmolysis) |
| What is the unit for measuring WP | kPa (kiloPascals) |
| WP of pure water | 0kPa (highest WP) |
| Is a WP of -500kPa low or high | Low |
| 5 | 5 |
| An example of a single celled organism | Amoeba |
| An example of a multicelluar organism | Oak trees Humans |
| What does the cell cycle refer to | A series of events in which new daughter cells are formed from parent cells Daughter cell must be able to carry out same functions |
| What does each chromosome contain | One molecule of DNA |
| What does each molecule of DNA contain | Gene (specific length of DNA) |
| What do the chromosomes hold | Vital instructions for making new cells |
| What must the daughter cells contain | An exact copy of the instructions Full set of chromosomes (humans 46) |
| What are histones | 1) Proteins that wrap around molecules of DNA that make chromosome |
| DNA + Histone proteins = | Chromatin |
| Describe the Copying and Seperating process of cell division | 1) DNA of each chromosome is replicated 2) Two replicas are produced 3) Each is an exact copy of the original 4) They remain held together at centromere point 5) Chromosomes are not visible under light microscope 6) Each chromosome now consists of two replica strands (sister chromatids) 7) Each chromatin must be supercoiled |
| Disadvantages and advantages of super coiled chromosomes | - Can take up stains - Sturdy and short enough to be moved around more easily - Cant perform their normal functions in the cell (need to be coiled up for as short as possible) |
| How can the copying be checked | During chromosome replication, proof-reading enzymes move along new DNA strands |
| What happens if genes are not copied precisely | Mutation can occur as a result New cells may fail to function |
| How fast is the cycle | Time taken depends on the species and cell type |
| Stages of cell cycle | - Interphase S phase - DNA replicates Growth phase - proteins, organelles and other cell components are made - Mitosis Nucleus divides and chromatids seperate - Cytokinesis Cytoplasm divides or cleaves |
| How does Asexual reproduction work in organisms | - Single celled organisms divide to produce two daughter cells - Some multicelluar organisms produce offspring from parts of the parent |
| How do multicelluar organisms grow | Grow by producing new extra cells (Each new cell is genetically identical to parent cells, can perform the same functions) |
| Why is making new cells important | 1) Replacement (red blood cells and skin cells) 2) Repair (damaged cells) 3) Growth 4) Asexual reproduction |
| What are the 4 stages of mitosis | - Prophase - Metaphase - Anaphase - Telophase |
| What happens in Prophase | Replicated chromosomes super coil (Nuclear envelope breaks down and disappears Centriole divides into two Each daughter centriole moves to opposite poles to from spindle) |
| What happens in Metaphase | Replicated chromosomes line up down middle of cell (Each becomes attached to spindle thread by its centromere) |
| What happens in Anaphase | Chromosome replicas are pulled apart to opposite poles of cell |
| What happens in Telophase | |
| In what organism are all cells capable of mitosis and cytokinesis | Animals |
| What is the name of the only cells in plants that can carry out mitosis | Meristem cells |
| As plants do not have centrioles, where are their tubulin protein threads (spindle) made | In the cytoplasm |
| What are the cells produced by mitosis and cytokinesesis genetically identical to | The parent cell and each other |
| What is the name given to genetically identical cells | Clones |
| What is vegetative propogation | A form of asexual reproduction in plants where clones can be produced (e.g.strawberry plant runners) |
| What is Binary Fission | Process in which a single colony of bacteria clones can be produced from a single bacteria dividing |
| An example of how farmers have used artificial cloning | Taking cuttings from parent plants, to make clones with desirable features |
| An example of how scientists have used artificial cloning | Artificial cloning of animals - Dolly the sheep, placed cell from adult sheeps udder into a egg cell and placed in surrogate mother, raising many ethical issues |
| What are stem cells | Cells that have the ability to divide and develop into any cell type |
| What are embryonic stem cells (that can develop into any adult cell type) classified as | Totipotent |
| What are adult stem cells (that can be found in small numbers in adult tissue) classified as | Pluripotent |
| Where are plant meristem cells located | Roots and shoots |
| How can genetically different organisms be made (sexual reproduction) | Male gamete + female gamete fuse to form zygote Zygote then divides by mitosis to form new individual organism |
| What is the name of the cell division usually responsible for producing gametes | Meiosis |
| In what regions of the adult organism does meiosis take place | Sex organs or gonads |
| Normal eukaryotic adult cells are 'diploid', what does this mean | They contain two sets of chromosomes |
| Normal eukaryotic daughter cells are 'haploid', what does this mean | Each contains only one set chromosomes |
| Why do the resulting daughter cells differ | Each recieves only one part of the pair of each homologous pairs, the alleles found on each pair side will differ |
| Ways in which meiosis differs from mitosis | - Meiosis produces cells containing half the number of chromosomes - Produces cells that are genetically different from each other and parent cell |
| 6 | 6 |
| What governs the physical size that a single cell can reach | - The need to support structures within the cell - Increasing difficulty of getting enough O2 and nutrients to cell as size increases |
| What type of organism has a large surface area to volume ratio | Single-celled organism |
| The benefit for single-celled organisms with a large surface area to volume ratio | Can receive O2 and remove CO2 by simple diffusion through their membrane |
| Why do multi-cellular organisms need specialized tissues (organs,tissues) | Small SA to Volume ratio - To deliver O2 and remove waste from cells that aren't in contact with external medium |
| What is specialisation | When a cell can carry out a particular role very well |
| What is differentiation | When a cell becomes specialized to perform particular role or function |
| What are the 3 ways in which a cell can differentiate | - Number of a particular organelle - Cells shape - Contents of the cell |
| There are two types of human blood cells that each began with the same number of chromosomes, what are they called | - Erythrocytes (red blood cells) - Neutrophils (white blood cells) |
| What are both blood cells produced from | Undifferentiated stem cells in bone marrow |
| How do Erythrocytes differ | - No nucleus, mitochondria, golgi or RER - Packed full of haemoglobin - Biconcave disc shape - Capable of transporting O2 from lungs to tissue |
| How do Neutrophils differ | - Keep their nucleus - Granular looking cytoplasm (large amounts of lysosomes produced) - Ingest invading microorganisms (assisted by digestive enzymes in lysosomes) |
| What is a 'tissue' | Collection of similar cells that perform a common function |
| Example of a Tissue | Xylem Phloem Nervous Epithelial |
| What is an 'organ' | Collection of tissues working together to form particular function (Liver, leaves) |
| What is an 'organ system' | Number of organs working together to perform an overall life function |
| What is an 'organ system' | Number of organs working together to perform an overall life function |
| Two types of plant transport tissues | Xylem Phloem |
| Why are transport tissues necessary in plants | - Move munerals and water from soil, thrpough their roots and stems , up into the leaves - Move products of photosynthesis from leaves to other parts for storage or growth |
| Where do Xylem and Phloem come from And why do they differentiate | Dividing meristem cells (e.g. cambium) - Differentiates to form different cells in tissues |
| What does Xylem transport and in what direction | Water and minerals Up the plant |
| What does Phloem transport and in what direction | Sugars, products of photosynthesis Up and down the plant |
| Key features of Xylem | - Vessels with parenchyma cells and fibres - Lignified walls (waterproof) - Wide lumen, no end walls - Dead cell contents - Provides support for plants - pITS |
| Key features of Phloem | - Sieve tubes - Companion cells - End to end long tube - Sieve plates between cells |
| 4 categories for animal tissues | - Epithelial tissues (layers, linings) - Connective tissues (e.g. cartilage, bone) - Muscle tissue (specialized to contract and move parts of body) - Nervous tissue ( cells that convert stimuli to electrical impulses and conduct impulses) |
| Types of epithelial tissues | Squamous and Ciliated |
| Features of Squamous epithelial tissue | - flattened, thin cells - Thin smooth flat surface - Ideal for lining blood vessels - Form thin walls (e.g. alveoli) to maintain short diffusion pathway - Held in place by basement membrane made of collagen and glycoproteins |
| Features of Ciliated epithelial tissue | - Column shaped cells - Found on inner surface of tubes (e.g. trachea, bronchi) - Exposed region covered with cilia, some produce mucus (rhythmic waves) |
| Requirements for photosynthesis | Light Water CO2 supply Chlorophyll presence |
| What is the major organ of photosynthesis | Leaves |
| How are leaves adapted to photosynthesize excrete waste products | - Transparent upper epidermis to let light through - Lower epidermis with stomata pores, allow gas exchange - Cylindrical palisade cells layer beneath epidermis , packed with chlorophyll containing chloroplasts |
| How are stomata opened and closed | Guard cells - Found on lower epidermis - Water moves into cell - Become turgid, outer walls stretch - Cells bulge at both ends, pore opens between them (stomata) |
| Cells Completed | Good Luck :)!!! |
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