Section 2 - Chapter 3 : Cell Structure Flashcards

Question

What is the structure of the **Cell Wall** in a plant cell?

Answer 1

* Cell wall consists of microfibrils of the polysaccharide **cellulose**, embedded in a matrix * Cellulose **microfibrils** provide strength to the cell wall * There is a thin layer called **middle lamella,** which marks the boundary between adjacent cell walls and cements adjacent cells together

Answer 2

* To provide **mechanical strength** in order to prevent cell from **bursting** under pressure due to the osmotic entry of water (water intake) * To give **mechanical strength** to the plant as a whole * To allow **water to pass along it** and contributes to movement of water through the plant

Answer 3

* Fungi: Nitrogen- containing polysaccharide called **chitin** (polysaccharide called glycan and glycoproteins) * Algae : Made of either cellulose or glycoproteins or a mixture of both

Answer 4

* A fluid-filled sac bounded by a single membrane (tonoplast) * A plant vacuole contains a weak solution of mineral salts, sugars, amino acids. (cell sap)

Answer 5

* Maintains pressure and makes plant cell **turgid;** adds to support * The sugars and amino acids may act as a **temporary food store** * The pigments may **colour petals** to attract pollinating insects

Answer 6

* As the embryo develops, some cells differentiate fully into specialised cells

Answer 7

* Epithelial cells * Villi - large surface area * Villi have microvilli - large surface area for absorbtion * Lots of mitochondria - Provide energy for transport of digested food * Red Blood Cells * Adapted to carry oxygen - no nucleus to make more room for more haemoglobin. * Sperm Cells * Lot of mitochondria - large amounts of energy to get to egg.

Answer 8

* A collection of **similar cells** that perform a specific function * Is a **combination of tissues that are co-ordinated** to perform a variety of functions although have a major function * Organs work together **as a single unit** known as an organ system

Answer 9

* **Muscle** - to churn and mix the stomach contents * **Epithelium** - it lines the stomach wall to **protect** and produce **secretions**. Consists of sheets of cells. * **Connective** - To hold other tissues

Answer 10

* **Palisade Mesophyll** - made of leaf palisade cells that carry out photosynthesis * **Spongy Mesophyll** - Adapted for gaseous diffusion * **Epidermis** - To protect leaf + allow gaseous diffusion * **Phloem** - To transport organic materials away from the leaf * **Xylem** - To transport water and ions into the leaf + give meachanical support

Answer 11

* **Digestive System** : * Digests and processes food * Made of oesophagus, salivary glands, stomach, duodenum, ileum, pancreas and liver * **Respiratory System**: * Used for breathing and gas exchange * Made of trachea, bronchi, lungs * **Circulatory System**: * Pumps and circulates blood * Made of heart, arteries, and veins

Answer 12

* Cell Wall (made of murein): * **Physical barrier** that excludes certain substances + protects mechanical damage/osmotic lysis * Capsule: * **Protects bacterium** from other cells + helps bacteria to stick together for further protection * Cell Surface Membrane + 70s ribosomes: * Acts as a permeable layer/ **controls entry + exit** of chemicals * Circular DNA: * Possesses genetic material for **replication** of cells * Plasmid: * Possesses genes to **aid in survival** in adverse conditions

Answer 13

* Binary Fission * The **circular DNA molecule replicates** and both copies attach to the **cell membrane** * The plasmids also replicate * The **cell membrane begins to grow** between the 2 DNA molecules and begins to pinch inwards, **dividing cytoplasm into 2** * The new **cell wall forms between the 2 molecules of DNA**, dividing the original cell into 2 identical daughter cells, each with a single copy of circular DNA and some plasmids (variable)

Answer 14

* Are acellular, non-living particles. * Smaller than bacteria (20-300nm) * Contain nucleic acids such as DNA or RNA as genetic material but can only multiply inside living host cells

Answer 15

* Nucleic acid is enclosed within a protein coat called a **capsid** * Some viruses are surrounded by a **lipid envelope** * The lipid enevelope (if not present), the capsid has **attachment proteins** to allow the virus to identify and attach to a host cell * Are accellular, non-living and smaller than bacteria

Answer 16

* As viruses **are non-living they cant undergo cell division.** * Instead they replicate by attaching to their host cell with the attachment proteins on their surface to the complementary receptor proteins. * Inject their nucleic acid into the host cell. * The genetic information on the injected viral nucleic acid then provides the 'instructions' for the host cell. and Genetic materials and proteins are replicated. * This produces viral components which are the assmebled into new viruses

Answer 17

* The degree to which the size of the image is larger than the object itself * Usually expressed numerically x40, x100

Answer 18

* Magnification = image size / actual size

Answer 19

* The degree to which it is possible to distinguish between 2 objects that are close together

Answer 20

Metres→multiply by 100 = cm Cm→multiply by 10 = mm mm→ multiply by 1000 = um um→multiply by 1000 = nm

Answer 21

* To calibrate an eypiece graticule you first need to use a special microscope slide called a **stage micrometer.** * This slide has a scale etched onto it 1. Place the stage micrometer onto the microscope stage 2. Line up the divisions on the eyepiece graticule with those of the micrometer 3. Work out the length of 1 eyepiece graticule (glass disc with scale etched on it) in micrometers 4. Repeat for each of the objective lenses on the microspe

Answer 22

1. Place the slide onto the microscope stage 2. Measure the length of the specimen of 1 cell in eyepiece graticule 3. Calculate the length in micrometers by multiplying length in the eye piece graticule by the callibration value for 1 unit

Answer 23

* Optical (light) microscopes * Transmission Electron Microscopes * Scanning Electron Microscopes

Answer 24

* Measure the sizes of objects by using an eyepiece graticule * This is a glass disc that is placed in the eyepiece and has a scaled etched on it * The graticule must first be calibrated for a particular objective lens

Answer 25

1. Start by clipping slide prepared onto stage 2. Select lowest powered objective lens 3. Use the coarse adjustment knob to bring the stage just below objective lens 4. Look down eyepiece. Use coarse adjustment to move stage downwards, away from objective lens until image is in focus 5. Adjust focus with fine adjustment knob until clear image 6. If you need to see slide with higher magnification swap to higher powered objective lens and refocus

Answer 26

* Use light to form an image * Focussed by a condenser lens and focussed further by an objective and eye piece lens * Have a maximum resolution of about 0.2µm can't see objects smaller than this

Answer 27

* Cheaper * Shows in colour * No complex staining process required * Only living specimens * Easy to use

Answer 28

* Larger organelles only * Lower resolution and Magnification * Longer wavelength therfore a low resolving power

Answer 29

* Use electromagnets to focus a beam of electrons which is transmitted through a thin section of the specimen * Denser parts absorb more electrons making it looker darker

Answer 30

* Ultrastructure (smaller organelles can be seen) * Have a short wavelength (high resolution/resolving power)

Answer 31

* Vacuum is needed as electrons can be deflected by air molecules * Only dead specimens are viewed * High energy electrons may destroy the specimen * Must be thinner than light preparation (TEM extremely thin) * More complex staining process required * Black and white image - not coloured * The image may contain artefacts - result from preparation (not naturally)

Answer 32

* Direct a beam of electrons across the surface of specimen (from above) * The beam is passed back and forth across the specimen in a regular pattern * The electrons are scattered - the pattern of the scattering depends on the contours of the surface * The images show the surface of the specimen can be 3D

Answer 33

* Higher Resolution * 3D * Doesn't need to be extremely thin (can be used on thicker specimens)

Answer 34

1. Pipette a **small drop of water** onto the centre of the slide 2. Then use tweezers to place a thin section of the **specimen** on the water drop 3. Add a drop of **stain** (highlights objects in the cell) 4. Finally **add coverslip** (protects specimen). To do this, stand the slip upright on the slide next to specimen and lower it carefully do avoid air bubbles

Answer 35

* Staining increases contrast so chromosmes become visible

Answer 36

* Is the process where cells are broken up and the different organelles they contain are separated out * This is to study the structure and function of organelles - obtain large numbers of isolated organelles * Nuclei → Chloroplasts → Mitochondria → Lysosomes → Endoplasmic Reticulum →Ribosomes

Answer 37

* Homogenation * Ultracentrifugation

Answer 38

* The tissue is placed in a cold, buffered solution of the same water potential as the tissue. The solution is: * **Cold** - to reduce enzyme activity that might break down the organelles * **Same water potential as the tissue** - prevent organelles bursting or shrinking due to osmotic gain/loss of water * **Buffered** - So pH does not fluctuate. Any change in pH can alter the structure of organelles or functioning of enzymes

Answer 39

* Homogenation * Cells are broken up by a homogeniser (blender). * This releases the organelles from the cell * The resultant fluid (homogenate) is filtered to remove any complete cells/large pieces of debris

Answer 40

* Ultracentrifugation * Process where fragments in the filtered homogenate are separated in a machine called a centrifuge. * This spins tubes of homogenate at high speeds in order to create centrifugal force For animal cells: * The tube of filtrate is placed in the centrifuge and spun at low speed * Heaviest organelles (nuclei) are forced to the bottom of the tube where they form a thick sediment or pellet * The fluid at the top (supernatant) is removed and transferred to another tube just leaving the sediment of nuclei. * Supernatant is spun in the centrifuge at a faster speed than before * The next heaviest oragnelles are forced to the bottom * This process is continued so each increase in speed the next heaviest organelles is sedimented and separated

Answer 41

* Enabled considerable advances in biological knowledge. * Allowed a detailed study of the structure and function of the organelles - by showing what isolated components do

Answer 42

* Mitosis - produces 2 daughter cells that have the same number of chromosomes as the parent cell and eachother * Meiosis - produces 4 daughter cells with half the number of chromosomes of the parent cell

Answer 43

* Interphase - most of its time (cell isnt dividing). * Considerable cellular activity - replication of DNA + new organelles synthesised + chromosomes are joined at the centromere and arent visible * Mitosis (split into 4 stages) * Prophase * Metaphase * Anaphase * Telophase * Cytokinesis

Answer 44

* Chromosomes become visible, initially as long, thin threads, which later shorten and thicken * Animal cells contain centrioles which move to opposite poles (2 cylindrical organelles). * From each centriole spindle fibres develop which span the cell from pole to pole * The nucleolus disappears and the nuclear envelope, leaving chromosomes free in the cytoplasm * The chromosomes are drawn to the equator of the cell by spindle fibres attached to the centromeres

Answer 45

* By metaphase the chromosomes are seen to be made of 2 chromatids. Each chromatid is an identical copy of DNA from the parent cell * Chromosomes align across the middle of the cell - spindle fibres attach to the centromeres and help aligning * This helps next stage so when chromosmes are separated they have 1 copy of each chromosome

Answer 46

* In anaphase, the centromeres divide into 2 and the spindle fibres contract and pull the individual chromatids apart. * The chromatids move to the opposite poles of the cell and are referred to as chromosomes * The energy for this process is provided by mitochondria * If cells are treated with chemicals this destroys spindle fibres and chromosomes remain at the equator

Answer 47

* The chromosomes reach their respective poles and become longer and thinner, finally disappearing altogether leaving widely spread chromatin * The spindle fibres disintegrate and nuclear envelope and nucleolus reform. * Finally the cytoplasm divides in a process called cytokinesis

Answer 48

* Growth * Repair - damaged so cells have same structure as original * Reproduction of single-celled organisms Mitotic Index = number of cells with visible chromosomes/ total number of cells observed

Answer 49

1. Get onion roots - use roots as they have meristem (have a lot of mitosis 2. Cut some root tips and put into watch glass 3. Add 2 mol of hydrochloric acid and then add an equal volume of stain (acetic orsein stain) 4. Heat the mixture (gently) and liquid eveporate use a hot plate for about 5 minutes 5. Transfer to a clean microscope slide + add 1 drop of aceitic orsein stain 6. Cover with coverslip 7. Use tissue to blot dry and add some pressure to make sure it is thin and be able to transmit light 8. Observe under optical microscope

Answer 50

* Benign - grow slowly, less life threatening and more compact * Malignant - grow rapidly, less compact, and more life threatening

Answer 51

* Involves killing dividing cells by blocking a part of the cell cycle * Drugs used to treat cancer usually disrupt the cell cycle by * Preventing DNA replicating * Inhibiting the metaphase stage of mitosis by interfering with the spindle formation

Answer 52

* They disrupt the cell cycle of normal cells * However the drugs are more effective against rapidly dividing cells (cancer cells) . * Hair cells are also vulnerable as they divide rapidly

Section 2 - Chapter 3 : Cell Structure Flashcards

Cover Chapter 3 from Kerboodle Textbook