Topic 1 - key concept in Biology

• Eukaryotic cell: animal call and plant cell

  Prokaryotic cell: bacterial cell (smaller and simpler)
• Animal cells:

  • Mitochondria: reaction for aerobic respiration take place
  • Cell membrane: control what goes in and out
  • Ribosomes: synthesis of protein
  • Cytoplasm: most chemical reaction happens. I contains enzymes
  • Nucleas: contains genetic material
• Plant cell:

  • Chloroplasts: where photosynthesis occur , contain chlorophyll
  • Vacuole: contain cell sap to maintain the internal pressure of the cell
  • Cell wall made of cellulose to strengthen the cell
• Prokaryotic cells:

  • Cell membrane
  • Ribosome
  • Chromosomal DNA: control cell's activity and replication
  • Plasmid DNA: contain exta genes e..g drug resistant can be passed between bacteria
  • Flagellum: hellp bacteria to move away from harmful substance e.g. toxin and towards beneficial things like nutrients
• Specialised cell: cell that has a structure adapted to it's function
• Egg cell: carries female DNA and feeds developing embryo

  • haploid nucleas: half of the chromosomes, when an egg and sperm join together, they make cell with the normal number of chromosomes
  • nutrients in the cytoplasm to feed embryo
  • cell membrane change structure after fertilisation to prevent more sperm entering
• Sperm cell: transport male DNA to egg

  • haploid nucleas
  • acrosome: enzymes for digesting egg membrane
  • Lots of mitochondria: provide energy for swiming
  • tail: swiming to egg
• Ciliated epithelial cell: move substance along internal surface e.g. mucus in airways

  • beat to move substance in one direction along the surface of the tissue
• Enzymes: catalyse chemical reaction

  • each enxyme only catalyse one specific reaction because f it's unique shape of active site
  • Substrate fit into the active site
  • enzyme remain unchange and products are produced
• Microscopy

  • Electron microscope are invented after ligt microscope
  • electron microscope have a higher magnification and resolution than light microscope
  • They'll let us see smaller things in more detail and understand subcellular structure better
  • However they are hard to carry around and can only see dead things (vaccum)
• Resolution: how well a miscroscope distinguish between 2 points that are close together
• Factors affecting enzyme activity

  • High temperature and high and low pHs denature enzymes ( change the shape of the active site so the enzymes no longer work )
  • optimum (temperature)
  • More substrate means enzyme and subtrate are more likely to meet, until all active site is full
• Enzyme in organisms: Enzyme break big molecule into smaller ones, which are used for life processes + catalyse synthesis reaction

  • carbohydrate (starch) -- carbohydrases --> sugars
  • protein -- Proteases --> amino acids
  • Lipid -- Lipase --> glycerol and fatty acids
• Calorimetry: used to find amount of energy in food

  1. weight food sample and put it on mounted needle
  2. add a set volume of water to a boiling tube and record it's temperature
  3. Set fire to the food. Hold it under the boiling tube until it goes out. Repeat until the food no longer catch fire
  4. record water temperature

  Energy in food (J) = mass of water (g) x temperature change of water ( Celcius) x 4.2
• DIffusion: the net movement of particle from an area of high concentration to an area of low concentration

  only very small molecule (e.g. glucose) can diffuse across cell membrane
• Active transport : the movement of particles aginst a concentration gradient. It requires energy from respiration
• Osmosis: the net movement of water molecules across a partially permeable membrane from high water concentration to low water concentration
• total magnification = eyepiece lens magnification x objective lens magnification
• magnification = image size / real size
• Microscopy:

  1. start with the lowest - powered lens then move the stage up with the coarse adjustment knob
  2. Look down the eyepiece and adjust the focus wit the adjustment knob (use the fine one first)
  3. Switch the lamp on
  4. To see the slide with a greater magnification, swap to a higher - powered lens and refocus
• For the spciment:

  • stained
  • water drop
  • cover with a slide at an angle
• Microscope

  A) coarse adjustent knob

  B) eye piece

  C) objetive lens

  D) Stage

  E) Fine adjustment knob

  
• Test for biological molecules:

  • Iodine test : add iodine solution in a food sample and mix, browny - orange = blue - black for starch
  • Biuret test: Add potassium hydroxide solution to a food sample, followed by copper sulphate solution, blue to purple for proteins
  • Emulsion test: Add ethanol to food sample and shake for a minute. Pour the solution into water, clear = milky emulsion for lipids
  • Benedict's test: Add Benedic's regent to a food sample and leave in water bath at 75, blue to green, yellow, brick-red (increasingly sugar concentration) for reducing sugar
• Investigate osmsis in potatos:

  1. cut potatos into identical cylinder
  2. divide cylinder into groups of three and measure the mass of each group
  3. Prepare beaker containing different concentration of surcrose solution and one of pure water. Put one group of cylinder in each beaker
  4. Leave foor at least 40 minutes then take out and dry them gently with a paper. Measure the mass again.
• Investigate osmosis in potatoes :

  • independant variables: concentration of surcrose solution
  • dependant variables: potato cylinder mass
• percentage change in mass = (final mass - initial mass) / initial mass x 100
• Effect of PH on Amylase activity:

  • independant variable: pH , dependant variable time taken for amylase to break down starch
  • check regularly on thermometer to keep heat constant
  • amylase broke down starch
  • mixture sampled every 10 s, record time when iodine solution remains browny-orange after sample is added

  A) 35

  B) 3 cm3 starcc

  C) 1 cm3 pH buffer solution

  D) Spotting tile

  E) dropping pipette

  F) thermometer

  
• Rate of reaction = 1000/ time (s)
• Mass transfer by osmosis

  • mass in potato cylinder decreasing as the concentration of surcrosse is larger in the outside therefore water move out by osmosis
  • In the point, where it is 0 is when the concentration of water iss balance in both side
  • Then mass started in increase again as water transfer back into the potato cylinder by osmosis

  
• Why coverslip is placed on top of the speciment

  To protect it
• Explain why only a small peal of speciment is used instead of a whole one?

  Too thick + enable light to pass through
• Explain how stomata is open?

  WHen the guard cell take in water by osmosis = turgid
• What is the contollable variable for water

  The starting temperature of water
• Give one way in which the student can ensure the measurement of mass of the cube is accurate

  Repeat the reading of the mass and calculate the mean or use a more sensitive mass balance that reads more decimal place
• Explain why potato cell wall didn't burst when placed in water

  • cell wall
  • gives strength and support
• Describe how to use a microscope to obtain a clear image of the cells 


  • switch the lamp on
  • Start with the lowest object lens and look through the eyepiece lens
  • Use the wheel to obtain a clear image
• Describe how a student will prepare microscope slide using these cells

  • use a thin section of meristem
  • add a stain such as iodine
  • place a cover slip at an angle on top of that sample
• Precaution when heating hydrochlori acid

  • avoid direct contact by wearing gloves
  • heat in fume cupboard
• Convertion of units

  Convertion of units

  A) 1000

  B) 100

  C) 10

  D) 1000

  E) 1000

  F) um

  G) nm

  
• How does synapse transmission work?

  • neurones transmit electrical impulses
  • synapse is a gap between 2 neurones
  • triggering the release of neurotransmitters
  • which diffuse across the synapse
  • as chemical signal
  • neurotransmiter bind to receptor on the next neurone
  • trigger an electrical impulses in the next neurone