biology - key concepts in biology (1.1 - 1.17)

1.1 animal cells - sub-cellular structures (4) & functions

nucleus: controls cell; contains chromosomes

cell membrane: controls what enters & leaves

mitochondria: site of aerobic respiration; provide energy

ribosomes: site of protein synthesis

1.1 plant cells - sub-cellular structures (7) & functions

nucleus: controls cell; contains chromosomes

cell membrane: controls what enters & leaves

cell wall: made of cellulose; supports & protects

chloroplasts: site of photosynthesis; contain chlorophyll - traps energy transferred from sun for photosynthesis

mitochondria: site of aerobic respiration; provide energy

ribosomes: site of protein synthesis

vacuole: stores cell sap; keeps cell firm & rigid

1.1 bacteria - sub-cellular structures (5) & functions

chromosomal DNA: controls most of cell’s activities

plasmid DNA: controls a few of cell’s activities

cell membrane: controls what enters & leaves

ribosomes: site of protein synthesis

flagella: allows cell to move

1.2 sperm cells - adapted to function

acrosome: contains enzymes that break down egg’s cell membrane - sperm can penetrate egg

haploid nucleus: 23 chromosomes - cell produced by fertilisation has 2 copies of each chromosome

mitochondria: lots - release lots of energy to power tail

tail: allows cell to swim

1.2 egg cells - adapted to function

nutrients in cytoplasm: supplies fertilised egg cell for growth of embryo

haploid nucleus: 23 chromosomes - cell produced by fertilisation has 2 copies of each chromosome

changes in cell membrane after fertilisation: cell membrane becomes hard - stops other sperm cells entering

1.2 ciliated epithelial cells - adapted to function

cilia: sweep substances along

resolution definition

smallest distance between 2 distinguishable points

1.3 development of microscope technology

higher resolution & magnification

see cell structures & organelles with more clarity & detail

understand role of sub-cellular structures better

electron microscope - beams of electrons pass through specimen, build up image

how to find magnification of microscope

multiply magnifications of 2 lenses

e.g. eyepiece lens: x5; objective lens: x10 → 5 × 10 = x50

1.5 SI units

millimetres (mm): x10^-3

micrometres (µm): x10^-6

nanometres (nm): x10^-9

picometres (pm): x10^-12

1.6 core practical: investigate biological specimens using microscopes

1. collect small specimen of cells

2. add drop water/stain to centre of microscope slide

3. place specimen on drop of water/stain

4. use toothpick to slowly lower coverslip onto specimen

5. examine specimen under microscope - start with lowest magnification

6. draw cells seen & annotate drawing

1.7 enzyme action

active site: where substrate of enzyme fits at start of reaction

enzymes only works with specific substrates that fit active site

1.8 enzymes denatured

changes in pH/temp. - affect how protein folds → affect active site shape

active site shape changes too much - substrate doesn’t fit, enzyme won’t catalyse reaction, enzyme denatured

1.9 effect of temperature on enzyme activity

temp. increases - molecules move faster, more frequent successful collisions between substrate & enzyme molecules

temp. too high - active site shape starts to change (amount of change increases as temp. increases), increasingly difficult for substrate molecule to fit into active site

optimum temp.: temp. enzyme works fastest at

1.9 effect of substrate concentration on enzyme activity

high conc. - most enzyme active sites contain substrate molecules, rate of reaction fastest it can be

low conc. - many enzyme active sites are empty, low rate of reaction

1.9 effect of pH on enzyme activity

pHs below & above optimum - active site shape affected, enzyme doesn’t work as well

optimum pH: pH enzyme works best at

1.10 core practical: investigate effect of pH on enzyme activity

1. set up heating apparatus: tripod; gauze; heat-resistant mat; Bunsen burner; large beaker half-filled with water

2. heat water to 40°C & keep it at this temp.

3. place 1 drop iodine solution in each depression of dimple tile

4. measure 2cm³ amylase solution into tube

5. add 1cm³ solution with particular pH to tube

6. add 2cm³ starch solution to tube & place in water bath, start stop clock & stir mixture

7. every 20 secs, place 1 of mixture drop into fresh drop of iodine solution; stop testing when iodine solution stops changing colour

8. repeat experiment using diff. pH solution in step 5

shortest time to digest substrate = enzyme’s optimum pH

1.11 rate calculations for enzyme activity

amount of substrate broken down/time

amount of product formed/time

e.g. 100g starch broken down in 5 min → 100/5 = 20g/min

1.12 importance of enzymes as biological catalysts - food molecules

digestive enzymes - large molecules (food) → small subunits

digested molecules small enough for absorption by small intestine - used to build larger molecules cells & tissues need

synthesis

building larger molecules from smaller subunits

1.12 importance of enzymes as biological catalysts - time

breakdown of large molecules very slow - only if bonds between small subunits have enough energy to break

synthesis very slow - subunits rarely collide with energy force/right orientation to form bond

too slow to supply all body needs & keep it alive

enzymes speed up reactions needed to stay alive

biological catalyst

speeds up reactions without being changed itself

1.12 what does protein break down into?

protein → amino acids

1.12 what does starch break down into?

starch → glucose molecules

1.12 what do lipids break down into?

lipid → fatty acids & glycerol

1.13 core practical: food tests

1.14 measuring energy contained in food using calorimetry

burn in calorimeter - measures energy taken in & given out in chemical reaction

amount of energy transferred from burning food → water - calculated from increase in water temp.

1.15 diffusion

movement of particles from area of high concentration → area of low concentration

particles diffuse down concentration gradient

steeper conc. gradient = faster diffusion

1.15 osmosis

movement of water molecules across semi-permeable membrane from area of high water conc. → area of low water conc.

1.15 active transport

movement of particles across cell membrane from area of low conc. → area of high conc. requiring energy from cellular resp.

by transport proteins in cell membranes

core practical: osmosis in potatoes

1. label diff. boiling tubes with diff. sucrose conc.

2. cut similar-sized pieces of potato, 1 per tube

3. blot each potato piece dry; measure & record its mass; put in empty tube

4. fill each tube with sucrose solution of appropriate conc. (ensure potato is covered)

5. after at least 15 mins, remove each potato piece & blot dry; measure & record mass

1.16 calculate percentage gain & loss of mass in osmosis