bio mod 1 year 11

cell theory

• all living things are made of cells

• cells are the smallest unit of life

• all living things come from pre-existing cells

cell membrane

• semi permeable barrier that surrounds all cells

• separates cell’s contents from surroundings and controls what enters and leaves the cell

protoplasm

• consists of nucleus and cytoplasm

• 90% of cytoplasm is water that chemicals can be dissolved in

• responsible for making cellular products and respiration

nucleus

• large oval structure that stores information needed to control cell activities

• located in cytoplasm - essential for it to be able to communicate with surrounding organelles

• nucleolus: manufactures ribosomes

endoplasmic reticulum

• network of flattened, interconnected membranes

• provides transport path between nucleus and cells environment

• immense folding of sheets of membrane increases SA which allows for more efficiency for protein folding and transport

what does the rough ER do?

protein synthesis and folding

what does the smooth ER do?

lipid and steroid production

ribosomes

• attached to rough ER

• made of RNA

• site of protein synthesis

• small size increases surface area which increases efficiency

golgi bodies (post office)

• flat membrane stacks that process, package and sort cell products

• vesicles help transport and provide a membrane around cell products to package them

lysosomes

• formed by golgi bodies

• contains digestive enzymes responsible for splitting complex chemical compounds into simpler ones

  • simpler molecules are used as building blocks for new compounds and organelles

mitochondria

• double membrane organelle that performs cellular respiration

• membrane is folded into cristae which increases the surface area for attachment of enzymes

  • which produce energy for the cell during cellular respiration

vacuoles (plant)

• large, permanent fluid filled sacs with single membrane for storing water and nutrients

• water filled vacuole exerts pressure on cell wall which provides support and structure to plant cell

chloroplasts (plant)

• double membrane, conducts photosynthesis

• grana stacked on top of each other

  • increases surface area and capture more light for photosynthesis

• inner thylakoid membrane surrounding granum CONTAINS CHLOROPHYLL

  • keeps reactants and products separate

  • maintains optimal concentration for best rate of reaction and efficiency

cell wall (plant)

• rigid outer layer surrounding cell membrane

• non-selective, permeable to most molecules

• made of cellulose and provides strength and support for plant cell

• can withstand pressure

phospholipid bilayer

• made of 2 layers of phospholipids

• hydrophobic tails facing inwards and hydrophilic heads facing outwards

transport proteins (type of integral protein)

• proteins that penetrate membrane

• assist particles (e.g nutrients, ions) to cross membrane

• selectively permeable

floating + fixed proteins (type of integral protein)

proteins scattered in the lipid bilayer, used for cell signaling and anchorage for the cytoskeleton

integral proteins

• proteins embedded within bilayer

• span partially or completely across membrane

• for transport, receptors, structure/support

receptor proteins (type of integral protein)

• penetrates membrane

• has binding sites on outer surface

• substances attach to receptor sites and start chemical reactions in cell

• eg neurotransmitters and hormones

glycoproteins and glycolipids (uniform)

• proteins and lipids which have carbohydrates attached for cell recognition

• important for immune system to recognise its own/foreign cells

diffusion

• net movement of molecules from a region of high concentration to a region of low concentration along a concentration gradient until equilibrium is reached

• no energy input required

the rate of diffusion…

• depends on concentration gradient

• if there is a greater difference in concentration

  • concentration gradient will be steeper and diffusion will occur faster

facilitated diffusion

when carrier/channel proteins assist large or charged molecules in diffusing into the cell

osmosis

net movement of solvent molecules from region of high solvent concentration to region of low solvent concentration through a semi-permeable membrane

isotonic

fluids inside and outside a cell are of equal solute concentration, no net water movement

hypertonic

• a solution of higher solute concentration (lower water concentration) surrounds a cell

• net movement of water molecules will be out of the cell

hypotonic

a solution of lower solution concentration (higher water concentration) surrounds a cell, net movement of water molecules will be into the cell

tonicity

refers to a solution’s solute concentration relative to that of another solution on the opposite side of the cell membrane

active transport

• movement of molecules from region of low concentration to region of high concentration through a semi permeable membrane

• requires energy input as it move against concentration gradient

• process does not stop when equilibrium is reached

passive transport

• movement of molecules from region of high concentration to region of low concentration across a semi-permeable membrane

• along a concentration gradient, no energy required

• process stops when equilibrium is reached

endocytosis

• moves large molecules that cannot cross the cell membrane

• requires energy

• cell membrane changes its shape and engulfs the particle so that it enters the cell

• e.g white blood cells engulfing bacteria

phagocytosis

• process whereby solid particles are engulfed by the cell membrane

exocytosis

• when substances inside the cell are moved elsewhere in the organism

• during exo., a membrane bound vesicle move to the cell membrane, fuses with it and releases its contents outside the cell

• e.g insulin secretion by pancreas cells

carbohydrates

• 1 molecule = monosaccharide (monomer) (e.g glucose)

• molecule structure of H, C, and O

• 2 linked monosaccharide = disaccharide (e.g sucrose)

• polysaccharide = many monosaccharides linked together in a repetitive chain

proteins (biomolecules)

• molecule made of N, O, H and C atoms

• 1 molecule = amino acid (monomer)

• 2 linked amino acids = peptide

• polypeptide = many amino acid monomers linked together in a repetitive chain

lipids (biomolecules)

• molecules made of H, C and O

• 1 molecule = fatty acid (monomer)

• 3 fatty acid chains attach to 1 glycerol to make a lipid

nucleic acid (biomolecules)

• aka DNA (but DO NOT write DNA as it could also be RNA)

• made of N, O, H, P, C

• 1 molecule = nucleotide monomer

• DNA / RNA = nucleotides linked together in a long repeating chain (polymer)

photosynthesis

process where plants use light energy,

trapped by chlorophyll,

to break down water and carbon dioxide molecules to build them up into

oxygen, glucose and water molecules

photosynthesis (light dependent stage)

• occurs in grana

• involves absorption of light energy by chlorophyll

• energy is used to split H2O into

  • H ions (saved for next stage)

  • O (released into atmosphere)

• ATP formed at this stage

photosynthesis (light INdependent stage)

• occurs in stroma

• involves combining CO2 w/ H ions made in first step

  • forms glucose

  • ATP is needed for this reaction

light microscope

• up to 2000x mag, but mag is limited because of lenses

  • resolution is limited because of wavelength of light

• light source passes thru condenser lens

  • then it passes thru a thin specimen to illuminate specimen

• used to observe samples of living tissues and cells

electron microscope

• SEM scans surface, TEM looks into a thin slice of specimen

• bombards a specimen with a beam of electrons, causing secondary electrons to be emitted from surface layers of specimen

• electrons have a much smaller wavelength than light → better resolution

• - used for viewing organelles

prokaryotic cell

• unicellular

• has cell wall

• no membrane-bound organelles

• no nucleus

• 0.1-5 um

• e.g bacteria (e.coli) or archaea

eukaryotic cell

• uni/multicellular

• some have cell wall

• has nucleus

• has membrane-bound organelles

• 10-100 um

• e.g animals

endosymbiosis

• theory to explain how eukaryotes evolved

• proposes that organelles found in euk. were once prok. living in a larger host cell

• chloroplasts + mitochondria - were once prokaryotes engulfed by another prok. to form an early eukaryote

  • both organelles have their own DNA

difference between mag and res

• mag: increase in size of image

• res: smallest distance between 2 objects where each can be observed as separate

bacteria cell structure

• pili - facilitates adhesion to host cells

• flagellum - propels them to move/swim

• plasmid - contains DNA

how does the shape of the cristae (in mitochondria) relate to its function?

• immense folding of cristae increase SA, increases no. of sites available for chemical reactions, thus increasing efficiency

how does the shape of the inner membrane (in mitochondria) relate to its function?

• seperates inner matrix from rest of organelles

  • increases efficiency of mitochondria by maintaining optimal concentration of reactants for best rate of reaction

how are wastes/cellular products removed in cells?

• simple diffusion - O2, CO2, urea

• proteins get broken down by lysosomes

• osmosis - water

• fat soluble substances - attached to small charged molecules to make them water soluble

  • so they can be removed when water diffuses out

• exocytosis - secretion of hormones and enzymes

alcohol fermentation - anaerobic cellular respiration

• breakdown of glucose in the absence of oxygen to form ethanol and CO2

• 2 ATP molecules produced as a result

• glucose → ethanol + carbon dioxide + ATP

lactic acid fermentation - anaerobic cellular respiration

• 1 glucose molecule broken down in absence of oxygen

• produces 2 molecules of lactic acid + 2 ATP

• occurs during strenuous exercise when body cannot deliver enough O2 to muscles to produce energy required

• once exercise is over → lactic acid converted to pyruvate to be used during aerobic respiration

• glucose → lactic acid + ATP

aerobic cellular respiration - word equation

glucose + oxygen → carbon dioxide + water + ATP

what happens in glycolysis?

• occurs in cytosol

• breaks down glucose into 2 pyruvate molecules

• accompanied by release of energy - 2 ATP molecules

what happens after glycolysis (in aerobic respiration)?

• 2 pyruvate molecules enter mitochondria to undergo series of chemical reactions

  • each reaction catalysed by a specific enzyme

• energy from these reactions is released in 34 ATP

  • makes a total of 36 ATP from breakdown of every glucose molecule

enzymes

biological catalysts, usually made of protein (or RNA) that speed up rate of a specific chemical reactions within a cell or an organism’s body fluids

enzymes are:

• substrate specific

• operate under optimum conditions of temperature, pH and substrate conc.

• control metabolic reactions in cells

• control rate of reaction in each step of all chemical reactions taking place in cells

• lower activation energy required for chem. reactions

properties of enzymes:

• unchanged by process → only substrate changes

• reusable → enzymes only need to be made/present in small quantities

• specific

• enzyme reactions are reversible

composition of enzymes: protein/RNA

• polypeptide chain folding itself over forming a 3D structure

  • 3D shape determines specificity of enzyme

• 3D shape unravels completely when enzyme is denatured (pH or extreme temp.)

composition of enzymes: active site

• part of enzyme that binds to substrate

• co-enzymes or co-factors (non-proteins) may be required to complete active site

  • e.g vitamin B2 (co-factor)

induced fit model

• enzyme changes shape on contact w/ substrate

• substrate is released - enzyme returns to original shape

enzyme pracs: pH (range of IV, DV, CVs)

• range of IV: pH 4, 5.5, 7, 9, 11

• DV: enzyme activity (measured by height of bubbles, representing oxygen production)

• CVs:

  • same temp of solution

  • same substrate conc.

  • same size of potato

  • same volume of H2O2

  • same time potato was left to react before measuring DV

enzyme pracs: pH (graph)

enzyme pracs: pH (explanation)

• if solution is too acidic/basic:

  • enzyme shape changes → denatures

  • substrate can no longer bind to active site

• on either side of optimal, enzyme can still work but not as efficiently/effectively

enzyme pracs: substrate concentration (range of IV, DV, CVs)

• range of IV: 0%, 10%, 20%… 100%

• DV: enzyme activity (measured by height of bubbles, representing oxygen production)

• CVs

  • same pH of solution

  • same temp. of solution

  • size of potato (i.e volume of catalase)

  • same volume of detergent

  • same time potato was left to react w/ DV

enzyme pracs: substrate concentration (graph)

enzyme pracs: substrate concentration (explanation)

• as substrate concentration (H2O2) increases, enzymes have more molecules of substrate to bind to (i.e collisions increase), so activity increases

• once saturation point is reached (i.e all active sites are full), enzymes cannot bind to any more substrate molecules so enzyme activity plateaus

• if more enzymes were added, enzyme activity would begin to increase again

enzyme pracs: temperature (range of IV, DV, CVs)

• range of IV: 2°C, 20°C, 37, 60, 80

• DV: enzyme activity (measured by height of bubbles, representing oxygen production)

• CVs:

  • same pH of solution

  • same volume of H2O2

  • size of potato (i.e volume of catalase)

  • same volume of detergent

  • same time potato was left to react w/ DV

enzyme pracs: temperature (graph)

enzyme pracs: temperature (explanation)

• at low temps, enzyme and substrate molecules do not have as much KE

  • fewer collisions → less enzyme activity

• as temp increases (up to optimal temp)

  • rate of collision increases → enzyme activity increases

• beyond optimal temp.

  • enzyme begins to change shape and bind to substrate less efficiently

• if temp is too hot, enzyme becomes denatured and won’t work anymore

catalase H2O2 equation

2H2O2 → 2H2O + O2

catalase

enzyme pracs: substrate concentration (POTATO DISC)

explain the trend

• as concentration of H2O2 increases, time taken taken for the discs to rise decreased at a decreasing rate

• this is because as H2O2 concentration increases, collisions between H2O2 and catalase increase, increasing the rate of reaction

  • leads to bubbles of oxygen being produced faster and thus discs floating more quickly

enzyme pracs: substrate concentration (POTATO DISC)

how was validity ensured?

• experimental control - 0% H2O2 concentration

  • used to check whether presence of H2O2 causes discs to rise

• control variables: pH, temperature, amount of enzyme

  • important to keep constant so they don’t cause enzyme activity to change in addition to substrate concentration

  • pH - only diluting w/ distilled water

  • temperature - keeping reactants at room temp

  • amount of catalase - using same size discs to absorb same amount of potato extract on each one