Qualification > Reference Material
AS BIOLOGY ( C.I.E ) Notes
WARRIOR:
Note : After i finish writing the whole syllabus in the long exhausting way i will make a short hand written one . Also i will try to make classified past papers ..i say i will but i mean i hopeHi , i will be writing the AS biology course as i study it . I thought it's a good idea to share my notes + its also good revision for me. If anyone wants to add or criticize any information , please do that ! I will follow the syllabus. Obviously i can't help with the practicals :P
A Cell structure
Content
• The microscope in cell studies
• Cells as the basic units of living organisms
• Detailed structure of typical animal and plant cells, as seen under the electron microscope
NB : I have attached the structure ( i.e diagram ) of typical SECTION ofANIMAL and PLANT cells.
We have to know how to draw and identify these ORGANELLES by heart. I learn them in an easy way but
only after i learned the functions of each organelle . Here is the way ( i start from the centre of cell ))
Nucleolus-> Chromatin -> Nuclear Pore-> Nuclear Envelope-> !I know Nucleolus makes ribosomes!
Ribosomes-> !Ribosomes go to the ER for protein synthesis!
Rough and Smooth Endoplasmic reticulum -> !Now ER makes Golgi Apparatus!
Golgi Apparatus -> !Golgi Apparatus makes Golgi vesicles!
Golgi Vesicles-> !Vesicles make Lysosomes!
Lysosomes-> Only thinking of Nucleolus,i got all this. !Now what is closest to nucleus ?
***These are all both in ANIMAL AND PLANT CELLS , starting from here ANIMAL,PLANTS,BOTH***
Centriole-> !Microtubules (str.diff.2.idntfy) are used together during cell division!
Microtubules-> !Now, common sense. The most obvious in both are!
Mitochondrion->Cytoplasm-> Cell membrane*-> !Now in animals we just add!
Microvilli-> !After cell membrane in plants we just obvious differences in plants
Chloroplasts -> Grana->Tonoplast->Sap Vacuole->Cell wall->Plasmodesma-> Middle Lamellae
Now the only confusion is with Centriole and microtubules.True,there are NO centrioles in plant cells but there are microtubules in both animal and plant. Just learn this by heart. [ The diagrams are attached at the end of the post. ]
Structures revealed by electron microscope and not light microscope =
Rough & Smooth ER/ribosomes/lysosomes/vesicles/microtubules/nuclear envelope made of 2 membranes/mitochondrion made of 2 membranes/chloroplast made of 2 membranes /centriole seen as 2 structures/ nuclear pores/grana and lamellae in chloroplast
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A Cell structure
Content
• Outline functions of organelles in plant and animal cells
ORGANELLE = A Structurally & Functionally distinct part of a cell , mostly bounded by a membrane
COMPARTMENTATION = Organelles bounded by membrane , so their activities are seperated from cytoplasm , leading to division of labour
MEMBRANE SYSTEM = Organelles that are bounded by membranes or envelopes
TISSUE = A group of cells , with any inter cellular secretions ( Capectate ) produced by them that perform similar functions. In tissue cells may be all of same type (e.g cuboidal epithelium ) or may be of mixed type ( e.g xylem and phloem )
ORGAN = A structure made of different tissues that perform specific functions (i.e flower , leaf , stem , heart , eye )
NUCLEUS
The largest organelle = Bounded by a NUCLEAR ENVELOPE (i.e 2 membranes),which has NUCLEAR PORES- Outer membrane has RIBOSOMES on it -Has CHROMATIN ( DNA & HISTONE proteins in EUKARYOTIC cells),this condenses to form CHROMOSOMES during nuclear division - Has NUCLEOLUS.
* Controls CELL DIVISION & INHERITANCE (by genes on chromosomes )
* Controls cell activities [metabolism] (by genes on chromosomes ) why? genes makes protiens = enzymes = reactions
* Nucleolus makes RIBOSOMES
* Pores allow mRNA and ribosomes OUT and nutrients IN LYSOSOMES
SPHERICAL SAC- Bounded by a membrane- Contains HYDROLYTIC (digestive) ENZYMES - 0.1-0.5 mm in DIAMETER
* Digests worn out organelles
* Digests WHOLE CELLS to replace old damaged cells
* Digests bacteria by WHITE BLOOD CELLS
* ACROSOME , a special lysosome in sperm head digests a way into ovum
ENDOPLASMIC RETICULUM [ER]
FLAT SACS (cisternae)- Bounded by a membrane - Rough ER has ribosomes on it's surface - Smooth ER does not have ribosomes.
* Rough ER= 1. ISOLATES and TRANSPORTS proteins made in RIBOSOMES 2.Makes GOLGI APPARATUS
* Smooth ER= Makes LIPIDS & STERIODS ( cholestrol and sex hormones ) RIBOSOMES
Made in NUCLEOLUS - Made of RNA & PROTEINS - Found in surface of NUCLEAR ENVELOPE & ROUGH ER/ FREE IN THE CYTOPLASM/CHLOROPLAST/MITOCHONDRION - 2 TYPES =
70 s Ribosomes (smaller) 18nm in diameter found in prokaryotic cells
80 s Ribosomes (Larger ) 22 nm in diameter found in eukaryotic cells
"A functional ribosome" = Consists of a LARGE & SMALL ribosomal subunit that float independently if ribosome is not making protein.
* Protein synthesis [Translation of Genetic Code to a sequence of amino acids ]
NB : Strange that , even though it says 80 s ribosomes in eukaryotic cells , but inside CHLOROPLAST & MITOCHONDRION there are 70 s. We have to know that by heart . Also Translation of genetic code has to do with mRNA and tRNA which we will learn later.
GOLGI APPARATUS
STACK OF FLAT SACS ( cisternae ) - Bounded by a membrane -At one end being continuously made by SHUTTLE VESSICLES from ROUGH ER , and at other end continuously being budded off as GOGLI VESICLES
* PROCESSES & PACKAGES proteins in GOLGI VESICLES
* Makes LYSOSOMES
* Makes GLYCOPROTEINS
* Makes POLYSACCHARIDES
CENTRIOLE
HOLLOW Cylinders - Occur in PAIRS - the two pairs are at RIGHT ANGLES - Each cylinder is made of a RING OF MICROTUBULES
* Helps form SPINDLE FIBRES during nuclear division in ANIMAL CELLS
LARGE SAP VACUOLE
Bounded by a membrane (TONOPLAST )-has CELL SAP : water , minerals , pigments , enzymes , wastes , oxygen and carbon dioxide
* Fills with water by osmosis , makes cell turgid , supports plant
* Stores food , waste , pigments that give colour for flowers and fruits
MICROVILLI
Increase surface area for absorption or secretion
CELL WALL
5mm THICK- Made of CELLULOSE FIBRES,HEMICELLULOSE,PECTIN= STRONG- in a MATRIX that is strongly HYDROPHILIC and has WATER FILLED CHANNELS - has PLASMODESMATA " CYTOPLASMIC threads linking the CYTOPLASM OF ADJACENT PLANT CELLS , through PORES in cell walls- has MIDDLE LAMELLA which hold plat cells together ( CaPectate)
* SUPPORTS,PROTECTS cell & Give it it's SHAPE
* Allows substances in and out freely
* Allows tugidity to develop , supports plant , prevents osmotic bursting
* Plasmodesmata allow transport of substances between cells
MITOCHONDRION AND CHLOROPLASTS are ATTACHED.
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A Cell structure
Content
• Characteristics of prokaryotic and eukaryotic cells
Prokaryotic cell = Bacteria [NB : DIAGRAM IS ATTACHED ]
* Size = 0.5-5mm in diameter
* No nucleus , circular DNA
* DNA not associated with protein ( histones ), has plasmids
* 70 s ribosomes
* No ER present
* Very few organelles , none have envelopes
* peptidoglycan cell wall
Eukaryotic cell = protoctists , fungi , plants , animals
* Up to 40 mm
* Linear DNA in a nucleus
* DNA associated with proteins ( Histones ) , no plasmids
* 80 s ribosomes
* ER present
* Many organelles , some have envelopes
* cellulose cell wall in plants [/list]
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* MAGNIFICATION : The number of times larger an image is , compared to real size of object.
* MAGNIFICATION = SIZE OF IMAGE /ACTUAL SIZE OF OBJECT
* Maximum magnification of LIGHT microscope = X1500 , of ELECTRON microscope = X250,000-X500,000
* RESOLUTION: The ability to distinguish two separate points
* Maximum resolution of LIGHT microscope = 200nm , of ELECTRON = 0.5nm
* Limit of resolution is about 1/2 the wavelength of radiation used (i.e , light microscope- wave length of visible light 400nm ->200nm)
* In electron microscope we use electrons beam because 1. Have very short wavelength , so great resolution 2. are negatively charged so can be focused on object by electromagnet , but unfortunately picture is black and white , only dead matter can be studied ( as beams will burn the live matter ) , heavy metals used as stains (expensive )
WARRIOR:
B Biological molecules
Content
• Structure of carbohydrates, lipids and proteins and their roles in living organisms
The 4 most common elements are : Carbon , Hydrogen , Oxygen , Nitrogen
Macromolecule : A 'GIANT' molecule
Polymer : A MACROMOLECULE made up of MANY,REPEATED subunits called MONOMERS Examples of polymers -> Proteins (POLYPEPTIDES) , Carbohydrates (POLYSACCHARIDES),NUCLEIC ACIDS,DNA/RNA(POLYNUCLEOTIDES)
Carbohydrates are made of the following ELEMENTS: Carbon , hydrogen and Oxygen General Formula : Cx(H2O)y
The Subunits of Carbohydrate are -MONOSACCHARIDES (or hexoses which is the maximum no. of Carbon bonds we are supposed to know)
Properties of MONOSACCHARIDES
* General Formula : (CH20)x
* Readily*(very) soluble in water, sweet , reducing sugar Types of MONOSACCHARIDES ->
* Trioses -> C3H6O6 ->Is an INTERMEDIATE product in respiration
* Pentoses* [ eg.Ribose , deoxyribose] -> C5H10O5 -> Ribose (builds RNA & ATP) Deoxyribose (Builds DNA)
* Hexoses (eg. Glucose)-> C6H12O6 ->1. Used in respiration to release energy & make ATP 2. Used to build di-&polysaccharides-------------------------------------------------
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CONDENSATION REACTION : LOSS OF WATER AND FORMATION OF BONDS
HYDROLYSIS REACTION : GAIN OF WATER AND BREAK BONDS .i.e DIGESTION
Properties of DISACCHARIDES ( Monosaccharides + Monosaccharides )
* General Formula : (C12H22011) loss of a WATER molecule- LOOK AT ATTACHED DIAGRAM TO UNDERSTAND.
* soluble in water , sweet , reducing sugar Except SUCROSE[/b]
* Made of 2 MONOSACCHARIDES by a CONDENSATION REACTION
* Sucrose: Translocated in phloem , lactose : milk sugar , maltose : In germinating seeds NB : IN DRAWING OF DISACCHARIDE IT IS SUPPOSED TO BE CONDENSATION NOT HYDROLYSIS
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Properties of POLYSACCHARIDES-Macromolecules and polymers made of many MONOSACCHARIDES
* General Formula : (C6/H10/O5)
* More or less insoluble in water , not sweet , not reducing sugars
* Starch: Storage material in plant cells (Chloroplasts , tubers ,seeds).Glycogen : Storage material in animals cells. Cellulose: Cell wall
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NB: STRUCTURE OF , STARCH AND CELLULOSE AND GLYCOGEN IS VERY IMPORTANT , SEE ATTACHED TO UNDERSTAND
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STRUCTURE OF STARCH [AMYLOSE + AMYLOPECTIN]
* Amylose : Unbranched Chain-Made of Alpha Glucose molecules linked by 1,4 Glycosidic Bonds-Chain coiled into a Helix [ Not to react ] See diagram
* Amylopectin : branched Chain-Made of Alpha Glucose molecules linked by 1,4 Glycosidic Bonds & 1,6 glycosidic bonds form BRANCHES. See diagram
PROPERTIES OF STARCH [AMYLOSE + AMYLOPECTIN]
* More or less INSOLUBLE in water , doesn't leave cell
* Compact , occupies little space
* Intert , doesn't react in cell ( HELIX + COMPACTNESS AND BRANCHING )
* Has no osmotic effect
* Easily hydrolysed to sugar when needed [/list]
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STRUCTURE OF GLYCOGEN [AMYLOPECTIN ]
* Amylopectin : branched Chain-Made of Alpha Glucose molecules linked by 1,4 Glycosidic Bonds & 1,6 glycosidic bonds form BRANCHES (MORE BRANCHES THAN STARCH ) . See diagram
PROPERTIES OF GLYCOGEN [AMYLOPECTIN]
SAME AS STARCH EXACTLY BUT IT HAS MORE BRANCHES THEREFORE MORE COMPACT ( OCCUPIES LESS SPACE )--------------------------------------------------------------------------------------------------------------------------------
STRUCTURE OF CELLULOSE
* UNbranched Chain-Made of BETA Glucose molecules linked by 1,4 Glycosidic Bonds . - Chain is FLAT , OH groups stick out , hydrogen bonds form cross links with other chains to form Microfibrils & Fibres . See diagram.
PROPERTIES OF CELLULOSE
* Insoluble in Water
* Compact
* High tensile strength
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LIPIDS - Triglycerides and Phospholipids See attached diagram.
Lipids Subunits - GLYCEROL ( BOTH ) FATTY ACID chains/tails ( BOTH ) PHOSPHATE GROUP ( ONLY PHOSPHOLIPIDS )
NB:Glycerol is the SAME in all Lipids
The FATTY ACIDS differ BY :
the number of hydrocarbons in the chain
If it is Saturated or Unsaturated
Saturated -> The hydrocarbon chain DOES NOT have any C-C double bonds. Or only has single C-C bonds.
Unsaturated->The hydrocarbon chain has 1 OR MORE C-C double bonds.
Unsaturated ->Causes lipids to 1. MELT EASIER 2. CAUSE KINK IN HYDROCARBON CHAINS.
NB: If ONE double bond : monoUNSATURATED bond. If MORE than ONE : PolyUNSATURATED. If NO double bonds then : SATURATED
Fatty acid tails are -> NON POLAR ( i.e no charge ) , HYDROPHOBIC ( Hates water ) therefore INSOLUBLE
Animal lipids are often SATURATED (solid at room temperature ) . Plant lipids are often UNSATURATED ( Liquid at room temperature )
* Subunits of Triglycerides:3 [tri]Fatty acid tails ATTACHED TO &glycerol head -Bonded by ESTER BONDS . See Diagram
* Subunits of Phospholipids:2 Fatty acids tails ATTACHED TO &glycerol&Phosphate group to make a Glycerol Phosphate Head See Diagram.
NB : GLYCEROL PHOSPHATE is POLAR ( HAS CHARGE BECAUSE OF PHOSPHATE GROUP ) , HYDROPHILIC(loves water) , Soluble in water.
Roles of Lipids : ( Triglycerides )
Economic storage material ( When used in respiration , release more than double the energy released from carbs or proteins )
Heat insulation ( Adipose tissue underskin)
Electric Insulation ( myelin sheath)
Source of Metabolic water ( during respiration )
Buoyancy
: ( Phospholipids)
Form cell membranes.
SEE DIAGRAMS TO UNDERSTAND LIPIDS
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PROTEINS[/color]
Elements : Carbon , Hydrogen , Oxygen , Nitron +- SULFUR +- PHOSPHOROUS
Subunits : Amino Acids
Amino Acids is Made of A carbon atom attached to
CARBOXYL GROUP
AMINE GROUP
AND H ATOM
A RESIDUAL GROUP ( R GROUP ) ( SIDE CHAIN ) , The only part that differs between aminoacids
Proteins can be classified on to the following stuctures :
PRIMARY -> the TYPES & SEQUENCE of amino acids in a POLYPEPTIDE CHAIN
Linked by PEPTIDE BONDS
SECONDARY-> the COILING of a POLYPEPTIDE chain into an ALPHA HELIX or a B PLEETED SHEET
Linked by HYDROGEN BONDS
TERTIARY-> the folding of the ALHPA HELIX into a 3 dimensional shape
Linked by HYDROGEN , IONIC , DISULFIDE bonds AND HYDRPHOBIC interactions
QUARTENARY -> Association of MORE THAN ONE DIFFERENT polypeptide chains (e.g haemog)
Linked by same bonds as in tertiary.
DIAGRAMS OF TYPES OF BONDS ARE ATTACHED , THEY MAKE NO SENSE AT ALL BUT THEY ARE TO LEARNED BY HEART.
There are TWO types of Proteins . GLOBULAR ( FUNCTIONAL ) & FIBROUS ( STRUCTURAL )
GLOBULAR FIBROUS
Coiled into Ball or Globe shape Long chains or forms helix
Has hydrophilic R groups outside making it soluble in water Insoluble in water ( Helix shape )
Has hydrophobic R groups pointing inside forming
hydrophobic interactions protecting the globe shape
Tertiary structure is important as it helix coils to form Secondary structure is important ( only helix )
a 3D structure ( GLOBE )
HAEMOGLOBIN Collagen
Made of 4 polypeptide chains. (2 Alpha , 2 Beta ) Made of 3 polypeptidechains.
Each chain has a HAEM goup that has an IRON ion Each collagen molecule is
attached that combines with one OXYGEN MOLC. formed by a triple helix forming a triple helix held by hydrogen atoms.
Hb Molecule combine with 4 oxygen 1/3 of AA is small AA Glycine ( has short R groups),
molecules (8 oxygen atoms ) to form helix have to come close to bond to each other
OXYHAEMOGLOBIN. Each molecule of collagen forms cross-links with other collagen
End of molecule is staggered , so no weak points ->great tensile str.
HAEMOGLOBIN ROLE COLLAGEN ROLE
Transport of oxygen as OXYHAEMOGLOBIN from lungs to Structural material in skin , bld. vessels , bone
body organs
Other roles of Globular proteins Other roles of fibrous proteins
1.Enzymes( catalyse)2.Hormones3.antibodies4.Found in cell membranes 1.Keratin : from structural material in hair , nails , wool , horn
Prosthetic group : A permanent part of a protein molecule that is not made of amino acids.
WATER [polar - has uneven distrib. of charge ]
Weak Hydrogen bonds form between H+ of one water molecule and O- of another
Properties of Water :
Solvent properties : Good solvent for Polar molecules ( water molecules are attracted to them and collect around them ) Why is it important ? Metabolic reactions occur in solution and water is a transport medium in plants and animals.
Thermal properties :
1. Has high specific heat capacity ( large amount of energy needed to raise its temperature Why is it important ? Bodies of water are a stable habitat and keeps body temperatue stable
2. Has high latent heat of vaporisation ( large amount of energyy needed to change to gas )
Why is it important ? Water on earth has not evaporated so life goes on and eveaporation is effective in cooling the body
3.To change to solid ( ice ) large amount of energy is need, so less likely to freeze Why? Bodies of water are stable habitat .
Density and freezing properties
Below 4* water starts to decrease in density so ice floats and insulates water beneath it ( Bodies of water will not freeze completely therefore its a stable habitat )
Cohesion : Water molecules stick to each other [ due to large no. of hydrogen bonds] Why is it important ? For transport in vascular tissues in plants and causes high surface tenstion
High Surface Tension : The force that causes the surface of the liquid to contract to occupy lease area { due to cohesion due to large no of hydrogen bonds } why is it important ? water surface is a habitat for organisms i.e pond skater
Roles of Water
Solvent for metabolic reactions in cells
Reactant in metabolic reaction in cells like hydrolysis and photosynthesis
Keeps temp of cells constant
Keeps plant Turgid to support plant
Inorganic ions.
Calcium: Component in bones and teeth
Iron : To build haemoglobin that transports oxygen
Sodium ions : For nerve impulse transmission along neurones
Potassium : For nerve impulse transmission along neurones
Magnesium: To build chlorophyll that traps light
Nitrate ions : In plants to make amino acids and nucleotides
Phosphate : To make nucleotides , ATP
Chloride : To balance the +ve charge of cations in and around cells
WARRIOR:
ENZYMES " Globular Proteins that act as biological catalysts"
" Biological catalysts: Chemicals made in living cells that speed up rate of metabolic reaction ( converting substrate into product) and not used up or changed in reaction"
" Substrate: The molecule that can fit into the active site of an enzyme to be converted to product "
How enzymes work :
Each enzyme is a globular protein , soluble in water
Each enzyme has specific active site ( a depression ) with a specific shape to which only one type of substrate can fit into like a lock and key
Enzyme-Substrate complex is formed holding enzyme and substrate tightly , R groups of enzymes interact with substrate ( Bonds are either built or broken)
Product leaves active site
Enzyme is a biological catalyst because it lowers the activation energy ( energy needed to start a reaction ) substrate is held tightly in a way that molecules react more easily)
See attached diagrams for the next half of enzyme chapter explanation.
Effect of enzyme controlled reaction
Time-Course of an enzyme-catalysed reaction
Effect of enzyme concentration on initial rate of reaction of an enzyme-catalysed reaction
Effect of Substrate concentration on initial rate of reaction of an enzyme-catalysed reaction
Effect of Temperature on initial rate of reaction of an enzyme-catalysed reaction
Effect of pH on initial rate of reaction of an enzyme-catalysed reaction
Effect of enzyme inhibitors on initial rate of reaction of an enzyme-catalysed reaction
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Effect of enzyme inhibitors on initial rate of reaction
A -INHIBITORS THAT BIND TO ACTIVE SITE OF AN ENZYME
Temporarily- Competitive , reversible inhibition. Shape of inhibitor is like shape of substrate. Both compete for active site depending on the concentrations . If substrate concentration is increased , inhibition is reduced or reversed .
Example : Ethanol inhibits an enzyme that changes ethylene glycol to oxalic acid that damages the kidney
Permanently-Non-competitive irreversible inhibition. As above but increasing substrate concentration does not reduce or reverse inhibition.
Example : Penicillin inhibits enzymes that build bacterial cell walls
B - INHIBITORS THAT BIND TO A PLACE OTHER THAN ACTIVE SITE OF ENZYME
Temporarily- Competitive , reversible inhibition .Alters shape of enzyme & active site , cannot bind to substrate . The end product binds to enzyme to stop a metabolic reaction. Or lead arsenic or other heavy metals used
Permanently -Non-competitive irreversible inhibition . As Above!
WARRIOR:
Cell Surface Membrane (7nm) [Fluid mosaic model]Why fluid mosaic?
Fluid : Phospholipids and proteins move about in monolayer,
Mosaic : The patter of scattered proteins when seen from above.
GENERAL FUNCTION : 1.Allows entry and exit of substance 2.Gives cell its shape
See attached diagram to understand.
Structure and Function of Phospholipid Bilayer
* Phospholipid Polar heads pointing Outwards and their non-polar tails pointing inwards, facing each other
* Hydrophobic interaction occur between monolayers [holding each other]
* Phospholipid tails [ some saturation and some unsaturated ]move by diffusion in monolayer
* Allows passage of oxygen and carbon dioxide gas by diffusion
* Allows passage of water by osmosis
* Acts as a barrier to polar molecules ( Glucose and Amino acids ) and polar ions
* Helps in regulating the fluidity of the membrane
Structure and Function of Proteins
* Globular proteins scattered in mosaic pattern. Some EMBEDDED in external surface , some in inner surface and some span the whole membrane
* Allows facilitated diffusion and active transport of polar molecules and ions
* Acts enzymes
* Held by hydrophobic interactions between R groups of amino acids and tails of phospholipids
Structure and Function of Glycoproteins
* Globular proteins with short , branching carbohydrate chains on the external surface of th emembrane
* Specific receptors for chemicals
* Their carbohydrate chains form hydrogen bonds with water & stabilises the membrane
* Act as antigens for cells to recognise each other
Structure and Function of Glycolipids
* Specific receptor for chemicals
* Their carbohydrate chains form hydrogen bonds with water & stabilises the membrane
Structure and Function of Cholesterol
* Has polar head and 2 non-polar tails
* Embedded between phospholipid moloecules
* Regulates fluidity of membrane
* Regulates Stability of membrane
* Acts as a barrier to polar molecules and ions.
* Held by hydrophobic interaction between tails of cholesterol and tails of phospholipds.
Factors that affect fluidity of the membrane
* Type of fatty acids in membrane : The more unsaturated fatty acids the more fluid the membrane because they have kinks so fit together more loosely
* Temperature : The more the temperature the more the movement of phospholipids by diffusion , the more the fluidity of membrane
* Amount of Cholesterol : The more cholesterol the less the fluidity
Methods of transporation1.Diffusion [ oxygen and carbon dioxide] (passive ): The movement of molecules from a region of THEIR higher concentration to a region of THEIR lower concentration down a concentration gradient
Rate depends on : Concentration gradient
Temperature
Surface area of diffusion
Size of molecules
2. Facilitated diffusion [ Polar molecules and ions ] (passive ) : Molecules pass on specific transport(carrier , channel) proteins down their concentration gradient
Rate depends on : No. of carrier/channel/transport proteins
If channels open or not.
3.Active Transport (polar molecules and ions ) : Movement of particles from a region of their lower concentration to a region of their higher concentration , against a concentration gradient.
Molecules pass on specific transport proteins against their concentration gradient , so need ATP to make the transport protein change it's shape and deliver molecule to other side.
ACTIVE : Consumes metabolic energy ( ATP)
Rate depends on : No. of specific transport proteins
No. Of mitochondria
4.Osmosis ( passive ) [water] : Movement of water molecules from a region of their higher concentration to a region of their lower concentration down a concentration gradient through a partially permeable membrane.
5.By bulk transport : Transport of large quantities of materials in or out of a cell,
A. Endocytosis : Transport of large quantities of materials into a cell.
a) Phagocytosis : Transport of large quantities of solid materials into a cell.
b) Pinocytosis : Transport of large quantities liquid materials into a cell
B. Exocytosis : Transport of large quantities of materials out of cells
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About osmosis :
Importance= Absorption of water from soil and movement of water across root to xylem in plants
Fills sap vacuole with water , makes cell turgid , supports plant
Movement of water in and out of organisms
Hypertonic : More concentrated than cell or tissue
Hypotonic : Less concentrated than cell or tissue
isotonic : Same concentration as cell or tissue
Water potential : The tendency of water molecules to move from one place to another
Solute potential : How much a solute helps water molecules to move from one place to another
Pressure potential: The turgor pressure that pushes water out of a plant cell
[See attached diagram for symbols and equation]
Water potential of pure water is zero.
Any solute put in it will lower its water potential
Water potential of any solution is negative.
Effect of osmosis on cells
Animal : If water potential outside animal cell is higher than inside cell , water moves into cell by osmosis --> cell swells or bursts
If water potential outside animal cell is lower than inside cell, water moves outside cell by osmosis--> cell shrinks
Plants : If water potential outside plant cell is higher than inside cell, water moves into cell by osmosis --> cell turgid
If water potential outside plant cell is less than inside cell, water move outside cell by osmosis --> cell is plasmolysed
Plasmolysis :When protoplast ( living part of cell ) shrinks and is pulled away from cell wall..
WARRIOR:
GENETIC CONTROL AND INHERITENCEFunctions of DNA
1. Is the genetic material inherited in nuclear (cell ) division
2. Initiates and guides protein synthesis ( including enzymes so controls all cell activities ( metabolic reaction )
Structure Of DNA
* A MACROMOLECULE and POLYMER made of of monomers called : NUCLEOTIDES
* NUCLEOTIDES : A pentose sugar ( Deoxyribose ) + Phosphate group + Nitrogenous base (part that varies ). See Diagram to understand.
* A polynucleotide is made by condensation reaction controlled by DNA POLYMERASE enzyme , P group of nucleotide is joined to C3 of next nucleotide , this is repeated to form a poly nucleotide strand [ Sugar phosphate backbone + bases stick out at side ]
* DNA is a DOUBLE HELIX made of two , twisted , complementary , anti-parallel polynucleotide strands which are help by their nitrogenous bases linked by hydrogen bonds
Types of bases
Pyrimidine ( single -ringed ) - Thymine ( T ) & Cytosine (C)
Purine ( double -ringed ) - Adenine ( A ) & Guanine ( G)
One pyrimidine base pairs with one purine !
T with A ( complementary ) & C and G (complementary )
T and A linked by two hydrogen bonds . C and G linked by three hydrogen bonds
The Process of SEMICONSERVATIVE REPLICATION of DNA
* DNA molecule UNWINDS and UNZIPS (hydrogen bonds broken by DNA HELICASE enzyme)
* In nucleus , there are ACTIVATED NUCLEOTIDES ( to which to extra phosphate groups have been added to activated them
* Each polynucleotide strand acts as a template ( mould ) to form a complementary strand : Bases of activated nucleotides pair with their complementary bases on the strands by hydrogen bonds / DNA polymerase enzymes links the sugar and the original phosphate groups together
* The 2 extra phosphate groups are realeased
* DNA molecules rewinds
Why called semiconservative ?
Each polynucleotide strand ( half DNA molecule ) is conserved and acts as a template to make a complementary strand .
Differences between RNA & DNA
RNA DNA
Pentose sugar is ribose Deoxyribose
Made of on polynuclotide strand 2 ( double helix)
Has Cytosine , Guanine , Adenine No Uracil
,Uracil but no Thymine
RNA has three types
mRNA ( messenger RNA )
rRNA ( ribosomal RNA )
tRNA ( Transfer RNA )
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Define :
Genetic Code : A sequence of bases or nucleotides in a DNA molecule that codes for a sequence amino acids in a polypeptide
Gene : A part of DNA , a sequence of nucleotides at a specific locus that code for just one polypeptide
Genome : Total set of genes in a cell , that represents the genetic code of the organism
Codon : A sequence of bases on an mRNA that code for 1 amino acid
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Protein synthesis ( SEE DIAGRAM TO UNDERSTAND )
1. Transcription of mRNA from DNA in nucleus
a)Part of DNA unwinds and unzips ( hydrogen bonds broken by DNA helicase Enzyme )
b)One polynucleotide strand acts as a template to form one complementary mRNA strand thats is built by RNA polymerase enzyme
c) mRNA carries genetic code in the form of codons through the nuclear pore to cytoplasm to ribosome
2.In cytoplasm
a)There are tRNA molecules
b)At one end of a tRNA molecule there is a base triplet ( anticodon ) and at other end a site at which a specific amino acid can bind
c)Each tRNA with a specific anti-codon binds to a specific amino acid
3.mRNA binds to ribosome
a)mRNA binds to ribosome , 6 bases at time (2 codons ).
b)The first three bases are always AUG ( start codon ).
c)A tRNA with a complementary anti-codon UAC and carrying amino acid methionine enter. Codon and anti-codon base-pair by hydrogen bonds
4.A second tRNA
a)A second tRNA binds with next 3 bases (codon ) it carries a specific amino acid. The two amino acids held close together form a peptide bond ( between carboxyl group of an AA which loses a hydroxyl group and an amine group of other AA which loses a hydrogen atom) in a condensation reaction controlled by peptidyl transferase enzyme ( made in small ribosomal unit )
5. Ribosome moves along mRNA
a)A third codon
b)A third codon brings another complementary anti-codon ( tRNA ) with a specific amino acids
c)third amino acid forms a peptide bond
d)first tRNA leaves ribosome without its amino acid and goes to cytoplasm to replace it.
6. Termination
Polypeptide chain continues to grow until a stop codon ( UAA,UGA,UAG ) is exposed on ribosome.
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