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Biological Molecules: - Carbohydrates

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- Carbohydrates -

- Monosaccharides - 

The monomer for carbohydrates is called monosaccharides. 
Common forms of monosaccharides are  -Glucose - Galactose - Fructose 
In order for a two monosaccharides to form, there needs to a condensation reaction.
The bond that is formed between =glycosidic bond.
2 monosaccharides with a glycosidic bond in between = Disaccharide

- Disaccharides -

Examples of this = 





The picture above shows the different types of disaccharides and the structures for each of them. 

Glucose is needed for each of the disaccharide formation. 
This is because Glucose is an isomer
Glucose has 2 isomers - 
- (Alpha) α-glucose
- (Beta) β-glucose




As shown above which has been circled, the positioning of the OH is the difference in the structure of both molecules. This can make all the difference in a molecule, which can change its function, structure, etc. 

- Polysaccharides -
A polysaccharide is formed from many glucose units by condensation. 
There are 3 forms of polysaccharide…

Energy Transfer In And Between Organisms: - Oxidative Phosphorylation

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Oxidative Phosphorylation
Oxidaive phosphorylation and mitochondria 
Mitochondria is the site for oxidative phosphorylation // occur in great numbers in metabolic active cells - muscles, live and epithelial cells. 

Electron transfer chain and the synthesis of ATP
Electrons transfers down a series of electron carrier molecules // forms electron transfer chain.

- Hydrogen from glycolysis & krebs cycle combine with coenzyme NAD & FAD.
- Reduced NAD & FADgive electron from hydrogen atom they gained into the electron transfer chain
- Electrons pass through series of oxidation-reduction reactions // as electrons pass releasing energy // actively transport protons into inter-membranal space.
-  Before they are transported back into the inter-mitochodrial matrix by ATP synthase channels, protons accumulate in the inter-membranal space.
- End of the chain // protons and electrons combine with oxygen to form water // oxygen is the final acceptor of electrons in the electron transfer c…

Exchange And Transport Systems: - Size And Surface Area.

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- Size And Surface Area - 
Every organism's needs to be able to exchange substances or molecules with its environment in order to sustain life.

For example, Humans exchanges oxygen and carbon dioxide with its environment.

Cells need to take in oxygen (for aerobic respiration) and nutrients. // Also need to excrete (get rid of) waste products i.e. carbon dioxide and urea // heat needs to be exchanged so that the organism can maintain a constant temperature.


Smaller animals have a higher surface area : volume ratios

A mouse has a much larger surface area : volume ratio compared to an elephant.

However they are unable to perform exchange via their surface.

Although some mammals or other organisms have a large surface area to volume ratio, they are multi-cellular which means that they have a large diffusion distance and high demand as well as this they have a specialised exchange and transport system. They also have impermeable surface - this is to prevent pathogens entering and reduc…

Exchange And Transport Systems: - Exchange Of Gases In The Lungs

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- Exchange Of Gases In The Lung - 

Role of the alveoli in gas exchange 
Epithelial cells // alveolus is a network of pulmonary capillaries // narrow // red blood cells are flatterned against the thin capillary walls in order to squeeze through.
Diffusion of gases between the alveoli and the blood will be very rapid.


Red blood cells slow down passing through pulmonary capillaries allowing more time for diffusion.

Distance between the alveolar air and red blood cells is reduced as red bloods are flattened against the walls of the capillaries.

Alveoli and capillaries are very thin = short diffusion pathways // made of specialised squamous cells





Exchange And Transport Systems: - Mechanisms Of Breathing.

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- Mechanisms Of Breathing -  There is two types of ventilation 
Inspiration = Active process - requires energy 
External intercostal muscle - Contracts  Internal intercostal muscle - Relax  Ribs - Upwards and outwards  Thoracic cavity - Increases in volume Diaphragm - Contract 




Expiration = Passive process - does not require 
External intercostal muscle - Relaxes  Internal intercostal muscle - Contracts Ribs - Downwards and inwards Thoracic cavity - Decreases in volume Diaphragm - Relaxes

Movement of the intercostal muscles = antagonistic - opposing. 




Exchange And Transport Systems: - Structure Of The Human Gas-Exchange System

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- Structure Of The Human Gas-Exchange System - 
Mammalian lung:
Lungs are site of gas exchange in mammals 
They are in the body as the air is not dense to support and protect Body as whole would otherwise lose a great deal of water and dry out. 



Lungs are specialised for gas exchange: When you breath in air this travels down the Trachea // windpipe.    ↓ Bronchi/Bronchus is the split of the trachea at the end of the wind pipe.  ↓ Bronchioles is the further branching of the bronchi into smaller tubes.  ↓ Alveoli are at the end of the bronchioles which are 'air sacs'.  ↓ The rib-cage, intercostal muscles and diaphragm all work together to move air in and out.








Exchange And Transport Systems: - Limiting Water Loss

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- Limiting Water Loss - 

Limiting water loss in insects 
Insects have evolved the following adaptations:
- Small surface area to volume ratio = minimise area over which water is loss - Waterproofing covering = outer skeleton of chitin is covered with waterproof cuticle. - Spiracles = opening of the tracheae at the body surface can be closed due to water loss occurs when the body is asleep. 



Limiting water loss in plants 

Terresteral plants have waterproof covering Some have restricted supply of water = limiting water loss through transpiration // xerophytes
Modifications of a plant is made by: - Thick cuticles - Rolling up of leaves - Hairy leaves - Stomata in pits and grooves - Reducing surface area to volume ratio of the leaves








Exchange And Transport Systems: - Gas Exchange In Plants

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- Gas Exchange in plants - 
Gas exchange is able to occur in plants due to their adaptations.

These adaptations would include - 
Thin = Short diffusion pathway// Carbon dioxide and oxygen can pass in and out of the plant cell.  Large surface area = this would allow for an effective gas exchange because its able to occur over a larger area.  Air spaces between the spongy mesophyll = allows a diffusion gradient to be maintained  Guard cells = controls the amount of Carbon dioxide and oxygen diffuses in and out of the cell. 






For a most gaseous exchange to occur:
- There are many small pores // stomata // no cell is far from a stoma // short diffusion path.
- Numerous interconnecting air-spaces occur throughout the mesophyll
- Large surface area of mesophyll cells // rapid diffusion

Stomata:

Each stoma is surrounded by pair of special guard cells which open and closes the stomata pores // controls the rate of gaseous exchange // plants evolved to balance the conflict between gas exchange and…

Exchange And Transport Systems: - Gas Exchange In Fish

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- Gas Exchange in fish -

Fish have many different adaptation that give would give the fish large surface area for gas exchange. 
In a fish there are rows of gill filaments which are stacked like pages of a book. 
On the gill filaments there are gill lamellae which has a network of capillaries on them. This provides a larger surface area for gas exchange. 

counter-current flow 
The water enters the mouth of the fish and leaves through the gills. 

As the water passes through the gills the water passes over the filaments and over the lamellae. 
Water and blood flow over and through the lamellae in the opposite direction. // Parallel.  When the blood first comes close to the water, water is fully saturated with oxygen and the blood has small amounts. 






This creates a steep concentration gradient // oxygen diffuses out of the water and into the blood. 
As the blood is absorbing more oxygen as it moves along the lamellae // blood reaches the end of the lamella 80% saturated with oxygen. The …

Exchange And Transport Systems: - Gas Exchange In Insects

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- Gas Exchange in insects -
Insects do not have a transport system so gases would need to transported directly into the respiring tissues. 




Insects use tracheae to exchange gases 
Insects have microscopic air-filled pipes = Tracheae The air moves into the tracheae through the pores on the surface = Spiracles On the insect there are spiracles which are placed along side the body // These spiracles are openings of small tubes running into the insects body. 
Oxygen moves down a concentration gradient towards the cells.

The tracheae branches off into tracheoles //
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Adaptations =
- Thin = quicker rate of diffusion
- Permeable walls = diffusion occurs down a gradient (active transport not needed to pass the molecules)
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Oxygen diffuses into the respiri…

Energy Transfer In And Between Organisms: - Link Reaction And Krebs Cycle.

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- Link reaction and Kreb cycle - 
Link reaction:  Pyruvate is oxidised to acetate // pyruvate loses a CO₂ and (X2) H // H is accepted by NAD to reduced NAD later used to produce ATP. 2-Carbon acetate combinescoenzyme A (CoA) = acetylcoenzyme A 



Krebs cycle


2-Carbon acetylcoenzyme A from link reaction combined with the 4-carbon molecule to produce a 6-carbon molecule.  6-Carbon molecule loses carbon dioxide and hydrogen to give 4-Carbon molecules and single molecule of ATP produced as result of substrate-level phosphorylation 4-Carbon molecule combines with new molecule of acetylcoenzyme A // cycle starts again. 

Pyruvate, link reaction and krebs cycle produces 
- Reduced coenzymes NAD and FAD // by oxidative phosphorylation potential to provide energy to produce ATP  - 1 ATP molecule - 3 CO₂ molecules

2 Pyruvate molecules produced for each original glucose molecule. 
Coenzymes = molecules that enzymes require to function, includes:
NAD - important throughout repsiration FAD - important in th…

Energy Transfer In And Between Organisms: - Glycolysis

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- Glycolysis -
2 Different forms of cellular respiration =
Aerobic respiration = requires O₂ produces CO₂, H₂O, ATP
Anaerobic respiration = takes place absence of O₂ produces lactate or ethanol and CO₂ // little ATP. 
Aerobic respiration summeriesed into 4 stages 
Glycolysis Link reaction Kreb cycle Oxidative phosphorylation  Glycolysis 
1. Phosphorylation of glucose to glucose phosphate = glucose is made reactive with the addition of 2 phosphate molecules (phosphorylation) // Phosphate molecules come from hydrolysis of ATP (X2) ⇒ ADP. // Energy provided to activate glucose lowering activation energy for enzyme controlled reactions 
2. Phosphorylated glucose is split = Glucose is split into 3-carbon triose phosphate (X2)
3. Triose phosphate is oxidised = H₂ removed from triose phosphate (X2) transformed into hydrogen-carrier molecule NAD to formreduced NAD
4. Production of ATP = enzyme controlled reaction converts triose phosphate into 3-carbon molecule Pyruvate // (X2) molecules of ATP …

Energy Transfer In And Between Organisms: - Light Independent Reaction

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- Light Independent Reaction -
The Calvin Cycle - 
The products of the light dependent reaction is ATP and reduced NADP // both used to reduce glycerate-3-phosphate.  This would have occur with or without light





1. The CO₂ diffuses into the leaf through the stomata // dissolves in water around the walls of mesophyll cells // diffuses through the cytoplasm and chloroplast membrane into the stomata of chloroplast.  2. In stroma CO₂ reacts with 5 carbon compound // catalysed by enzyme ribulous bisphosphate carboxylase (Rubisco) 3. Reaction CO₂ + RuBP = 2X 3-carbon glycerate 3-phosphate. 4. Reduced NADP from light dependent reaction, reduces glycerate 3-phosphate ⇒ triose phosphate using energy supplied by ATP. 5. NADP is re-formed // goes back into the light dependent reaction = gaining protons.  6. Triose phosphate converted into organic substances // starch, cellulose, lipids, glucose, amino acids, and nucleotides.  7. Most triose phophate is used to generate ribulose bisphosphate //…

Energy Transfer In And Between Organisms: - Light Dependent Reaction

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- Light Dependent Reaction -

Oxidation and Reduction 
Oxidation is when the substance gains oxygen or loses hydrogen. 
Reduction is when the substance loses oxygen or gains hydrogen.
Oxidation results in energy being given out, whearas reduction results in it being taken in. 
Making of a ATP

Photoionisation is a result of the chlorophyll molecule becoming ionised. 
The electrons leave the chlorophyll are taken up by a molecule electron carrier // the chlorophyll is oxidised // electron carrier is reduced. 
Electrons are passed along a series of oxidation-reduction chain reactions. // A transfer chain that is located in membrane of the thylakoids. 
With each carrier the energy level is lowered in the electron, the energy released is used to combine the inorganic phosphate and the ADP molecule to create ATP. 

Chemiosmotic theory This explains the ATP production 
Proton pumps // protein carrier are used to pump the protons (H+) from the stroma in the thylakoid membrane. Electrons released f…

Energy Transfer In And Between Organisms: - Photosynthesis

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- Photosynthesis - 

Site of Photosynthesis. 
Within eukaryotic plants this is the main site of photosynthesis // Within the chloroplast of cellular organelles. 
Structure of the leaf.


Large surface area = more sunlight is absorbedArrangement of leaves = avoids overlapping // leaves do not overshadow each other. Thin // diffusion distance is kept short = light absorbed within few micrometers Transparent cuticle and epidermis let light through to photosynthetic mesophyll cellsLong, narrow upper mesophyll cells packed with chloroplast = collecting sunlight. Numerous stomata = gas exchnage // short diffusion pathway from the mesophyll cells Stomata open and closes = result of light intensityMany air spaces in lower mesophyll layer to allow rapid diffusion in the gas phase of carbon dioxide and oxygen. Network of xylem = brings water to leaf cells // Phloem = carries away the sugar (product of photosynthesis) 
There are 3 stages in photosynthesis. 
- Capturing the light energy 
- Light-dep…

Organisms Respond To Changes In Their Environment: - The Role Of Hormones In Osmoregulation

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- Regulation of the water potential of the blood -


Osmoreceptors in the hypothalamus monitors the water potential in the blood. If the water potential decreases in the blood, water would move out of the osmoreceptor cells by osmosis // cells decrease in volume as a result of this // signal is sent to other cells in the hypothalamus // signal then sent to the posterior pituitary gland. - this secretes the antidiuretic hormone (ADH) into the blood.

ADH makes the walls of the distal convoluted tubule and collecting ductmore permeable to water.
More water is reabsorbed from these tubules into the medulla and into the blood by osmosis // small concentration of urine is produced = reduction of water loss. 
Specific protein receptors on cell surface membrane of these cells binds to ADH molecules // activation of phosphorylase (enzyme) within cell // vesicles within the cell move and fuse with the cell surface membrane.

Vesicles contain plasma membrane and have numerous water channel proteins…

Nucleic Acids: - Inorganic Ions

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- Inorganic Ions -
Inorganic ions are found in organisms in solution in the cytoplasm of cells and in body fluids, including parts of larger molecules. They may be in areas that range from very high to very low concentration. Functions of the ions can vary, however the specific function of a particular ion is based on the relation to it's properties.

Organisms Respond To Changes In Their Environment: - Role Of The Nephron In Osmoregulation

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- Nephron filtering the blood -




Blood from the renal artery enters smaller arterioles in the cortex of the kidney.Arterioles splits into a glomerulus // bundle of capillaries looped inside a Bowman's capsule // Ultrafiltration takes place.Efferent arterioles that takes blood into each glomerulus // afferent arteriole take the filtered blood away from the glomerulus. Efferent arterioles are smaller in diameter than afferent arterioles // blood is under high pressure. High pressure forces liquid and small molecules in the blood out of the capillary and into the Bowman's capsule. Liquid and small molecules pass through 3 layers get into Bowman's capsule enter the nephron tubules - capillary wall // basement membrane and epithelium of Bowman's capsule.Larger molecule - protein and blood cells can't pass through - stay in blood. Substances enter Bowman's capsule // glomerular filtrateGlomerular filtrate passes along the rest of nephron - useful substances are reabso…

Organisms Respond To Changes In Their Environment: - Control of Blood Water Potential

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- Structure Of The Nephron - 

Osmoregulation = the homeostatic control of the water potential of the blood. 
Structure of the mammalian kidney
In the mammal there are two kidneys found at the back of the abdominal cavity.  A section through the kidney 

Fibrous Capsule = outer membrane that protects the kidney
Cortex = lighter coloured outer region made up of renal (Bowman's) capsule, convoluted tubles and blood vessels. 
Medulla = darker coloured inner region made up of loops of Henle,collecting ducts and blood vessels 
Renal pelvis = funnel-shaped cavity that collects urine into the ureter 
Ureter = tube that carries urine to the bladder
Rental artery = supplies the kidney with blood from the heart via the aorta
Renal vein = returnsblood to the heart via the vena cava


Structure of the nephrons 
Renal (Bowman's) capsule = closed end at the start of the nephron. It cup-shaped and surrounds a mass of blood capillaries - Glomerulus. The inner layer of the renal capsule made of specialis…

Organisms Respond To Changes In Their Environment: - Diabetes And Its Control

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- Diabetes and its control - 

Types of sugar diabetes 

Type 1 - insulin dependent // body unable to produce insulin 
The body attacks its own cells - 𝛽 cells - result of autoimmune response.  This develops quickly over a few weeks once the individual is born. Usually develops at a very young age. 
Type 2 - insulin independent // body glycoproteinsreceptors have lost or losing their responsiveness to insulin // body producing an insufficient amount of insulin.  This develops in people over age of 40 - increases due to obesity and poor diet.  Symptoms are less severe and may go unnoticed.  90% of people have type II diabetes 

Control of diabetes 
Diabetes can be successfully treated which depends on the type of diabetes
Type 1 diabetes = controlled by injections of insulin - cannot be taken orally as it is an enzyme and would be digested. Typcially taken 3-4 times a day. Dose of insulin would match the dose intake of glucose // glucose concentration is monitored usingbiosensors
Type 2 di…

Organisms Respond To Changes In Their Environments: - Hormones And The Regulation Of Blood Glucose Concentration

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- Hormones and their mode of action - 
Hormones differ chemically but there are characteristics which would be the same also. 
Hormones :
- Produced in glands // secrete hormones directly into blood - Carried in blood plasma to cells which are acted on // target cells // specific receptors on their cell-surface membrane // complementary to specific hormones.
- Effective in very low concentrations // widespread // long-lasting.


 Second Messenger Model 
2 hormones are used - Adrenaline and glucagon 
Adrealinebinds to the transmembrane protein receptor within the cell-surface membrane of the liver cell.Binding of the adrealine causes the protein to change the shape on the inside of the membraneChange in shape of the protein leading to the activation of an enzyme - adenly cyclase // activated adenly cyclase converts ATP to cyclic AMP (cAMP)cAMP acts as second messenger that binds to the protein kinase enzyme, its activiated by changing its shape.Active protein kinase enzyme catalyses the …