human biology 1.1.2 molecules

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Describe the structure of an amino acid?

consists of a central carbon atom which is attached to an hydrogen atom an amino goup and carboxyl acid group and r group

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Describe the condensation reaction between two ami

condensation reaction joins two amino acids to make a dipeptide an hydrogen atom is removed from one amino acid and then oxygen and hydrogen removed from carboxyl acid group of another amino acid to make a molecule of water.

Bond formed is a peptide bond 

many amino acids can join together to form a polypeptide

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outline the primary and secondary structure of pro

primary- sequence of amino acids along its length 

secondary- weak hydrogen bonds produces alpha- helix or beta pleated sheet

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Outline tertiary and quartenary structure of prote

Tertiary- 3d shape held together by bonds between r groups which are:

- strong disulfide, weak hydrogen, ionic bonds, hydrophobic+hydrophillic interactions

Quartenary- proteins that contain more than one polypeptide chain

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Difference between globular and fibrous proteins?

Globular- spherical shape soluble in water and tend to have biochemical functions. folded so hydrophilic r goups are on outside enabling them to be soluble in water based liquids such as blood plasma and cytoplasm- haemoglobin myglobin

Fibrous- extended sheets which are strong and insoluble- keratin and collagen

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Outline role of hb in carrying oxygen?

complex quarternary structure 

made up of 4 polypeptides- 2 beta pleated and 2 alpha helix 

each polypeptide has a heam group attached to it ( prosthetic group) and haem contains an iron ion which associates with oxygen making hbo2

as 4 polypeptides 4 haem groups so can carry 4 oxygens as one haem binds to oxygen it changes the structure slightly making it easier to pick up more o2

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What is thalassemia?

inherited disorder where alpha and beta pleated sheets in hb are shorter so unable to carry as much o2 as normal which can leads to problems with growth and development systems in the body

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How does diabetes affect hb?

high blood glucose levels can cause glucose to bind with hb making glycosylated hb which picks up o2 more readily but doesnt release o2 into respiring tissues very well which can lead to parts of the body being damaged such as diabetic retinopathy which causes blood vessels in eye to become damage eventually leads to blindness

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What is sickle cell anaemia

mutation in amino acid sequence which causes valine to be produced instead of glutamic acid this causes rbcs to clump together and block capillaries and straves tissues of 02- sickle cell crisis

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Describe diffusion

Net movement of substance from a region of high conc to low conc. 

This continues until evenly distributed and is a passive process

e.g small lipid molecules diffuse across plasma membrane through phopholipid bilayer

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Describe facilated diffusion?

diffusion across a membrane via carrier proteins or protein channels 

proteins channels are permentally open lined with hydrophilic AA and water

Carrier proteins molecules bind to receptors on carrier proteins which changes the shape and releases molecule on other side of membrane/ into cytoplasm

e.g diffusion of glucose into rbcs

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Describe osmosis

movement of water from a region of high water potential to low water potential over selectively peremeable membrane.

water moves to conc of high solutes as this is where conc of water is the lowest. this occurs until an equilibrium is reached

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What is an isotonic solution?

a solution which doesnt causes an osmotic flow as water potential of solution is same as the cell

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What is an hypotonic solution?

solution has a higher water potential than the cell so water moves via osmosis into cell causes it to swell and eventually rupture

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What is an hypertonic solution?

solution has a lower water potential than the cell so water leaves the cell via osmosis causing it too shrink and dehydrate (crenation) 

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Describe active transport

ATP provides energy to move molecules across membrane against its concentration gradient (low to high)  with the help of proteins. All cells contain carrier proteins that actively transport sodium out of cell and potassium into the cell

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Describe endocytosis?

molecules move towards membrane

membrane invaginates forming a vesicle around the membrane

vesicle moves into cytoplasm, to be engulf by phagocytes

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describe exocytosis

vesicle containing molecule moves towards membrane

vesicle fuses with membrane 

molecules are realeased outside the cell 

usually secretory products- such as hormones or waste products

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Describe how cholesterol is taken into the cell?

taken in by endocytosis, however is a lipid and non polar which is too big to diffuse across membrane.

transported in the blood by  lipo-proteins such as low density lipoproteins (LDLS)

ldls bind to receptors on specific proteins on cell membrane  taken in via endocytosis and cholesterol is realeased to be used by the cell and the proteins returns to membrane to act as an receptor again

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What is hypercholesterolemia?

inherited disorder with high cholesterol levels in the blood- suffer lots of heart attacks in early life

scientists have found these people do not have specific protein receptors on membrane for LDL therefore they can not take ldl up from the blood

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Explain meaning of water potential

tendency of a solution to lose or gain water 

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Outline how gylcogen structure is adapted to its f

branched- can release glucose quickly as many ends

compact- lots of glucose can be stored in small place

insoluble- doesnt affect water potential

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Outline how conc of blood glucose is measured?


test strip placed on biosensor

disinfect skin using alcohol based solution

use sterile lacnet to ***** skin

small amount of blood produced which should be squeezed onto test strip

test strip has enzyme glucose oxidase which converts glucose in the blood to gluconolactone

as this happens a small electric curent is produced and transferred to electrode on test strip 

measurement on digital display appears and has memory to store measurements

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Describe structure of monosaccharide?

simple sugar such as glucose or fructose 

ring form of alpha glucose C6H12O6

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Describe structure of disaccharide?

2 mono join together by condensation reaction to form a glycosidic link 

very soluble 

2 glucose = maltose

1 maltose + 1 fructose= sucrose

hydrolysis breaks it done 

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Describe structure of polysaccharide?

many mono join together by condensation reactions

one glucose form glysocidic links with 3 other molecules

makes branched

e.g alpha glucose makes glycogen

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Explain how glucose is respiratory substrate?

Easily broken down in cellular respiraiton and energy released used to make ATP.

easily transported

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Describe structure of fatty acid and glycerol?

fatty acid- long hydrocarbon chain which can be saturated or unsaturated

saturated have single bonds and each carbon has hydrogen attached so has many hydrogen

unsaturated- double bonds between carbon so less hydrogen

mono unsaturated- single double bond in chain

poly unsaturated- many double bonds in chain

insoluble in water


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Explain how a triglyceride is formed?

condensation reaction form ester bond between one glycerol and 3 fatty acids 

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Function of triglycerides?

Energy source- can be disablemed to fatty acids that can be broken down to provide energy 

insulation- fat deposits under the skin provide insulation preventing heat loss to the environment

protection- fat deposits around vital organs protect them from blows and shocks

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Describe structure of phospholipid?

2 fatty acids 1 phosphate group  1 glycerol molecule

phosphate group (head) hydrophillic fatty acid (tail) hydrophobic 

form bilayer where tail moves away from the water and head arrange facing the water 

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how are electrolytes measured?


small sample of blood plasma/urine placed into machine

measures voltage that develops between inner and outer suface of ion selective electrode

electrode is selectively permeable to the ion being measured

potential measured is compare to reference electolyte- current is constant

difference in voltage between two electrodes must equal the conc of ions

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Explain importance of electrolytes?

directly affects water balance

electrolytes are ions with a postive or negative charge

postive-cations negative- anions

moinitoring electrolytes is essential for diagnosis and management of conditions such as diabetes and kidney disease

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How is water an ideal transport medium?

oxygen is slighty negatively charged and hydrogen is slighty postively which form covalent bonds and makes in polar

water molecules are attracted to each other as hydrogen attracts slighty negative oxygen from another water molecule and form weak hydrogen bonds therefore they stick to each other

water can from shells around other ions and polar molecules causing them to disslove which makes it a very good solvent

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How is water an ideal transport medium?

oxygen is slighty negatively charged and hydrogen is slighty postively which form covalent bonds and makes in polar

water molecules are attracted to each other as hydrogen attracts slighty negative oxygen from another water molecule and form weak hydrogen bonds therefore they stick to each other

water can from shells around other ions and polar molecules causing them to disslove which makes it a very good solvent

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How is tissue fluid formed?

As blood enters aetrial end of capillary its under strong hydrostatic pressure which causes small components of blood to be pushed out od the capillary leaving plasma proteins which are too big

here tissue fluid is made which bathes in the cells supplying them with AA, o2 etc

as blood left carries on to venule end of capillary it has low hydrostatic pressure as most of the fluid has been lost this causes tissue fluid to enter the capillary as osomitic pull is stronger

tissue fluid which is left drains into the lymphatic capillaries to become lymph, it moves through lymph vessels by contactions in the body and contains valves to prevent backflow until eventually in enters the bloodsteam

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What is serum

blood plasma in which fibrinogen (clotting factor) has been removed

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What is the composition of blood plasma?

plasma proteins- antibodies, albulmin, fibrinogen



dissolved food substances-glucose, AA, glycerol (stays in gut until needed)

dissolved o2

waste products-urea and co2 

heat keep body temp constant

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