combined sets idk

what type of protein is haemoglobin

quaternary protein

what is a quaternary protein

a protein consisting of four polypeptide chains

in haemoglobin, what are the four polypeptide chains composed of?

2 alpha globin chains and 2 beta globin chains

what is a prosthetic group in haemoglobin

where each polypeptide chain contains a haem group, which includes an iron (Fe2+) ion that binds to oxygen

haemoglobin is a globular protein. how does this help its function?

haemoglobin is water-soluble, allowing it to dissolve in blood plasma for efficient transport in the blood.

haemoglobin’s relationship with oxygen

• haemoglobin has an affinity for oxygen

• haemoglobin associates with oxygen in the lungs

• haemoglobin dissociates with oxygen in the tissues

what does haemoglobin’s ability to associate with oxygen depend on?

concentration of oxygen in the surrounding tissues

how do you measure concentration of oxygen in the surrounding tissues?

partial pressure - pressure contributed by 1 gas in a mixture of gases

oxygen transport in the lungs

haemoglobin loads/associates with oxygen in the lungs due to high partial pressure of oxygen in the lungs

oxygen transport in tissues

haemoglobin unloads/dissociates with oxygen at respiring tissues due to lower partial pressure of oxygen in respiring tissues

what is co-operative binding?

a property where the binding of one molecule to a protein influences the binding of subsequent molecules

what happens during the first oxygen molecule binding?

initially, haemoglobin has a lower affinity for oxygen so the first oxygen molecule binds with difficulty because the haem groups are less accessible

what happens during the second and third oxygen molecules binding?

after the first oxygen molecule binds, haemoglobin undergoes conformational shift which makes haem groups more accessible and increases haemoglobin’s affinity for oxygen. this means that the second and third oxygen molecules bind more easily.

what is a conformational shift?

when the tertiary and quaternary structure change

what happens when the fourth oxygen molecule binds?

it is harder to bind because the majority of binding sites are occupied so it is less likely that a single oxygen molecule will find the fourth binding site.

what does maximum saturation mean?

all haemoglobin proteins associated with 4 oxygen molecules

what gets absorbed in the ileum?

glucose, amino acids, fatty acids & monoglycerides

where does glucose, amino acids, fatty acids and monoglycerides take place?

ileum

what features of the ileum make a large surface area for absorption?

• it is lined with folds called villi

• there are further folds called microvilli on the epithelial cells that lines each villus

what do epithelial cells contain and why?

• they have many mitochondria which produce ATP for active transport

• they have many transport proteins for absorption of glucose & amino acids, such as carrier proteins & co-transport proteins

what feature of villi increases diffusion?

• the wall of the villi consists of a single layer of epithelial cells providing a short diffusion pathway

why is co-transport important in the ileum?

• the epithelial cells of the ileum absorb glucose and amino acids from digested food

• since their concentration in the intestine may be lower than in the blood, active transport and co-transport are needed

how do sodium ions move in glucose and amino acid absorption?

• the sodium-potassium pump (a carrier protein that actively transports Na+ ions out & K+ ions in using ATP) actively transports Na+ ions out of the epithelial cells into the blood. This requires energy from ATP.

• this creates a concentration gradient whereby there is a lower concentration of Na+ in the epithelial cells and a higher concentration of Na+ in the lumen of the ileum

• Na+ ions diffuse back into the epithelial cells from the lumen of the ileum via a co-transport protein

• as Na+ moves in, glucose or an amino acid is transported in with it

• the glucose or the amino acid is moving against its concentration gradient

how do glucose and amino acids move into the bloodstream?

• facilitated diffusion through specific carrier proteins

• this ensures efficient absorption and maintains blood glucose levels

what is co-transport?

co-transport is a type of facilitated diffusion where the movement of a molecule across a membrane is coupled with the movement of another molecule

function of proteases

break down proteins, polypeptides or dipeptides into smaller units and eventually into amino acids

where are proteases produced and where do they act?

stomach → stomach

pancreas → small intestine

epithelial cells lining the ileum → small intestine

what are the 3 types of proteases

• endopeptidases

• exopeptidases

• dipeptidases

what do endopeptidases do

hydrolyse internal peptide bonds in the middle of proteins to form shorter polypeptides, increasing the number of ends for other proteases to work on

what do exopeptidases do

hydrolyse peptide bonds at the end of polypeptides to remove terminal amino acids/dipeptides

what do dipeptidases do

break down any remaining dipeptides into amino acids

step one of lipid digestion?

emulsification

what happens during emulsification

• partially digested food arrives in the small intestine and mixes with bile

• bile salts bind to large lipid droplets and breaks them into smaller droplets - this is emulsification

what are small lipid molecules known as

micelles

why can lipases act after emulsification

the micelles have a large surface area

what is step two of lipid digestion

lipase enzymes in the lumen of the small intestine break down lipids to glycerol, monoglycerides and fatty acids

examples of carbohydrases

amylase, maltase, lactase

where is amylase made

• salivary glands

• small intestine

• pancreas

what is starch hydrolysed into

it uses amylase to be hydrolysed into the disaccharide maltose

what is maltose hydrolysed into

it uses maltase to be hydrolysed into the monosaccharide glucose

what is maltase

a membrane-bound disaccharidase, meaning it is attached to the cell surface membrane of the epithelial cells lining the small intestine.

it also breaks down maltose into 2 glucose monosaccharides

two types of digestion + definitions

• physical digestion - breakdown of large food pieces into smaller ones to increase the surface area for chemical digestion

• chemical digestion - enzymes catalyse hydrolysis reactions that break bonds in large insoluble molecules to form smaller soluble molecules

structure of human digestive system

mouth & salivary glands → oesophagus → stomach → liver → pancreas → duodenum → ileum → rectum

path that food travels through

mouth → oesophagus → stomach → small intestine → large intestine → rectum → anus

function of mouth & salivary glands

teeth do physical digestion. salivary lands secrete amylase to begin to digest starch → maltose

function of oesophagus

transports food to stomach

function of stomach in digestion

protease enzymes begin protein digestion and hydrochloric acid provides suitable pH for enzymes and destroy any pathogens in food

function of liver in digestion

produces bile salts to aid lipid digestion and neutralise stomach acid as it leaves the stomach

function of the pancreas in digestion

produces amylase, protease and lipase and releases them into the duodenum

function of the duodenum in digestion

acidic stomach contents are neutralised by bile and become slightly alkaline. enzymes complete chemical digestion here.

function of ileum in digestion

food and water are absorbed into the blood via villi in the lining of the ileum

function of the rectum in digestion

stores faeces before removal via egestion through the anus

why do lipids form an emulsion in the emulsion test?

lipids are insoluble in water but soluble in ethanol. when mixed with water, lipid droplets disperse, forming a white emulsion.

properties of lipids

• non-polar

• hydrophobic

• made of CHO

• insoluble in water but soluble in organic solvents e.g. alcohols

lipids as energy storage

lipids store twice as much energy per gram as carbs, making them an efficient energy store

lipids used for insulation

fat deposits under the skin provide thermal insulation in mammals (e.g. blubber in whales) which reduces heat loss

lipids for protection

lipids cushion vital organs, protecting them from physical damage

lipids used for waterproofing

waxes and oils prevent water loss in plants and animals (e.g. cuticle on leaves, sebum on skin)

lipids in membrane structure

phospholipids form biological membranes, controlling substance transport into and out of cells

definition of polysaccharide

a complex carbohydrate formed from the condensation reactions of many repeated monosaccharides joined by glycosidic bonds

main types of polysaccharides found in living organisms

glycogen, starch and cellulose

property of polysaccharides that makes them suitable for storage?

they are insoluble, making them suitable for storage

properties of glycogen

• storage in animals

• made of many alpha glucose

• highly branched structure with 1,4 and 1,6 glycosidic bonds, allowing enzymes to rapidly hydrolyse glycogen into glucose (to be used in respiration)

• found in animal cells, particularly in liver and muscle cells

• insoluble, preventing osmotic effects in animal cells as it does not affect the water potential

• large molecule meaning it cannot diffuse out of cells

properties of starch

• storage in plants

• made of many alpha glucose molecules

• exists as amylose and amylopectin

• amylose - helical, unbranched structure with 1,4 glycosidic bonds, making it compact, which means that it can be stored in a small space

• amylopectin - branched, with 1,4 and 1,6 glycosidic bonds allowing rapid hydrolysis by enzymes to release glucose for respiration

• insoluble, preventing osmotic effects in plant cells as it does not affect the water potential

• large molecule meaning it cannot diffuse out of cells

properties of cellulose

• structural in plants

• made of many beta glucose molecules

• long, straight, unbranched chains with 1,4 glycosidic bonds

• straight chains held together by many hydrogen bonds to form microfibrils

• microfibrils joined together to make macrofibrils

• many hydrogen bonds help give structural strength to cellulose and plant cell walls, preventing plant cells from bursting under osmotic pressure

definition of monosaccharides

monomers of carbohydrates, containing carbon, hydrogen and oxygen

properties of monosaccharides

• soluble in water

• serve as fundamental components in metabolism and biosynthesis

structure of glucose

• alpha glucose and beta glucose

• both isomers of each other

• alpha glucose - H on top, OH on bottom

• reverse for beta glucose

definition of disaccharides

carbohydrates formed when two monosaccharides join via a glycosidic bond

examples of disaccharides

• maltose - alpha glucose x2

• sucrose - glucose + fructose

• lactose - glucose + galactose

how do disaccharides form and break down

• condensation

• polymerisation

what bond is formed between two monosaccharides

glycosidic bond (1,4 and 1,6)

what elements are in carbohydrates

carbon, hydrogen and oxygeen

what are the 3 types of carbohydrates

monosaccharides, disaccharides, and polysaccharides

functions of carbohydrates

• energy supply for cells

• energy storage (starch, glycogen)

• structural components (cellulose)

• building blocks for biological molecules (deoxyribose and ribose)

main function for each type of carbohydrate

• monosaccharides - energy source

• disaccharide - transport form

• polysaccharide - storage form

advantages of optical microscopes

• can observe living cells

• simple sample prep

• inexpensive in comparison to electron microscopes

disadvantages of optical microscopes

• lower magnification

• lower resolution

• light has a longer wavelength than electrons, so lower resolution of light microscope

• can’t see smaller organelles such as ribosomes/lysosomes

magnification

how many times larger the image is compared to the actual object

resolution

the ability to distinguish between 2 separate points

how do transmission electron microscopes work

• beam of electrons passes through a very thin specimen

• denser areas absorb more electrons & appear darker, while less dense areas appear lighter

• produces a 2D, black & white image with extremely high resolution

uses of TEM

• studying the ultrastructure of cells (e.g. smaller structures like ribosomes)

• examining internal details of viruses and bacteria

how does a SEM (scanning electron microscope) work

• a beam of electrons is directed onto the surface of a specimen

• electrons are reflected off the surface and detected to produce a 3D image

• provides detailed surface structure rather than internal details

uses of SEM

• studying surface structures of cells, viruses, & tissues

• examining insects, pollen grains, & other surfaces in high detail

advantages of electron microscopes

• much higher magnification than light microscopes

• higher resolution so finer details can be seen

• can reveal details of smaller organelles (TEM) & 3D surface structures (SEM)

disadvantages of electron microscopes

• specimens must be dead since electron microscopes require a vacuum

• complex sample prep - very thin sections for TEM & coating with metals for SEM

• expensive - requires specialist training & maintenance

• images are black & white

the nucleus

• DNA contains genetic instructions for proteins

• sequence of bases in DNA will determine the sequence of amino acids in a polypeptide

ribosomes & RER

• ribosomes in the cytoplasm & RER join amino acids together to form a polypeptide. this requires energy from ATP.

• polypeptide folded and processed in the lumen of the RER

• vesicles bud off from the RER carrying the protein

• vesicles fuse with the golgi apparatus for further processing

golgi apparatus

• proteins are modified

• proteins then sorted & packaged into secretory vesicles

• hydrolytic enzymes are packaged into vesicles called lysosomes which remain in the cell

transport to cell surface/other locations

• secretory vesicles move towards cell surface membrane

• proteins can then be secreted out of the cell via exocytosis

exocytosis at the cell surface membrane

• vesicles fuse with the plasma membrane

• proteins are released outside the cell

capsid

a protein coat that protects the genetic material and aids in attachment to host cells

attachment proteins

glycoproteins on the capsid/lipid envelope that bind to receptors on host cells, allowing entry

lipid envelope

a phospholipid membrane surrounding the capsid, derived from the host cell membrane. helps evade the immune system.

enzymes

replication inside host cell

cell wall

• provides structural support & prevents osmotic lysis

• made of murein

circular DNA (nucleoid)

• contains genetic material that codes for polypeptides

• not enclosed in a nucleus

capsule (slime layer)

• protects against desiccation and phagocytosis

• helps bacteria stick to surfaces

flagellum

enables movement via a rotating motion