MOLECULES AND CELLS Flashcards by Shannon Nelson

Monosaccharide examples

a glucose (OH low) and b glucose (OH high), fructose

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Disaccharides definition

Formed when two monosaccharides join by condensation reaction (broke down by hydrolysis)

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Disaccharides example

maltose (2 a glucose with a a1,4-glycosidic bond) and sucrose (a gluocse and fructose)

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Polysaccharides examples

Starch, glycogen and cellulose

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Starch types

Amylose- (a1,4-glycosidic bonds) chains are coiled to form a spiral, held together by H bonds, branched
Amylopectin- ( a1,4-glycosidic bonds and a1,6-glycosidic bonds) much more branched than amylose

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Why is starch such a good storage molecule

-Compact
-Insoluable
Large molecule (will not easily pass through the cell membrane)
-branching= many terminal ends= easily hydrolysed when in high demand

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Glycogen structure

The same as amylopectin, just more branched and much shorter. stored in the form of small granules

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Glycogen function and location

-Found in animal and fungal cells
-Stored in the liver and muscle cells in mammals for fast hydrolysis= faster energy can be supplied

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Cellulose structure

Two b glucose molecules, with every other molecule being inverted (b1,4-glycosidic bonds)

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Effects of flipping the monomers in cellulose

-Unbranched chains are straighter
-Hydrogen bonds can form cross-linkages between adjacent chains

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Cellulose location

Cellulose chains are grouped together in microfibrils (plant cell walls) increases tensile strength

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Lipid properties and types

-Hydrophobic
-triglycerides(fats and oils), phospholipids waxes and steriods

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Triglycerides structure

One glycerol is joined to 3 fatty acids by 3 condensation reactions, ester bonds are formed

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Saturated fatty acid

Contains the maximum number of hydrogen atoms, carbons are linked by C-C bonds (no double bonds)

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Unsaturated fatty acids

Have at least one C=C bond in the chain
-Monounsaturated (1 C=C)
-Polyunsaturated (>1 C=C)

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Triglyceride functions

-Energy store
-Insulation
-Buoyancy

Phopholipid structure

Instead of 3 fatty acids (hydrophobic), one is a phosphate group (hydrophillic)

Protein structure

-Amino acids are linked by peptide bonds by condensation reactions between the amino and carboxyl group
-Two amino acids joined is a dipeptide
-Many amino acids is a polypeptide

Primary protein structure

Sequence of amino acids in the polypeptide chain

Secondary protein structure

a-helix or b-pleated sheets

Tertiary protein structure

Further folding of the secondary structure, this gives it it’s 3D shape
-Hydrogen bonds
-Ionic bonds
-Disulfide bonds
-Hydrophobic interactions

Quaternary structure

Two or more polypeptide chains bonded together

Fibrous proteins

-Collagen
-Found intendons that link muscle to bone

Globular proteins

Have a metabolic role and include enzymes and antibodies. Haemoglobin is an example

Prions

A particular type of protein found in mammals. Found in the nervous system and they are involved in synaptic transmission.

How does prion disease work?

Normal form of prion protein can convert to a disease causing form. this form has a higher proportion of b-pleated sheets which causes a chain reaction. Once the amount of b-sheets are over a certain threshold, this causes neurodegenerative disorders, and eventually death.

How can diseases with prions arise?

-Normal prion protein 'spontaneously' adopting the disease form -Mutations that code for the prion protein -Eating contaminated food that contains the disease form

Prion diseases examples

-Scrapie (sheep) -Bovine spongiform encephalopathy (BSE, cattle) -Variant Creutzfeldt-Jakob disease (vCJD, humans)

Nucleic acids structure

Made up of nucleotides which are made up of: - Pentose sugar -Phosphate group -Nitrogenous base Phosphodiester bonds are formed between the pentose sugar and phosphate group, and also between adjacent nucelotides (nucleic acid)

DNA defintion

A molecule of DNA consists of two anti-parallel strnds with the two strands being held together by ydrogen bonds between adjacent bases.

DNA structure

The DNA molecule is organisee as a double helix. Each strand of the DNA is wound rounch each other like a twisted ladder, linked and held together by the bases, following base pairing rules (A-T G-C)

RNA structure

-It's sugar is ribose -Single stranded and shorter than DNA -The base uracil replaces thymine (A-U, G-C)

Functions of DNA

-Regulates the development of living organisms through the control of protein syntheis.

Messenger RNA

Carries the code from the DNA in the nucleus to a ribosome in the cytoplasm where protein synthesis takes place

Transfer RNA

Carriesthe amino acids to the mRNA/ribosome where protein synthesis takes place. It is a single chain folded into a 'clover leaf' shape

Ribosomal RNA

Made in the nucleolus and formsover half the mass of each ribosome

DNA replication

The enzyme DNA helicase unzipsthe two strands of DNA by breaking the hydrogen bonds between the bases. this allows each of the original strands to become a template for the formation of two DNA molecules.Free nucleotides are linked to the template strands by base pairing rules. The nucleotides of each strand are joined together by the enzyme DNA polymerase. Each of the new DNA molecules contains one original strand and one new strand,this is known as semi-conservative replication