Lecture 1 Flashcards
What type of bonds can water create ?
Weak hydrogen bonds with other polar molecules
What happens when the water activity is too low ? (what is the limit)
Water is not available as a solvent anymore (it’s strongly bound to specific sites) -> microorganisms can’t grow. Limit around 0.611
What does ionic strength influence ?
protein folding, osmosis, interaction with metals, …
Explain hypertonic and hypotonic solutions
hypertonic = more ions outside, so water goes outside
hypotonic = more ions inside so water goes inside
Why can bacteria withstand high pressures ?
Because they not only have a plasma membrane, but also a cell wall.
What is a buffer ?
solution consisting of a mixture of weak acid and its conjugate base (or vice versa). Its pH changes very little when small amount of strong acid or strong base is added to it.
What is the pH of biological fluids ?
Mostly around 7, with a fiew exceptions (digestive trackt for example)
What are the three main buffer systems in the body ?
- carbonate / bicarbonate
- phosphate
- protein (less capacity than the 2 others)
What are the 4 main types of building blocks ?
Sugars, fatty acids, amino acids, nucleotides
Are amino acids only found in proteins ?
No, there are circa 800 other amino acids that are not found in proteins (ex L-DOPA or GABA)
How is protein synthesis different in prokaryotes and eukaryotes ?
- pro : everything happens in the same cell compartment
- eu : transcription in the nucleus and translation in the cytoplasm
Why are sugars important for microbes ?
They represent a large fraction of their cell wall. They also use them to build their biofilms.
What are excreted polysaccharides ?
Produced by microbes to adhere to surfaces (biofilms). Also important in biotech and food industry.
What are glycosaminoglycans and where are they found?
They are unbranched polysaccharide chains composed of repeating disaccharide units. Produced by animal cells to adhere to each other and maintain cohesion. They are found in ECM and connective tissues (fill the space between our cells).
Why do GAGs occupy a large volume?
They are strongly hydrophilic -> become a hydrated gel
