IGCSE Biology

Penicillin: an antibiotic produced by a fungus called penicillium.

Stainless steel fermentation vessel is filled with medium containing sugars and ammonium salts.

Penicillium is added to produce penicillin. They use sugar for respiration and ammonium salts to make protein and nucleic acids

The fermentation vessel consists of:

PAWS

Probes monitor temperature and pH

Air provides oxygen for aerobic respiration in fungus

Water-cooled jacket removes heat to maintain temperature of 24C.

Stirrer keeps the microorganism suspended (allowing access to nutrients and oxygen) while maintaining an even temperature. 

Seeds to germinate: the enzymes turn insoluble food stores to soluble.

Biological washing powders: enzymes are added to washing powders to help remove stains for example:

Lipase for lipids from fatty foods and greasy fingerprints 

Protease for proteins from blood stains 

Food Industry:

Isomerase converts glucose to fructose which is sweeter, so less is needed to give a sweet taste 

Effect of Temperature

Effect of pH

Catalyst: a substance that speeds up a chemical reaction and is not changed by the reaction.

Enzymes: proteins that function as biological catalysts.

Enzymes lowers amount of energy needed for reaction to take place.

Lock and key theory:

Substrate: the molecule(s) before they are made to react

Product: the molecule(s) that are made in a reaction

Catabolic reaction: molecules are broken down

Anabolic reaction: molecules are combined (reverse of the diagram above)

Effects of pH on Enzymes

Enzymes are sensitive to pH

Some enzymes work best in an acid and others in an alkaline 

If the pH is changed then the enzyme will denature and will no longer fit with the substrate- no reaction will take place

Diffusion of water molecules from a region of their higher concentration to a region of their lower concentration, through a partially permeable membrane.

Conc. of solute outside cell = conc. inside cell → no change in size 

Conc. of solute outside cell > conc. inside cell → cell shrinks 

Conc. of solute outside cell < conc. inside cell → cell swells 

In Animals:

Increasing solute concentration inside of cell can cause cell to explode as a result of it having too much water, crenation. 

In Plants:

Increasing solute concentration inside of cell causes cell to become turgid, vacuole fills up.

Movement of ions in or out of a cell through the cell membrane, from a region of lower concentration to a region of higher concentration against a concentration gradient, using energy released during respiration.

This is the movement of molecules from a region of high concentration to a region of low concentration down the concentration gradient. 

This results in random movement of molecules until equilibrium is reached 

Organelle: a specialized part of a cell that has its own function, e.g. the nucleus

Cell: the smallest part of a living structure that can operate as an independent unit e.g. red blood cell 

Tissue: a group of cells with similar structures, working together to perform a shared function e.g. muscle tissue 

Organ: a structure made up of a group of tissues, working together to perform specific functions e.g. the heart 

Organ system: group of organs with related functions, working together to perform body functions e.g. respiratory system 

All living things are made of cells. 

All typical cells have: o Cell membrane: deferentially or partially permeable to allow certain substances to enter and leave the cell. 

Cytoplasm: where chemical reactions take place o Nucleus: contains DNA and controls the cell o Mitochondria: organelle where aerobic respiration happens. 

A typical animal cell (e.g. the liver cell) has all the above things. 

Only plant cells have:

Vacuole: stores food & water & helps to maintain shape of cell 

Cell wall: rigid to keep shape of cell 

Chloroplasts: contain chlorophyll, which absorbs light energy for photosynthesis 

A typical plant cell (e.g. the palisade cell) has all the aforementioned things. 

There are other classification systems e.g. cladistics (based on RNA/DNA sequencing data)

Dichotomous Key

Monocotyledons

One Cotyledon

Parallel Veins

Fibrous root

Floral parts in 3s

Dicotyledons

Two cotyledons

Veins net like (compound veins)

Taproot present