Nature and Variety of Organisms

Movement
Respiration
Sensitivity
Growth
Reproduction
Excretion
Nutrition

Multicellular organisms
Contain chloroplasts and are able to carry out photosynthesis
Have cellulose cell walls
Store carbs as starch or sucrose
eg flowering plants (maize) and herbaceous legume (peas or beans)

Multicellular organisms
Do not contain chloroplasts and are not able to carry out photosynthesis
Have no cell walls
have nervous coordination and are able to move from one place to another
Store carbs as glycogen
eg mammals (humans) and insects (housefly and mosquito)

Not able to carry out photosynthesis
Body is organised into a mycellium made from thread-like structures called hyphae, which contain many nuclei
Some are single-celled
Have cell walls made of chitin
Feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products (saprotrophic nutrition)
May store carbs as glycogen
eg Mucor (has typical fungal hyphal structure) and yeast (single-celled)

Microscopic single-celled organisms
Some (like Amoeba) that live in pond water have features like an animal cell
Others (like Chlorella) have chloroplasts and are more like plants
A pathogenic example is Plasmodium, responsible for causing malaria

Small particles (smaller than bacteria)
Parasitic and can only reproduce inside living cells
Infect every type of living organism
Wide variety of shapes and sizes
No cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA
eg tobacco mosaic virus (causes discolouring in tobacco leaves by preventing formation of chloroplasts), influenza virus (causes flu) and HIV virus (causes AIDS)

Can be eukaryotic (complex and have a nucleus) such as plant and animal cells
Or prokaryotic (smaller and do not have nucleus) such as bacteria cells
organelles are structures within cells
a tissue is a group of similar cells that work together to carry out a particular function
an organ is a group of different tissues that work together to perform a function
Organs work together to form organ systems

Biological catalysts
Specific
every enzyme has an active site and the substrate needs to be the correct shape to fit into the active site (called lock and key model)

a molecule that is changed in a reaction to form products

A substance which increases the speed of a reaction without being changed or used up in the reaction

Higher temp increases the rate at first as the enzyme and substrate have more energy and move about more so aremore likely to collide and form an enzyme-substrate complex
If it gets too hot, some of the bonds holding the enzyme break, changing the shape of the active site so that the enzyme is denatured
All enzymes have an optimum temp at which they work best

If it gets too high or low, some of the bonds holding the enzyme break, changing the shape of the active site so that the enzyme is denatured
All enzymes have an optimum pH at which they work best (it is often neutral 7)

Can measure how fast an enzyme appears (testing how quickly catalase catalyses the breakdown of hydrogen peroxide into water and oxygen)
Can measure how fast a substrate disappears (using amylase which catalyses breakdown of starch into maltose)

The net movement of particles from an area of high concentration to an area of low concentration
The bigger the difference in concentration, the faster the diffusion rate

Net movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration

the movement of particles against a concentration gradient using energy released during respiration

surface area to volume ratio
distance
temperature
concentration gradient

when plant cells lose water (as it moves out of the cell due to osmosis) and the cytoplasm shrinks away from the cell wall
before it becomes completely plasmolysed, the cell is flaccid

when plant cells take in water by osmosis and the cytoplasm pushes against the cell wall and the cell swells, becoming turgid