Topic 2 - Structures and functions in living organisms

Levels of organisation

organelles, cells, tissues, organs, organ systems

Organelle

Part of the cell with a particular function e.g. chloroplast

Cell

Basic structural unit of living organisms e.g. muscle cell

Tissue

Collection of similar cells working together to form a function e.g. muscle tissue

Organ

Structure in the body of an animal or plant that is a collection of different tissues working together to form a function e.g. heat

Organ system

Collection of different organs working together e.g. heart and blood vessels in the circulatory system

Organism

Collection of organ systems working together to form a living organism e.g. human

Animal cell structures

Mitochondria, nucleus, cell membrane, cytoplasm

Plant cell structures

Cell membrane, cell wall, large vacuole, mitochondria, chloroplast, nucleus, cytoplasm

Mitochondria

Is where aerobic respiration takes place

Nucleus

Controls the function of the cell (what the cell does)

Cell membrane

Controls what enters and leaves the cell

Cytoplasm

Where chemical reactions in the cell take place

Cell wall

Is a non-living material that provides the cell with support and protection. The cellulose it is made of helps it to keep its shape

Large vacuole

Is used to store molecules such as amino acids and sugars

Chloroplast

Absorbs light energy to make food in the process of photosynthesis. Where starch is stored

Ribosome

Where proteins are assembled

Chemical elements present in Carbohydrates

Carbon, hydrogen, oxygen

Chemical elements present in Proteins

Carbon, hydrogen, oxygen, nitrogen

Chemical elements present in Lipids (fats and oils)

Carbon, hydrogen, oxygen

Structure of Carbohydrates

Starch and glycogen from simple sugars

Structure of Proteins

Amino acids

Structure of Lipids

Fatty acids and glycerol

Enzyme

Biological catalysts that speed up chemical reactions without being used up itself

Effect of temperature of enzymes

As the enzyme is heated to its optimum temperature, the rise in temperature increases the rate of reaction, the higher temperatures give the molecule of the enzyme and the substrate more kinetic energy, so collisions are more frequent, from 40°C upwards the heat destroys the enzyme and the active site changes shape so that the substrate cannot fit, the enzyme is denatured.

Effect of pH of enzymes

The pH inside cells in neutral (pH7) and this is the optimum pH for enzymes to work at, either side of this optimum the pH affects the structure of the enzyme molecule and changes the shape of its active site, so its substrate does not fit into it so well, decreasing the number of successful collisions

Active site

Area on the surface of an enzyme where the substrate attaches and products are formed

Activated complex

The combination of the substrate and enzyme

Denaturing

Process where the structure of a protein is damaged by high temperatures, if the protein is an enzyme it will no longer catalyse its reaction