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Structures and Functions in Living Organisms
Characteristics of Living Organisms:
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Nutrition
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Excretion
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Movement
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Reproduction
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Levels of Organisation:
Organelles:
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Organelles are tiny structures within cells
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o Cell Membrane – Forms the outer surface of the cell and controls the
substances that go in and out
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Plant cell:
o Chloroplasts – Makes food for the plant, through photosynthesis
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o Vacuole – Large organelle that contains the cell sap and supports the cell
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Red blood cells are specialised for carrying oxygen and white blood cells are
specialised for defending the body against diseases
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Plants have xylem tissue and phloem tissue
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Organs:
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An organ is a group of different tissues that work together to perform a function
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Plants, Animals and Fungi:
Plants:
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Multicellular
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Cell walls made of cellulose
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Animals:
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Multicellular
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Most have nervous coordination
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Store carbohydrates as glycogen
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Others have a body called a mycelium, made up of hyphae
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Cell walls made of chitin
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Store carbohydrates as glycogen
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Some have chloroplasts and are similar to plant cells
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E
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Chlorella and Amoeba

Bacteria:
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Single-celled and microscopic
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Circular chromosome of DNA
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Most feed off other organisms
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g
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Viruses:
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Particles, smaller than bacteria
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Infest all types of organism
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Have a protein coat around genetic material
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g
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Pathogens are organisms that can cause disease
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Enzymes reduce the need for high temperatures and we only have enzymes that
speed up useful reactions
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Enzymes are all proteins and all proteins are made up of chains of amino acids
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Enzymes are specific:
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A substrate is a molecule that is changed in a reaction
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Enzymes usually only speed up one reaction
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This is called the lock and key model
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This is because more
heat means the enzymes and the substrate particles have more energy
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If it gets too hot, some of the bonds holding the enzyme together will break; the
enzyme is denatured
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Happens in both liquids and gases
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Substances can move in and out by osmosis
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Osmosis:
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Osmosis – The net movement of water molecules across a partially permeable
membrane from a region of higher concentration to a region of lower concentration
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This happens because
molecules move randomly all the time
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Cells:
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Tissue fluid surrounds the cells in a body (tissue fluid is basically water, oxygen,
glucose and stuff that is dissolved in it)
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This means that water will either move into the cell, or out of the cell, through
osmosis
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If the cell has a
higher concentration of water, water will move out
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e
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Digestive System:
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When there’s a higher concentration of nutrients in the gut, they diffuse naturally
into the blood
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The means the concentration gradient is the wrong way
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Active transport allows nutrients to be taken into the blood, despite the fact that
they would be going against the concentration gradient
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Affecters:
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Surface area to volume ratio:
o The rate of diffusion, osmosis and active transport is higher in cells with a
larger surface area to volume ratio
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o This means as temperature increases, substances move in and out of cells
faster
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If there are lots
more particles on one side, there are more there to move across
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