Pearson Edexcel GCSE (9-1) Biology revision notes
Key concepts in biology Revision Notes
Review revision notes for Key concepts in biology in Edexcel Biology.
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Key concepts in biology
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Substance Transport in Cells: Diffusion, Osmosis, and Active Transport Revision Notes
Diffusion
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration. This is a passive process, meaning it does not require metabolic energy from the cell. It occurs down a concentration gradient until equilibrium is reached. Substances like oxygen and carbon dioxide move into and out of cells via diffusion. The rate of diffusion is affected by factors such as temperature, surface area, concentration gradient, and the distance particles need to travel.
Osmosis
Osmosis is the net movement of water molecules across a selectively permeable membrane from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution). It is a special case of diffusion involving only water. This passive process is crucial for maintaining turgor in plant cells and preventing animal cells from bursting or shrivelling. Water potential refers to the likelihood of water molecules to move out of or into a solution.
Active Transport
Active transport is the movement of particles across a cell membrane against their concentration gradient, from a region of lower concentration to a region of higher concentration. This process requires energy, typically in the form of ATP, which is produced by respiration. Specific carrier proteins in the cell membrane are involved in binding to the substance and moving it across. Examples include the absorption of mineral ions by plant roots and glucose absorption in the small intestine.
Mitochondria (1) diagram
Specification Link
This cell structure diagram is used for: Build an explanation of the way changes in microscope technology, covering electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures.
What To Explain
A correct answer links the visible cell structure to its function, such as control, respiration or protein synthesis.
Exam Answer Move
The mapped objective is: Build an explanation of the way changes in microscope technology, covering electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures. Exam answers need a structure-function link.
Mitochondria (2) diagram
Specification Link
This cell structure diagram is used for: Build an explanation of the way changes in microscope technology, covering electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures.
What To Explain
A correct answer links the visible cell structure to its function, such as control, respiration or protein synthesis.
Exam Answer Move
The mapped objective is: Build an explanation of the way changes in microscope technology, covering electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures. Exam answers need a structure-function link.
Nucleus (2) diagram
Specification Link
This cell structure diagram is used for: Build an explanation of the way changes in microscope technology, covering electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures.
What To Explain
A correct answer links the visible cell structure to its function, such as control, respiration or protein synthesis.
Exam Answer Move
The mapped objective is: Build an explanation of the way changes in microscope technology, covering electron microscopy, have enabled us to see cell structures and organelles with more clarity and detail than in the past and increased our understanding of the role of sub-cellular structures. Exam answers need a structure-function link.
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