Cells 1.1.1.f

compare the ultrastructure of a leucocyte and a palisade mesophyll cell, as seen with an electron microscope, to illustrate the differences between animal and plant cells as examples of eukaryotic cells (to include the cell surface membrane, Golgi apparatus, rough and smooth endoplasmic reticulum (ER), ribosomes, lysosomes, vesicles, mitochondria, chloroplasts, cytoskeleton, cell wall, nucleus and nucleolus);

Draw and label an animal cell and a plant cell. Task Draw and label an animal cell and a plant cell.

Boardworks AS Biology Cell Structure What is a cell? Cells are the basic unit of life. They are small membrane-bound structures containing several smaller structures called organelles. There are two main categories of cell, each of which have important different structural properties: eukaryotic cell, including the cells of animals and plants prokaryotic cell, including bacterial cells.

The cell membrane and cytoplasm Boardworks AS Biology Cell Structure The cell membrane and cytoplasm All cells, and all true organelles, are contained within a membrane, based on a phospholipid bilayer. The cell membrane holds a cell together and controls what enters and leaves the cytoplasm, as it is a selectively permeable barrier. The cytoplasm comprises a liquid called cytosol, and all the organelles suspended in it (except the nucleus in eukaryotes). Teacher notes See the ‘Cell Membranes’ presentation for more information about the structure and roles of membranes. The cell membrane and cytoplasm are universal features of the living cell.

Cells need energy to carry out vital processes. Where does this energy come from? What is the name of the process that releases energy?

The universal energy carrier Boardworks AS Biology Cell Structure Cells need a constant supply of energy to carry out vital processes such as protein synthesis, DNA replication and cell division. ATP This energy originally comes from fuel molecules, such as glucose, consumed by the organism. These are broken down during aerobic or anaerobic respiration, and the energy released is used to make adenosine triphosphate (ATP). ADP ATP diffuses throughout the cell, and breaks down into adenosine diphosphate (ADP), releasing chemical energy wherever it is needed.

Eukaryotic Cells

Boardworks AS Biology Cell Structure What is a eukaryote? Boardworks AS Biology Cell Structure A eukaryote is any organism consisting of one or more cells that contain DNA in a membrane-bound nucleus, separate from the cytoplasm. Eukaryotes include: animals plants fungi Photo credit: Jupiterimages Corporation Teacher notes See the ‘Classification’ presentation for more information about the relationship between the eukaryote kingdoms. a diverse group known as the protists (or protoctists). All eukaryotic cells contain a large number of specialized, membrane-bound organelles.

The organelles of protein synthesis Boardworks AS Biology Cell Structure The organelles of protein synthesis Teacher notes It may be worth pointing out to students that the membranes surrounding the organelles in this animation are all based on the same structure – the phospholipid bilayer – but are coloured differently for clarity. In addition, it could be noted that the membrane of endoplasmic reticulum is an extension of the nuclear membrane. See the ‘Nucleic Acids and the Genetic Code’ presentation for information about DNA, transcription and translation.