BTEC SCIENCE UNIT 1 REVISION: BIOLOGY:
Cell structure and function:
Define a prokaryotic cell:
This is shown as a cell with no true nucleus or nuclear membrane and is made up with single - cellular organisms.
Bacteria are prokaryotes. They do not have a membrane-bound nucleus and their DNA is free in the cytoplasm.
Bacteria have a single circular chromosome in the centre of the cell that holds all the genes needed for that bacterium. Bacteria also have extra circles of DNA called plasmids.
These plasmids contain additional genes, such as for antibiotic resistance, which may increase a bacterium’s chance of survival. Bacteria can exchange plasmids with other bacteria through hair-like extensions on their surface called pili.
Define a eukaryotic cell:
This is shown as a cell that contains genetic information with the use of linear chromosomes and is made up with multi - cellular organisms.
Animals, plants and fungi are eukaryotes. They have a membrane-bound nucleus and their chromosomes are linear rather than circular.
Interestingly, circular chromosomes are also found in mitochondria and chloroplasts.They both use their own DNA to make some proteins needed for their function. This gives evidence for the theory that mitochondria and chloroplasts originated from prokaryotic cells that were engulfed by a larger cell.
Animal Cell Ultrastructure:
Plasma membrane: This is composed with proteins embedded in the layer as the membrane being selectively permeable and regulating the transport of materials in and out of the cell.
Cytoplasm: This is a semi - transparent fluid that maintains the cell shape and stores in chemicals needed by the cell for metasolic reactions.
Nucleus: It is the largest organelle and is surrounded by the nucleus envelope and this controls and regulates the cellular activity that houses in genetic material.
Nuclelous: This is a dense spherical structure in the middle of the nucleus which makes RNA and ribosomes.
Rough Endoplasmic Reticulum: These are networks of fattened sacs studded with ribosomes and these are used for where protein synthesis takes in place.
Smooth Endoplasmic Reticulum: These are networks of fattened sacs with no ribosomes which uses it for the transport of lipids and carbohydrates.
Golgi Apparatus: It is a stack of membrane bound with fattened sacs and modifies proteins for them to be transported in vesicles where they are needed.
Vesicles: These are small spherical membrane bound sacs with fluid inside them. These are used to transport materials inside the cell and then uses secretory vesicle transport proteins.
Lysosomes: These are small spherical membranes where they break down waste material including old organelles.
Ribosomes: These are tiny organelles attached to the rough ER or freely moving around in the cell, protein synthesis occurs in the ribosomes.
Mitochondria: These are two membranes and they reach the final stages of cellular respiration which involves the use of aerobic respiration that is shown.
Centrioles: These are small tubes of protein fibres that form spindle fibres during cell division.
Plant Cell Ultrastructure:
Cell wall: These are made of cellulose, this…