biology GCSE topic 1

• cell walls are rigid, providing support to the plant cells
• Light microscopes use light to form an image of the specimen.
• The electron microscope can magnify up to 200 million times.
• Electron microscopes have higher resolution than light microscopes but require vacuum conditions and special staining techniques.
• Scanning Electron Microscope (SEM) uses electrons to scan the surface of a sample, creating a three-dimensional image with high contrast.
• Prokaryotes are cells that do not have a nucleus or membrane bound organelles
• Eukaryotic cells are larger than prokaryotic cells and have a nucleus
• Eukaryotic cells are more complex than prokaryotic cells
• Animal and plant cells are eukaryotic
• Bacteria and archaea are prokaryotic
• The cell wall is made up of peptidoglycan in bacteria and chitin in fungi
• Plant cells contain chloroplasts which produce food through photosynthesis
• Cell walls protect against pathogens and give support to plants
• Mitochondria produce energy through respiration
• Eukaryotes are organisms that are made up of eukaryotic cells. A prokaryote is an organism that is made up of prokaryotic cells.
• Prokaryotic cells have no nucleus, while eukaryotic cells do
• A bacterium is a type of prokaryotic cell
• An animal cell is a type of eukaryotic cell
• Bacteria are single-celled microorganisms with a diameter of about 0.2 micrometres (μm)
• The cytoplasm contains the cytosol (the jelly-like substance) and various structures such as ribosomes, mitochondria, chloroplasts, vacuoles
• The nucleus contains genetic information that controls the activities of the cell. Genetic material is arranged into chromosomes.
• Protein molecules are long chains of amino acids joined together by peptide bonds. They carry out many functions within the body including structural support, movement, transporting substances around the body and digestion.
• The cytoplasm is the site of chemical reactions and is where most of the cell's chemical reactions take place. It contains enzymes which carry out these reactions.
• The cell membrane is a selectively permeable barrier that controls the movement of substances in and out of the cell
• The mitochondria is the site of aerobic respiration and is where most of the energy is released
• Ribosomes are the second stage of protein synthesis
• plant cells usually have the same bits an animal cell do but with a few extra
• The cell wall is a rigid structure made of cellulose that supports and strengthens the cell
• The large vacuole contains cell sap, a weak solution of sugar and salts. It maintains the internal pressure to support the cell.
• chloroplasts is where photosynthesis takes place, where the light energy is converted into chemical energy. This makes food for the plant
• the stoma allows gases such as carbon dioxide and oxygen to enter and leave the leaf
• the xylem transports water up through the stem and leaves
• the xylem transports water from roots up through the stem to leaves
• phloem transports sugars produced by photosynthesis around the plant
• root hair cells absorb nutrients and water from soil
• Chloroplasts contain a green substance called chlorophyll which absorbs light energy
• A bacteria cell has a cytoplasm, containing DNA, ribosomes and cell membrane surrounded by a cell wall.
• a bacteria cell doesn’t have a nucleus, instead it has a single cellular strand of chromosomal DNA that floats freely in the cytoplasm . This controls the cells activities and replication.
• Bacterial cells may also contain one or more small loops of DNA called plasmids. These aren't part of the main chromosome. Plasmids contain genes for things like drug resistance, and can be passed between bacteria.
• Some bacterial cells also have a flagellum. This is a long hair-like structure that rotates to make the bacterium move. It can be used to move the bacterium away from harmful substances like toxins and towards beneficial things like nutrients or oxygen