Cells and organisation

• Eukaryotic cells contain a true nucleus along with membrane-bound organelles.
• The structure of the nucleus is surrounded by a nuclear envelope which is semi-permeable and double membraned.
• Nuclear pores allow substances to enter/exit the nucleus.
• The dense nucleolus, made of RNA and proteins, assembles ribosomes.
• The function of the nucleus is to contain DNA coiled around chromatin into chromosomes and to coordinate cellular activities.
• Chromatin is a DNA-protein complex found in eukaryotic cells.
• Viruses are smaller and simpler in structure than prokaryotic and eukaryotic cells.
• An organ system is a group of organs working together to carry out a specific function.
• An organ is a group of tissues working together to carry out a specific function.
• Viruses have genetic material in the form of DNA or RNA, while prokaryotic and eukaryotic cells have genetic material in the form of DNA.
• Viruses can only reproduce within a host cell, while prokaryotic and eukaryotic cells can reproduce independently, through cell division, either sexual or asexual.
• A tissue is a group of cells working together to carry out a specific function.
• Viruses do not contain ribosomes, while prokaryotic and eukaryotic cells contain ribosomes.
• Multicellular organisms are organised into many cells making up a tissue, many tissues making up an organ, and many organs making up an organ system.
• The mesosome is an infold of the cell membrane that increases the surface area of the cell, aiding cellular respiration.
• Organelles found in both eukaryotic and prokaryotic cells include the cell membrane, cytoplasm with a form of cytoskeleton, and ribosomes.
• A prokaryotic cell is a type of cell that does not contain any membrane-bound organelles or a true nucleus.
• Genetic information is stored in prokaryotes through plasmids, which are small rings of DNA that carry non-essential genes, and pili, which are hair-like microfibers made of pilin that extend through the cell wall and enable the attachment of bacteria to each other and to other surfaces.
• The flagella in prokaryotic cells are long, whip-like protrusions made of flagellin that rotate to propel the organism and are sensory organs.
• The capsule in prokaryotic cells is a protective, slimy layer that helps the cell to retain moisture and adhere to other surfaces.
• Plasmodesmata are microscopic channels between plant cell walls that facilitate communication and symplastic transport.
• The structure of mitochondria is surrounded by a double membrane, the mitochondrial envelope, and has a folded inner membrane that forms cristae, a large surface area, and a fluid matrix that contains mitochondrial DNA, respiratory enzymes, lipids and proteins.
• The function of mitochondria is to be the site of aerobic respiration to produce ATP.
• The structure of the endoplasmic reticulum (ER) consists of a series of flattened membrane-bound sacs (cisternae) within the cytoplasm, continuous with the nuclear envelope, and is divided into the smooth ER and the rough ER.
• The function of ribosomes is the site of protein synthesis (translation), where the large subunit joins amino acids and the small subunit reads RNA.
• The function of the permanent vacuole in plants is to store cell sap.
• The structure of the permanent vacuole in plants consists of a single membrane, the tonoplast, containing cell sap (mineral ions, water, enzymes, soluble pigments).
• The function of the Golgi body is to modify and package proteins for export and synthesise glycoproteins.
• The structure of a chloroplast consists of a disk-shaped structure surrounded by a double membrane, with thylakoids stacked to form grana containing photosystems with chlorophyll, grana containing photosystems with chlorophyll, and intergranal lamellae tubes attaching thylakoids in adjacent grana.
• The structure of centrioles consists of a cylindrical structure organised into microtubules in a 9+0 pattern, found in pairs in centrosomes, and involved in the organisation of spindle fibres during cell division.
• The structure of the Golgi body consists of a planar stack of membrane-bound, flattened sacs, with the cis face aligning with the RER, and molecules being processed in cisternae.
• The structure of lysosomes consists of fluid-filled vesicles surrounded by a single membrane, containing enzymes, with a role in phagocytosis, digesting unwanted materials in the cytoplasm.
• The function of centrioles is to migrate to opposite poles of the cell during prophase and are involved in the organisation of spindle fibres.
• The function of a chloroplast is photosynthesis.
• The function of the smooth endoplasmic reticulum (SER) is for lipid synthesis.
• The function of the rough endoplasmic reticulum (RER) is for protein synthesis and transport.
• Ribosomes are made from rRNA and proteins and are found free in the cytoplasm or associated with the RER.
• The function of ribosomes is not known.
• Prokaryotic cells reproduce via binary fission, while eukaryotic cells reproduce via sexual or asexual reproduction.
• The magnification of an image can be calculated by dividing the size of the specimen by the size of the image.