Cell structure Flashcards
Starch granules
Carbohydrates stored in amyloplasts (plastids specialised in storage)
Chloroplasts
2-5 micrometers. Contain the green pigment chlorophyll. They contain dense stacks of membrane (grana) within a colourless fluid, much like cytosol. They are the site of photosynthesis and are mainly in leaves. Contain 70s ribosomes
Cell wall
A semi rigid structure outside the plasma membrane, 0.1 to several micrometers thick. Composed mainly of cellulose. It supports the cell and limits its volume.
Mitochondria
1.5 to 2.8 micrometers. They are the cells energy transformers, converting chemical energy into ATP. It contains 70s ribosomes. It is bounded by a double membrane system, the number in a cell depends on its metabolic activity.
Large central vacuole
Filled with an aqueous solution of ions. Its function is storage, waste disposal and growth. It is surrounded by a membrane called a tonoplast
Cell surface membrane
Located inside the cell wall in plants. It is 3 to 10 nanometers thick. It is semi-permeable and controls what substances enter or leave the cell
Cytoplasm
A watery solution containing dissolved substances, enzymes and the cells organelles and structures. It is the site of many chemical reactions.
Ribosomes
80s. These small 20nm structures manufacture proteins. They may be free in the cytoplasm or associated with the surface of an endoplasmic reticulum.
Endoplasmic reticulum (ER)
A network of tubes and flattened sacs. The ER is continuous with the plasma membrane and the nuclear membrane.
Smooth endoplasmic reticulum (ER)
The ER without ribosomes. The site of lipid and carbohydrate metabolism, including hormone synthesis.
Rough endoplasmic reticulum (ER)
Site of protein synthesis, also synthesises new membranes by adding proteins and phospholipids
Golgi apparatus
A series of flattened disk shapes sacs stacked on top of each other and connected with the ER. The Golgi stores, modifies and packages proteins. It “tags” them so that they go to the right location.
Centrioles
Structures associated with nuclear division. Composed of microtubules, but appear as small featureless particles. 0.25 micrometers in diameter
Lysosomes
A sac bounded by a single membrane. They are pinched off from the Golgi apparatus and contain and transport enzymes. They have little internal structure but contain fragments of material being broken apart
Plasmodesmata
Connects plant cells with fine strands of cytoplasm. They pass through pore like structures in the cell wall
Nucleus
Contains the nucleolus which is a dense, solid structure composed of crystalline protein and nucleic acid. Is involved in ribosome synthesis. The nuclear pore is a hole in the nuclear membrane which allows the nucleus to communicate with the rest of the cell. The nucleus is surrounded by a double layered nuclear membrane. It contains chromosomes which controls the cells activity
Resolution
The ability to distinguish between two separate points
Magnification
Actual size of image
ATP
Produced by the mitochondria and chloroplasts. It is an energy store in cells. Energy is released when it is broken down into ADP.
Prokaryotic cell
Diameter of cell is 0.5-5 micrometers. DNA is circular and lies free in the cytoplasm. DNA is naked. 70s ribosomes (smaller then in eukaryotes). Very few cell organelle - no separate membrane bound compartments unless formed by the infolding of the cell surface membrane. Cell wall containing murein which is a peptidoglycan.
Eukaryotic cell
Up to 40 micrometers in diameter. DNA is contained within a nucleus, the nucleus is surrounded by an envelope of two membranes. DNA is associated with proteins forming chromosomes. 80s ribosomes. ER present. Many types of cell organelle (extensive compartmentalisation and division of labour). Cell wall sometimes present, in plants in contains cellulose and in fungi it contains chitin.
Viruses
Has a protein coat (capid) made up of separate protein molecules called a capsomere. About 20-300nm. All viruses are parasitic and only reproduce by infecting and taking over living cells. The viruses DNA or RNA takes over the protein synthesising machinery of the hosts cell which can be used to make new virus particles. They are non-cellular
Plant cell
Cell surface membrane, cytoplasm, nucleus, rough ER, smooth ER, mitochondria, Golgi apparatus, chloroplast, plasmodesmata, starch granules, cell wall and vacuole
Animal cell
Cell surface membrane, cytoplasm, nucleus, rough ER, smooth ER, mitochondria, Golgi apparatus, centrioles and lysosomes
