Biology 2.1 Cell Structure

What is the Endoplasmic Reitculum?

A system of flattened cavities lined by a thin plasma membrane. It is the site of synthesis of many substances within the cell and also provides a compartmentalised area in which this takes place. The cavities also function as a transporting system, whereby substances can move through them from one part of the cell to another.

Where do cells arise from?

All cells arise from other cells, by binary fission in prokaryotic cells, and by mitosis/meiosis in eukaryotic cells.

Which cells are eukaryotic cells?

All cells that aren't prokaryotic: - fungi - animals - plants - some unicellular organisms

Why might prokaryotic cells be adjacent to one another?

Because they might not have separated after cell division or because they remained enclosed in a common sheath (slime excreted by the cells).

What is a prokaryotic capsule?

Capsule - This is a thick polysaccharide layer outside of the cell wall, like the glycocalyx of eukaryotes. It is used for sticking cells together, as a food reserve, as protection against dissociation and chemicals, and as a protection against phagocytosis

What is a prokaryotic cell wall?

Cell Wall - made of murein (not cellulose as in plant cells), which is a glycoprotein (i.e. a protein/carbohydrate conmplex, also called peptidoglycan). There are two linds of cell wall, which can be distinguished by a Gram Stain developed by Hans Christian Gram in 1884. Gram positive bacteria have a thick cell wall and stain purple, while Gram negative bacteria have a thin cell wall and stain pink.

What is a prokaryotic cell membrane?

Cell membrane - This is made of phospholipids and proteins, like eukaryotic membranes.

What is a prokaryotic cytoplasm?

Cytoplasm - contains all the enzymes needed by the cell for all metabolic reactions, since their are no organelles

What is the difference between cytoplasm and cytosol?

Cytoplasm refers to the jelly-like substance that houses organelles. If the organelles were removed from the cytoplasm, the soluble part that would be left is the cytosol. It consists mainly of water with proteins, enzymes and dissolved amino acids.

What is prokayotic DNA?

DNA - always circular. It is compacted by a method called supercoiling and it not associated to any proteins to form chromatin, as it is in eukaryotic cells. Not to be confused with plasmids

How does the size of prokaryotic cells compared to eukaryotic cells?

Eukaryotic cells are about 10 times the size of prokaryotic cells, and can be as much as 1000 times greater in volume.

What is the key difference between eukaryotic and prokaryotic cells?

Eukaryotic cells contain membrane bound compartments in which specific metabolic activities take place. The most important among these is the presence of a nucleus; a membrane delineated compartment that houses the eukaryotic cells' DNA.

What is a prokaryotic flagellum?

Flagellum - a rigid, rotating, helical shaped tail used for propulsion. The motor is embedded in the cell membrane and is driven by an H+ gradient across the membrane. Clockwise rotation drives the cell forwards, while anticlockwise rotation causes a chaotic spin. This is the only known example of a rotating motor in nature.

What is a prokaryotic mesosome?

Mesosome - a tightly folded region of the cell membrane containing all the membrane-bond proteins required for respiration and photosynthesis. This can also associate with the nucleoid.

What us a prokaryotic nucleoid?

Nucleoid (or nuclear zone) - the region of prokaryotic cytoplasm that contains DNA. It is not surrounded by a nuclear membrane

What is the theory of endosymbiosis?

Prokaryotic cells are far older and far more diverse than eukaryotic cells. Prokaryotic cells have probably been around for about 3.5 billion years, whilst eukaryotic cells have only existed about 1 billion years. It is thought that the organelles of the eukaryotic cell, such as the nuclei, mitochondria and chloroplasts, could be originally derived from prokaryotic cells that have become encorporated into other, larger prokaryotic cells.

How does the sizes of a prokaryotic cell, a eukaryotic animal cell and a eukaryotic plant cell compare?

Prokaryotic: 0.5-5 um Eukaryotic animal: 15 um Eukaryotic plant: 40 um

How do the ribosomes compare in a prokaryotic, eukaryotic animal and eukaryotic plant cell?

Prokaryotic: 70s (smaller) ribosomes Eukaryotic animal: 80s (larger) ribosomes Eukaryotic plant: 80s (larger ribosomes

What structure is the genetic material in a prokaryotic, eukaryotic animal, and eukaryotic plant cell?

Prokaryotic: DNA is a naked, single, circular molecule Eukaryotic animal: DNA linear, associated with histones (proteins). In a nucleus surrounded by a nuclear envelope Eukaryotic plant: DNA linear, associated with histones (proteins). In a nucleus, surrounded by a nuclear envelope

Does a prokaryotic, eukaryotic animal or eukaryotic plant cell contain ER and Golgi apparatus?

Prokaryotic: No Eukaryotic animal: Yes Eukaryotic plant: Yes

Does a prokaryotic, eukaryotic animal or eukaryotic plant cell contain mitochondria?

Prokaryotic: No (respiration occurs on an infolding of the cell membrane called the mesosome) Eukaryotic animal: Yes Eukaryotic plant: Yes

Does a prokaryotic, eukaryotic animal, or eukaryotic plant cell contain a cell wall?

Prokaryotic: Yes, contains peptidoglycan Eukaryotic animal: No Eukaryotic plant: Yes, contains cellulose

Do prokaryotic cells have a nuclear membrane?

Prokayotic cells do not have a nuclear membrane (the membrane that surrounds the nucleus of a cell).

What are prokaryotic ribosomes?

Ribosomes - these are the smaller 70s ribosomes

What are organelles?

Small specialised structures in cells, which perform dedicated functions.

Which is the largest organelle in the cell?

The nucleus

What where the first types of cell to arise?

The simplest, prokaryotic cells, which arose approx. 3.5 billion y/a.

What is the main difference between prokayotes and eukaryotes?

Their nuclear organisation, specifically prokaryote's lack of a nuclear membrane. Prokaryotes also lack any of the intracellular organelles and structures that are characteristic of eukaryotic cells. Most of the functions of organelles are taken over by the plasma membrane.

What is the cytoplasm (or cytosol)?

This is the solution within the cell membrane. It contains enzymes for glycolysis (the splitting of simple sugars to generate energy as part of respiration process) and other metabolic reactions together with sugars, salt, amino acids, nucleotides and everything else needed for a cell to function.

Does communications exist between prokaryotic cells?

Typically, no

What are the two types of cell?

Prokaryotic and eukaryotic.

What observations support endosymbiosis?

- Organelles, like prokaryotes, contain 70s ribosomes - Organelles, like prokaryotes, contain circular DNA - Organelles have double membranes, as though a single membrane had been engulfed and surrounded by a larger cell - Organelles, like prokaryotes, reproduce by binary fission - Organelles are very like some bacteria that are alive today

List the key features of a eukaryotic cell.

1. Cytoplasm 2. Microtubules 3. Ribosomes 4. Rough endoplasmic reticulum 5. Nucleus 6. Nuclear envelope 7. Plasma membrane 8. Golgi apparatus 9. Centriole 10. Smooth ER 11. Lysosome 12. Free ribsome 13. Nucleolus 14. Nuclear pore 15. Chromatin 16. Mitochondrion

What are the component parts of a prokaryotic cell?

1. Cytoplasm 2. Ribosomes 3. Nucleoid (or nuclear zone) 4. DNA 5. Plasmid 6. Cell membrane 7. Mesosome 8. Cell Wall 9. Capsule 10. Flagellum

List the features of a prokaryotic cell

1. Flagellum 2. Capsule 3. Cell wall 4. Plasma membrane 5. Fimbrae/pilli 6. Cytosol 7. Ribosome 8. DNA strand in nucleoid 9. Plasmid

How did the eukaryotic cell impact evolution?

Although eukaryotes use the same genetic code and metabolic processes as prokaryotes, their higher level of organisational complexity has permitted the development of truly multicellular organisms. Without eukaryotes, the world would lack mammals, birds, fish, invertebrates, mushrooms, plants and complex single-celled organisms.

What is a nucleus?

An organelle which is the site of the DNA. It is separated from the surrounding cytoplasm by a double membrane known as a nuclear envelope.

Give two examples of prokaryotic cells.

Bacteria (such as E.coli) and cyanobacteria (which used to be called blue-green algae)

What are prokaryotic plasmids?

Plasmid - These are small circles of DNA, used to exchange DNA between bacterial cells. They are very useful for genetic engineering and have a role in antibiotic engineering.

Define cell ultrastructure.

The close detail of a cell, with all organelles visible, that can be seen by using an electron microscope.

What is the nuclear envelope and what is its role?

The double membrane separating the nucleus form the surrounding cytoplasm. It also regulates and controls the flow of material into and out of the nucleus.