Eukaryotic Cell

The Cell

This site provides a study guide on the cell, starting at GCSE level and working towards A level standard.

Click onto these sites to help you with your GCSE revision and then have a look at two other links which take you onto AS/A level work. They all have tests at the end of each topic.

More GCSE Revision - Try this link for extra tuition on the cell.

BBC Guru - A Level study guide on the cell.

When you have finished these, look at our study guide on the cell. It examines animal and plant cells (eukaryotic) and bacterial cells (prokaryotic). Work your way through to build up your confidence on this topic.

This subsequent sections relating to the cell, we examine the electron microscope and its ability to see clearly the ultra structure of the cell. Cell fractionation allows us to separate out the cell organelles and to examine their properties.

Cells can be divided into eukaryotes or prokaryotes. Animal and Plant cells are given the term eukaryotic whilst the simpler bacterial cells are given the term prokaryotic. Eukaryotic cells are more complex than prokaryotic cells in that they have membrane bound organelles which enable chemical reactions to occur away from the cytoplasm.

When we look at the eukaryotic cell in more detail using powerful microscopes such as the electron microscope, we see a lot more detail of the organelles.

The nucleus compartmentalises the cell's genetic material, contained within chromosomes. The nuclear material is bound by a nuclear envelope which is perforated by pores to allow the exchanges of material with the rest of the cell.

The endoplasmic reticulum consists of sheets of membranes Rough ER is covered with ribosomes and is the location of protein synthesis. Smooth ER lacks ribosomes and is the site of lipid synthesis.

The Golgi apparatus is made up of a stack of flattened membrane bound cisternae. It chemically modifies proteins to glycoproteins and is involved in the formation of lysosomes. Lysosomes are responsible for intracellular digestion of unwanted materials.

Mitochondria are the source of most of the cell ATP. This is the universal energy currency and is synthesised in the inner membrane of the mitochondria.

Cells contain a network of protein tubules to form a cytoskeleton involved in the movement of organelles and cell motility. They are present in other organelles such as the centrioles, as well as the (9+2) structure of cilia).

Microvilli serve to increase the surface area for absorption

Plants differ from animal cells by having a cell wall made of cellulose to
support it. It has cytoplasmic connections with other neighbouring cells by cytoplasmic plasmodesmata. Chloroplasts are the site of photosynthesis. Chlorophyll molecules are found on the inner thylakoid membranes. The light energy that they trap is used to synthesis carbohydrates from carbon dioxide in the stroma between the membranes. The tonoplast membrane of the vacuole can also be seen.

Cell components can be isolated by cell fractionation.

Information Guide On The Prokaryotic Cell

Bacteria have a cell wall, but it is composed of murein or peptidoglycan. Some have slime layers or thick capsules to protect the cells. Some produce pili or fimbriae for attachment to cell surfaces. Others have flagella consisting of the single rod of protein fibres. The prokaryotic cells (bacteria) lack a nucleus and have just a circular loop of naked DNA. They also have no membrane-bound organelles such as mitochondria or chloroplasts. In some bacteria , enzymes for aerobic respiration are attached to infolds known as mesosomes and photosynthestic bacteria have similar thylakoids
where bacterial chlorophyll and enzymes of photosynthesis are located. The bacteria also have plasmids which confer antibiotic resistance and which are also used in genetic engineering.