About 1.5 million animal species have been scientifically described worldwide. Each species differs from other species in aspects such as appearance, behavior and occurrence. However, what all these animals have in common is their cellular structure made up of many animal cells. Because the smallest unit of all animals is the animal cell.
Due to the different organelles in the cells and the later differentiation of the cells, it is possible for animals to live. The differentiation of animal cells is also the reason for the diversity in the animal world.
Animal cell definition
One animal cell is, like fungal cells and plant cells, one eukaryotic cell (eucyte), which is the basic building block for animal tissue represents. It includes one nucleus and many more cell organelles.
By separating the cytoplasm into the individual compartments, several different reactions can take place simultaneously in the animal cell.
The cytoplasm is a gel-like substance inside the cell that contains the organelles and the cytoskeleton.
Structure and components of the animal cell
An animal cell is made up of different membrane-enclosed cells organelleslocated inside the cell, the cytoplasm of the cell.
Figure 1: Structure of an animal cell
cell membrane
the cell membrane, also called the plasma membrane, encloses the cell and thus separates it from the environment. It is about a semipermeable biomembraneprovided by the transport proteinsallows selected substances to be transported into and out of the cell.
Cell membranes are made of one double lipid layer built that out amphiphilic phospholipids consists. amphiphile means that the phospholipid both hydrophilic as well as hydrophobic is.
The head group of these phospholipids is hydrophilic (water loving) and the tail group is hydrophobic (water avoiding). In the lipid bilayer, the hydrophilic head groups face outward and the hydrophobic tail groups face inward.
Figure 2: Representation of a semi-permeable biomembrane
Feel free to take a look at the explanation about the biomembrane and the transport of substances if you want to know more about the topics!
nucleus
Of the nucleus is often also referred to as the control center of the cell and is therefore probably the most important organelle of all eukaryotic cells, including that of animal cells.
Of the nucleus (nucleus) contains all the genetic information of the animal cell in the form of chromosomes. He is surrounded by a double nuclear envelope, which separates it from the cytoplasm. The nucleolus is also located in the cell nucleus nucleoli called, which consists of various enzymes, proteins and RNA.
endoplasmic reticulum
That Endoplasmic Reticulum (short: ER) is a cell organelle that has a tube-like, coiled structure and is located in the cytoplasm. It mainly fulfills tasks in the membrane synthesis and in the storage of calcium ions.
That HE is often in close proximity to nucleus and is with the nuclear envelope tied together. It consists of many interconnected membrane-enclosed cavities.
A distinction is made between smooth and the rough ER. The rough ER is with single ribosomes occupied on the surface and is both for the membrane formationas well as for the vesicle formation and the protein biosynthesis responsible. In contrast, on the surface of the smooth ERs no ribosomes to be found. The functions of the ER are mainly that storage of calcium ions and the fat metabolism.
ribosomes
ribosomes are proteins made up of two subunits, one large and one small. they consist of ribosomal ribonucleic acid.
Ribosomes can be free in the cytoplasm or bound to the ER. Your job is that protein biosynthesis.
Golgi apparat
Of the Golgi apparat consists of a stack of membrane cisterns and vesicles, forming a cavity. A stack of several of these membrane cisterns is called dictyosomes.
dictyosomes are 1 μm stacks of membrane-bounded cisternae. This is where proteins are stored, packaged and finally excreted as vesicles. 4 – 10 closely packed dictyosomes then form the Golgi apparatus.
Of the Golgi apparat is an organelle found only in eucytes. It has several functions, one of which is the formation of vesicles and membranes and the processing of proteins and lysosomes.
mitochondria
mitochondria are also called the power plants of the cells, because they are responsible for the energy production, more precisely the cellular respiration are responsible.
mitochondria are elongated cell organelles that are double diaphragm are surrounded. They represent the general energy currency ATP (adenosine triphosphate), which is required for some substance conversions and the like.
ATP (adenosine triphosphate) is a nucleotide, which releases energy by splitting off its phosphate groups. ADP (adenosine diphosphate) is formed by splitting off a phosphate group, and AMP (adenosine monophosphate) is formed by further splitting off.
In cells that require a lot of energy, such as muscle cells, the density of mitochondria is particularly high.
lysosomes
at lysosomes are small membrane-enclosed vesicles, which are produced by the Golgi apparatus. you are with digestive enzymes filled and can break down foreign substances or endogenous substances. The substances to be digested are enclosed in the lysosomes and broken down there, which is why the lysosomes are also referred to as the «stomach of the cell».
vacuole
Actually, animal cells do not have any typical ones cell sap vacuolesas found in plant cells, but there are exceptions.
Serve in eukaryotic protozoa food vacuoles of food intake. You merge with lysosomesthe digestive enzymes contain and digest the ingested food.
There are also eukaryotic ones living in fresh water protozoa With contractile vacuoles. These are used for osmoregulation, i.e. they pump water that is in the unicellular organism back out.
Examples of such a protozoa are both the paramecium and Euglena. If you would like to know more about this, please take a look at the relevant explanations on !
peroxisomes
peroxisomes are similar organelles to the lysosomes, but these are not produced by the Golgi apparatus. They are surrounded by a membrane and contain certain enzymeswith which it detoxifies the cell.
cytoskeleton
Unlike the plant cells, which keep their shape through the cell wall, animal cells need it cytoskeletonto stabilize and move the cell. That cytoskeleton consists actin, intermediate filaments and microtubulesthat form a network.
actin filaments are thin fibers that consist of actin exist and are spanned through the entire cell. They stabilize and hold the shape of the cell through a network-like arrangement under the plasma membrane membrane proteins in their place.
microtubules are hollow, cylindrical structures that carry out longer transport processes through motor proteins. They also attach the organelles.
intermediate filaments are different protein filaments, which are more stable than microtubules and actin filaments due to their larger diameter. It is therefore the task of the intermediate filaments to absorb mechanical tensile forces and to stabilize the cell.
Actin filaments interact with the motor protein myosinenabling actin to facilitate short-distance transport for vesicles or other larger molecules can take over.
Functions of the cell organelles at a glance
In the following table you can see a brief overview of the individual functions of the cell organelles.
For some of these organelles there are separate explanations on where you can read everything in detail.
Differentiation of Animal Cells
However, the structure of an animal cell shown here only represents the structure of one undifferentiated cell In order for the animal to be able to survive, the cells have to differentiate and therefore different tissue and organs form.
Under the cell differentiation one understands the change of an undifferentiated progenitor cell to a cell with an altered shape and special function. This happens through the expression of certain geneswhich in turn does not occur in other cell types.
The differentiated cells differ from the undifferentiated cells in structure, size and function. the cell differentiation can also be due to external factors such as hormones or cell contacts be triggered, as is the case with the epithelial cells the case is.
If you would like to know more about cell differentiation, please take a look at the corresponding explanation on .
Example epithelial cell
That epithelial tissue located at the boundary surfaces of the body. The single ones epithelial cells are the cellular elements of the epithelial tissue. The cells are by different cell contacts connected with each other. Through this cell-cell contacts Signal substances can be passed on to surrounding cells, which then cause differentiation.
adhesive contact adhering junctions)
the epithelial cells are very close together and are therefore characterized by the so-called adhesive contactsalso e.gonula adherens (lat.) or adhering junctions (Engl.) called, linked together, by actin filaments are formed. This close connection mechanically strengthens the cells and makes them more resistant to tensile forces.
desmosomes
desmosomes are punctiform solder joints between the cells, which pass through fibrils are connected to each other. The fibrils are through intracellular anchor proteins, the plaques, fixed in the cell. in the extracellular space connect special adhesion proteinsthe cadherins, the two cells.
shutter contacts thigh junctions)
locking contactsalso tight junctions (English) or zonula occlusal (lat.) connect the gap between the cells and thus form a barrier for the diffusion of substances. are particularly important tight junctions in organ tissues, such as the urinary bladder, in which an inflow of urine into the abdominal cavity must be prevented.
Comparison between animal cell, plant cell and bacterial cell
In the following table you can see that the prokaryotic cells (bacterial cell) strongly from the eukaryotic cells (animal cell, plant cell) distinguish. However, there are also relevant differences between the animal– and the plant cell.
In summary, one can say that the bacterial cell is most active in the compartmentalization differs from the animal and plant cells because prokaryotes are unicellular organisms and do not have individual organelles. Also have eucytes a cell nucleus, whereas procytes heritage store in a plasmid.
The main differences between eukaryotic cells are that plant cells, as opposed to animal cells, have a cell wall and plastids (chloroplasts) possess.
Animal Cell – The Most Important
- at animal cells is, as with the plant cells, to eukaryotic cells (eucytes).
- The animal cell contains various cell organellesall of which differ in their task and structure
-
The biggest difference between the…