Animals are made of eukaryotic cells (Animal Cells). Eukaryotic cells have a nucleus, organelles, and are surrounded by a cell membrane.
Animals have been evolutionarily successful because of their flexible cell membranes, which give them many helpful abilities.
Animal Cells Labelled
Cilia and Flagella
Some eukaryotic cells either have cilia or flagella. Cilia are small, wiggling arm-like structures, and flagella are like a tail.
Both structures are made of long protein fibers called microtubules, with a structure where nine microtubules form a ring around two central microtubules.
The cell membrane encloses the cell’s contents. It monitors what comes in, and what goes out. It has a characteristic called semi permeability, meaning it can “choose” what molecules can come in and out of the cell.
There are water and nutrients within the cell. The cytoskeleton is a collection of protein strands that reinforce the cell.
Centrosomes are a part of this reinforcement. They assemble long microtubules out of proteins. The cytoplasm provides the infrastructure that is necessary for cells to thrive and for the organelles to do their jobs within the cell.
The nucleus of the cell has its own type of cytoplasm, called the nucleoplasm.
The endoplasmic reticulum(s) are organelles that create a network of membranes that transport substances around the cell.
They have phospholipid bilayers. There are two types: the rough ER, and the smooth ER The rough endoplasmic reticulum is rough because it has ribosomes (which I will explain later) attached to it. It helps in the synthesis and packaging of proteins.
The smooth endoplasmic reticulum doesn’t have ribosomes attached. It contains enzymes that help with the creation of important lipids. It has a role in the process of cell detox. The smooth ER adds a carboxyl group to noxious substances, making them soluble in water.
Ribosomes create proteins. They can float freely in the cytoplasm or can be attached to the nuclear envelope. They create proteins by assembling amino acids into polypeptides.
As the ribosomes build an amino acid chain, the chain is pushed into the endoplasmic reticulum. When the protein chain is complete, the endoplasmic reticulum pinches it off and sends it to the Golgi apparatus.
The Golgi apparatus focuses on protein processing and packaging. Golgi bodies are the Golgi apparatus’s layers. Golgi bodies cut up large proteins into smaller hormones.
They can combine proteins with carbohydrates to make various molecules. They then package these products into sacs called vesicles, which will ship the products of the Golgi body to other parts of the cell, and outside the cell as well.
Lysosomes are enzyme sacs that break down cellular waste – they process cell digestion. They can take substances from outside of the cell and cellular waste and turn them into simple compounds.
The compounds are then transferred into the cytoplasm where they can be used as a cell building material.
The nucleus is a highly specialized organelle that lives in its own double membrane with the nucleolus. The nucleus stores the cell’s DNA and holds all the information the cell needs to do its job.
Chromatin is a web-like substance that holds the nucleus’s DNA. Chromatin gathers into rod-shaped chromosomes that hold DNA molecules when the cell is ready to split during cell division.
The nucleolus lives inside the nucleus and is the only organelle that is not enveloped by its own membrane. IT makes ribosomal RNA, rRNA, which is important during protein synthesis.
Ribosomal RNA or rRNA combines with proteins to form the basic units of ribosomes. When the units are done, the nucleus spits them out of the nuclear envelope, where they are assembled into ribosomes.
The nucleus sends orders in the form of messenger RNA, or mRNA. The messages are sent to ribosomes, which carry out the orders in the rest of the cell.
The mitochondria is the “power plant” of the cell. This is where cellular respiration takes place. During this, energy is derived and converted into ATP from fats, carbohydrates, and other fuels.
Mitochondria almost act as their own organism and have their very own DNA which is an exact replication of the mother’s DNA
Animal Cells Citations
- Relationships between the central spindle and the contractile ring during cytokinesis in animal cells. Microsc Res Tech . 2000 Apr 15;49(2):202-8.
- Establishment of the mechanism of cytokinesis in animal cells. Int Rev Cytol . 1986;105:245-81.
- Cytokinesis in plant and animal cells: endosomes ‘shut the door’. Dev Biol . 2006 Jun 1;294(1):1-10.
- Cytokinesis in animal cells. Cold Spring Harb Perspect Biol . 2015 Feb 13;7(4):a015834.