Cell Parts Components And Their Functions - Structure Of A Cell - Functions Of A Cell
In this video we discuss the structure of a typical human cell, the components of a cell, and the functions of many of the organelles of a cell.
Notes (partial)
The main components of a typical human cell include, the plasma membrane, the cytoplasm, including the organelles and cytoskeleton, and the nucleus.
The plasma membrane is the outer boundry of a cell. It is composed mainly of a double layer of phospholipid molecules that are held together by chemical attractions. These phospholipid molecules have a water soluble head and lipid or fat soluble tails, so they form a bilayer that acts like a fence, allowing lipid soluble molecules to pass through easily.
The cytoskeleton is the internal framework of a cell as it provides structural support and allows movement of materials.
There are 3 different types of fibers, microfilaments, intermediate filaments and microtubules.
Microfilaments are the smallest of the three, and they are made of twisted strands of proteins. They can be pulled together to shorten the cell, such as in muscle contraction.
Intermediate filaments are also twisted strands of proteins that provide much of the framework support in a cell as they hold the cell together.
Microtubules are made of proteins that take on a spiral shape to from a hollow cylinder. They help maintain the cells shape, and move some organelles within a cell.
The centrosome is typically found near the nucleus and it basically builds and breaks apart microtubules in the cell.
The cytoplasm consists of the cytosol, which is a watery solution also referred to as intracellular fluid. It has a syrup like consistency and contains a high water content. The cytoplasm also houses the tiny organs, or organelles in the cell.
The first organelle we are going to look at is the endoplasmic reticulum. There are two types of endoplasmic reticulum, the rough er and smooth er. The rough er extends out from the nucleus and has ribsomes attached to its membrane giving it a rough appearance. Here they are modified, packaged and stored until they are released.
The smooth er is a membranous organelle that does not have any ribosomes. The smooth er contains enzymes that alter polypeptides, synthesize lipids and carbohydrates and destroy toxins. Most of the phospholipids and cholesterol that form cell membranes are synthesized in the smooth er.
Ribosomes can be found attatched to the rough er, or scattered freely throughout the cytoplasm. Ribosomes are protein factories, the two sub units come together as transfer RNA brings amino acids to the ribosome, and messenger RNA provides the code of how to assemble the amino acids into a polypeptide chain.
The golgi apparatus is a membranous organelle that’s main function is to modify package and store proteins. Here they release the proteins which are modified by enzymes. After modification is complete they are pinched off in another vesicle called a secretory vesicle where many are sent to the cells plasma membrane.
Lysosomes are membranous vesicles that pinch off from the golgi apparatus, and they contain digestive enzymes. Lysosomes are like garbage bags, picking up cellular waste, or picking up defective organelles, and recycling the contents.
Proteasomes are cylindrical protein destroying organelles found throughout the cytoplasm. They are responsible for breaking down abnormal and misfolded proteins, and normal proteins that are no longer needed by the cell. A targeted protein is marked by having a separate protein called ubiquitin bound to it. The resulting smaller peptide chains and amino acids are then released to be recycled by the cell.
Peroxisomes are membranous vesicles that are pinched off from the rough er.
Mitochondria, which are found in the cytoplasm, are the power plants of cells, as they can take energy from food molecules and use it to build ATP molecules. ATP being the energy currency of cells needed to do cellular work. Mitochondria have an inner and outer membrane, and very in numbers depending on the amount of work a cell does. For instance liver cells contain 1000 or more mitochondria, and frequent aerobic exercise increases the number of mitochondria in skeletal muscle cells.
The nucleus is one of the largest cell structures, and it has two membranes that form a nuclear envelope, that, along with nuclear pores enclose the nucleoplasm. The nuclear pores allow certain molecules into and out of the nucleus. Inside the nucleus is the nucleolus, which is comprised of protein and RNA.
Timestamps
0:00 Overview of the main components of a cell
0:11 The structure of the plasma membrane
0:38 The cytoskeleton
1:26 The centrosome
1:40 The cytoplasm
1:58 The endoplasmic reticulum
2:58 The ribosomes
3:23 The golgi apparatus
4:07 The lysosomes
4:29 The proteasomes
5:00 The peroxisomes
5:16 The mitochondria
5:47 The nucleus
6:02 The nucleolus
