Chloroplasts are the sites of photosynthesis within plant cells. Golgi Apparatus The Golgi apparatus modifies, sorts and packages macromolecules for delivery to other organelles or secretion from the cell via exocytosis - see 9. Lysosomes Lysosomes tiny sacs containing enzymes are the main sites of intracellular digestion. They enable the cell to make use of nutrients.
Cells and tissues Overview of the main cellular components and tissues. Plasma membrane The plasma membrane surrounds the cell to create a barrier between the cytosol and the extracellular matrix. Plasma membranes also enclose lumens of some cellular organelles.
The structure of the membrane resembles a fluid mosaic made up of phospholipids, cholesterol, and membrane proteins.
Phospholipid molecules, the main structural components of the membrane, form an amphipathic bilayer.
An amphipathic structure is both hydrophilic and hydrophobic; part of the structure has a high affinity for water and the other part is repelled by water.
The inner surface of each layer is made up of lipid chains and thus is hydrophobic. The outer surface of each layer is made up of the polar heads of the phospholipids and is hydrophilic.
Cell Membrane Proteins associated with the plasma membrane are either peripheral membrane proteins or integral membrane proteins. Peripheral membrane proteins interact closely with the membrane through ionic interactions.
Integral membrane proteins are embedded within or pass through the lipid bilayer. There are six broad categories of integral membrane proteins: Pumps - transport ions, sugars, and amino acids across membranes Channels - allow small ions and molecules to pass freely in and out of the cell Receptors - recognise and bind with ligands Linkers - anchor the cytoskeleton to the extracellular matrix Enzymes - have many roles, for example ATPases participate in ion pumping Structural proteins - form junctions with neighboring cells Membranous Organelles Endoplasmic reticulum The endoplasmic reticulum ER is a large network of membranes responsible for the production of proteins, metabolism and transportation of lipids, and detoxification of poisons.
There are two types of endoplasmic reticulum with separate functions: The outer plasma membrane of rough endoplasmic reticulum rER is carpeted with ribosomes, causing it to appear dotted under a microscope. Protein production occurs in the ribosomes of rER.
The ribosomes synthesize a peptide strand which enters the lumen of the rER and folds into its functional shape.
From there it will be transported to the Golgi apparatus in a membrane bound vesicle formed from budding of the rER membrane.
Cells have many structures inside of them called organelles. These organelles are like the organs in a human and they help the cell stay alive. Each organelle has it’s own specific function to help the cell survive. The Cell Wall is a rigid structure mainly made out of the carbohydrate cellulose, a tough chemical that helps plants to maintain their shape and structure. When plant cells divide, a new cell wall is formed between the two dividing cells to separate them. The cytoplasm is composed of water minerals vitamins salts a variety of chemicals as well as different organelles. Inside the cell, there are organelles which are suspended in the cytoplasm. Nucleus. It is one organelle the nucleus is the control center of the cell.
Smooth endoplasmic reticulum, abbreviated sER, lacks ribosomes and thus appears smooth under a microscope. Its functions vary among cell types. For example, sER in cells of the liver have detoxifying functions while sER in cells of the endocrine system mainly produce steroid hormones.
Detoxification occurs through enzymes associated with the sER membrane and usually involves adding hydroxyl groups to molecules.Cellular Organelles.
Cells are the smallest units of life. They are a closed system, can self-replicate, and are the building blocks of our bodies.
In order to understand how these tiny organisms work, we will look at a cell’s internal structures. The cell membrane is often included in sections about the structure and functions of cell organelles.
However, the cell membrane (also known as the plasma membrane) is not within the cell but one of the structures that defines the cell - together with the cell wall in the cases of plant cells and prokaryotic cells. An organelle (think of it as a cell’s internal organ) is a membrane bound structure found within a cell.
Just like cells have membranes to hold everything in, these mini-organs are also bound in a double layer of phospholipids to . Cells have many structures inside of them called organelles. These organelles are like the organs in a human and they help the cell stay alive.
Each organelle has it’s own specific function to help the cell survive. Organisms are composed of cells, and these cells have specific structures within in them that allow them to carry out their functions.
These structures are called Organelles. The fine detail of the cell (which may be revealed by an electron microscope) is called the cell’s ultrastructure. With the exception of red blood cells, all cells have a nucleus in the human body.
The nucleus of human cells is surrounded by a membrane called the nuclear envelope. The nuclear envelope is a double-membrane structure consisting of two layers of phospholid similar to the plasma membrane.