P15 Biology
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Biology 1st SEM. Module II
Contents |
[edit] Unit 2 - The Cell
[edit] Concepts
- Plasma Membrane
- Phospholipid bilayer, which contains great amount of proteins, the most important functions are the following:
- It selectively isolates the content of the cell of the external atmosphere.
- It regulates the interchange of substances between the cytoplasm and the environment.
- Communicates with other cells.
- Model of the fluid mosaic
- Describes the structure of the plasma membrane, this model was developed in 1972 by cellular biologists J. Singer and L. Nicholson.
- Phospholipid bilayer
- Is in the plasma membrane and produces the fluid part of membranes.
- Proteins
- Long chains of amino acids.
- Glucose proteins
- Proteins together with carbohydrates in the plasma membrane, mostly in the outer parts of the cell.
- Functions of proteins
- Transport oxygen, they are components of hair and nails, and allow the cell interact with its environment.
- Transport Proteins
- Regulate the movement of soluble water molecules, through the plasma membrane. Some transport proteins called channel proteins form pores or channels in the membrane so that water soluble molecules pass.
- Carrying proteins
- Have union sites that can hold specific molecules.
- Reception proteins
- They activate cellular responses when specific molecules join.
- Proteins of recognition
- They work as identifiers and as place of union to the cellular surface.
- Fluid
- It is any substance that can move or change of form.
- Concentration
- Number of molecules in a determined unit of volume.
- Gradient
- Physical difference between two regions of space, in such a way that the molecules tend to move in response to the gradients.
- Diffusion
- Movement of the molecules in a fluid, from the regions of high concentration to those of low concentration.
- Passive transport
- Movement of substances in a membrane that doesn’t need to use energy.
- Simple diffusion
- Diffusion of water, gases or molecules across the membrane.
- Facilitated diffusion
- Diffusion of molecules across the membranes with the participation of proteins.
- Osmosis
- Diffusion of the water across a membrane with differential permeability.
- Transport that needs energy
- Movement of substances across a membrane generally in opposition to a gradient of concentration with the requirement of energy.
- Active transport
- Movement of small molecules using energy (ATP).
- Endocytosis
- Movement of big particles towards the interior of the cell using energy. The cells enclose particles or liquids.
- Pinocytosis
- (Literally cell drinking) Form in which the cell introduces liquids.
- Phagocytosis
- Way of eating of the cells. It feeds in this case of big particles or entire microorganisms.
- Pseudopods
- False feet (the amoeba).
- Exocitosis
- Movement of materials out of the cell with the use of energy. It throws waste material.
- Isotonic
- The cytoplasm fluid of the interior of the cells is the same that the outer.
- Hypertonic solution
- The solutions that have a higher concentration of dissolved particles than the cellular cytoplasm and that therefore water of the cells goes out with osmosis.
- Hypotonic
- The solutions with a concentration of dissolved particles lower than the cytoplasm of a cell and that therefore do that water enters the cell with osmosis.
- Swelling
- Pressure of the water inside the vacuole.
- Endoplasmic Reticulum
- It is the place of the synthesis of the cellular membrane.
[edit] Structure and function of the cell
- Rudolf Virchow
- Zoologist, who proposed the postulates of the cellular theory, observes that the living cells could grow and be in two places at the same time, he proposed that all the cells come from other equal cells and proposed 3 postulates:
- Every living organism are formed by one or more cells
- The smallest organisms are unicellular and these in turn are the functional units of the multicellular organisms.
- All the cells come from preexisting cells.
[edit] Common characteristics of all the cells
- Molecular components
- Proteins, amino acids, lipids, sweeten, DNA, RNA.
- Structural components
- Plasmatic membrane, citoplasm, ribosomes.
- Robert Hook
- He postuled for the first time the term cell
- Prokaryotes
- Their genetic material is not enclosed in a membrane ex. Bacterias
- Eukaryotes
- Their genetic material it's contained inside a nucleus closed by a membrane
