Unit 3: Cells Flashcards
Name and describe the 3 main parts of a cell.
1) The Plasma membrane: forms the cell’s outer surface. Which then manages the internal environment and acts as a gatekeeper to anything coming into and out of the cell.
2) Cytoplasm: consists of the cellular contents between the plasma membrane and the nucleus.
This is divided into 2 parts: cytosol and organelles.
Cytosol is the liquid portion of the cell.
Organelles which has a character structure and specific functions.
3) Nucleus: Acts as the control center for a cell, due to it containing genes. Which controls cellular structure and most cellular activities
What is cell biology
is the study of cellular structure and function
What is the Cytosol and what it’s composition?
This is the liquid portion of the cell. (intercellular fluid)
It is made up of water plus dissolved solutes and suspended particles. Site of many chemical reactions.
Describe the structure of the Plasma Membrane.
The plasma membrane is a flexible, sturdy barrier that surrounds and contains the cytoplasm of the cell.
The fluid mosaic model describes the structure of the plasma membrane, which is composed of a double layer (bilayer) of phospholipid molecules with many protein molecules dispersed within it.
The surfaces of the membrane are hydrophilic due to the polar phosphate heads. The internal portion of the membrane is hydrophobic due to the nonpolar fatty acid tails.
Integral proteins are firmly inserted into and extend across the lipid bilayer. Most of these proteins are glycoproteins, which serve as channels (pores), transporters (carriers), receptors (recognition sites), or enzymes.
Peripheral proteins lie loosely on the inner and outer surface of the cell membrane, serving as enzymes or cytoskeletal anchors.
Membranes are fluid structures, somewhat like cooking oil, because most of the membrane lipids and many of the membrane proteins easily move within the bilayer.
Cholesterol serves to stabilize the membrane and reduce membrane fluidity.
Plasma membranes are selectively permeable, meaning that some things can pass through and others cannot.
The lipid bilayer portion of the membrane is permeable to small, nonpolar, uncharged molecules, but impermeable to ions and charged or polar molecules. This bilayer also is permeable to water.
Transmembrane proteins that act as channels or transporters increase the permeability of the membrane to molecules that cannot cross the lipid bilayer.
Macromolecules are unable to pass through the plasma membrane except by vesicular transport.
Describe the function of the plasma membrane
1) Acts as a barrier separating inside and outside of the cell.
2) Controls the flow of substances into and out of the cell.
3) Helps identify the cell to other cells
4) participates in intercellular signalling.
what is meant by Selective Permeability
The membrane has selective permeability meaning it is able to control what comes into and out of the cell. The cell allows water and nonpolar (lipid-soluble) molecules to pass through the membrane however does not allow ions, and large, uncharged polar molecules to pass freely
Describe membrane transport, and compare and contrast the different processes.
Intracellular fluid is located inside the cell, and extracellular fluid is located outside the cell.
The types of extracellular fluid include the following:
- Interstitial fluid
- Plasma
- Lymph
Solutes are substances dissolved in a solvent.
A concentration gradient is the difference in the concentrations of a substance between two areas (e.g., the amount of water in your cells compared to the amount of water in the lake in which you are swimming, or the amount of sodium ions in extracellular fluid compared to the amount of sodium ions in intracellular fluid).
Transport processes are classified according to two criteria:
- Active or passive
- Vesicular
Living cells use three passive transport processes, two of which are nonmediated (diffusion through the lipid bilayer and diffusion through a channel) and one that is mediated (facilitated diffusion).
Vesicular transport involves the formation of membrane-surrounded vesicles to move materials into or out of the cell by endocytosis or exocytosis. See also Objective 5 in this module.
What is simple diffusion and what substances are able to move in and out of the cell?
Molecules move down the concentration gradient a passively pass through cell membrane bilayer.
lipid-soluble substances include;
oxygen, carbon dioxide, nitrogen gases, fatty acids, steroids, fat-soluble vitamins (A, E, D, K), polar molecules (water, and urea)
What is Facilitated Diffusion? What substances are involved with this process?
- require integral membrane proteins to enter cell
- can form channels called ion channels
- mostly found; k, cl,
fewer channels are; Na, and Ca,
-contain gates
-others function as carriers bind to 1 side of cell then get released into the opposite side. Includes glucose, galactose, and fructose.
what is a concentration gradient? How does it work?
- difference in concentration btw 2 areas
- down gradient means, the concentration moves from high to low
- up gradient means, the concentration moves from low to high
Define solute and Solvent. Then explain concentration.
solute - material dissolved in a solution
solvent - substance that dissolves a solute
concentration - amount of solute in a solution. more solute = more concentration.
what is osmotic pressure?
solutes particles that can’t pass through cell membrane exert pressure on the cell membrane.
The higher the concentration of solute in a cell the greater the osmotic pressure.
What are the different solutions based on osmotic pressure?
Isotonic Solution: any solution where cells maintain their normal shape and volume inside and outside of cells have even solute distribution.
Hypotonic solution: a solution contains lower concentration of solutes (higher concentration of water) the cell will burst due to internal environment of cell having a more concentrated solution
-in red blood cells, this is called hemolysis.
Hypertonic solution: a solution contains a higher concentration of solutes (lower concentration of water) causing the cell to shrink, due to internal environment of cell having a less concentrated solution.
-in red blood cells, this is called Crenation
What is active Transport?
is an energy-requiring process that moves solutes such as ions, amino acids, and monosaccharides against a concentration gradient.
What is Osmotic Transport?
Osmosis:
- water molecules move down a concentration gradient.
- move from area of low solute concentration to high solute concentration.
- pass through lipid bilayer or integral proteins as water channels.
Define and contrast the terms diffusion, osmosis, isotonic, hypertonic, hypotonic, and facilitated diffusion.
Diffusion: When solutions of a high concentration move to an area of low concentration. gradually create equilibrium
Osmosis: water moves from an area of high concentration to an area of low concentration, balancing solutes.
Isotonic: A cell maintains its shape and volume because the solutions are equal to the internal and external parts of the cell.
Hypertonic: The extracellular fluid is more concentrated than internal fluid of cell causing fluid to rush out of the internal cell, causing shrinkage
Hypotonic: the extracellular fluid is less concentrated than the internal fluid of the cell causing fluid to rush into the cell, causing a rupture.
Facilitated Diffusion: require channels or carriers to enter into the cell. they still flow down the concentration gradient.
Define the terms active transport, endocytosis, and exocytosis.
Active Transport: cellular energy is used to transport substances across the cell membrane. Moves up the concentration gradient.
- Endocytosis: molecules or particles that are too large to enter the cell by diffusion or active transport are brought into a vesicle formed from a section of the cell membrane
- Exocytosis: materials move out of a cell by the fusion of a vesicle formed inside a cell with a plasma membrane.
Distinguish between endocytosis, phagocytosis, pinocytosis, and exocytosis.
Endocytosis: a substance that comes into a cell in a vesicle formed by the plasma membrane
Phagocytosis: type of endocytosis where large solid particles are taken in by the cell. (bacteria, viruses, aged/dead cells)
Pinocytosis: another type of endocytosis where cells take up tiny droplets of extracellular fluid
Exocytosis: This process results in the secretions of the cell. Getting rid of materials from the inside of the cell. `
Define cytoplasm
The cytoplasm consists of cytosol and organelles.
Cytosol, the intracellular fluid, is the semifluid portion of the cytoplasm that contains inclusions and dissolved solutes.
Cytosol is composed mostly of water, plus proteins, carbohydrates, lipids, and inorganic substances.
The chemicals in cytosol are either in solution or in a colloidal (suspended) form. Functionally, the cytosol is the medium in which many metabolic reactions occur.
