MEC322: Cells Flashcards
How many cells are in the body?
about 100 trillion cells (average human adult)
What is the largest and smallest cell?
The largest cell, a single neuron, can have an axon over a meter long. A red blood cell has a diameter of 8 μm (micrometers).
What are the three main parts of a cell?
Plasma membrane
Nucleus
Cytoplasm – cytosol and organelles
What is the structure and purpose of the plasma membrane?
Forms a cell’s flexible outer surface, separating the cell’s internal environment from its external environment.
It regulates the flow of materials into and out of a cell to maintain the appropriate environment for normal cellular activities.
It also plays a key role in communication among cells and between cells and their external environment.
What is the basic framework of the plasma membrane?
the lipid bilayer, two tail-to-tail layers made up of three types of lipid molecules: phospholipids, cholesterol, and glycolipids.
What are two types of proteins in the plasma membrane?
The proteins in a membrane are of two types: integral and peripheral.
Integral proteins extend through the lipid bilayer.
Peripheral proteins are loosely attached to the exterior or interior surface of the membrane.
Is the plasma membrane permeable or selectively permeable?
selectively permeable—it allows some substances to move into and out of the cell but restricts the passage of other substances.
What is the lipi bilayer permeable and impermeable to?
The lipid bilayer is permeable to water and to nonpolar (lipid-soluble) molecules (fatty acids, O2, CO2, etc.)
The lipid bilayer is impermeable to ions and large, uncharged polar molecules such as glucose and amino acids.
How do large molecules such as proteins pass through the plasma?
They are unable to pass through the plasma membrane except by transport within vesicles.
What allows small and medium-sized water-soluble materials to cross the membrane?
Integral proteins
Why is it important for materials to move across a plasma membrane?
Certain substances must move into the cell to support metabolic reactions. Other materials must be moved out because they have been produced by the cell for export or are cellular waste products.
Name the types of body fluid
Intracellular fluid (ICF) – fluid in body cells (~ 2/3rd of all body fluid volume)
Extracellular fluid (ECF) – fluid outside cells
Interstitial fluid – ECF between cells in tissues
Blood plasma – ECF in blood vessels
Lymph – ECF in lymphatic vessels
Cerebrospinal fluid (CSF) – surrounds the brain and spinal cord
Describe the two methods for substances to move across the plasma membrane.
Passive processes – substance moves down its concentration gradient through the membrane, using only its own energy of motion (kinetic energy), include simple diffusion and osmosis.
Active processes – cellular energy, usually in the form of ATP, is used to “push” the substance through the membrane “uphill” against its concentration gradient. An example is active transport.
What is diffusion?
A passive process in which a substance moves due to its kinetic energy. Areas of high concentration move to areas of low concentration.
What is simple diffusion?
when substances diffuse across a membrane through the lipid bilayer.
eg. fatty acids, steroids, fat-soluble vitamins, oxygen, carbon dioxide.
What is facilitated diffusion?
In this process, an integral membrane protein assists a specific substance to move across the membrane. The membrane protein can be either a membrane channel or a carrier.
What is osmosis?
a passive process in which there is a net movement of water through a selectively permeable membrane.
Water moves by osmosis from an area of higher water concentration to an area of lower water concentration
What is an isotonic solution?
Any solution in which cells maintain their normal shape and volume is called an isotonic solution (the concentrations of solutes are the same on both sides).
What is a hypotonic solution?
A hypotonic solution is a solution that has a lower concentration of solutes (higher concentration of water).
cell swells
What is a hypertonic solution?
A hypertonic solution has a higher concentration of solutes (lower concentration of water).
cell shrinks
What does the function of the plasma membrane depend on?
type of proteins that are present some form: receptors ion channels proteins act as enzymes carrier proteins (change shape) cell identity markers
What is dialysis good for?
removing small molecules from the bloods
What is ultra filtration better than dialysis for?
removal of fluid and medium sized molecules
What does URR measure?
Urea Reduction Ratio
How effectively a dialysis treatment removed waste products from the body
What percentage URR are patients said to live longer and have fewer hospital visits?
60%
Describe the measurement of URR
measured every 12-14 treatments so once a month
URR may vary considerable so average should not exceed 65%
How do you calculate dialysis efficiency?
K x t / V
K- dialyser clearance, rate at which blood passes thru the dialyser
t - time
V - volume of water in patients body
What are the limitations of the dialysis efficiency equation?
k values are measured by manufacturer with water so underestimate
patients do not all have same water percentage
bigger solute removal is not taken into account
What is active transport?
an active process where cellular energy is used to transport substances across the membrane against a concentration gradient
What is a vesicle?
a small round sac formed by budding off from an existing membrane
What do vesicles do?
transport substances from one structure to another within cells, take in substances from extracellular fluid and release substance into extracellular fluid
What is endocytosis?
– in which materials move into a cell in a formed vesicle
What is exocytosis?
in which materials move out of a cell by the fusion of a vesicle.
results in secretion or liberation of materials out of cell
What are the two types of endocytosis?
Phagocytosis is “cell eating”. Large solid particles, such as whole bacteria or viruses or dead cells, are taken in by the cell.
Bulk-phase endocytosis (pinocytosis) is “cell drinking.” The cells take up tiny droplets of extracellular fluid.
