Lect Chapter 3a Flashcards
Explain the cell theory
– A cell is a structural in functional unit of life
– How well a organism is doingDepends on the individual and combined activities of all it cells.
-Cells can only arise from other other cells
-Function of cells are dictated by the shape of the cells and specific sub cellular structure
How many different types of human cells aren there and speak of cell diversity
- 200 Types of human cells
- different structures have different functions
What are the three basic parts of a human cell
The plasma membrane and the nucleus and cytoplasm
What is the plasma membrane
Flexible outer boundary
What is the cytoplasm
Intracellular fluid containing organelles
What is the nucleus
DNA containing control center
Name some extracellular materials
Extracellular fluids
cellular secretions
extracellular matrix
Name extracellular fluids found in the body.
Interstitial fluid
Blood plasma
Cerebral spinal fluid
What are extracellular matrix
Substance that acts like glue to hold cells together
What are main functions of the plasma membrane
- Acts as an active barrier between intercellular and extracellular fluid
- plays a dynamic role in selectivity controlling what enters and leaves the cell
- aka cell membrane
Is the structure of the structure of the plasma membrane
- membrane lipids form flexible lipid bilayer
- specialized membrane proteins (fluid mosaic) float through this fluid membrane
- surface sugars form glycocalyx
- cell junctions help hold the soul together
What are the different Membrane lipids and what percentage are each?
- Lipid bilayer made up of 75% phospholipids consisting of two parts the phosphate head which is a polar (charged) and hydrophilic segment and a fatty acid tail which is a nonpolar (no charge)hydrophobic
- 5% glycolipids which is a lipid with a sugar group on the outer membrane surface and -20% cholesterol which increases the membrane as stability
Explain broadly what membrane proteins do and describe?
-Allow cell communication with Enviornment
– make up about half the mass of the plasma membrane
– most have specialized membrane functions
– some float freely, and some are tethered to intracellular structures
What tasks do the membrane proteins perform?
- transport
- receptors for signal transduction
- attachment to the cytoskeleton and extracellular matrix
- enzymatic activity
- intercellular joining
- cell to cell recognition
What are two types of membrane proteins
Integral proteins
peripheral proteins
Describe integral proteins
- Firmly inserted into membrane – most are trans membrane proteins the span the membrane
- have both hydrophobic areas that interact with lipids and hydrophilic areas that interact with water
- Function as transport proteins, enzymes, or receptors
Describe the peripheral proteins
- Loosely attached to integral proteins
- include filaments or intracellular surface used for plasma membrane support
- function as enzymes, cell to cell connections, motor proteins for shape change during cell division and muscle contraction
Describe how a membrane protein performs the task of transport
It could provide a hydrophilic channel across the membrane selective for a specific solute some transport proteins hydrolyze ATP as energy source to active Lee pump substances across the membrane
Describe how a membrane protein may perform the task of receptors for signal transduction
Select membrane proteins exposed to the outside of the cell may have a binding site that fits a specific chemical messenger such as a hormone. When triggered this chemical messenger may cause a change in shape in the protein that initiates a chain of chemical reactions in the cell.
Describe how a membrane protein may attach to the cytoskeleton and extracellular matrix.
Membrane proteins may anchor two elements of the cytoskeleton and the extracellular matrix hoping to maintain shape and fix the location of certain membrane proteins other membrane proteins play a role in cell movement or bind adjacent cells together
Describe the enzymatic activity of certain membrane proteins
- The membrane protein may be an enzyme with an active site exposed to substances in the adjacent solution
- a team of several enzymes in a membrane may capitalize sequential steps of a metabolic pathway. For example one enzyme me catalase solute a into solute be and another enzyme will catalase solute be into solute see and continues until it becomes metabolized into solutes Z
Describe how a membrane protein helps in intercellular joining
- membrane proteins may be hooked two adjacent cells in various kinds of intercellular junctions
– some membrane proteins (cell adhesion molecules or cams) of this group provide temporary binding sites that guide cell migration and other cell to cell interactions
How do you some membrane proteins perform cell to cell recognition
Some glycoproteins (Proteins bonded to short chains of sugar which help to make up the glycocalyx) serve as identification tags that are specifically recognized by other cells.
What is the glycocalyx and what purpose does it serve
It consists of sugars carbohydrates sticking out of the cell surface
-some sugars are attached to lipids glycolipids and some to proteins glycoproteins
This serves as specific biological marker for cell to cell recognition and allows the immune system to recognize self versus non-self.
Every cell tape has a different pattern of this sugarcoating
What are three ways cells can be bound together to form tissues and organs?
–Tight junctions
–desmosomes
–gap junctions
Explain the characteristics of a tight junction
- These are integral proteins on adjacent cells fuse to form an in permeable junction that in circles the whole cell
- prevent fluids in most molecules from moving in between cells for example stomach
Explain desmosomes cell junctions
Rivet like cell junction formed when linker proteins of neighboring cells interlock like teeth of a zipper or Velcro-linker protein is anchored to its cell through thickened button like areas on inside of plasma membrane called plaques
- keratin filaments connect plaques intracellularly for added anchoring strength – desmosomes allow give between cells reducing the possibility of tearing under tension
What are connexons what do they do
Form the pore for a gap junction between the cytoplasm of two adjacent cells. This channel allows for bidirectional flow of ions and signaling molecules.
What Are two ways substances move across the plasma membrane?
- Active processes where energy ATP is required
- passive processes were no energy is required
Are two types of passive membrane transport
Diffusion and filtration
Where does filtration normally occur
Usually occurs across capillary walls
What influences the speed of diffusion
Size of the molecule and temperature
How does the plasma membrane’s selectively permeable barriers affect diffusion?
They stop diffusion and create concentration gradients on either side
What molecules are able to passively diffuse through membranes
- Lipid soluble and non-polar substances
- very small molecules that can pass through membrane or membrane of the channels
- larger molecules assisted by carrier molecules
What will pass through via simple diffusion?
- Nonpolar lipid soluble hydrophobic substances diffuse directly through the phospholipid bilayer
Oxygen, carbon dioxide, fat soluble vitamins
What are the two types of facilitated diffusion?
- Carrier mediated facilitated diffusion
- channel mediated facilitated diffusion
What are The carriers in carrier mediated facilitated diffusion and explain how it works
The carriers are transmembrane integral proteins
and they transport specific polar molecules such as sugars and amino acids too large for membrane channels. Binding of molecule causes carrier to change shape moving the molecule in the process
Binding is limited by the number of carriers present
What are channel in the channel mediated facilitated diffusion and explain how it happens
Channels with aqueous filled cores are formed (aquaPorins) by transmembrane proteins
-channels transport molecules such as ions or water down there concentration gradient.
Specificity based on poor size and/or charge
What are two types of channels in the channel mediated facilitated diffusion?
-Leakage channels always open -gated channels controlled by chemical or electrical signals
What are two ways water diffuses via osmosis through the plasma membrane
- go to specific water channels called aquaPorins
- Through the lipid bilayer even though it’s polar because it is so small it could still get through the non-polar phospholipid tails
When does osmosis occur?
When water or other solvent concentration is different on the two sides of the membrane
What is Osmolarity
It’s the measure of total concentration of solute particles
What is hydrostatic pressure?
Pressure of water inside the cell pushing on the membrane
What is Osmotic pressure
Tendency of water to move into a sell by osmosis the more solutes inside a cell the higher the osmotic pressure
What is changing cell volume affect
Can disrupt cell function especially in neurons
What is tonicity
The ability of a solution to change the shape or tone of cells by altering the cells internal water volume
Example hypertonic solutions pull water out of the cells hypotonic solutions are never give in because it results in hemolysis
