Cells Are The Smallest Unit Of Life Flashcards
Cell
Structural and functional unit of life
Organismal functions depend on
Individual and collective cell functions
3 Human cells
- Plasma membrane
- Cytoplasm
- Nucleus
The basic functional unit of living organisms is the
Cell
The three main components of all cells include the plasma membrane, the nucleus, and the
Cytoplasm
Phospholipids orient themselves in aqueous solutions such that
The polar heads face the interior and exterior of the cell with the tails forming the center of the membrane
Membrane protein:2 Types
- Integral Proteins
2. Peripheral Proteins
Integral Proteins
-Firmly inserted into membrane
(Most are transmembrane)
- Have hydrophobic and hydrophilic regions
- Function as transport Proteins(channel and carriers),enzymes,or receptors
Peripheral Proteins
- Loosely attached to integral Proteins.
- Include filaments on intracellular surface for membrane support
- Functions as enzymes;motor proteins for shape change during cell division and muscle contraction;cell-to-cell connections
Plasma Membrane
•Cells are surrounded by
Interstitial fluid (IF)
Plasma membrane allows cell to:
- Obtain from (IF) exactly what it needs,exactly when it is needed
- Keep out what it does not need
- AKA “selectively” permeable membrane
Membrane Transport
Plasma membranes selectively permeable
•Some molecules pass through easily; some do not
Two ways substances cross membrane
- Passive processes
2. Active Processes
Types of membrane Transport
- Passive processes
2. Active Processes
Passive Processes
~No cellular energy (ATP)required
~Substance moves down its concentration gradient
Active Processes
- Energy (ATP)required
2. Occurs only in living cell membranes
Passive Processes
•Diffusion
- Simple diffusion
- Carrier-mediated facilitates diffusion
- Channel-mediated facilitated diffusion
- Osmosis
Molecule will passively diffuse through the cell membrane if:
- It is lipid soluble,or
- Small enough to pass through membrane channels,or
- Assisted by carrier molecule
Passive Processes Diffusion
•Collisions cause molecules to move down or with their concentration gradient
*Difference in concentration between two areas
Speed influenced by molecule size
Smaller=Faster
Warmer=Faster
Passive Processes: Facilitated Diffusion
Certain Lipophobic Molecules transported passively by
1.Binding to protein carriers
2.Moving through water-filled channels
(Don’t like Lipids)
Carrier-Mediated Facilitated Diffusion
-Transmembrane integral Proteins are carriers.
-Transport specific polar molecules too large for channels
-Binding of substrate causes shape change in carrier the passage across membrane
-Limited by number of carriers present
•carriers saturated when all engaged
Channel-Mediated Facilitated Diffusion…Two Types
1.Leakage Channels
•Always open
2.Gated Channels
•Controlled by chemical or electrical signals
Carrier-Mediated Facilitated Diffusion
Via protein carrier specific for one chemical; binding of substrate causes transport protein to change shape
Channel-Mediated Facilitated Diffusion
Through a channel protein;mostly ions selected on basis of size and charge
Osmolarity
Measure of total concentration of solute particles
Aquaporins
Through specific water channels
Osmosis causes cells to
Swell and shrink
Water moves by
Osmosis
Tonicity
Ability of solution to alter cell’s water volume
Isotonic
Solution with same non-penetrating solute concentration as cytosol
Hypertonic
Solution with higher non-penetrating solute concentration than cytosol
Hypotonic
Solution with lower non-penetrating solute concentration than cytosol
Why don’t RBC’s lyse or shrink while in circulation ?
Because they are in a isotonic solution
Where would steroid hormones most likely interact with their target cell
Inside the target cell’s cytoplasm or nucleus
A red blood cell placed into a container of distilled water will
Gain water via osmosis
Simple Diffusion
Gas exchange in our lungs
A dissolving sugar cube
Popcorn odor permeating the room
