Chapter 3: The Cellular Level of Organization Flashcards
The basic, living, structural and functional units of the body
the study of these is called cytology
Cells
Name the three main parts of a cell
- Plasma Membrane
- Cytoplasm
- Nucleus
The cells flexible outer surface that separates the internal environment from the external environment
A selective barrier that regulates the flow of materials in and out of the cell
Roll in communication among cells and between cells and external environment
Plasma Membrane
This part of a cell consists of all cellular contents between the plasma membrane and the nucleus
Cytoplasm
What are the two components of the cytoplasm?
Cytosol
Organelles
What is cytosol?
The fluid portion of cytoplasm (aka intracellular fluid)
What are organelles?
“little organs” inside the cell, each with a characteristic shape and specific function
What the cell part that is a large organelle that houses most of the cells DNA?
Nucleus
What is a chromosome?
A single molecule of DNA associated with several proteins
What does each chromosome contain?
Thousands of hereidtary units called genes
What do genes do?
Control most aspects of cellular structure and function
Define plasma membrane
A flexible, but sturdy, barrier that surrounds and contains the cytoplasm of a cell
What is the fluid mosaic model?
Where the arrangement of the plasma membrane resembles a continually moving sea of fluid lipids that contains a mosaic of many different proteins.
The basic strucural framework of the plasma membrane
Lipid bilayer
Describe the lipid bilayer
two back to back layers made up of phospholipids, cholesterol and glycolipids
What type of lipid makes up about 75% of the membrane?
Phospholipids
What does ampiphatic mean?
Having both polar and non-polar parts (lipids in bilayer)
This is the polar part of the phospholipid
It is hydrphyllic (love water)
The arrange on the outside layers of the plasma membrane, that way they are facing the watery fluids
Head
This is the non polar part of the phospholipid
It is hydrophobic
They point in towards the middle layer of the plasma membrane, away from watery fluids
tail made of two long fatty acids
This lipid is weakly ampiphatic and are spear among the other lipids in both layers of the membrane
The -OH group is the polar region and forms hydrogen bonds with the polar heads of the phospholipids and glycolipids
Stiff steroid rings and hydrocarbon tail are nonpolar; they fit among the fatty acid tails
Cholesterol
These have polar heads and nonpolar tails. Their heads are only found in the plasma membrane layer the is on the outer surface of the cell
Glycolipids
Integral proteins
extend through the lipid bilayer and are firmly embedded; most are transmembrane proteins and amphiphatic
Transmembrane proteins
proteins that span the entire lipid bilayer and protrude into both the cytosol and extracellular fluids; ampiphatic
Peripheral proteins
not firmly embedded; attached to the polar head of membrane lipids or to integral proteins at the inner or outer membrane surface
Integral proteins that have carbohydrate groupds attached to the ends that protrude into the extracellular fluid
Glycoproteins
An extensive sugary coat formed by the carbohydrate portions of glycolipids and glycoproteins
Varies from cell to cell
Hydrophylic and attracts a film of fluid that prevents cells from drying out
Used in immunity to recognize invader cells
Glycocalyx
Integral protein that specific ions can flow through to get in or out of a cell
Ion Channel Proteins
What does it mean if an ion channel is selective?
It only allows a single type of ion to pass through
These integral proteins selectively move substances from one side of the cell to the other by changing shape
Carrier proteins
Integral protein that serve as cell recognition sites. Specific to certain molecules called ligands
Receptor proteins
Integral proteins that catalyze a reaction inside or outside of a cell
Enzymes
Integral proteins that anchor proteins of neighboring cells to one another or to protein filaments inside and outside of the cell
Linker proteins
What type of molecules serve as cell identity markers?
glycoproteins and glycolipids
What two functions do cell-identity markers play a role in?
- Recoginition of other cells fo the same kind during tissue transformation
- Recognition and response by the immune system to potentially dangerous foreign cells
Allowing some substances to pass more readily than others through the plasma membrane
Selective permeability
What substances is the lipid bilayer portion of the plasma membrane HIGHLY permeable to?
Nonpolar molecules like oxygen, carbon dioxide, and steroids
What substances is the lipid bilayer portion of the plasma membrane MODERATELY permeable to?
small, uncharged polar molecules like water and urea
What substances is the lipid bilayer portion of the plasma membrane IMpermeable to?
ions and large, uncharged polar molecules like glucose
Difference in concentration of a chemical from one place to another
Concentration gradient
Difference in electrical charges between two regions
Electrical Gradient
The inner surface of the plasma membrane is more negatively charged and the outer surface is more positively charged; the charge difference is called this
membrane potential
The combined influence of the concentration gradient and the electrical gradient on movement of a particular ion is called
Electrochemical gradient
When a substance moves down its concentration or electric gradient to cross the membrane using only its own kinetic energy; no input of energy from the cell
Passive processes
When cellular energy is used to drive the substance “uphill” against its concentration or electrical gradient; usually energy in form of ATP
Active processes
When vesicles detach from the plasma membrane while bringing materials into a cell
endocytosis
When vesicles merge with the plasma membrane to release materials from a cell
exocytosis
Tiny spherical membranes that transport substances into and out of a cell
vesicles
A passive process in which the random mixing of particles in a solution occurs becaues of the particles kinetic energy
Both the solute and the solvent undergo this process
Diffusion
What does it mean to move down their concentration gradient?
Move to an area of high concentration to an area of lower concentration until evenly distributed
5 factors that influence the diffusion rate of substances across the plasma membrane
1.Steepness of concentration gradient - greater differences, high rate of diffusion
2. Temperature - higher temp, faster rate
3. Mass of the diffusing substance - larger mass, slower rate
4. Surface area - larger membrane surface area, faster the rate
5. Diffusion distance - the greater distance, longer it takes
Three types of diffusion
- Simple diffusion
- FAcilitated diffusion
- Osmosis
A passive process in which substances (small, nonpolar, hydrophobic) move freely through the lipid bilayer of the plasma membranes of the cells without the help of membrane transport proteins
Simple Diffusion
* very important in movement of oxygen and carbon dioxide*
A passive process of diffusion where an integral membrane protein (either carrier or membrane channel) assists a specific substance across the membrane.
Facilitated diffusion
When a solute moves down its concentration gradient across the lipid bilayer through a membrane channel
Eg ion channel
Channel mediated facilitated diffusion
What are the most numerous ion channels selective for in typical plasma membrane?
Fewer?
potassium K+
Chloride CL-
Fewer for Na+ and Ca+
WHen a part of the channel protein acts as a plug or fate, changing shape in one way to open the pore and in another way to close it
Gated channel
Facilitated diffusion where a carrier protein moves a solute down its concentration gradient across the plasma membrane
Carrier mediated facilitated diffusion
Once all of the carrier proteins are occupied, the _____________ is reacher and a steeper gradient will not increase the rate of diffusion further
Transport maximum
This energy source for making ATP, enters many cells by carrier-mediated facilitated diffusion
GLucose
Process of glucose entering cells through carrier mediated facilitated diffusion
- GLucose binds to GluT (glucose transporter protein) on outside of cell
- Transporter protein changes shape and glucose passes through the membrane
- Glucose released on the other side of membrane
This ligand works to elevate the transport maximum for facilitated diffusion of glucose into cells
insulin
A type of diffusion in which there is net movement of a solvent (water) through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration; passive process
Osmosis
Moves through semipermeable membrane from an area of lower solute concentration to an area of high solute concentration
Two ways water molecules pass through a plasma membrane
- Between phospholipid molecules via diffusion
- Moving through Aquaporins
An integral membrane protein that function as water channels
Play a critical role in controlling the water content of cells
Responsible for the production of CSF, aqueous humor, tears, sweat, saliva and the concentration of urine
Aquaporin
Pressure exerted by a liquid that that forces water molecules to move back to its original location
Hydrostatic pressure
The force exerted by a solution with impermeable solute that is proportional to the concentration of the solute particles that cannot cross the membrane
Osmotic pressure
the higher the solute concentration, the higher the pressure
The measure of a solutions ability to change the volume of cells by altering their water content
Tonicity
A solution in which a cell maintains its normal shape and volume; concentration of solutes that cannot cross membrane are the same both in and outside of the cell
Isotonic solution
A solution with a lower concentration of solutes than the cell; causes water to rush into the cell and the cell eventually bursts
Hypotonic; pure water is very hypotonic
The bursting of cells by the exposure to a hypotonic solution, causing them to over fill with water and rupture
Lysis
For RBCs its called hemolysis
A solution with a higher concentration that the inside of the cell
Causes water to rush out of cells and the cells shrink
Hypertonic
The term for cells shrinking because of exposure to a hypertonic solution
Crenation
Active process that allows some polar or charged colutes to move against their concentration gradient across a cell membrane; requires energy
Active transport
Two sources of cellular energy needed for active transportation of molecules through carrier proteins
- Primary Active transport
- Secondary Active transport
Active transport using energy from hydrolysis of ATP molecules
Energy changes the shape of the carrier protein which “pumps” a substance across the membrane against its concentration gradient
Primary Active Transport
Active transport using energy stored in an ionic concentration gradient
Secondary Active Transport
Carrier proteins that mediate primary active transport are called
Pumps
The most prevalent primary active transport mechanism in the body?? Na+ K+
Part of this protein acts as an enzyme that hydrolyzes ATP
Maintain higher Na+ outside cell and higher K+ inside cell. These ions slowly diffuse back down their electrochemical gradients they need to be pumped back across
Sodium-potassium pump
aka Na+-K+ATPase
This form of active transport uses energy stored in a Na+ of H+ concentration gradient to drive other substances across the membrane against their own concentration gradients.
Indirectly uses energy obtained from hydrolysis of ATP
Secondary active transport
When a carrier protein binds to a sodium ion and another substance and then changes its shape so that both substances cross the membrane at the same time. What are the two types of transporter/ carrier proteins?
Symporters - both substances move to the same direction across the membrane
Antiporters - both move in opposite directions across the membrane
Three types of endocytosis
- Receptor mediated endocytosis
- phagocytosis
- bulk-phase endocytosis
A highly selective type of endocytosis by which cells take up specific ligands
Receptor-mediated endocytosis
A form of endocytosis in which the cell engulfs large solid particles, like worn out cells, whole bacteria or viruses
Phagocytosis
Two types of phagocytes (cells that can carry out phagocytosis) are called
Macrophages - located in many body tissues
Neutrophills - a type of WBC
Projections of a phagocytes plasma membrane and cytoplasm that surround a particle outside the cell
Pseudopods
The vesicle formed around the particle by the pseudopod of the phagocyte that fuses with lysosomes
Phagosome
What happens when a phagosome containing a particle binds to one or more lysosome within a phagocyte?
Lysosomal enzymes break down the particles; any undigested materials remain indefinitely in a residual body vesicle and are either excreted through exocytosis or remain in the cell as lipofuscin granules
What is pinocytosis (bulk phase endocytosis) and what is the process?
The taking up of tiny droplets of extracellular fluid into the cell
The cell membrane folds inwards and forms a vesicle containing the droplet of extracellular fluid; the vesicle pinches off and fuses with a lysosome in the cell where the contents are degraded by enzymes; the resulting smaller molecules leave the lysosome to be used elsewhere in the cell
THis occurs in most cells especially absorptive cells in intenstines and kidneys
This process releases substances from within a cell using a vesicle
All cells do it, however most important for secretory cells and nerve cells
Exocytosis
What do secretory cells use exocytosis to release from within?
Digestive enzymes, hormones, mucous, other secretions
Why is it important for nerve cells to use exocytosis
They release neurotransmitters
When vesicles undergo endocytosis on one side of a cell, move across the cell and then undergo exocytosis on the opposite side to release contents
Transcytosis
Occurs most often across epithelial cells that line blood vessels
