The Cell Level Flashcards
What is the smallest structural and functional unit of a living organism?
the cell
What is the cell doctrine?
1.all living things consist of one or more cells, 2. each cell can live independently of the rest, 3. cells can arise only from other cells
What are the two types of cells?
prokaryotic, eukayoitc
What is a eukaryote cell?
animal or plant cell
What is a prokaryote cell?
bacterium
On average how many cells is the adult body made of?
about 37.2 trillion
How many different cells types can cells be classified into?
200
What are the types of human cells?
reproductive cells (gametes) and somatic cells (all other body cells)
What are the parts of a cell?
plasma membrane, cytoplasm, nucleus
What are the basic characteristics of the plasma membrane?
flexible outer surface, selective barrier, plays key role in communication among cells and their enviroment
What is the cytoplasm? What does it consist of?
includes all cellular contents, except the nucleus. Consists of cytosol and organelles
What is the largest organelle?
nucleus
What does the nucleus contain?
contains the chromosomes (that house the DNA molecules with the genes)
What is the fluid mosaic model?
continually moving sea of fluid lipids with a mosaic of many different proteins, some proteins float freely as icebergs and others are anchored at a specific locations
What is the most important property of the plasma membrane?
its selective permeability
What is the selective permeability of the plasma membrane?
lipid soluble substances pass, barrier for polar substances, some membrane proteins allow polar substances to pass and move in
The plasma membrane is a ______________ structure composed of _______________ molecules
The plasma membrane is a LIPID-BILAYER structure composed of AMPHIPATHIC molecules
What is an amphipathic molecule?
one that have one water-soluble end and another lipid soluble end
Which are the amphipathic lipids of the plasma membrane?
phospholipids (75%), cholesterol (20%), glycolipids (5%)
What amphipathic lipid of the plasma membrane appears only on the extracellular side of the membrane?
glycolipids
What is the arrangement of proteins in the plasma membrane?
- integral proteins - many are glycoproteins and extend through the bilayer (Transmembrane) and they are anchored, 2. peripheral protein are attached to the polar heads, and are attached to the integral proteins at the inner or outer surface
What is the ‘glyco’ portion of glycoproteins in the membrane?
oligosaccharides (sugar) and protrudes into the extracellular fluid
True or false: the ‘sugar’ portion of the glycolipids in the membrane protrudes into the intracellular fluid
false: protrudes into the extracellular fluid
What is the glycocalyx of the plasma membrane?
the sugar portions of both the glycoproteins and glycolipids form an extensive sugary coat in the outside of the membrane which is called the glycocalyx
True or false: the pattern of sugars in the glycocalyx is the same on each cell
False: the pattern of sugars int he glycocalyx is unique to the cell, the molecular signature of the cell
What are the functions of the glycocalyx?
cells can recognize each other, WBC can recognize a foreign glycocalyx, enables cells to adhere to one another, protects cells against digestive enzymes, attracts a film of fluid to the surface of many cells making cell slippery which helps RBC circulating within narrow capillaries and protects the cells from the airways and GI tract from drying out
What are the membrane integral proteins?
ion channels, carrier (transporter) protein, receptor protein, enzyme protein, linker protein, and cell identity protein markers
What are ion channels?
pores for one specific ion
What are carrier proteins?
move one polar substance or ion across plasma membrane
What is a receptor protein? Give an example.
serves as a recognition site, binds to one specific molecule (ligand) ie. insulin
What is an enzyme protein?
catalyzes reaction at the membrane or inside the cell
What are linker proteins?
anchor membrane proteins of neighbouring cells
What are cell identity protein markers?
glycocalyx
What are the functions of peripheral proteins?
- Support plasma membrane
- Anchor integral proteins
- Participate in the intracellular
movement of materials - Attach cells to one another
What makes the plasma membrane fluidity?
Most membrane lipids and many proteins rotate and move sideways
At the body’s temperature what makes the bilayer stronger?
Cholesterol makes the bilayer stronger but less fluid at body’s temperature.
In a low temperature what does cholesterol do to the plasma membrane fluidity?
In low temperature, cholesterol makes it Weaker: the membrane is more fluid but less strong
What is membrane fluidity important?
Allows interactions within the membrane, including:
- Movement of components:
• Growth
• Division
• Secretion - Formation of the cellular junctions
- Self-healing if torn or punctured
How permeable is the plasma membrane to non-polar molecules?
The plasma membrane shows selective permeability
How permeable is the plasma membrane to small uncharged molecules?
- Due to the non polar lipid interior of the bilayer:
• Highly permeable to non polar molecules:
• O2, CO2 and steroids - Moderately permeable to small uncharged molecules:
• H2O, urea
What is the plasma membrane impermeable to?
The membrane is impermeable to:
• Ions
• Large uncharged molecules (glucose)
What do the transmembrane proteins (Channels and carriers) allow to pass through the plasma membrane?
allow a variety of ions and uncharged polar molecules (very selectively) to pass
How do proteins pass through the plasma membrane?
only by endocytosis and exocytosis
What are the types of passive transport across the plasma membrane?
- Simple Diffusion
- Facilitated Diffusion
• Channel-mediated
• Carrier-mediated - Osmosis
What can pass through the plasma membrane via simple diffusion?
Non polar, hydrophobic substances move freely through the bilayer down their concentration gradient.
What are the two types of channel mediated facilitated diffusion?
- Channel-mediated Facilitated Diffusion (slower than simple diffusion)
• Substance moves down its concentration gradient through a channel, very fast
• Most membrane channels (pores) are ion channels
• K+ , Cl- (most numerous)
• Na+ , Ca2+ (fewer) - Carrier-mediated Facilitated Diffusion
• An integral membrane protein undergo changes in shape to move a substance
across down its concentration gradient
True or false: channel mediated facilitated diffusion is faster than simple diffusion
False (slower than simple diffusion)
How do substances move through a channel mediated facilitated diffusion?
Substance moves down its concentration gradient through a channel, very fast
What type of channels are most membrane channels (pores)?
Most membrane channels (pores) are ion channels
How does carrier mediated facilitated diffusion work?
An integral membrane protein undergo changes in shape to move a substance across down its concentration gradient
What is osmosis?
Osmosis is a net passive movement of water through a selectively permeable membrane
True or false: high water concentration moves to an area of lower water concentration
True
How does water from high concentration move to an area of lower water concentration?
- Simple diffusion
* Aquaporins (channels for water)
What is osmotic pressure?
Osmotic pressure: The pressure exerted by the solute particles in the solution that cannot cross the membrane
• Directly proportional to the concentration of the solution
Why does a normal cells volume remain constant?
The normal cell’s volume remains constant because the osmotic pressure in the ECF is the same as the osmotic pressure of the ICF
The solution in which the cell maintains its normal shape is called what?
The solution in which the cell maintains its normal shape is called isotonic
The solution in which the cell shrinks is called what?
Hypertonic
The solution in which the cell swells is called what?
Hypotonic
What are the two types of active transport across the membrane?
- Active Transport:
• Primary active transport
• Secondary active transport
2. Transport in Vesicles: • Endocytosis • Phagocytosis • Exocytosis • Transcytosis
What is primary active transport?
“Pumps” a substance across the membrane
against its concentration gradient.
What is an example of primary active transport?
The sodium-potassium pump is an example
What is the sodium potassium pump also known as?
The sodium-potassium pump is also known as the
Na+/ K+ ATPase
What is ATPase?
The ATPase is the enzyme that breaks down the ATP molecule for energy to be released
What are the types of transport in vesicles?
endocytosis and exocytosis
What is secondary active transport?
The Na+ gradient generated by the pump is used to drive transport of other
solutes.
• In the kidney and intestines, glucose and amino acids enter or leave the cells
only when accompanied by Na+.
• In the heart, Na+ moving down its gradient is coupled to Ca++ moving out.
What are symporters?
Symporters: move substances in the same direction
What are antiporters?
Antiporters: move substances in opposite directions
What is endocytosis?
Materials are moved into the cell in a vesicle formed from the plasma membrane
What is exocytosis
Materials are moved out of the cell by the fusion of vesicles with the plasma membrane
True or false: transport in vesicles don’t require energy
False (Transport in vesicles requires energy!)
What are the three types of endocytosis?
- Receptor-mediated endocytosis
- Phagocytosis
- Bulk-phase endocytosis (pinocytosis)
Describe receptor-mediated endocytosis.
• Highly selective, cell takes up a specific substance that binds to the
membrane
• Membrane in-vaginates and forms a vesicle
• In the cytoplasm, the vesicle is surrounded by lysosomes and digested
Describe phagocytosis
The cell engulfs large solid particles: • Psudopods surround the particles • Forms the phagosome • Phagosomes are surrounded by lysosomes • Particle is digested
What carries out phagocytosis?
- Macrophages
* Neutrophils
What is bulk-phase endocytosis also known as?
• Also called pinocytosis
Describe bulk-phase endocytosis
Droplets of ECF are brought into the cell:
• Membrane forms vesicles
• Vesicles are surrounded by lysosomes
• Contents are digested
Does exocytosis release or receive materials?
Releases materials from the cell
What cells carry out exocytosis?
1. Secretory cells, secrete: • Hormones • Enzymes • Mucus • Sweat
- Neurons, secrete:
• Neurotransmitters
What do secretory cells secrete?
- Secretory cells, secrete:
- Hormones
- Enzymes
- Mucus
- Sweat
What do neurons secrete?
- Neurons, secrete:
* Neurotransmitters
How does exocytosis work?
• Membrane-enclosed vesicles within the cytoplasm fuse to the membrane and
release the contents into the ECF
How are nutrients absorbed in the intestines into the blood?
The Transcytosis
Used by the cell to move substances in, across, and then out of the cell
