Chapter 3: Cell Structure and Function Flashcards
Cytoskeleton
A protein network that maintains the cells shape, allows cell to move, and directs movement of substances within the cell
What is the cytoskeleton composed of?
Proteins such as actin filaments, microtubules, intermediate filaments
Nucleus
- Contains DNA (genes —> proteins)
- Controls the cell by regulating proteins synthesis (controls what proteins the cells needs to make)
- Proteins made by cells can function as enzymes, be structural components of the cell part of membrane receptors or serve other functions
Ribosomes
Part RNA and part proteins
What is the role of ribosomes and where can we find them in the cell?
- This is where proteins synthesis occurs.
- We find ribosomes in the cytoplasm of the cell OR on the rough ER
Endoplasmic reticulum
Interconnecting membrane network within cell includes rough ER and smooth ER
Rough ER
- Contains ribosomes which are the site of protein synthesis
- Used for making proteins that will be exported out of the cell or will become part of the cell membrane
Smooth ER
Lacks ribosomes and is the site of lipid metabolism for storage of calcium ions (muscle cells)
Golgi apparatus
Modifies and packages proteins and lipids into vesicles for transport
the UPS of cells
Lysosomes
Vesicles formed by the Golgi that are filled with hydrolytic enzymes
What types of cells do we find lots of hydrolytic enzymes?
Neutrophils and macrophages (phagocytosis)
Mitochondria
Organelle that converts chemical energy into the form of ATP energy
Aerobic Respiration
- Occurs in mitochondria
- Reaction where energy of glucose and other food molecules are converted into ATP (requires oxygen for final step)
True for False:
ATP is a stable molecule that can be stored for later expenditure in the cell.
False
ATP must be continuously synthesized, therefore if the cell is deprived of oxygen it cannot make sufficient ATP to meet its energy demands, so the cell dies.
Plasma membrane
A phospholipid bilayer surrounding cells
Is embedded with proteins that perform many of the membranes functions
List the functions of the plasma membrane.
- Regulates what gets into or out of the cell
- Generates membrane potential
- Cell to cell recognition (WBC, antigens, glycoprotein…)
- Communication between cells (Nervous & endocrine)
- Sensor to environment (enables cell to sense environment)
- Growth (cell division) regulation (mitosis/neoplasia)
Simple diffusion
Occurs when molecules freely across the plasma membrane
What kind of molecules pass through the PM via simple diffusion? Why can they pass so freely?
Small, lipid soluble (nonpolar) substances.
They can pass through because they are nonpolar just like the hydrophobic inner layer of the plasma membrane
List molecules of simple diffusion
Steroids, gases (O2 & CO2), and alcohols
True or False:
Simple diffusion does not require energy or carrier proteins.
True; they flow down the concentration gradient
flow from high concentration to low concentration
Facilitated diffusion
Used by small polar molecules that need assistance to pass through the membrane (making them polar mlcs)
High to low; down concentration gradient
What structures are needed for facilitated diffusion? Why do we need them?
Carrier proteins/transport proteins
Molecules passing through are polar and do not mix with the hydrophobic layer like nonpolar substances
Any energy required for facilitated diffusion?
Nope, all flow down the concentration gradient
How do carrier proteins actually move polar substances down the gradient?
Substances of high conc. bind to the protein, changing that protein’s shape and therefore its function, which is to now transport the molecule into the cell
True or False:
Carrier proteins can carry any polar molecule into the cell.
False:
Carrier proteins can only transport one specific type of molecule due to specific protein conformation, making transport a highly specific process
True or False:
The number of carrier proteins in the cell membrane limits the rate of diffusion by facilitated diffusion (transport maximum)
True; you can have oodles of molecules and substances that can pass the membrane, but there are only so many carrier proteins in the membrane. This limits how quickly substances can pass through.
Active Transport
Movement of molecules across the membrane that requires energy via ATP or an ion gradient
What does the flow of substances look like in active transport?
With active transport, the cell can move substances from where the substance has a low concentration to an area where the substance has a high concentration
Do we still need transport proteins for active transport?
YES!
Active transport allows the cell to concentrate certain ions either inside or outside of the cell. Why is this so important?
It’s important for maintaining the normal resting membrane potential
We see this commonly and Na/K pumps where active transport is used to maintain normal concentration gradients of sodium and potassium in an outside of the cell
What are the concentrations of sodium and potassium in a cell?
Outside cell = more Na
Inside cell = more K
Osmosis
The movement of water across the plasma membrane
What proteins are involved in osmosis?
Aquaporins (protein channels)
Is energy required for osmosis? Why or why not?
Nope because water will diffuse from the side of the membrane with higher water concentration to the side with lower water concentration
How are substances moved into and out of the cell if they are much larger molecules?
Via vesicle formation
What is the point of using vesicles?
It protects the cell and prevents it from damage/interruption.
The vesicles are formed by the plasma membrane, therefore the vesicles ARE the plasma membrane.
Endocytosis
The process of substances being brought into a cell via vesicles
pinocytosis and phagocytosis
Pinocytosis
When the cell takes in extracellular fluid and the molecules in that fluid //”cellular drinking”
Occurs in most cells
What substances are taken in by the vesicles in pinocytosis?
Fat droplets or polypeptides
Phagocytosis
“cell eating”
Used to take in very large substances such as cell fragments or microbes (ex: WBC like neutrophils or macrophages)
Exocytosis
Moves vesicles out of the cell
Also called cell secretion
The coordination between cells that allows for growth, cell division, and the functions of various tissues and organs systems is accomplished by what three ways?
- Gap junctions
- Direct cell to cell contact
- Secretion of chemical mediators that influence distant cells
Gap junctions
Direct connection of cytoplasm of adjacent cells that allows direct passage of small molecules and ions between cells
What do gap junctions allow for a group of cells?
It allows them to act in unison
ex: used by cardiac muscle cells and some smooth muscle in the G.I. tract to coordinate contractions
How do cells have direct contact with each other?
Cells use glycoproteins are glycolipids on their membranes to identify cells
We see this a lot in our immune system (ex: MHC cells, B-lymphocytes etc…)
How do cells influence each other from great distances?
They secrete chemicals
What is synaptic signaling?
When a neuron secretes a neurotransmitter diffuses across the synaptic cleft and ask on a post synaptic receptor to relay a message
Where do we find synaptic signaling in our body cells?
Only in the nervous system
Paracrine signaling
When cells secrete chemicals that only affect LOCAL cells before the chemical signals are destroyed
Can you give an example of paracrine signaling?
Growth factors. They promote wound healing without affecting the entire organism. Only local cells grow to repair the wound.
Endocrine signaling
When cells secrete hormones that travel throughout the bloodstream influencing only those cells which have the appropriate receptor for that hormone
Autocrine signaling
When cells respond to the molecules they themselves secrete
Well functioning in the autocrine signaling pathway can be involved with what type of disease?
Cancers
