Chapter 3: Structure and Function of the Cell Flashcards
Briefly explain the transcription in protein synthesis.
Transcription is transcribing the DNA into a message in a cell.
- RNA polymerase binds to a promoter with the help of proteins called transcription factors.
- RNA polymerase then initiates mRNA synthesis at the start codon, moves downstream along the gene in a process called elongation, synthesizing the mRNA strand as it goes. In RNA it will have Uracil instead of Thymine which is the one that pairs with Adenine in DNA.
- Once polymerase reaches another special sequence called the terminator, then the enzyme detaches from the gene and the DNA is returned to its original state. mRNA is now produced with the information encoded in the gene.
- After few modifications during RNA processing, the mRNA will leave the nucleus into the cytoplasm where it will find a ribosome where translation occurs.
Explain genetic code.
set of rules that relate the base triplet sequence of DNA to the corresponding codons of RNA and the amino acids they specify.
Explain nucleotide
it is the repeating units of nucleic acid with each consisting of a nitrogenous base, a pentose sugar, and a phosphate group.
Explain sense strand
It is the strand readable on the RNA or the coding side. However, proteins involved in making RNA reads the antisense strand in order to create the sense strand for the mRNA.
Explain antisense strand
It is the non-coding side strand. When making the RNA, the proteins involved in making RNA reads the antisense strand in order to make the sense strand for the mRNA.
Explain introns
a segment of DNA or RNA molecule within the gene that do not code for parts of a proteins.
Explain exons
a segment of DNA or RNA molecule located between regions that do code for segments of a protein.
Explain termination
it is when the RNA polymerase reaches the terminator and the enzyme detaches from the transcribed RNA molecule and the DNA strand.
Explain the difference between mitosis and meiosis.
Meiosis is the reproductive cell division that occurs in the gonads, it produces gametes in which the number of chromosomes is reduced by half. While mitosis is a cell division that produces two genetically identical cells, each with the same number and kind of chromosomes as the original cell.
What are the three main parts of an animal cell?
Plasma membrane, cytoplasm, nucleus
Plasma membrane
It forms the cell’s outer boundary and separates the cell’s internal environment from the outside environment.
It is also a selectively permeable barrier, allowing the passage of some things and not others. It also plays a role in cellular communication.
Cytoplasm
It contains all the cellular contents between the plasma membrane and the nucleus.
What is a cytosol?
It is the fluid portion of the cytoplasm
Describe organelles
A subcellular structures embedded in the cytosol, having characteristics, shapes, and specific functions.
Nucleus
large organelle that contains DNA in molecules called chromosomes
Describe the structure of the plasma membrane.
Its basic structural framework is the lipid bilayer that is composed of lipid molecules such as the phospholipid (75%), cholesterol (about 20%) and glycolipids (about 5%), and lipids with attached carbohydrate groups.
What is the function of the cholesterol in the plasma membrane?
it gives stability to the membrane
What is Glycocalyx? give its 3 functions.
Fatty acid “tails,” which are hydrophobic hydro carbon chains
What does selectively permeable mean?
Only allows the passage of some things and not others depending on some factors such as the size. Larger and polarized molecules have a great difficulty entering; therefore in need of assistance getting through.
Give the 6 membrane proteins and give their functions.
- Ion channel (Integral) - allows specific ion to move through water-filled pore.
- Carrier (Integral) - carries specific substances across membrane by changing shape. They are also known as transporter.
- Receptor (integral) - recognizes specific ligand and alters cell’s function in some way.
- Enzyme (integral and peripheral) - catalyzes reaction inside or outside cell, depending on which direction the active site faces.
- Cell-identity marker (glycoprotein) - distinguishes your cells from anyone else’s (unless you are an identical twin).
- Linker (Integral and peripheral) - Anchors filaments inside and outside the plasma membrane, providing structural stability and shape for the cell. May also participate in movement of the cell or link two cells together.
Describe the membrane’s fluidity.
Exchange, meaning shifting from position to position.
Self-sealing, has the ability to seal itself.
Give the 5 types of gradient across the plasma membrane.
Concentration gradient, electrical gradient, electrochemical gradient, membrane potential, resting membrane potential
describe what is a passive process.
passive processes moves down a connection gradient or electrical gradient using own kinetic energy. From high to low or from positive to negative, does not use energy or ATP.
Describe what the principle of diffusion means and what the 5 things composing it.
The principle of diffusion are factors that influence the diffusion rate of substances across plasma membranes.
Those factors are the steepness of the concentration gradient, temperature, mass of diffusing substance, surface area, diffusion distance.
Describe what a simple diffusion is.
A substance moves across the lipid bilayer of the plasma membrane without the help of membrane transport proteins.
Facilitated diffusion
has 2 types:
- Channel-Mediated Facilitated diffusion - a solute moves down its concentration gradient across the lipid bilayer through a membrane channel.
- Carrier-Mediated Facilitated diffusion - needs carrier or transporter to get across the membrane
Osmosis
It is a type of diffusion, and also a passive process, where there is net movement of a solvent through selectively permeable membrane. In osmosis, water likes to move where the particles are more concentrated.
Explain the process of osmosis.
During osmosis, water molecules pass through a membrane via 1) phospholipid bilayer and 2) aquaporins. Osmosis only occurs when a membrane is permeable to water but not permeable to certain solutes.
What is hydrostatic pressure?
it is the pressure exerted by water (liquid) on a membrane, which forces water molecules to move to either left or right until equilibrium is reached.
What is osmotic pressure?
it is the pressure exerted by a fluid with impermeable solute (the higher the solute, the higher the pressure); it is the pressure needed to counteract osmosis.
Tonicity
A solutions ability to change the volume of cells by altering their water content.
Describe what is an active process.
- Active processes needs cellular energy to drive substances against concentration or electrical gradient (uphill) using ATP.
- Many polar or charged solutes can’t diffuse across the membrane
- low to high concentration if we wish
What are the two sources of energy for active transport?
- Primary Active Transport
- energy from hydrolysis of ATP drives solutes across the membrane
