Module 3 - Cells

What are the 3 components of a cell?

plasma/cell membrane, cytoplasm (cytosol & organelles), nucleus

What is the structure of the plasma membrane?

phospholipid bilayer with proteins dispersed within; fluid structure - most membrane lipids and proteins move easily within the bilayer

What is the nature of the external and internal surfaces of the plasma membrane?

external surfaces are hydrophilic due to polar phosphate heads while internal portion is hydrophobic due to nonpolar fatty acid tails

What are plasma membrane integral proteins? What 4 roles do they serve as?

firmly imbedded in and across the lipid bilayer; most are glycoproteins that serve as channels, transporters, receptors, or enzymes

What are plasma membrane peripheral proteins? And what 2 things do they serve as?

lie loosely on inner and outer surfaces of the cell membrane; serve as enzymes or cytoskeletal anchors

What is the role of cholesterol in the membrane?

provides stability and reduces fluidity

Describe the permeability of the cell membrane.

selectively permeable

The lipid bilayer is permeable to…

small, nonpolar uncharged molecules and to water.

The lipid bilayer is impermeable to…

ions and charged/polar particles.

What are transmembrane proteins? What do they serve as? And what does this do to permeability?

integral proteins that span the membrane and act as channels or transporters that increase permeability to molecules that cannot cross the lipid bilayer

Macromolecules pass through the membrane via…

vesicular transport.

What are 3 types of extracellular fluid (ECF)?

interstitial fluid, plasma, lymph

What are solutes?

substances dissolved in a solvent

What is a concentration gradient?

the difference in concentrations of a substance between 2 areas

What are 2 (or 3) classifications of transport processes?

active or passive transport and vesicular transport

What is passive transport?

movement of substances from an area of higher concentration to an area of lower concentration (i.e. with the gradient); does not require energy

What is active transport?

movement of substances from an area of lower concentration to an area of higher concentration (i.e. against the gradient); requires energy

What are 3 forms of passive transport?

diffusion through lipid bilayer, diffusion through a channel (these are non-mediated), or facilitated diffusion (mediated)

What is vesicular transport?

involves formation of a membrane surrounded vesicle to move material into (endocytosis) or out of (exocytosis) the cell

What is diffusion?

the movement of particles from an area of high concentration to an area of low concentration (i.e. down a concentration gradient) to produce a state of equilibrium; is spontaneous

What 5 factors influence diffusion?

steepness of concentration gradient, temperature, size or mass of substance; surface area; diffusion distance

What can diffuse across the lipid bilayer? What does this allow for?

nonpolar hydrophobic molecules such as respiratory gases, some lipids, small alcohols, and ammonia. This allows for gas exchange, absorption of some nutrients, and excretion of some waste

Most membrane channels are…

ion channels.

Ion channels allow for passage of…

small, inorganic, hydrophilic ions.

facilitated diffusion

a method of passive transport; movement of a substance across the membrane by way of a binding to a specific transporter protein; the transporter undergoes a conformational change; diffusion of glucose is an example

Ion channels are _ and _ and may be __ or always open.

selective and specific; gated

What is osmosis?

the diffusion of water through a selectively permeable membrane (from an area or high concentration to an area of low concentration)

What is tonicity?

the concentration of solutes outside of the cell relative to the inside of a cell; a measure of the effective osmotic pressure gradient; the capability of a solution to modify the volume of cells by altering their water content

What is an isotonic solution?

concentrations of solutes is the same inside and outside the cell and its shape is maintained; water diffuses in and out equally

What is a hypotonic solution?

the concentration of solutes outside the cell in lower than inside the cell (i.e. more water outside)

What happens to cells in a hypotonic solution?

water diffuses into the cell and the cell to expand and burst (plasmolysis [hemolysis of red blood cells])

hypertonic solution

the concentration of solutes outside the cell is higher than inside the cell (i.e. less water outside)

What happens to cells in a hypertonic solution?

water diffuses out of the cell and the cell to shrink/collapse (crenation)

What does active transport require and what does it do? What are 3 things it moves?

requires energy (ATP); moves solutes across the plasma membrane against its concentration gradient; moves ions, amino acids and monosaccharides

What are secondary active transporters?

energy stored in the form of sodium or hydrogen ion concentration gradients can also be used to drive other substances against their own concentration gradients

What is a vesicle?

a small membranous sac that forms by budding off the cell membrane

What is endocytosis?

a form of vestibular transport where larger molecules are brought into the cell via the formation of a vesicle from a section of the cell membrane

What is exocytosis?

a form of vestibular transport where molecules are taken out of the cell via a secretory vesicle which forms inside the cell and then fuses with the cell membrane to release the contents into the extracellular fluid

What are types of endocytosis?

phagocytosis, pinocytosis, receptor-mediated endocytosis

What is phagocytosis? Is it selective?

endocytosis of large particles; relatively non-selective; e.g. used to "eat" pathogens

What is pinocytosis? Is it selective?

endocytosis of fluid containing dissolved substances; relatively non-selective

What is receptor-mediated endocytosis?

substance binds to receptors on cell membrane and once these bind, a coated vesicle is formed; e.g. bringing iron into red blood cells

What is cytoplasm?

inner content of the cell including the cytosol and the organelles

What is cytosol?

the intercellular fluid (or semifluid), which contains inclusions and solvents (either in solution or suspended); composed mostly of water, plus proteins, carbohydrates, lipids and inorganic substances; the medium in which many chemical reactions take place

What is the cytoskeleton and what 3 things does it provide?

a network of protein filaments that provide structure, support, and movement

What 3 things are the cytoskeleton made up of?

microfilaments, intermediate filaments, and microtubules

What are microfilaments composed of and what is their function?

typically composed of actin; function in movement and mechanical support

What are intermediate filaments composed of and what is their function?

composed of various proteins, function in support and helping to anchor organelles

What are microtubules composed of and what is their function?

composed of tubulin; help to determine cell shape and provide structural support, and intracellular transport of organelles and the migration of chromosomes during cell division

What are centrosomes? What is their function?

dense areas of cytoplasm that contain centrioles; serve as centres for organising microtubules in interphase cells and the mitotic spindle during cell division

What are centrioles? How to they arrange themselves?

paired cylinders made of microtubules; cylinders arranged at right angles to one another

What are cilia and what is their function? Where are they found?

hair-like projections that function to move materials, such as mucus, over the cell's surface; in the lining of the respiratory tract and fallopian tubes

What are flagella? Where are they found?

long appendage that moves the entire cell; eg. human sperm cell tail

What are ribosomes? What are they composed of? Where are they found?

site of protein synthesis; composed of 2 ribosomal RNA subunits; found attached to rough endoplasmic reticulum and free in the cytoplasm

What is endoplasmic reticulum (ER) and what does it do?

network of membranes that form flattened sacs or tubules called cisterns; functions in transporting, synthesizing, and storing materials

What is rough ER and what does it do?

is continuous with the nuclear membrane and the outer surface is studded with ribosomes; proteins synthesized by ribosomes enter these network channels

What is smooth ER and what does it do?

extends from the rough ER and does not have ribosomes; synthesizes phospholipids, steroid hormones, regulates cellular calcium concentration, metabolizes some carbohydrates, and breaks down certain chemicals

What is the Golgi apparatus/complex/body and what does it do?

comprised of 4 to 6 flattened membranous sacs, called cisterns; primary function is to process/modify, sort, and deliver proteins (ie. products from the ER) to the plasma membrane, lysosomes, and secretory vesicles

What are lysosomes and what do they do?

membrane-enclosed vesicles that form in the Golgi apparatus and which contains powerful digestive enzymes; function in intracellular digestion to digest worn-out organelles or other cellular contents, and in extracellular digestion of materials such as bone

What are peroxisomes and what do they do?

similar to but smaller than lysosomes and contain enzymes that use molecular oxygen to oxidize organic substances; important in lipid metabolism and chemical detoxification

What is a proteasome and what does it do?

a tiny membrane-bound sac that contain proteases, which degrade proteins

What are mitochondria and what do they do?

bound in a double membrane, the outer is smooth and the inner folded; the site of ATP production by the catabolism of nutrient molecules; self-replicate using their own DNA

How many nuclei does a cell have? Describe the structure of the nucleus.

a cell usual has one, but may have none or multiple; covered by a nuclear envelope perforated with nuclear pores, and contains the nucleolus, and genetic material (i.e. genes) for all protein manufacture

What is the nucleolus responsible for?

making RNA for the ribosomes

What is chromatin and what is it composed of?

threads within the nucleus; composed of DNA strands and associated proteins

What are chromosomes? How many does a human cell contain?

condensed chromatin, which happens during cell division; a human cell contains 46 chromosomes arranged in 23 pairs

What are the 5 levels of DNA packaging?

nucleosomes, chromatin fibers, loops, chromatids, and chromosomes

What is a gene?

a functional length of DNA that provides the genetic information necessary to build a protein; a specific sequence of nucleotides in DNA that determines the amino acid sequence of a protein.

The physical and chemical characteristics of a cell is determined by its…

proteins.

What 2 processes are involved in protein synthesis?

transcription and translation

What is transcription? What is this process catalyzed by?

the process of copying the genetic information encoded in DNA onto a strand of mRNA (messenger RNA); the copying of a base sequence of DNA into a base sequence of RNA; catalyzed by RNA polymerase

What are tge types of RNA that DNA can synthesize?

messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA)

What is translation?

reading the mRNA nucleotide sequence to determine the amino acid sequence of the protein; the use of a base sequence of messenger RNA to assemble a corresponding sequence of amino acids

What are the matching base pairs/nucleotides (DNA-RNA)?

C-G

T-A

A-U

G-C

What is a codon?

a sequence of 3 nucleotides on an mRNA that correspond to a specific amino acid

What is an anticodon?

a sequence of three nucleotides on a tRNA molecule, which allow the tRNA to bind to a specific sequence of three nucleotides (codon) on the mRNA

What is the termination/stop codon?

a 3 nucleotide sequence that signifies the end of translation and the release of the completed newly synthesized protein

What is the seqeunce of events in the translation process?

mRNA binds to a ribosome (formed by rRNA and proteins), tRNAs bring appropriate amino acids by matching their anticodons (3 nitrogenous bases) with the mRNA's codons (3 complementary bases), the ribosome moves along the strand of mRNA as amino acids are joined and the polypeptide chain grows

What is cell division? What 2 types of division take place during cell division?

cells reproducing themselves; consists of nuclear division and cytoplasmic division (cytokinesis)

What are the 2 types of nuclear division?

mitosis and meiosis

What is the purpose of somatic cell division and what does it include?

to increase number of body cells; includes mitosis and cytokinesis

What is the purpose of reproductive cell division?

to produce sperm and eggs (gametes); includes meiosis and cytokinesis

What are the 2 phases of the cell cycle?

interphase and mitotic phase (includes mitosis and cytokinesis)

What is interphase?

phase when the cell is not dividing; it is growing and performing its carrying out normal functions and processes; cells spend most of their time in interphase

What is mitosis?

the division of genetic material; division of the nucleus; distribution of 2 sets of chromosomes, one set for each nuclei

What are the 4 phases of mitosis?

prophase, (prometaphase), metaphase, anaphase, telophase

What happens in prophase?

chromatin condenses into chromosomes, spindle fibers emerge from centrosome, nuclear envelope breaks down, centrosomes move toward opposite poles

What happens in metaphase?

chromosomes line up at the metaphasic plate, each sister chromatid is attached to a spindle fiber originating from opposite poles

What happens in anaphase?

centromere splits in two and sister chromatids (now chromosomes) are pulled towards opposite poles, spindle fibers begin to elongate the cell

What happens in telophase?

chromosomes arrive at opposite poles and begin to decondense into chromatin, nuclear envelopes form and new nucleoli appear, mitotic spindle breaks down, spindle fibers continue to push poles apart (i.e. elongate cell)

What happends in cytokinesis?

division of the cytoplasm and organelles; begins in late anaphase or early telophase; a cleavage furrow separate the parent cell into 2 daughter cells