Describe some of the basic characteristics of cells
Smallest living subdivision of the human body
Diverse in structure and function
Principle Parts of Cells
- Plasma Membrane
- Cytoplasm & Organelles
What is the interaction between the environment and the cell?
Cells need to exchange materials with the extracellular fluid
- Take in resources (O2, nutrients, etc.)
- Release materials (CO2, wastes, cell signals, etc.)
Outer boundary of cell
Separates intracellular environment from the extracellular environment (and compartmentalizes intracellular).
Forms a selective mechanical barrier
What is the plasma membrane structure?
Bilayer of phospholipids with porteins suspended within it – "fluid mosaic model."
What is the function of the plasma membrane?
- Controls movement of molecules
- Participates in joining cells to form tissues and organs
- Participates in cell signaling
What are the types of proteins in the membrane and their roles?
Proteins within the membrane can be integral or peripheral.
- Integral: embedded into the membrane.
- Peripheral: partially embedded on surface or embedded on other protein.
Roles of proteins in membrane
- Structural Support
- Self Makers
How are large molecules exhange between the two compartments?
Large numbers of molecules can be exchanged with extracellular fluid simultaneously = bulk transfer.
Invagination of the plasma membrane to pull materials into the cell.
- Merging of vesicle membrane with plasma membrane
- Materials released into the extracellular the extracellular fluid
- Used to export materials (enzymes, cell signals) and add material to the plasma membrane.
The process in which cells which exhibit amoeboid motion – as well as certain liver cells, which are not mobiel – use pseupods to surround and engulf particles of organic matter (such as bacteria).
A nonspecific process performed by many cells: the plasma membrane invaginates to produce a deep, narrow furrow then this pinches off. Pinocytosis allows a cell to engulf large molecules such as proteins.
- Hair-like structures projecting into the extracellular fluid
- Beat = generate flow in extracellular fluid
- Long whip-like structures found on mature sperm
- Allows sperm to swim
- Small fingerlike projections
- Greatly increases surface area
Portion of cell interior not occupied by the nucleus
- Organelles ('little organs")
- Dinstinct, highly organized, membrane-enclosed structures
- Framework of Cell
What is the function and consistancy of the cytoplasm?
Gel-like material inside cells outside organelles
- Enzymatic regulation of intermediate metabolism
- Place where proteins are made
- Storage of fat, glycogen and secretory vesicles.
What is the cytoskeleton and its function?
Network of protein fibers throughout cytosol
- Structural support and shape of cell
- Railway = movement of materials inside the cell
- External movement
List the Organelles inside the Cell
- Endoplasmic Reticulum
- Golgi Complex
Sac-like organelles which contain digestive enzymes
Break down large molecules
- Old Organelles
- Food Molecules
The process by which structures and molecules within a vacoule are digestive by the enzymes within lysosomes.
- Contain H2O2
- Breakdown of fatty acids
- Oxidative reactions
Contain both Ooxidases and catalases
- Oxidases: promotes removal hydrogen to oxidize molecule
- Catalases: prevents excessie build up H2O2
- Double Membrane
Power generators of the cell
- Synthesize cellular fuel (ATP)
- Large protein-RNA complexes
- Found free floating in cytosol or attached to endoplasmic reticulum
- Function = synthesize proteins
Endoplasmic Reticulum (ER)
System of membranous passageways from the nuclear membrane to the plasma membrane
- Granular ER is also called rough ER.
- Agranula ER is also called smooth ER.
What are the functional differences between rought and smooth ER?
- Has ribosomes embedded on the outer surface
- Functions in protein modification
- Has many functions, depending on the cell – generally, lipid metabolism.
Coated with ribosomes
Synthesizes proteins for:
- Cell membranes
- Interior (lumen) of membrane-bound organelles
- Protein modification
- Synthesizes steroid hormones
- Ca2+ storage
Stacks of flattened sacs (cisternae)
- Processes ER products into final form
- Sort and direct finished products to final destinations (intracellular or extracellular)
- Cell's "control center"
- Largest Organelle
- Surrounded by double lipid bilayer (nuclear envelope) linked to the cytosol by nuclear pores
- Sequences of DNA containing information needed to make proteins.
- Genes can encode for more than one protein.
Highly coiled DNA containing genes
- The total of all the genes in the human body
- approximately 20,000 genes.
- All the different proteins produced in the human body
- Approximately 100,000
In what comformation does DNA primarily exist in?
DNA exists primarily as chromatin
- DNA & associated proteins (histones)
- Highly Folded
- One Single DNA double-helix + associated proteins forms a chromosome
What are the functions of DNA?
Storage of genetic information
Template for making protein
- Expression of genetic information
Steps of Protein Synthesis
Summarize the Flow of Genetic Information
Transcription is the synthesis of RNA from DNA.
- Promoter on gene
- Transcription factors that help RNA polymerase bind to the promoter to begin transcription
How does transcription allow for information to be transferred?
Complimentary base pairing of DNA
How do you read DNA?
- Triplet = group of 3 nucleotides
- Codon = mRNA
How is RNA modified prior to release into cytoplasm?
Initial mRNA is not the same as final mRNA = splicing
Introns v. Exons
Regions of noncoding DNA within a gene are called introns: the coding regions are known as exons.
The process by which stretches of DNA that serve as introns (noncoding) sequences in the formation of one mRNA (protein coding) can serve as exons (coding sequences) in the formation of a different mRNA.
How does the code transfer from transcription to translation?
The sequence of the DNA triplets determines the final sequence of amino acids in a protein
- Genetic Code
How many amino acids does the geneti code encode for?
Each codon (mRNA) encodes for one of 20 amino acids.
How is the genetic information transformed into proteins?
The process by which genetic information is transformed into proteins is called translation.
mRNA read by ribosomes
- Ribosomes binds to mRNA
- Reads codon
- tRNA binds with complementary sequences (anticondon)
- Specficity: tRNA carries specific amino acids
- A single strand of RNA bent into a cloverleaf leaf
- One end has the anticodon, which is three nucleotides that will be complementary to the proper codon.
- The other end has the corresponding amino acid.
What are the steps during translation?
- mRNA moves through the ribosome, with proper tRNA attaching at each codon.
- Amino acids attached to the tRNAs form peptide bonds, disassociate from the tRNA.
- Continues until stop codon.
List the three types of RNA that can be synthesized...
Messenger RNA (mRNA): encodes the structure for a particular protein
Transfer RNA (tRNA): carries amino acids to ribosomes for inclusion in a newly synthesized polypeptide.
Ribosomal RNA (rRNA): structural components of ribosoems.
- DNA must be copied prior to cell division
- Strands of a double helix are separated
- Each strand used as a template to synthesize a new copy of the complementary strand
The Cell Cycle
Not all cells cycle
Formation of two identical daughter cells
The phase a nondividing celll wil find its cell. Chromosomes are in their extended form, their genes actively direct the synthesis of RNA. Through their direction of RNA synthesis, genes control the metabolism of the cell.
The cell may be growing during this interphasic stage; although somtimes described as "resting," cells in the G1 phase perform the physiological functions characteristics of the tissue in which they are found.
The interphasic stage the cell finds itself if it is going to divide – it replicates its DNA.
The interphasic stage proceeding the S phase in which the DNA has replicated and the chromatin condenses to form short, thick structures that are not yet considered chromosomes.
- Humans have 23 pairs of chromosomes, one set from each parent. 22 pair are autosomes and 1 pair are sex chromosomes.
- Each pair is called homologous chromosomes, and they have the same genes on them (but not identical DNA).
Process by which two cell division steps produce gametes (ova and sperm)
- Reduction Division
Only occurs in the gonads (ovaries & testes)
Necrosis - pathological cell death
- Death of cells damages adjacent cells
Apoptosis - homeostatic cell death
- Process where specific cells die off in a controlled fashion that does not damage adjacent cells.
Each of the two daughter 23 homologous pairs contained in the parent. The daughter cells, in other words, contain rather than 46 chromosomes. For this reason, meiosis (from the Greek meion = less) is also known as reduction division.
What are the methods through which growth of cells from fertilized eggs occurs?
It is the growth that is due to an increase in cell number results from an increased rate of mitotic cell division.
Its the growth of a tissue or organ due to an increase in cell size.
Not all DNA is actively expressed
- Different types of cells express different sets of genes
Epigenetics = controlling expression of DNA
- Methylation of cytosine bases in DNA that precedes guanine: silences gene.