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What are the basic characteristics of cells
- smallest living subdivision of human body
- diverse in structure and physiology
- divided into organelles
- -isolation of chemical reactions
- -each organelle performs a specific function
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Three primary regions of cell
- plasma membrane
- cytoplasm
- nucleus
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components/functions of plasma membrane?
- outer boundary of cell
- seperates intracellular enviro from extracellular enviro
- regulates movement of materials into and out of cell
- -a selective barrier
- -helps maintain internal cell homeostasis
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plasma membrane structure?
- composed of lipids, proteins, and carbohydrates
- -arranged in bilayer of phospholipids with proteins suspended
- -"fluid mosaic model"
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amphipathic molecules
polar heads face extracellular fluid and cytoplasm
nonpolar tails prevent random movement across the membrane
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microvilli
- found on apical surface of some hollow tube like organs
- fingerlike projections
- increase surface area
- facilitate movement of materials between intra and extracellular fluids
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cilia
projects into extracellular fluid
contains microtubules, and uses ATP
capable of movement and generates flow
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cytosol
semi liquid, gel like-has a water solvent
surrounds organelles
contains various disolved materials, enzymes, etc
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cytosol functions
location for metabolic reactions
protein synthesis
storage of fat, glycogen, and secretory vesicles
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cytoskeleton
- network of protein fibers in cytosol
- -microtubules
- -microfilaments
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cytoskeleton functionsstry
structual support and shape of cell
movement of materials inside the cell
- -external movement
- cilia and flagella
- amoeboid movement
- endocytosis and exocytosis(secretion)
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lysosomes
membrane bound organelle with digestive enzymes
break down large molecules(cells digestive system)
destroy bacteria, old organelles
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mitochondria
- surrounded by two cell membranes
- -inner membrane cristae and surrounds the matrix
posses own DNA
- power generators of cell
- -produces ATP using energy released from the breakdown of food
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ribosomes
large protein-RNA complexes
found free floating in cytosol or attached to ER
synthesizes proteins based on triplets of mRNA molecules
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RER
Production of Protein
coated with ribosomes on cytosolic side
- synthesizes proteins for;
- cell membranes
- lysosomes
- export of the cell
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smooth ER
No protein synthesis
No ribosomes
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smooth ER functions
lipid synthesis
Ca+ storage and release
metabolize various molecules
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golgi complex
- stacks of flattened sacs(cisternae)
- Functions:
- posttranslational modifications(finishing steps)
- sort and direct finished products to final destinations
- "directs traffic"
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vesicles
small membrane-enclosed chambers used to transport material within the cell
- -delivers membrane molecules
- -fluid within vesicle can be emptied into another organelle(lysosomes) or secreted into extracellular fluid(secretory vesicles)
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nucleus
control center-contains info for protein synthesis
surrounded by double membrane(nuclear envelope) with nuclear pores open to cytosol
- contains chromatin
- -DNA and assoc proteins
- -chromosome= strand of DNA
- nucleolus-synthesis of RNA
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genes
sequences of DNA containing info for amino acid sequence to make proteins
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genome
the total of all the genes in the human body(approx 25,000)
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proteome
all the different proteins produced in the human body(approx 100,000)
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Note!
genes can encode for more than one protein
not all genes in a genome are active (approx 300)
different types of cells express different sets of genes within the person's genome
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mRNA
encodes the structure for a particular protein
"reads the code on DNA"
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tRNA
carries amino acids to ribosomes to add into newly synthesized polypeptide
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rRNA
structural component of ribosomes
produced in nucleolus
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From RNA to protein
translation
mRNA sequence read by ribosomes to generate a protein with a specific amino acid sequence
-ribosome binds to mRNA
-ribosomes reads triplets(codons)
-tRNA delivers specific amino acids
-amino acid is transferred from the tRNA to polypeptide chain
-ribosome reads next codon and repeats process
-polypeptide becomes protein
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DNA replication
DNA must be copied before cell division
double helix seperated
each strand used as template to synthesize new copy
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Mitosis Stages
- Interphase-what a cell is in most of the time
- the nucleus is visible
Prophase-the centrioles move apart and spindle fibers are formed.
Metaphase-chromosomes are lined up at the equator
Anaphase-the centromeres split to opposite polls
Telephase- cell division nearly complete
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2 forms of cell death
necrosis- pathological cell death(i.e. disease)
- apoptosis- homeostatic cell death
- -cells die off in controlled fashion that does not damage adjacent cells
-signals received by target cell activate specific enzymes(caspases) which fragment DNA and disassemble organelles
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metabolism
- all chemical reactions occuring in a living organism
- -breakdownn of some substances
-build up of other substances
-requires enzymes to catalyze reactions
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