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40 Cards in this Set
- Front
- Back
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Cells |
All living organism are made of cells. Cells are the basic functional units of the body Differences: -they come in a variety of shapes & sizes -with diverse functions. Similarities: -Plasma membrane & associated proteins -Cytoplasm & organelles -Nucleus (not all cells) |
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A typical Cell |
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Plasma Membrane |
Phospholipid barrier between the intracellular and extracellular environments
Double membrane: -Hydrophobic center of the double membrane restricts movement of water, water-soluble molecules, & ions -Water soluble things can't pass through the lipid layer, but lipid soluble things can -many substances are selectively allowed to pass through protein channels. |
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Membrane Proteins (which types) |
Integral proteins (aka transmembrane proteins) -span the membrane
Peripheral proteins -embedded on just one side of the membrane
Specialization of the plasma membrane is a result of the type of membrane proteins
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Membrane Proteins Functions |
1. Structural support 2. Transport 3. Enzymatic control of cell processes 4. Receptors for hormones and other molecules 5. “Self”markers for the immune system |
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3 cellular mechanism of bulk transport |
In order for cells to survive they must be able to acquire things from outside of themselves. There are 3 ways to "ingest" large particles & fluids from the outside:
1.Phagocytosis 2. Endocytosis -Pinocytosis -Receptor-mediated endocytosis 3. Exocytosis
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Phagocytosis |
"cellular eating" -Some white blood cells can perform "amoeboid movement" by extending pseudopods to pull the cell forward. pseudopods-engulf bacteria, dead cells, or other organic materials & then fuse together to form a food vacuole -The food vacuole fuses with a lysosome, and the bacterium is digested |
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Endocytosis |
A way for bringing large materials INTO the cell The plasma membrane furrows inward (rather than extending outward). -A small part of the membrane surrounds the substance pinches off and is brought in as a vesicle.
-Pinocytosis: nonspecific -Receptor-mediated endocytosis: specific |
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Exocytosis |
Large cellular products (proteins) are moved out of the cell -signaling hormones, antibodies, neurotransmitters
The Golgi apparatus packages proteins into vesicles that fuse to the plasma membrane, & the contents spill out of the cell |
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Plasma membrane structures |
Cilia & Flagella -hair-like structures that protrude from plasma membrane -important for movement -used for locomotion (cells moving themselves) -movement of materials (ex: cells have cilia move mucous through the respiratory tract) -Flagella are longer than cilia & move in a different pattern
Microvilli -important for absorption |
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Cilia |
Tiny, hair-like structure composed of microtubules that project from the plasma membrane.
1. Motile cilia beat in unison to move substances through hollow organs (found in respiratory tract & uterine tubes)
2. Primary cilium may have a sensory function (found on almost every cell in the body) |
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Flagellum |
A single whiplike structure that can propel a cell forward -composed of microtubules -sperm in the only cell in the human body with a flagellum |
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Microvilli |
Extensions of the plasma membrane They increase the surface area for a rapid diffusion!
Highly specialized: -Intestines: rapid & efficient absorption of ingested nutrients -Kidneys: mechanoreception & reabsorption of water -White blood cells: movement |
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Cytoplasm |
Material within a cell includes organelles, cytosol, and a organized system of microtubules & microfilaments (called the cytoskeleton) |
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Cytoskeletal Proteins |
The shape and size of a cell is maintained internally by the presence of proteins that form a network within the cell (these proteins are cytoskeletal proteins: microtubules/ microfilaments)
Function: -Support & moves organelles (Lysosomes & Mitochondria) -critical for cell division -Very dynamic: continually being formed, degraded, & reformed |
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Lysosomes |
Organelles filled with digestive enzymes – Fuse with food vacuoles after an immune cell engulfs a bacterium or dead cell – Primary lysosome: only contains digestive enzymes – Secondary lysosome: contains the partially digested contents of the food vacuole or worn-out organelles – Residual body: a lysosome filled with waste, which can be expelled through exocytosis |
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Lysosomes also... |
• Besides digesting bacteria, lysosomes are responsible for: – Autophagy: process of digesting worn-out organelles and proteins in the cell – Apoptosis: programmed cell death. The lysosome spills its contents, killing the cell.
Lysosomal contents can be emptied by way of exocytosis |
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Peroxisomes |
Contain enzymes specific to certain oxidative reactions – Found in most cells but most numerous in the liver; often oxidize toxic molecules (such as alcohol) – Enzymes used to remove hydrogens from a molecule and transfer it to O2, forming hydrogen peroxide(not good) – Also contain the enzyme catalase, which converts hydrogen peroxide into water and O2 – Important in lipid breakdown |
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Mitochondria Functions |
Sites of energy production that allow cells to do work
Mitochondria can migrate around the cell and can make copies of themselves. – Movement is due to microtubules
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Mitochondria structure |
-Have a complex membrane structure -Have an inner membrane and an outer membrane separated by an inter membranous space -Inner membrane is folded into cristae – Inner portion called the matrix
These structures are very important for the generation of adenosine triphosphate (ATP) |
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Ribosomes Function |
Responsible for manufacturing proteins -Operate by “translating” mRNA templates that encode specific genes |
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Ribosomes Structure |
Large and complex macromolecular structure – Composed of 3 types of RNA and 52 proteins – 2 major structures • Small subunit: reads mRNA template • Large subunit: joins amino acids together to make polypeptide chain |
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Endoplasmic Reticulum (ER) |
A system of interconnected networks of membrane vesicles
• Important for the synthesis, modification, and sorting of proteins • Integral component for the synthesis of membrane proteins and the sorting (– trafficking of proteins to the correct cellular destination ) |
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Rough ER (granular ER) |
contains ribosomes for protein synthesis and functions in protein modification |
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Smooth ER (agranular ER) |
ER that does not have ribosomes embedded in the membranes
Lipid synthesis – Cells that make steroid hormones typically have a large amount of SER.
• Calcium Storage calcium that is readily released upon stimulation » Turning things “on” or “off”
• Cellular detoxification |
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Golgi Complex (Apparatus) |
Large organelle composed of many stacks of membrane-bound structures called cisternae (flattened sacs)
Required for modifying, sorting, and packaging proteins for secretion |
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Golgi Complex (Apparatus) process |
Proteins synthesized in the rough ER enter the
• Within the Golgi sacs (cisternae) there are modifying enzymes that will add carbohydrates, |
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Cell Nucleus Structure |
Most cells have one nucleus. – Muscle cells have hundreds; RBCs have none
The nucleus is enclosed by the nuclear envelope made of two membranes: – Outer membrane continuous with rough ER – Inner membrane often fused to outer by nuclear pore complexes, which allow small molecules and RNA to move into/out of the cell |
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Cell Nucleus contains... |
Nucleuscontains the cell’s DNA Enclosedbya double membrane: nuclear envelope |
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Nuclear pore complexes |
fuse inner & outer membranes together
– Small molecules can diffuse through pore – Proteins, RNA must be actively transported |
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Nucleoli |
• The nucleus also has one or more darker regions not surrounded by a membrane; these are called nucleoli. Nearly it's only function: • The nucleoli contain the DNA that codes for the production of ribosomal RNA (rRNA). |
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Gene |
A gene is a length of DNA that codes for a specific protein. |
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Genetic expression |
1 – The gene on the DNA is transcribed as messenger RNA, which can leave the nucleus. 2 – The messenger RNA is then translated at the ribosome to assemble the proper amino acid sequence. |
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Genome & Proteome |
The genome is all the genes in a particular individual or all the genes of a particular species. – Researchers believe humans have ~25,000 genes. The proteome is all the proteins that are produced from the genome. |
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How can a gene code for more than one protein? |
– mRNA is altered after transcription. – Proteins are made of many polypeptide chains.
– Protein modification occurs by: post-translational modification: • Adding something to it: – Lipid – carbohydrate • Rearranging the pieces of DNA in the gene – Making it longer or shorter |
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Stages of Gene Expression |
• Replication: The faithful reproduction of DNA so that cell division ends with both cells having the same copy of DNA
• Transcription: The process by which DNA is copied in the format of an mRNA strand – Turning DNA into RNA – mRNA single-stranded
• Translation: The creation of a protein that is based on the instructions encoded by the mRNA – Ribonucleotide sequence determines the amino acid sequence |
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Chromatin |
DNA in the nucleus is packaged with proteins called histones to form chromatin.
– Histones are positively charged proteins. This positive charge allows the negatively charged DNA to interact and wrap itself around the histones. Allows for efficient packaging of DNA.
– Euchromatin: active in transcription, looser. Changes in histones allow molecules access to the DNA during gene expression.
– Heterochromatin: inactive regions, highly condensed. Much of the DNA is inactive. |
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RNA Synthesis |
AKA transcription – Start and stop regions at the beginning and end of the gene – Promoters, areas of DNA that are not part of the gene but tell enzymes involved where to begin – Transcription factors that bind to the promoter to begin transcription |
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RNA Synthesis involves |
Involves – RNA polymerase, the enzyme that “reads” the DNA and assembles the appropriate RNA nucleotide • Assembly is complementary. If the DNA is GCTA, the RNA will be CGAU. • RNA has uracil instead of thymine. • Forms precursor messenger RNA |
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Fluid-mosaic model |
a constantly changing pattern, (like a "sea") of the hydrophobic part of the membrane. -peripheral protein are particley embedded in one face of the membrane. -integral proteins span the membrane from one side to the other
-the membrane is not solid sooo.. phospholipids & proteins are free to move laterally. -the proteins within the phospholipid "sea" are not uniformly distributed. |
