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MCAT 2003 Biology (The Cell)


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What is Cell Theory?
* All living things are composed of cells.
* The cell is the basic functional unit of life.
* Cells arise only from pre-existing cells.
* Cells carry genetic information in the form of DNA. This genetic material is passed from parent cell to daughter cell.
What are the three primary tools available to study the cell and it's structure today?
1. Microscopy
2. Autoradiography
3. Centrifugation
What is magnification related to microscopy?
The increase in apparent size of an object.
What is resolution related to microscopy?
The differentiation of two closely situated objects.
What uses two lenses of lens systems to magnify an object?
A compound light microscope.
The total magnification of a compound light microscope is equal to what?
The product of the eyepiece (usually 10x) & the magnification of the objective lens selected (usually 4x, 10x, 20x, or 100x).
What is a special type of microscope used primarily for studying living cells?
Phase Contrast Microscope.
What does the Phase Contrast Microscope use as it's special technique?
Differences in refractive index are used to produce contrast between cellular structures. This technique does not kill the specimen.
This equipment uses a beam of electrons to allow a thousandfold higher magnification than is possible with light microscopy. But the specimen must be non-living
Electron Microscope
This technique utilizes radioactive molecules to trace & identify cell structures and biochemical activity.
What is autoradiography typically used for?
Protein synthesis - labeling amino acids with radioactive isotopes allows the pathway of protein synthesis to be examined. Similar techniques are used to study the mechanisms of DNA and RNA synthesis.
This technique can be used to separate cells or mixtures of cells without destroying them in the process.
Structurally, what are the two categories of cells?
1. Prokaryotes - Bacteria & cyanobacteria (blue-green algae). Unicelllular organisms with a simple sell structure.
2. Eukaryotes - Multicellular & non-bacterial unicellular organisms.
What is this?
1. Bacteria
2. Cell wall present
3. No nucleus
4. Ribosomes w/sub units of 30S-50S
5. No membrane bound organelles
What is this?
1. Protists, fungi, plants and animals
2. Cell walls present in fungi & plants only.
3. Nucleus
4. Ribosomes w/sub units of 40S-60S
5. Membrane bound organelles
A typical eukaryotic cell is bound by a cell membrane and contains what as the fluid?
The eukaryotic cytoplasm contains what structures.
Cytoplasmic organelles are suspended in the semifluid medium of a eukaryotic cell called what?
Cytosol - Contains free proteins, nutrients and other solutes.
The genetic material consists of linear strands of DNA organized into what?
Where are chromosomes located in membrane enclosed organelle called what in an eukaryotic cell?
What eukaryotic cell structure has a cell wall & chloroplasts?
Plant cells
Found in animal cells (not plant cells), what is located in the centrosome area. These are a special form of microtubules. These are not bound by the membrane.
The cytoskeleton is composed of what?
1. Microtubules
2. Microfilaments
3. Intermediate fibers
4. Other accessory proteins
This gives the cell mechanical support, maintains it's shape and functions in cell motility.
These are hollow rods in the cytoskeleton that are made up of polymerized tublins that radiate throughout the cell and provide it with support.
Microtubules - also provide the framework for organelle movement within the cell.
These direct the separation of chromosomes during cell division by spindle formation and are composed of microtubules.
These are specialized arrangements of microtubules that extend from certain cells and are involved in cell motility.
Cilia and flagella
These contain their own DNA & ribosomes and exibit the same semiautonomy as mitochondria.
What is:
1. Water FEARING?
2. How does this relate to the cell membrane?
1. Hydorophobic
2. Found on the interior portion of the phospholipid bilayer of the cell wall of a eukaryotic cell. Cholesterol molecules embedded in the hydrophobic interior contribute to the membranes fluidity. In addition is the non-polar fatty acid region.
What is:
1. Water LOVING?
2. How does this relate to the cell membrane?
1. Hydrophillic
2. Found on the exterior portion of the phospholipid bilayer of the cell wall of a eukaryotic cell. In addition is the polar phosphoric acid region.
These are the membrane spanning molecules that allow certain ions and polar molecules to pass through the lipid bilayer.
Transport proteins
These are proteins that contribute to cell recognition and adhesion and are particularly important during development.
Cell Adhesion Molecules (CAMs)
These are complex proteins of glycoproteins that are generally embedded into the membrane that bind to specific molecules in the cells external environment.
These proteins assist larger charged proteins to cross the cell membrane.
Carrier proteins
This controls the activity of a cell including cell division.
This is a double walled envelope that maintains a distinct nuclear environment from the cytoplasm.
Nuclear membrane
These are interspersed throughout the nuclear membrane and allow selective two-way exchange of materials.
Nuclear pores
These are the structural proteins that form chromosomes in the nucleus.
This dense structure is where the ribosomal RNA (rRNA) synthesis occurs.
This is the site of protein production and are synthesized by the nucleolus.
Composed of rRNA and proteins, these are the larger ones and are found in the cytoplasm.
Free RNA
Composed of rRNA and proteins, these are the smaller ones and are found lining the outer membrane of the endoplasmic retiulum
Bound RNA
This is a network of membrane enclosed spaces connected at points with the nuclear membrane.
Endoplasmic Retuculum (ER)
This ER is involved in lipid systhesis and detoxification of drugs and poisons.
Smooth ER
This ER is involved in protein synthesis.
Rough ER
Protiens synthesized by the bound ribosomes cross into the cisternae of the rough ER where they undergo chemical modification. They then cross into the smooth ER where they are secreted into cytoplasmic vesicles and transported where?
Golgi Apparatus
This consists of a stack of membrane enclosed sacs. This receives vesicles and their contents from the smooth ER and modify them through what process? This organelle is particularly active in the distribution of newly synthesized materials to the cell su
Golgi Apparatus
The vesicles produced by the Golgi Apparatus release their contents into the cells exterior by what process?
Secretory vesicles
These are membrane bound sacs involved in the transport and storage of materials that are ingested, secreted, processed or digested by the cell.
These are larger than Vesicles and are more likely found in plant cells.
These are membrane bound vesicles that contain hydrolytic enzymes involved in intracellular digestion. They fuse with endocytotic vacuoles thereby breaking down the material ingested by the cell.
When a cell in an injured ot dying tissue "commits suicide" by rupturing the lysosome membrane and releasing its hydrolytic enzymes which digests its cellular contents.
Th optima pH of the lysosomal enzyme.
These are membrane bound organelles specialized as containers for metabolic reactions.
These microbodies contain oxidative enzymes that catalyze a class of reactions in which hydrogen peroxide is produced from the transfer of hydrogen from a substrate to oxygen. These breakdown fats into smaller molecules that can be used for fuel and are
These are usually found in fat tissues of germinating seedlings to convert fats into sugars until the seedling is mature enough to produce its own supply of sugars through photosynthesis.
This is the site of aerobic respiration within the cell and hence supplies energy. Each is bound by an outer and an inner phospholipid bilayer membrane. The outer layer is smooth and acts as a sieve allowing molecules through on the basis of size.
The convoluted inner membrane of the mitochondria made up of high protein that includes proteins of the electron transport chain.
Mitochondrial cristae
This is the areas bound by the inner membrane and is the site of many reactions of cellular respiration.
Mitrochondrial matrix
What is the term that describes how Mitochondria are different from all other organelles in that they contain their own DNA (circular) and ribosomes which enables them to produce their own proteins and to self replicate by what process.
Binary fission
Cell walls are designed to protect from external stimuli and desiccation. Plants have cell walls composed of what and fungi have cell walls composed of what?
Microfiliments are solid rods of what material? These are involved in cell movement and support.
Muscle contraction is based on interaction of actin and what in the muscle cells?
This is the net movement of dissolve particles down their concentration gradients from a region of higher concentration to a region of lower concentration. This is a passive process.
Simple diffusion
This is the simple diffusion of water from a region of lower solute concentration to a region of higher solute concentration.
When the cytoplasm of a cell has a lower solute concentration than the extracellular medium the medium is said to be what to the cell and water will flow out causing the cell to shrink.
When the cytoplasm of a cell has a higher solute concentration than the extracellular medium, the medium is said to be what to the cell and water will flow in causing the cell to swell?
If too much water flows into a cell, the cell may do what?
When the solute concentrations inside and outside the cell are equal, the cell and the medium are said to be what and there is no net flow of water in either direction.
This is the net movement of dissolved particles down their concentration gradient with the help of carrier molecules. This process like simple diffusion does not require energy.
Facilitated diffusion
This is the net movement of dissolved particles against their concentration gradient with the help of transport proteins and requires energy. This process is required to maintain membrane potentials in specialized cells such as neurons.
Active transport
This is the process in which the cell membrane invaginates, forming a vesicle that contains extracellular medium. The actual vesicle material never actually crosses through the cell
This process is the ingestion of fluids or particles. Particles may first bind to receptors on the cell membrane before being engulfed.
This is the engulfing of large particles. Particles may first bind to receptors on the cell membrane before being engulfed.
A vesicle within the cell fuses with the cell membrane and releases its contents to the outside. Fusion of the vesicle with the cell membrane can play an important role in the cell growth and intracellular signaling. The actual vesicle material never act
Nutshell of passive diffusion:
* Down gradient
* No carrier
* No energy required
Nutshell of Facilitated diffusion:
* Down gradient
* Carrier
* No energy required
Nutshell of Activated transport
* Against gradient
* Carrier
* Energy Required
Diffusion is the biological version of a ball doing what?
Rolling down the hill against its potential energy gradient
Active transport is the biological version of a ball doing what?
Being pushed up a hill. Energy in the form of ATP must be expended and work is performed.
MCAT favorites
Be on the lookout for examples in which gradients drive physiological functions like these
* Oxygen-carbon dioxide exchange in tissues & lungs.
* Urine formation in the kidneys.
* Depolarization of neurons and conduction of the actin potential.
* Proton gradient in mitochondria.
* Exchange of materials between the maternal and fetal blood across teh placenta.
MCAT favorite
You need to appreciate that the more non[polar a molecule, the easier time ti will have traversing the hydrophobic core of the cell membrane.
Example - The non-polar steroid hormones cross the cell membrane and meet up with their receptors inside the cell. By contrast, the protein hormones bind to the cell membrane receptors and modify the cellular activity via an internal secondary messenger (e.g. cAMP)
Four basic types of tissues are?
1. Epithelial
2. Connective
3. Nervous
4. Muscle
This tissue covers the surface of the body & lines the cavities protecting them against injury, invasion & desiccation. It's also involved in absorption, secretion and sensation.
This tissue is involved in body support and other functions. Specialized tissues of this type include bone, cartilage, tendons, ligaments, adipose tissue and blood.
This tissue is composed of specialized cells called neurons that are involved in the perception, processing and storage of information concerning the internal and external environments.
This tissue has a great contractile capability and is involved in body movement
The three types of muscle tissue are?
1. Skeletal
2. Cardiac
3. Smooth
This is a unique acellular structure composed of nucleic acid enclosed by a protein coat.
Size range of viruses
20-300 nm
The nucleic acid in a virus can be linear or circular and can be found the what 4 varieties?
1. Single stranded DNA
2. Double stranded DNA
3. Single stranded RNA
4. Double stranded RNA
It is called what when a virus can express their genes and reproduce only within a living host cell, since they lack the structures necessary for independent activity and reproduction.
Obligate intracellular parasites
Viruses that exclusively infect bacteria by injecting its nucleic acid into the bacterial cell.
Clinical correlate for viruses
To date, a few antiviral medications that exist work by interfering with enzymatic reactions involved with viral replication.

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