BIOL 2113 QUESTIONS AND ASWERS LATEST UPDATE
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Cell Theory
1. A cell is the structural and functional unit of life. How well the entire organism function
depends on individual and combined activities of all of its cells. Structure and function
are complementary. Biochemical functions of cell are dictated by shape of cell and
specific subcellular structures. continuity of life has cellular basis. Cell can arise only
from other preexisting cells. Cell diversity: there are 250 different types oof human cells.
Types differ in size, shape and subcellular components, these differences lead to lead
differences in functions.
Human cells have three basic parts.
1. Plasma Membrane: Flexible outer boundary.
2. Cytoplasm: intracellular fluid containing organelles.
3. Nucleus: DNA containing control center.
Extracellular Materials
Substance found outside cells.
-Classes of extracellular fluids such as
1. Interstitial fluid: cells are submersed in fluid
2.Blood Plasma: Fluid of the blood
3.Cerebrospinal fluid: fluid surrounding nervous system organs
-Cellular secretions (saliva, mucus)
-Extracellular matrix: substance that acts as glue to hold cells together.
Plasma Membrane
Acts as an active barrier separating intracellular (ICF) fluid from extracellular fluid
(ECF).
Plays dynamic role in cellular activity by controlling what enters and what leaves cell.
Also known as the "cell membrane"
Consists of membrane lipid that form a flexible lipid bilayer.
Specialized membrane proteins float through this fluid membrane, resulting in
constantly changing patterns.
-Referred to as fluid mosaic (made up of many pieces) pattern. Surface sugars form
glycocalyx. Membrane structure help to hold cells together through cell junctions.
Membrane Lipids
Lipid bilayer is made up of:
75% phospholipids, which consist of two parts:
Phosphate heads: are polar (charged), so are hydrophilic (water-loving)
Fatty acid tails: are nonpolar (no charge), so are hydrophobic (water-hating)
5% glycolipids
Lipids with sugar groups on outer membrane surface
20% cholesterol
Increases membrane stability
Membrane proteins
, Allow cell communication with environment
Make up about half the mass of plasma membrane
Most have specialized membrane functions
Some float freely, and some are tethered to intracellular structures. There are 2 types:
Integral proteins and Peripheral proteins.
Integral Proteins
Firmly inserted into membrane. Most are transmembrane proteins (span membrane).
Have both hydrophobic and hydrophilic regions. Hydrophobic area interacts with lipid
regions. Hydrophilic areas interact with water. Function as transport proteins (channels
and carrier), enzymes or receptors.
Peripheral proteins
Loosely attached to integral proteins. Include filaments on intracellular used for plasma
membrane support. Functions as: Enzymes
Motor proteins for shape change during cell division
and muscle contraction.
Cell to cell connections
Transport
A protein that spans membrane may provide a hydrophilic channel across the
membrane that is selective for a particular solute. Some transport protein hydrolyzes
ATP as an energy source to actively pump substances across the membrane.
Receptor for signal transduction
A membrane protein exposed to the outside of the cell may have a binding site that fits
the shape of a specific chemical messenger, such as a hormone. When bound, the
chemical messenger may cause a change in shape in the protein that initiates a chain
of chemical reactions in the cell.
Enzymatic activity
A membrane protein may be enzyme with its active site exposed to substance in the
adjacent solution.
A team of several enzymes in a membrane may catalyze sequential steps of a
metabolic pathway.
Cell-cell recognition
some glycoproteins (proteins bonded to short chains of sugars which help to make up
the glycocalyx) serve as identification tags that are specifically recognized by other cells
Attachment to the cytoslkeleton and extracellular matrix
Elements of the cytoskeleton and extracellular matrix (ECM)
Elements of the cytoskeleton (cell's internal framework) and the extracellular matrix
(fibers and other substances outside the cell) may anchor to membrane proteins. Help
maintain cell shape, fixes the location of certain membrane proteins and plays a role in
cell movement.
Cell to cell joining
membrane proteins of adjacent cells may be hooked together in various kinds of
intercellular junctions. Some membrane proteins (cell adhesions molecules of CAMs) of
this group provide temporary binding sites that guide cell migration and other cell to cell
interactions.
Glycocalyx
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Cell Theory
1. A cell is the structural and functional unit of life. How well the entire organism function
depends on individual and combined activities of all of its cells. Structure and function
are complementary. Biochemical functions of cell are dictated by shape of cell and
specific subcellular structures. continuity of life has cellular basis. Cell can arise only
from other preexisting cells. Cell diversity: there are 250 different types oof human cells.
Types differ in size, shape and subcellular components, these differences lead to lead
differences in functions.
Human cells have three basic parts.
1. Plasma Membrane: Flexible outer boundary.
2. Cytoplasm: intracellular fluid containing organelles.
3. Nucleus: DNA containing control center.
Extracellular Materials
Substance found outside cells.
-Classes of extracellular fluids such as
1. Interstitial fluid: cells are submersed in fluid
2.Blood Plasma: Fluid of the blood
3.Cerebrospinal fluid: fluid surrounding nervous system organs
-Cellular secretions (saliva, mucus)
-Extracellular matrix: substance that acts as glue to hold cells together.
Plasma Membrane
Acts as an active barrier separating intracellular (ICF) fluid from extracellular fluid
(ECF).
Plays dynamic role in cellular activity by controlling what enters and what leaves cell.
Also known as the "cell membrane"
Consists of membrane lipid that form a flexible lipid bilayer.
Specialized membrane proteins float through this fluid membrane, resulting in
constantly changing patterns.
-Referred to as fluid mosaic (made up of many pieces) pattern. Surface sugars form
glycocalyx. Membrane structure help to hold cells together through cell junctions.
Membrane Lipids
Lipid bilayer is made up of:
75% phospholipids, which consist of two parts:
Phosphate heads: are polar (charged), so are hydrophilic (water-loving)
Fatty acid tails: are nonpolar (no charge), so are hydrophobic (water-hating)
5% glycolipids
Lipids with sugar groups on outer membrane surface
20% cholesterol
Increases membrane stability
Membrane proteins
, Allow cell communication with environment
Make up about half the mass of plasma membrane
Most have specialized membrane functions
Some float freely, and some are tethered to intracellular structures. There are 2 types:
Integral proteins and Peripheral proteins.
Integral Proteins
Firmly inserted into membrane. Most are transmembrane proteins (span membrane).
Have both hydrophobic and hydrophilic regions. Hydrophobic area interacts with lipid
regions. Hydrophilic areas interact with water. Function as transport proteins (channels
and carrier), enzymes or receptors.
Peripheral proteins
Loosely attached to integral proteins. Include filaments on intracellular used for plasma
membrane support. Functions as: Enzymes
Motor proteins for shape change during cell division
and muscle contraction.
Cell to cell connections
Transport
A protein that spans membrane may provide a hydrophilic channel across the
membrane that is selective for a particular solute. Some transport protein hydrolyzes
ATP as an energy source to actively pump substances across the membrane.
Receptor for signal transduction
A membrane protein exposed to the outside of the cell may have a binding site that fits
the shape of a specific chemical messenger, such as a hormone. When bound, the
chemical messenger may cause a change in shape in the protein that initiates a chain
of chemical reactions in the cell.
Enzymatic activity
A membrane protein may be enzyme with its active site exposed to substance in the
adjacent solution.
A team of several enzymes in a membrane may catalyze sequential steps of a
metabolic pathway.
Cell-cell recognition
some glycoproteins (proteins bonded to short chains of sugars which help to make up
the glycocalyx) serve as identification tags that are specifically recognized by other cells
Attachment to the cytoslkeleton and extracellular matrix
Elements of the cytoskeleton and extracellular matrix (ECM)
Elements of the cytoskeleton (cell's internal framework) and the extracellular matrix
(fibers and other substances outside the cell) may anchor to membrane proteins. Help
maintain cell shape, fixes the location of certain membrane proteins and plays a role in
cell movement.
Cell to cell joining
membrane proteins of adjacent cells may be hooked together in various kinds of
intercellular junctions. Some membrane proteins (cell adhesions molecules of CAMs) of
this group provide temporary binding sites that guide cell migration and other cell to cell
interactions.
Glycocalyx
