BIOL 109 Lecture Notes - Lecture 7: Endoplasmic Reticulum, Extracellular Fluid, Nuclear Pore

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9 Dec 2016
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Cell theory
Cells are the building blocks of all plants and living animals
all cells come from the division of pre-existing cells
cells are the smallest units that carry out life's essential physiological functions
Each cell must maintain homeostasis at the cellular level
Sex cells are either sperm of the males or oocytes for eggs of females
Somatic cells or body cells include all other cells in the human body
3.1
Cell or Plasma Membrane- outer boundary of a cell
Functions
Physical isolation the cell membrane is a barrier that separates the inside
of the cell (cytoplasm) from the outside
Regulation of exchange with environment the cell membrane acts as a
gatekeeper controlling the entry of ions and nutrients end exit of wastes
sensitivity to the environment the plasma membrane is the first part of the
cell to affected by changes in composition or pH of the extracellular fluid it
also has receptors allowing the cell to recognize and respond to specific
molecules in its environment
Structural support specialized connections between plasma membrane
are membranes and extracellular materials gives tissues stability
The plasma membrane is a phospholipid bilayer because the phospholipid
molecules in its form two layers
Membrane proteins
Integral proteins are part of the plasma membrane structure and cannot
be easily separated from it
Most integral proteins span the width of the membrane one or
more times known as the transmembrane proteins
Peripheral proteins are bound to the inner or outer surface of the
membrane and are easily separated from it
Anchoring Proteins attached to the plasma membrane or to other
structures and stabilize its position
Recognition Proteins (identifiers) the cells of the immune system
recognizes other cells of normal or abnormal based on the presence or
absence of characteristics recognition proteins
Enzyme in the plasma membrane may be integral of peripheral proteins
receptor proteins in the plasma membrane are sensitive to the presence
of specific extracellular molecules called ligands
ligands can be anything from a small ion like calcium to a
relatively large and complex hormone
carrier proteins bind solutes and transport them across the plasma
membrane
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Some integral proteins contain a channel that forms of passageway
completely through the plasma membrane
the channel permits water and small solutes to move across the
plasma membrane
Membrane carbohydrates
examples include Proteoglycans and glycoproteins and glycolipids
The carbohydrate proportions of these large molecules extend beyond the outer
surface of the membrane forming the a layer known as glycocalyx
Lubrication and protection
anchoring and locomotion
specificity in binding
Recognition
3.2
Cytoplasm is the general term for the material between the plasma membrane and the
membrane that surrounds the nucleus
Cytosol or intracellular fluid contains dissolved nutrients ions soluble and
insoluble proteins and waste products
Concentration of potassium ions is very high
contains high concentrations of suspended proteins
Usually contains small quantities of carbohydrates and small reserves of
amino acids and lipids
Inclusion- masses of insoluble material
Organelles structures suspended within the title that perform specific functions
for the cell
Nonmembranous organelles- not completely enclosed by
membranes and all of their components are directly in contact with
the cytosol
cytoskeleton, microvilli, centrioles, cilia, ribosomes, and
proteasomes
Membranous organelles- isolated from the cytosol by phospholipid
membrane, just as the plasma membrane isolates the cytosol from
the extracellular fluid
endoplasmic reticulum, Golgi apparatus, ribosomes,
peroxisomes, and mitochondria
The cytoskeleton serves as the cell’s skeleton
internal protein framework that gives the cytoplasm
strength and flexibility
Microfilaments the smallest of the cytoskeletal elements
1. Microfilaments anchor the cytoskeleton to integral proteins
in the plasma membrane
2. Microfilaments interact with other proteins to determine the
consistency of the cytoplasm
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3. Actin can produce movement of the proportion of the cell to
change the shape of the entire cell by interacting with the
protein myosin
Intermediate filaments- Most large of the cytoskeleton elements
1. Strengthen the cell
2. Stabilize the position of organelles
3. Stabilize position of cell with respect of surrounding cells
Microtubules hollow tubes built from the globular protein
Largest part of cytoskeleton
1. Form the main functions of the cytoskeleton
2. Change the shape of the cell and may assist in cell
movement
3. Serve as any kind of monorail system to move
vessels or other organelles within the cell
4. During cell division microtubules distribute
duplicated chromosomes to opposite ends of
dividing cells
5. Microtubules form structural components of
organelles such as centrioles and cilia
thick filaments are relatively massive bundles of subunits made
up of myosin
appear only in muscles
microvilli small finger-shaped projections of the plasma membrane on
their exposed surfaces
Greatly increase the surface area of the cell exposed
Centrosome- region of the cytoplasm located next to the nucleus
In cell division the centrosome surrounds a pair of cylindrical
structures called centrioles
During cell division the centrioles of the formation of the
spindle apparatus needed for the movement of DNA
strands
Cilia really long and slender extensions of the plasma membrane
flagellum extension of the plasma membrane
Only in sperm cells
Ribosomes- Responsible for protein synthesis
There are two subunits of the ribosome, the small ribosomal
subunit and the large ribosomal subunit. The two are linked by
mRNA to begin protein synthesis in the cytoplasma.
Free ribosomes- scattered throughout cytoplasm
Fixed ribosomes- proteins with destinations other than the
cytosol Become temporary bound to the ER.
Proteasomes organelles that contain a assortment of protein digesting
enzymes
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