2 Cell Structure and Function Flashcards
smallest functional unit that performs essential vital functions (metabolism, growth, movement, reproduction, and hereditary transmission).
cell
a double layer of phospholipid molecules with protein molecules embedded within it. It is responsible for separating the cell from its environment and controls the movement of substances in and out of the cell
cell membrane (CM) or plasma membrane
Proteins in the CM that act as pores/channels, carrier proteins, receptors, enzymes are classified into
integral CM proteins
mainly act as enzymes attached to integral proteins.
peripheral CM proteins
What substances do not easily pass through the membrane
Water-soluble substances (such as ions, glucose, and urea)
What substances can easily move in and out of the membrane.
fat-soluble substances (such as oxygen, carbon dioxide, and alcohol)
a loose carbohydrate coat found on the entire outside surface of the cell composed of proteoglycans glycoproteins/glycolipids. The presence of this structure brings a negative charge, serves as an attachment and receptor, and is also important to immune reactions.
glycocalyx
a selectively permeable membrane which means that certain substances can easily move into the cells while other substances may require specialized transport systems.
Cell membrane
specialized transport systems (4)
- Pores in the CM
- Diffusion
- Active transport mechanisms
- Endocytosis
small molecules can pass through these pores.
Pores in the CM
-it is the random molecular movement of substances molecule by molecule, either through intermolecular spaces in the membrane or combination with a carrier protein.
-continual movement of molecules among one another in liquids or gases
Diffusion
a kinetic movement of molecules or ions occurs through a membrane opening or intermolecular spaces without any interaction with carrier proteins in the membrane and the rate of diffusion is determined by the amount of substance available, the velocity of kinetic motion, and the number and sizes of openings in the membrane through which the molecules or ions can move.
Simple diffusion
Two pathways of simple diffusion
(1) through the interstices of the lipid bilayer if the diffusing substance is lipid soluble
(2) through watery channels that penetrate through some of the large transport proteins
a carrier-mediated diffusion in which a substance diffuses through the membrane using a specific carrier protein.
Facilitated diffusion
The rate of diffusion approaches a maximum, called ____ as the concentration of the diffusing substance increases.
Vmax,
*Gating of Protein Channels
is when the molecular conformation of the gate or its chemical bonds responds to the electrical potential across the cell membrane.
Voltage gating
is when a protein channel gates are opened by the binding of a chemical substance (a ligand) with the protein.
Chemical (ligand) gating
is when the cell membrane moves molecules or ions “uphill” against a concentration gradient (or “uphill” against an electrical or pressure gradient).
Active transport mechanisms
– the energy is derived directly from the breakdown of ATP or some other high energy phosphate compound
– Sodium-Potassium Pump, Primary Active Transport of Calcium Ions, Primary Active Transport of Hydrogen Ions
Primary Active Transport
– the energy is derived secondarily from the energy that has been stored in the form of ionic concentration differences of secondary molecular or ionic substances between the two sides of a cell membrane, created originally by primary active transport.
Secondary Active Transport
a specialized function used by very large particles to enter the CM. Two principal forms of this include pinocytosis and phagocytosis.
Endocytosis
fluid that fills the interior of the cell providing support. The nucleus and organelles are found within here together with neutral fat globules, glycogen granules, ribosomes, and secretory vesicles.
Cytoplasm
clear fluid portion of the cytoplasm.
cytosol
structure that helps cells maintain their shape and internal organization, and it also provides mechanical support that enables cells to carry out essential functions like division and movement.
Cytoskeleton
Structures that comprise the cytoskeleton include (3)
microfilaments or actin filaments
intermediate filaments
microtubules.
important in muscle contraction, cytokinesis of mitosis, diapedesis, and phagocytosis of white blood cells.
Microfilaments or actin filaments
serve as anchors of attachment between cell to cell, cell to extracellular membrane, and cell to organelles.
Intermediate filaments
made of a and b tubulin and are important in intracellular transport, separation of chromatids in cell division, and form cell extensions like cilia and flagella.
Microtubules
control center of the cell. It is surrounded by a nuclear membrane and contains the chromosomes which are composed of DNA that determine the characteristics of the cell’s proteins, including the structural proteins, and controls and promotes the reproduction of the cell itself. It also contains several nucleoli where the ribosomes are manufactured.
Nucleus
responsible for cellular respiration and are the site where energy in the form of ATP is stored.
Mitochondria
Chemical energy produced by the mitochondria is stored in a small molecule called
adenosine triphosphate (ATP).
these floats within the cytoplasm and are the site of protein synthesis.
Ribosome
contains ribosomes thus it functions in the transport of proteins synthesized from ribosomes.
Rough or granular ER
its functions include the synthesis and transport of lipids and steroids.
Smooth or agranular ER
Other functions of the ER include
- It provides the enzymes that control glycogen breakdown when glycogen is to be used for energy.
- It provides a vast number of enzymes that are capable of detoxifying substances,
process ER vesicles to form lysosomes, secretory vesicles, and other cytoplasmic components, add carbohydrate molecules in proteins, and synthesize carbohydrates that cannot be formed in the ER (hyaluronic acid, chondroitin sulfate).
Golgi Apparatus
contains hydrolases and provide an intracellular digestive system that allows the cell to digest (1) damaged cellular structures, (2) food particles that have been ingested by the cell, and (3) unwanted matter such as bacteria.
Lysosomes
formed by self-replication (or perhaps by budding off from the smooth endoplasmic reticulum) rather than from the Golgi apparatus. These structures contain oxidases rather than hydrolases which combine oxygen with hydrogen ions producing hydrogen peroxide (H2O2). H2O2 works with catalase to oxidize poisonous substances.
Peroxisomes
centrosome contains one pair of centrioles. These are involved in cell division.
Centrosome and centrioles
extensions of the plasma membrane responsible for the locomotion of certain cells.
Cilia and flagella
usually found at the surface of cells responsible for the wave-like motion of fluid-like mucus (lining of the respiratory system).
Cilia
moves the cell along by undulating movements (spermatozoa).
Flagella
include all the cells of the body except for those included in reproduction. These cells divide by mitosis and contain the diploid number of chromosomes.
somatic cells
type of cells, include the ova and the spermatozoa. These cells divide by meiosis and contain the haploid number of chromosomes.
germ cells
stage wherein the new daughter cells grow and prepare for the next division.
interphase
This includes four active stages followed by interphase
Mitosis
The resting cell is in interphase before this stage begins, this has eight stages
meiosis
takes longer than prophase in mitosis. Homologous (identical) chromosomes lie side by side and duplicate; each pair is joined at the centromere. These chromosomes may become entangled and pieces of one chromosome may become attached to another – this process is known as ‘crossing over’ and may influence the characteristics of the offspring.
Prophase I
the cytoplasm begins to divide but the nuclear membrane does not reform. In some cells, the cytoplasm does not divide completely, and a dumb- bell-shaped cell is seen – this is known as a syncytium. This is the first meiotic division.
Telophase I
this may be transitory as there is no need to replicate the chromosomes.
Prophase II
the cytoplasm begins to divide; the nuclear membrane reforms and four identical daughter cells are formed. This is the second meiotic division.
Telophase II
