Cells Flashcards
What are the 3 main parts of the cell?
- Cell Membrane (Plasma Membrane)
- Nucleus
- Cytoplasm
Cell Membrane (Plasma Membrane)
– made up of 2 layers of
phospholipids and cholesterol molecules. Cholesterol helps
stabilize the phospholipid molecules to prevent breakage of the
membrane
-The cell membrane is the gateway of the cell that controls the passage of materials in and out of the cell.
Proteins in the cell membrane act as…
receptors that “communicate” chemical messages from hormones
that influence the function of the cell.
Carbohydrate chains on the membrane play a part in the…
identification of the cell as specifically belonging to an individual. This is used during tissue typing prior to
organ transplant.
Nucleus
– a small spherical structure in the central portion of the cell that is surrounded by the nuclear envelope.
It is the cell’s command center that controls every organelle in the cytoplasm.
- It contains the genetic material, the DNA (deoxyribonucleic acid)
- In the nucleus are chromatin granules which are made up of proteins (histones) around which the DNA is tightly bound.
Nucleolus
- dense region of the nucleus that produces subunits that form ribosomes.
Ribosome
Ribosome subunits migrate through the nuclear envelope into the cytoplasm to form ribosomes which produce proteins.
Cytoplasm
– the internal living material in cells
The cytoplasm contains the following organelles:
- Ribosomes
- Endoplasmic Reticulum (ER)
Endoplasmic Reticulum (ER)
– The ER is the transport system of the cell. It consists of a membranous
network of interconnected canals and channels that carry proteins and other substances through the cytoplasm of the cell.
- The rough ER has ribosomes attached to it. Fats, carbohydrates and proteins that make up the cell membrane are manufactured in the smooth ER.
Golgi Apparatus
– consists of tiny sacs stacked
on one another near the nucleus.
It chemically processes and ‘packages’ substances from the ER, exports them in vesicles outward to the plasma membrane
Example: mucus ‘packaged’ into the plasma membrane
Mitochondria
- “power plant” of the cell containing
enzymes and substances whose reactions release energy to recharge the cell’s “battery” – the Adenosine
Triphosphate (ATP)
Lysosomes
- the “digestive bags” of the cell
containing enzymes that break apart large food molecules through hydrolysis. Lysosomes digest and destroy microbes that invade
the cell.
Centrioles
are paired rod-shaped structures that
play an important role for moving the chromosomes during cell division
Microvilli
are small finger-like projections of the plasma membrane that increases the absorptive capacity of the cell Example: intestinal microvilli
Cilia
are extremely fine hair-like extensions on the exposed surface of the cell serving as “antennae” for the cell to sense its surroundings
Example: cilia in taste buds
- Some cilia are capable of moving as a group in one direction to propel mucus.
Example: cilia in respiratory tubes involved in mucociliary escalator
flagellum
is a single, long projection of the cell used for movement
(Example: flagellum of the sperm cell)
Passive Transport
involves the movement of substances from a high concentration to a low concentration.
- No cellular energy is required
Examples: diffusion, osmosis, filtration – movement “down a concentration gradient” until equal proportion of the substance is achieved on both sides of the membrane
Diffusion
- requires big pores for the particles to pass through the cell membrane. Solute as well as water both move from high to low concentration to achieve equilibrium.
Examples: movement of carbon dioxide from cells into blood
Osmosis
is the diffusion of water (only)through selectively permeable membrane that does not allow solutes to pass through.
Example: movement of water in and out of red blood cells
Filtration
- requires the force of hydrostatic pressure gradient that allows water and diffusible solutes to filter out from the solution with higher hydrostatic pressure to the solution with lower hydrostatic pressure.
Example: movement of water from plasma into renal tubules to begin formation of urine
Active transport
- involves the movement of substances from a low concentration to a high concentration therefore, cellular energy from ATP is required
- Active transport occurs only through living membranes.
Examples: ion pump, phagocytosis, pinocytosis – movement of substances against a concentration gradient
Principles in Active Transport Processes:
- Ion pumps are carriers that move ions against concentration gradients. Pumps may be particular to one ion or may be “coupled” to pump two ions simultaneously
Example: Na+/K+ pump - Large particles are engulfed during phagocytosis, whereas fluid and dissolved substances are brought into the cell in pinocytosis.
Example: phagocytosis by white blood cells pinocytosis by microvilli of intestinal cells to take up nutrients
Chromosomes
- housed in the cell nucleus, are
composed of lengthy and tightly bound DNA (deoxyribonucleic acid) strands
DNA
- made up of smaller sub-units called nucleotides each consisting of a sugar, phosphate and a nitrogen base. Complimentary base pairing(nitrogen-containing bases) include: adenine-thymine, cytosine – guanine – form the “rungs of the ladder”
DNA Structure:
Each strand has a backbone made up of (deoxy-ribose) sugar molecules linked together by phosphate groups. Each sugar molecule is linked to one of 4 possible bases (adenine,guanine,cytosine andthymine)
The Genes
DNA segments that contain hereditary information is the genetic code.
genetic code dictates?
- directions for protein synthesis – structural and functional proteins.
Proteins determine?
- cell structure and function and therefore the traits passed on by heredity.
The main differences between RNA and DNA are:
- RNA molecules are single-stranded
- The sugar in RNA is a ribose sugar (as opposed to deoxyribose
in DNA) - Thymine in DNA is replaced byuracil in RNA.
Transcription in Protein Synthesis
In the nucleus, the DNA unwinds and messenger RNA (mRNA) copies (transcribes) the gene sequence in the DNA. The mRNA moves out of the nucleus to the cytoplasm to direct protein synthesis in the ribosomes and the ER.
Translation in Protein Synthesis
- is the synthesis of proteins in the cytoplasm by ribosomes based on the information from mRNA.
In the cytoplasm, mRNA directs the assembly of amino acids as dictated by the genetic code. The amino acid strands fold and combine with other strands to complete the protein structure.
The shape and function of each protein in the cell is thus dictated by the DNA.
Stages of Cell Division in Mitosis
- Interphase
- Prophase
- Metaphase
- Anaphase
- Telophase
Interphase
The cell prepares for cell division; DNA makes a copy of itself in the process called DNA replication which ensures that genetic material would be the same for both daughter cells.
Prophase
The replicated DNA strands form pairs
of chromatids (tightly coiled, “visible” chromosomes) that are held together by the centromere. In the cytoplasm,
centrioles separate and form spindle fibers.
Metaphase
The chromosomes align at the center of the cell and centrioles migrate to the opposite poles of the cell. Spindle fibers attach themselves to the centromeres. The nucleolus and nuclear envelope disappear.
Anaphase
The centromeres break apart and the chromosomes move away from the center of the cell. The cleavage furrow forms to divide the cell into 2 daughter cells.
Telophase
The nuclear envelope and nuclei reappear; the cytoplasm and organelles divide equally resulting in two identical daughter cells each with identical genetic characteristics.
