Ch. 3 Cell Structure and Genetic Control Flashcards
Understand and be able to ID cell parts
Cell Structure: Plasma Membrane
Selectively permeable, gives form, and separates from the external environment
ALL cells have plasma membrane; we have to be able to control what enters/exits the cell
Cell Structure: Cytoplasm and Organelles
Fluid part of cell and cellular functions; most of our body’s water is stored in cytoplasm
Organelles include things such as the Golgi complex, mitochondria, lysosomes…
Cell Structure: Nucleus
Contains DNA and directs cell activities
Some cells have multiple nuclei (skeletal muscle)
Some cells have NO nuclei (RBCs)
What structure is this?
Plasma Membrane
Plasma Membrane
Phospholipid barrier (double layer) between the intracellular and extracellular environments
–Hydrophobic center restricts movement of water, water-soluble molecules, and ions
–Some substances can selectively be allowed to pass through protein channels
–Proteins and phospholipids contantly move laterally - the fluid mosaic model
Plasma membrane: location of hydrophobic part and hydrophilic part
Hydrophobic part (fatty acid) tucked inside
Hydrophilic part (double layer) faces outside
Going to move water-soluble substances through the phospholipid barrier
Membrane Proteins
Integral Proteins: span the membrane (stuck/integrated in there)
Peripheral proteins are embedded on just one side of the membrane (associated w/ the phospholipid head)
Membrane Proteins: Fxns
Fxns:
–structural support
–transport
–enzymatic control of cell processes
–receptors for hormones and other molecules
–“self” markers for immune system
Other Membrane Components: CHO
Attached to lipids (glycolipids) and to proteins (glycoproteins); seve as antigens and interactions with regulatory molecules
Tells body which cells are “self”
Other Membrane Components: Cholesterol
Gives flexibility to the membrane
–as we age, our cells become stiff. Cholesterol helps keep cells flexible
What is this structure?
Cell membrane
What is phagocytosis?
Bulk transport or large extracellular substances into the cell. Important for body defense, inflammation, and apoptosis
Cell-eating
What is endocytosis?
The plasma membrane furrows inward rather than extending outward. A small part of the membrane surrounding the substance pinches off and is brought in as a vesicle. May be mediated by a receptor, receptor-mediated endocytosis.
Bringing something from outside to inside the cell
What is exocytosis?
Large cellular products (proteins) are moved out of the cell
What are cilia?
Tiny, hairlike structures composed of microtubules that project from the plasma membrane
ALL cells have cilia
What are primary cilium?
Most cells have this nonmotile cilium; may have a sensory function in some cells
–kidneys have primary cilium
What are motile cilia?
Beat in unison to move substances through hollow organs. Found in respiratory tract and uterine tubes
What are flagella?
A single whip-like structure that can propel a cell forward; sperm cells are the only cells that have flagella
What are these?
Both are cilia
Left is 9+2 arrangement; right (nonmotile cilia) is 9+0 arrangement
Motile: 9 pairs on outside, pair on inside
Nonmotile: lack pair on inside, still have 9 pairs on outside
What is this?
Microvilli
Microvilli
Folds in the plasma membrane that increase the surface area, found in intestines and kidneys
NOT found in endothelium of blood (they’re just transporters)
Important in intestines for absorption of nutrients
Important in kidneys to pull back water
Cytoplasm
Includes organelles, a fluid called cytosol, the cytoskeleton, and inclusions (stored chemical aggregates such as glycogen)
*Cytoplasm and cytosol are the same (just different terms used interchangeably)
Cytoskeleton
Organized system of microtubules and microfilaments throughout the cytoplasm
Organize the intracellular environment and alloow movement of muscle cells and phagocytic cells
Form spindle apparatus that pulls chromosomes apart in mitosis
They also facilitate vesicle and organelle movement in the cell
- Actin (microfilaments)* - predominant one
- Keratin (intermediate)*
- Microtubules (cilia, flagella, microvilli)*
Cytoskeleton [in a nut shell]
Runs all throughout the cell; constant dymanic structure
Provides roadmap for where we need to move things throughout the cell
What is this?
Cytoskeleton
Lysosomes
Organelles filled with digestive enzymes (acidic)
–fuse w/ vacuoles after an immune cell engulfs a bacterium or dead cell
Membrane-bound organelle
Lysosome: Primary Lysosome
Only contains digestive enzymes
Waiting to do work
Lysosome: Secondary Lysosome
Contains the partially digested contents of the food vacuole or worn-out organelles
Doing work
Lysosome: Autophagy
Process of digesting damaged organelles and proteins in the cell
–degrading part of the cell, like those that have mistakes/are worn out
Lysosome: Apoptosis
Programmed cell death
“cell suicide”; does NOT cause inflammation
Necrosis
Cell blows up and releases lysosomes, leads to inflammatory response
Peroxisomes
Contain enzymes specific to certain oxidative reactions; degrade long-chain fatty acids and foreign molecules
Found in most cells but most numerous in liver; often oxidize toxic molecules (such as alcohol)
Generate hydrogen peroxide (H2O2)
–in the process of getting rid of toxic molecules, it generates a lot of hydrogen peroxide –> kills cells
Mitochondria
Site of energy production through aerobic cell respiration
–powerhouse of cell, makes ATP
Central area is fluid and called the matrix
Most cells have mitochondria, and there can be thousands of mitochondria in a single cell (RBCs are an exception)
Mitochondria can migrate and replicate; they have their own DNA, all maternal-derived
–mitochondria passed on from mother ONLY
Mitochondria: Structure
Have an inner membrane and an outer membrane separated by an intermembranous space
Inner membrane is folded into cristae to increase surface area for reactions
What is this?
Mitochondria
Ribosomes
Protein factories of the cell
Very small; made up of 2 subunits of ribosomal RNA and protein
Found free in the cytoplasm or associated with the endoplasmic reticulum
Endoplasmic Reticulum (ER)
System of membranous passageways from the nuclear membrane to the plasma membrane
Rough ER
Has ribosomes embedded on the outer surface, protein synthesis and modification
Smooth ER
Has no ribosomes, synthesis of fatty acids, steroids, lipid
Golgi Complex (Apparatus)
Consists of stacks of hollow, flattened sacs; cavities are called cisternae.
One side receives proteins from the ER, may modify proteins
Proteins are packaged in vesicles called endosomes, that bud off to fuse with the plasma membrane for exocytosis.
“Distribution center”
Membrane-bound organelles
Located close to rough ER, stacked to give itself a high membrane surface area
Describe how proteins from the Rough ER get packaged and distributed.
Proteins made in Rough ER move to Golgi, get packaged into vesicles, sent to plasma membrane via cytoskeleton, then proteins get dumepd out by exocytosis
Most cells have how many nuclei?
One
How many nuclei do muscle cells have?
Hundreds
How many nuclei do mature RBCs have?
None
The nucleus is enclosed by the ____ ____ made up of two membranes.
Nuclear Envelope
Describe the outer membrane of the nucleus
Continuous with the Rough ER
Describe the inner membrane of the nucleus
Often fused to outer membrane by nuclear pore complexes, which allow small molecules and RNA to move into/out of the nucleus through pores.
Nuclear pore acts as a channel; targets what is allowed in/out of cell
Nucleoli
The dark region not surrounded by a membrane, contains the DNA that codes for the production of ribosomal RNA.
What is this entire structure?
Cell Nucleus
*You should be able to ID the nucleoli, inner membrane, outer membrane, and pore complex.
What contains the DNA?
Nucleoli
What is a gene?
A length of DNA that codes for a specific protein
Describe genetic transcription
The gene on the DNA is transcribed as messenger RNA (mRNA)
DNA –> RNA (taking one nucleotide and making it into another)
Describe genetic translation
mRNA is then translated at the ribosome to assemble the proper AA sequence.
Nucleotide –> AA (happens at ribosome)
DNA in the nucleus is packaged with proteins called ____ to form ____.
Histones; Chromatin
Why is DNA packaged?
It has to be packaged in order to fit in the cell
Histones
Positively charged and will interact with negatively charged DNA to cause spooling
–creates particles called nucleosomes
Euchromatin
Active in transcription, looser; chemical changes in histones (such as acetylation) allow molecules access to the DNA during gene expression
DNA that’s loose; actively being transcribed
Heterochromatin
Inactive regions, highly condense; much of the DNA is inactive.
Often seen when you stain the nucleoli
Transcription (RNA Synthesis)
Nucleotide to Nucleotide; how we make RNA
Start and stop regions at the beginning and end of the gene
Promoters, areas of DNA that are not part of the gene but signal enzymes involved where to begin transcription
Transcription factors that bind to the promoter to begin transcription
–piece of DNA (often bound by a protein called a transcription factor) tells us to turn the gene on
Transcription (RNA Synthesis): RNA Polymerase
Breaks up the hydrogen bonds between the base pairs of DNA and assembles the appropriate RNA nucleotide
–RNA nucleotides pair up to the DNA template
Assembly is complementary. If DNA is CGTA, RNA will be GCAU
RNA has ____ instead of thymine
Uracil
In transcription, how many DNA strands are transcribed? What do those strands form?
1 strand is transcribed; form precursor mRNA
pre-mRNA
Made directly by transcription
mRNA
Messenger RNA
Modified pre-mRNA; contains the code to make a specific protein
tRNA
Transfer RNA
Carries AA to mRNA for translation
rRNA
Ribosomal RNA
Along with protein, forms ribosomes; site of translation; acts as an enzyme
What are Introns?
Noncoding regions within gene; found on pre-mRNA
What are Exons?
Coding regions
Translation (Protein Synthesis)
mRNA attaches to a string of ribosomes to form a polyribosome (mRNA has to leave nucleus to associate w/ ribosome)
A group of three bases on DNA, called a triplet, gives the complementary three base sequence in mRNA, called a codon.
– 1 triplet yields 1 AA
The codon codes for an AA, so the order of the codons gives the order of AA in a polypeptide
–more codons exist than AAs (only 20 AAs)
Transfer RNA
Single strand of RNA bent into a cloverleaf shape
One end has the anticodon, which is 3 nucleotides that will be complementary to the proper codon.
–anticodon reads codon that’s found on mRNA
The other end has the appropriate AA bonded by aminoacyl-tRNA synthetase enzyme
–reads mRNA and brings correct AA to peptide chain
What is this process?
Translation
Post-Translational Modification
Protein folding (chaperone proteins)
Cross-linkage (disulfide bonds)
Cleavage (to make active form… e.g. insulin)
Addition of other molecules or groups (phosphate, methyl)
Assembly into polymeric proteins
Lots of work to make proteins
Describe DNA Replication
- Before cell division, each DNA molecule must replicate (DNA –> DNA)
- Involves many enzymes and proteins; two important enzymes are:
a. Helicases break hydrogen bonds between the DNA strands. This creates a fork in the double-stranded molecule where nucleotides can be added to both strands
b. DNA Polymerase attaches complementary nucleotides to the exposed strand
What is this?
Mitosis
What is the cell cycle divided into?
Interphase, Mitosis, and Cytokinesis
Interphase
Divided into G1, S, and G2
Mitosis
Divided into Prophase, Metaphase, Anaphase, and Telophase.
Gives us 2 indentical daughter cells w/ 23 pairs of chromosomes
Cytokinesis
Overlaps the last part of mitosis
What is this?
Meiosis
What is Meiosis?
Process by which 2 cell divison steps produce gametes (ova and sperm); only occurs in gonads (ovaries and testes)
1st division: each of the daughter cells then has 23 (not 46) chromosomes, each consisting of 2 chromatids (duplicated chromosomes).
2nd division: chromatids separated. In ovaries, three of daughter cells die, only one becomes mature egg. In sperm, all 4 cells are functional.
Reduction to 23 chromosomes allows for sperm and egg to combine and “produce” 46 chromosomes.
Where does Meiosis occur?
Reproductive organs
