Chapter 3: Cellular Structures and Genetic Control Flashcards
Define cell.
Basic unit of structure and function ini the body
- 3 main components: plasma membrane, cytoplasm, organelles
Discuss the plasma membrane.
- Surrounds and gives cell its shape
- Selectively permeable
- phospholipid bilayer
- phosphorus end has charge; polar; water-loving: hydrophilic
- lipid tails have no charge: non polar; don’t like water
- “fluid mosaic model”
Discuss bulk transport.
4 Types
- Phagocytosis
- forms a vacuole (arms) that reaches out and grabs the object and brings it into the cell for digestion
- ie. Macrophages and WBC - Pinocytosis (type of endocytosis)
- NON-SPECIFIC!
- cell furrows inward instead of reaching out
- can engulf large molecules - Receptor-Mediated endocytosis
- SPECIFIC!
- Just like pinocytosis but uses receptor proteins to take in specific molecules/compounds from outside the cell - Exocytosis
- export products out of the cell; opposite of pinocytosis
Discuss the cytoskeleton.
- It is a latticework of primarily microfilaments and microtubules filling cytoplasm
- maintains shape
- made up of microfilaments and microtubules
- forms tracks to move things around the cell
Discuss lysosomes.
“Garbage men of the cell”
- organelles containing digestive enzymes
- involved in recycling cell components
- involved with programmed cell death
- Lots found in the liver
Discuss mitochondria.
“Powerhouse of the cell!”
- energy producing organelle
- have inner membrane, outer membrane, separated by inter membranous space
- inner membrane is folded into cristae
- they contain their own DNA
Discuss ribosomes.
“Protein factories”
- synthesizes cell proteins
Discuss endoplasmic reticulum (ER).
- system of membranes specialized for synthesis or degradation of molecules
- rough ER has ribosomes
- smooth ER does NOT have ribosomes
Discuss the golgi complex.
“Packaging and Shipping”
- vesicles enter from ER, contents are modified, then they leave the cell via exocytosis
- lysosomes and secretory vesicles are formed here
Discuss the nucleus.
- Contains the cells DNA
- Contains instructions for making proteins
- enclosed in nuclear envelope which becomes continuous with ER
- Proteins and RNA must be actively transported out of the nucleus (requires energy)
- small molecules can diffuse through pores (no energy required)
Discuss gene expression, transcription, and translation.
- Genes are lengths of DNA that code for making RNA
- mRNA carries info for how to make a protein and is transported out of the nucleus to ribosomes where proteins are made
Transcription:
- RNA synthesis
- DNA sequence in a gene is turned into mRNA sequence
Translation:
- mRNA sequence is used to make a protein (occurs in the ribosome)
- Together, Transcription and Translation are called “Genetic Expression”
DNA: Gene
RNA: Protein
Discuss RNA synthesis.
- Transcription: RNA synthesis
- Occurs in the nucleus
- Different enzymes unzip DNA, tells it where to start and stop; hormones bind to initiate transcription
- Copying one side of DNA strand and having new base pairs attach
Reminder:
- G pairs with C
- A pairs with U
- Human genome 150,000 different proteins; 1 gene codes for average of 3 different proteins
- Transcription produces 4 types of RNA
1. pre-mRNA
2. mRNA - contains code for making protein
3. tRNA - decodes info of mRNA
4. rRNA - forms part of ribosome
Discuss protein synthesis.
- Protein synthesis occurs in the cytoplasm
- Ribosomes read 3 mRNA bases (“codon”) at a time
- Anticodons are complementary to specific mRNA codons; tRNA carries the amino acid specified by its anticodon
- In a ribosome, anticodons on tRNA bind to mRNA condons
- Ribosomes translate codons into amino acid sequence which forms a protein (Translation)
General sequence of transcription and translation.
Genetic information in DNA is TRANSCRIBED into mRNA and then TRANSLATED into a protein.
Discuss DNA replication. Including semiconservative replication.
- Cell divides; DNA replicates into 2 identical copies which go into 2 daughter cells.
- Normal DNA base pairings
- Most cells in the body divide divide in this way (mitosis)
- Reproductive cells however divid by meiosis for genetic variation
Semiconservative Replication
- An enzyme unzips the DNA producing 2 free strands of DNA (half of the helix) so new base pairs are attached to each strand producing a copy of the DNA
- Each new copy is 1/2 old DNA and 1/2 new DNA
- “Conserves” 1/2 DNA on each side
Know the basic steps of the cell cycle.
- Interphase:
- non-dividing phase
- G1, S, G2 (growth, synthesis of DNA, more growth) - Mitosis
- Cytokinesis
Discuss the phases of Mitosis. (4)
- Prophase
- Chromosomes become visible and distinct structures - Metaphase
- Chromosomes line up single file along equator and positioned by spindle fibers
(all 23 chromosomes including 1 sex chromosome XX or XY) - Anaphase
- centromeres split
- spindle fibers pull each chromatid to opposite poles - Telophase
- cytoplasm is divided (= Cytokinesis)
Produces 2 identical daughter cells
Understand chromosome terminology.
Chromosome is:
2 chromatids attached at center by a centromere
The “X” looking chromosome is DNA that has already been replicated so it’s identical on each side.
Discuss the 2 ways cell death occurs.
Necrosis: pathological changes kill a cell
Apoptosis: normal physiological response: programmed cell death
Define and know the difference between Hyperplasia and Hypertrophy.
Hyperplasia
- growth due to an increase in the NUMBER of cells
- most cells in the body grow like this
- tumors take off this way
Hypertrophy
- growth due to increase in cell SIZE
- ie. increase in skeletal muscle mass
Discuss Meiosis.
- Type of cell division occurring in ovaries and testes to produce gametes (ova and sperm)
- Has 2 divisional sequences - DNA replicates once and divides twice
Meiosis I: Unique
Meiosis II: Looks like Mitosis
- In meiosis 1, genetic recombination occurs (crossing over of genetic material) homologous chromosomes PAIR along the equator of cell (rather than singly) and one is pulled to each pole, giving each daughter cell 23 different chromosomes
- In meiosis II, each daughter cell divides and the chromosomes are split into 2 chromatids - 1 goes to each daughter cell (going from 46 chromosomes to 23)
- That’s why Meiosis is also called “Reduction Division”
What is the difference in production between Mitosis and Meiosis?
From Mitosis you get TWO identical cells.
From Meiosis you get FOUR different cells.
