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
