Chapter 3 Flashcards
Cytology
Study of cells
Plasma (cell) membrane
Lipids
Proteins
Cytoplasm
Cytosol
Organelles
Nucleus
Chromosomes
Plasma membrane
flexible yet sturdy barrier ; surrounds / contains the cytoplasm of the cell
Lipid Bilayer
forms structural framework of the plasma membrane
The 3 lipid molecules
Phospholipids
Cholesterol
Glycolipids
Amphiphilic (weak)
molecule having both Hydrophilic & hydrophobic components
•Phospholipid
Glycocalyx (molecular signature)
made up by carbohydrate portion of glycolipids + glycoproteins
Types of membrane proteins
Integral proteins
Peripheral proteins
Integral (transmembrane) proteins
Goes through lipid bilayer
Peripheral proteins
goes through one side of bilayer
Membrane proteins
Ion channel
Carrier
Receptor
Enzyme
Linker
Cell identity maker
Ion channel (integral)
- Forms a pore where a specific ion can flow to get across membrane.
- Most plasma membranes have specific channels for common ions.
Carrier (integral)
- Transports specific substance across membrane by changing in shape
- also called “transporters”
Receptor (integral)
- Recognizes specific ligand & alters cell’s function
- Has specific side to bind to a ligand
Enzyme (integral & peripheral)
- Catalyzes reaction inside or outside cell
- (depending on which direction the active site faces)
Linker (integral & peripheral)
- Anchors filaments inside/outside plasma membrane
- Provides structural stability & shape for cell.
- Participates in movement of cell, or.. links 2 cells together.
Cell identity marker (glycoprotein)
- Distinguishes your cells from anyone else’s (unless you are an identical twin)
- Major histocompatibility (MHC) proteins ~ every cell has this
Membranes
-fluid structures ; since most membrane lipids & membrane proteins move easily in bilayer
Cholesterol
stabilizes the membrane and reduce membrane fluidity
Plasma membranes are..
selectively permeable
Lipid bilayers are..
Always permeable
Transmembrane proteins
increase permeability of the membrane
Macromolecules
only able to pass through plasma membrane by “Vesicular transport”
Concentration gradient
difference in concentration of a chemical between both sides of the plasma membrane
Electrical gradient
difference in concentration of ions between both sides of the plasma membrane
Electrochemical gradient
both concentration gradient & electrical gradient Together
Passive processes
1) Diffusion
2) Simple diffusion
3) Facilitated diffusion
4) Osmosis
Cytosol
intracellular fluid portion of cytoplasm
Organelles
- Centrosome
- Cilia & Flagella
- Ribosome
- Endoplasmic reticulum (ER)
- Golgi complex
- Lysosome Vesicle
- Peroxisome
- Proteasome
- Mitochondrion
Centrosome
the microtubule organizing centre. Consists of a pair of centrioles in the pericentriolar matrix. Important for cell division, and the production of cilia
Cilia and Flagella
composed mainly of microtubules which project from the cell. Movement. Cilia move fluids along a cell’s surface. A flagellum moves an entire cell
Ribosome
sites of protein synthesis
Endoplasmic reticulum
network of membranes in the shape of flattened sacs or tubules
Rough ER
produces various proteins, surface is studded with ribosomes
Smooth ER
a network of membrane tubules, does not have ribosomes, synthesizes fatty acids and steroids, detoxifies certain drugs
Golgi complex
Modify, sort, and package proteins for transport to different destinations outside of the cell.. Proteins are transported by various vesicles
Mitochondria
Generate ATP
Lysosomes
vesicles that form from the Golgi complex, contain powerful digestive enzymes
Peroxisomes
smaller than lysosomes, oxidize several toxic substances such as alcohol, abundant in the liver, neutralizes free radicals
Proteasomes
continuously destroy unneeded, damaged, or faulty proteins, found in the cytosol and the nucleus
Mitochondrion
Consists of external & internal mitochondrial membranes
- Site of aerobic cellular respiration reactions - Produces most of a cell’s ATP.
- Important early role in apoptosis.
Proteome
all of an organism’s proteins
Promoter
segment of DNA where transcription begins; special nucleotide sequence at beginning of a gene
Gene expression
a gene’s DNA is used as a template for synthesis of a specific protein
Base Triplet
A sequence of three such nucleotides in DNA
Genetic Code
set of rules for the base triplet sequence of DNA to the corresponding codons of RNA and the specific amino acids
Codon
base triplet transcribed to a complementary sequence of 3 nucleotides in mRNA ; codes for a particular amino acid in protein synthesis
Anticodon
tri-nucleotide units in tRNA
Stop Codon
when ribosome hits; the 2 subunits disatcosiate, tRNA falls off, mRNA falls off
Types of protein synthesis
Transcription
Translation
Transcription (inside nucleus)
• Genetic info from DNA is copied onto a strand of RNA
- Directs protein synthesis
• Info encoded in DNA is transcribed (copied)
- Produces specific molecule of RNA (ribonucleic acid)
• RNA moves into cytoplasm
- Binds with ribosome
Translation (inside cytoplasm)
• RNA attaches to ribosome
• Info in RNA is translated into a sequence of amino acids
- Forms new protein molecule
• Ribosome reads mRNA nucleotide sequence
- Determines amino acid sequence of the newly formed protein
DNA synthesis
process whereby a DNA makes a copy of itself
Exons
protein coding regions
Introns
non-coding protein region, between exons
3 types of RNA
Messenger RNA (mRNA)
Ribosomal RNA (rRNA)
Transfer RNA (tRNA)
Messenger RNA (mRNA)
directs the synthesis of a protein
mRNA codon
Complementary to DNA (every A in DNA bonds to U in RNA)
Ribosomal RNA (rRNA)
joins with ribosomal proteins to make ribosomes
Transfer RNA (tRNA)
binds to amino acid ; holds it on a ribosome until it is incorporated into a protein (translation)
• 1 end ~ carries amino acid
• 1 end ~ carries anticodon (triplet of nucleotides)
tRNA codon
Complementary to DNA (every T in DNA bonds to A in RNA)
Cell division
process by which cells reproduce themselves
Mitosis phase
Parent cell produces identical cells with identical chromosomes
Interphase
Period between cell divisions; chromosomes not visible under light microscope
Interphase phases
• 1. G1 phase — (8-10 hours)
• 2. S phase — (8 hours)
• 3. G2 phase — (4-6 hours)
• 4. G0 phase — non-dividing cell that exited from cell cycle after mitosis
G1 phase
- Active cell duplicates organelles / cytosolic components
- Replication of chromosomes begins.
S phase
Replication of DNA & centrosomes
G2 phase
- Cell growth, enzyme & protein synthesis continue;
- Replication of centrosomes complete.
