Cell Flashcards
What’s the difference between pro- and eukaryotic cells?
Pro: Smaller one cell organism, missing mitochondria and nuclear membrane. Bacterias are pro.
Eu: Larger cells. Can be either uni- or multicellular. Tiny minority.
Metabolism consists of which two processes?
Catabolism and anabolism, where the former breaks up and the latter builds.
Which four categories can organelles be placed in?
- Structure and communication
- Anabolic
- Catabolic
- Energy
What are the five structural organelles?
- Plasma membrane
- Cytosol
- Cytoskeleton
- Centrosome
- Membrane specialization, such as microvilli, cilia, and flagella
What are the six anabolic organelles?
- Nucleus
- Nucleolus
- Ribosomes
- Endoplasmic reticulum
- Golgi complex
- Vesicular transport, such as fagosome and endosome
What are the three catabolic organelles?
- Peroxisome
- Lysosome
- Proteasome
What is the energy organelle?
Mitochondrion
What are the components of the plasma membrane?
- Phospholopids
- Proteins, integral and peripheral
- Lipids, cholesterol and glycolipids
What are the functions of the plasma membrane? What is it permeable to?
Selective permeability. Permeable to water, nonpolar molecules (fatty acids, fat-soluble vitamins, steroids, oxygen, and CO2). Not permeable to ions and large uncharged polar molecules (glucose, amino acids)
Functions: Ion channels, transporters, receptors, enzyme, linker, and cell identity.
What are the transport alternatives across the plasma membrane?
Passive (no ATP)
- Diffusion, simple and facilitated
- Osmosis
Active (ATP)
- Primary
- Secondary
- Vesicular
Another name for adrenaline?
Epinephrine
What is the structure of cytosol?
- About 50% of cell volume
- 75 to 90% water
- Ions, glucose, amino acids, fatty acids, lipids, ATP, and waste products
- Lipid droplets, glycogen granules
Which chemical reaction occurs in the cytosol?
Glycolysis, protein synthesis, degradation, and intermediary metabolism
What are the three types of cytoskeleton, what are their sizes, and what are they made of?
Microfilaments
- Thin
- Made of the protein Actin polymer
Intermediate filaments
- Intermediate size
- More than 50 different proteins, e.g. keratin
Microtubuli - Transport coordinated by Centrosome
- Largest in size, long hollow tubes
- Made of protein Tubulin polymer
What are the functions of the three types of cytoskeleton?
General functions: Cell shape, cell adhesion, movement, and keeping organelles in place.
Microfilaments
- Forming microvilli : Increase surface area
- Cell strength and shape : Cell adhesion
- Movement: muscles, cell locomotion
Intermediate filaments
- Actual skeleton structure, strength : keeps organells in place
- Cell adhesion
Microtubuli
- Cell shape
- Cell functions : Movement of organelles
- Form cilia, flagellae, centrosome : movement
What is the structure and function of the centrosome?
Location and structure
- Located near nucleus
- Consists of a pair of centrioles with 9 clusters of microtubule triplets each
- Surrounded by pericentriolar area/material/matrix which are hundreds of proteins
Functions
- Microtubuli organisation center
- Mitotic spindle, in charge of the splitting of the nucleus during cell division
What are the three specialized membrane structures, what are they made of, and what are their functions?
Microvilli
- Actin (microfilaments)
- Increase surface area : e.g. intestinal epithelia
Cilium
- Microtubuli and basal bodies
- Movement of fluids at a surface : e.g. mucous out of the lungs
Flagellum
- Microtubuli and basal bodies
- Movement of entire cell : In human cells only in sperms
What is the structure and function of the nucleus?
Structure
- Usually one per cell – but can be none or several (muscle, hepatocytes, osteoclasts)
- Surrounded by a double membrane inner and outer nuclear, creates nuclear envelope
- Outer membrane continuous with ER, which contains ribosomes
- Nuclear pores, made up of 50-100 proteins
- Chromosomes wound up around chromatin (complex of DNA and protein)
Function
- Barrier! Separate biochemical compartment within the cell.
- Organised
- Contains and organise our genome
- DNA and RNA synthesis
What is the structure and function of the nucleolus?
Structure
- Located inside the nucleus
- No membrane
- Chromosomal regions that contain the rRNA genes for ribosomes
- Composition: DNA, RNA, and protein
Function
- Site of rRNA transcription
- Ribosome production factory
- Active protein synthesis (liver cells) : large nucleoli
What is transcription?
What is translation?
Transcript: Process of forming mRNA out of DNA
- In the nucleus
- DNA base triplets – corresponding RNA codon
- Proteins involved – RNA polymerase
- Promoter and terminator sequences determine where
- tRNA, mRNA and rRNA
Translation: Process of building protein based on mRNA
- In the cytosol
- Caused by ribosomes (Proteins/rRNA), tRNA, aa
What is the structure and function of the ribosome?
Structure
- No membrane
- A small “40S” and a large subunit “60S” (assemble in the cytosol to the ribosome “80S”)
- Composition: rRNA, protein. During protein synthesis: also tRNA and mRNA
- Free in the cytosol, attached to the ER or inside mitochondria
Function
- Site of protein synthesis
What is the structure and function of the endoplasmic reticulum?
Structure
- Large folded membrane structures. 50% of the membrane structures : 10% of the cell volume.
- Continuous with the Nuclear Envelope
- Two different portions
1. Rough Endoplasmic Reticulum - RER (Covered with ribosomes)
2. Smooth Endoplasmic Reticulum – SER (No ribosomes)
Function - Lipid and Protein synthesis and modification
RER:
- Glycoprotein synthesis, processing and sorting : for the membrane (pm or organelles) or for secretion
- Phospholipid synthesis
SER:
- Synthesis of fatty acids and steroids (estrogen/testosterone)
- Special functions in hepatocytes (liver cells): Smooth ER enzymes help release glucose into the bloodstream and detoxify a variety of drugs and potentially harmful substances, (alcohol, carcinogens).
- Special functions in myocytes (muscle cells): Calcium ions in sarcoplasmic reticulum.
What is the structure and function of the golgi complex?
Structure
- 2 to 20 membrane sacs called cisterns
- Cis-, medial- and trans- golgi
- Vesicles
Function
- First step after ER in a transport route for the membrane
- Processing and sorting of proteins to plasma membrane, lysosomes or secretion
- Modifcation results in Glycoproteins / Lipoproteins
- Trans Golgi network, a distribution and sorting center
What is the vesicular transport system, and what variations within this transport system is there?
Definition and variations
- Vesicles are small round structures formed when budding off an existing membrane
- Active transport, require ATP
- Endocytosis. Transport into the cell. Bulk phase or receptor mediated endocytosis. Phagocytosis.
- Exocytosis. Transport out of the cell.
Function
- Transport of substances from one part of the cell to another
- Exocytosis in secretory cells release enzymes, hormones, mucus
- Exocytosis in nerve cells secrete nerurotransmittors
What is the structure and function of the mitochondrion?
Structure
- 100 to 1000 in a cell
- Double membrane structure
- A mitochondrial matrix enclosed by, Inner (Cristae) rough folded and outer smooth membrane.
- Has some DNA, RNA, Ribosomes and synthesize a few proteins (37 genes : ribosomal RNA tRNA and mitochondrial component proteins.)
Function
- Most of the cells ATP production
- Citric acid cycle and Electron transport chain
What is the structure and function of the peroxisome?
Structure
- Small spherical membrane compounds (microbodies)
- Contain dense areas of proteins (enzymes, oxidases)
Function
- Performs oxidative/peroxidative reactions using oxygen and hydrogen peroxide
- Divides into new peroxisomes
- Synthesis of phospholipids like myelin
What is the structure and function of the lysosome?
Structure
- Lumen contain many different proteins: 60 digestive enzymes
- Membane enclosed in relatively large vesicles
- Membrane carrier proteins transport digested molecules into the cytosol
Function
- Catalytic reactions, degrade many different molecules from endocytosed vesicle
- Low pH in lumen (central cavity)
- Autophagy, reusing the cells own structures
- Autolysis, destroying the entire cell
What is the structure and function of the proteasome?
Structure
- Protein bodies made of proteases (No membrane)
- In the cytosol and nucleus
Function
- Selectively degrade unneeded, damaged or misfolded proteins in the cytosol
- The protein “Ubiquitin” is used as a marker : polyubiquinated proteins
- Some proteins has to be removed for control : transcription factors
What are prions?
Prions are infectious proteins. Misfolded proteins with the ability to transmit their misfolded shape onto normal variants of the same protein. They characterize several fatal and transmissible neurodegenerative diseases.
- Only difference is their folded three-dimensional structure. More β-sheets.
- Protease resistant, which leads to accumulation. No refolding or degradation.
What are the different pathogens?
- Viruses (DNA/RNA in shell of proteins)
- Bacteria (free living cells, more complex)
- Fungi, Protozoa, Metazoa (Parasitic worms, Ascaris lumbricoides)
What are the four different protein structures?
Primary, composition of amino acids.
Secondary, alpha helix and beta pleated sheet.
Tertiary, 3D shape of different secondary structures which form a specific subunit.
Quaternary, combination of different subunits.
Definition of a gene
- Genes are made up of fixed sequences of DNA, about 1000 make up a gene
- The basic physical and functional unit of heredity
- Act as instructors for Proteins (1,5%) and RNA
- Few hundred DNA bases to more than 2 million bases
- Estimated that humans have between 20,000 and 25,000 genes
- Change in sequence of nitrogenous bases is called mutation
How is the genome organised?
- In the nucleus
- 46 Chromosomes in 23 pairs
- Chromatin, histones package the DNA
What is the replication process?
- Process where a double stranded DNA molecule is copied to produce two identical DNA molecules
- Replication occur before cell division
- DNA polymerase, RNA primers
