Cell Types and Structure Flashcards
What are the characteristics of life? (8)
Cellular respiration, reproduction, metabolism, homeostasis, hereditary, response to stimuli, growth and development, adaptation through evolution.
What are the potential origins of life? (3)
Generation of biomolecules (hydrothermal vents)
Generation of replicating organisms (chelation)
Panspermia
When was the earliest life on earth?
4.5 billion years ago
What are the 4 things required for natural selection?
Variation, inheritance, selection, time
What are the three types of organisms?
Bacteria, eukarya, and archaea.
What type of organism are humans?
Eukarya
What is endosymbiosis?
That mitochondria (proteobacteria) and chloroplasts (cyanobacteria), are derived from bacteria
What is the key difference between prokaryotic and eukaryotic cells?
Membrane enclosed organelles are present in eukaryotes
What are macromolecules mainly composed of?
Atoms, giving them a large molar mass. Also monomers joined by covalent bonds.
What are the 4 levels of carbohydrates?
mono, di, oli, and polysaccharides.
What are the functions of carbohydrates? (3)
Recognition, energy, structure.
What are the 7 types of proteins?
Structural, regulatory, contractile, transport, storage, protective, catalytic, toxic.
What are the 3 functions of lipids?
Structural, regulatory, energy
What must a cell do? (5)
Manufacture cellular materials, obtain raw materials, remove waste, generate required energy
What is the function of a a plasma membrane?
Provide special conditions within the cell, act as a semi-permeable barrier.
What is the arrangement of the phospholipid bilayer?
Hydrophilic head on the outside of the layer and the tail are between them. Fatty acids affect membrane fluidity.
What can the membrane be affected by?
Saturation (when it is packed tightly together, there is less fluidity)
Temperature (higher, more fluidity)
Cholesterol (stabilises fluidity)
What are the functions of plasma membrane proteins? (5)
Signal transduction (from the body into the cell)
Cell recognition
Intercellular joining
Linking cytoskeleton and extracellular matrix.
Membrane transport (passive and active)
What are the channels for moving water across the membrane?
Aquaporins
What cell is only found in animal cells?
Lysosomes
What are the 2 cells individual to plant cells?
Chloroplast, central vacuole
What are the structures in the endomembrane system?
Nuclear envelope
endoplasmic reticulum
golgi appartus
vesicles
lysosomes
vacuoles
plasma membrane
What are the functions of the endomembrane system?
Synthesis of proteins, transport of proteins, metabolism and movement of lipids, detoxification of poisons.
What is the process of moving proteins out of a cell?
Synthesise (endoplasmic reticulum)
Tag and package (golgi apparatus)
Deliver (vesicles)
What is the function of the sER?
Metabolism of carbs
Lipid synthesis
Detoxification of poisons
Storage of calcium ions
What is the function of the rER?
Protein synthesis
What is the golgi complex structure?
Has polarity, vesicles arrive from the endoplasmic reticulum at the cis face and leave from the trans face.
What are the functions of the Golgi complex?
Glycosylation (Addition of carbohydrates to proteins), sorting proteins (by adding molecular markers),
Directing vesicle trafficking
What are the types of vesicles?
Membrane bound
Transport
Secretory
Vacuoles
What is exocytosis?
Transporting material out of the cell or to the cell surface
What is endocytosis?
Taking in of particular molecles
What is phagocytosis?
Uptake of food particles
What is pinocytosis?
Uptake of extracellular fluid containing various solutes
What is receptor-mediated endocytosis?
Specialised form of pinocytosis where receptor proteins are used to selectively capture required solute.
What are lysosomes?
Membrane -bound environments specific for enzymes to break down ‘stuff’ within the cell.
What is autophagy?
Breaking down of unwanted cellular material
What are the major energy requirements of the cell?
Mechanical work
Making new materials
Transport
Maintain order
What is the site of cellular respiration?
Mitochondria
How many mitochondria are there in a cell?
1-1000
How many membranes does a mitochondria have?
2
What are cristae?
Folds of the inner membranes
Describe glycolysis
Occurs in the cytosol
Glucose converted to 2 pyruvate molecules (2x 3C)
Generates 2ATP
NAD+ made to NADH
Describe Pyruvate Oxidation and the Citric Acid cycle
Occurs in the mitochondrial matrix
Pyruvate is converted to Acetyl CoA (which will then enter the citric acid cycle)
ATP, and NADH and FADH2 (high energy electron carriers will then be produced.
Describe Oxidative Phosphorylation parts
Electron transport chain
Chemiosmosis
Describe the electron transport chain
Electron carriers take electrons to inner mitochondrial membrane through protein complexes.
This causes protons to be pumped across into the intermembrane space, creating a proton gradient.
Describe chemiosmosis
Inner mitochondrial membrane contains ATP synthase.
Proton gradient powers ATP synthesis.
How to plant cells absorb energy?
Via chlorophyll located in the thylakoid membrane
What occurs in the photosynthetic electron transport chain?
Occurs in the thylakoid membrane
Chlorophyll captures light energy and converts in into chemical energy, these high energy electrons then move through the photosynthetic chain.
What happens in the light reactions?
Occurs in the thylakoid membrane
High energy protons pumped to build a concentration gradient.
Photosystem I gives them an energy boost
Photosystem II draws electrons from water (forming oxygen biproduct)
With the proton gradeint we can now move through the ATP synthase to make ATP.
DRAW DIAGRAM (lecture 7)
Describe the Calvin Cycle (Carbon Fixation).
Occurs in the stroma.
The output of this is a 3 carbon sugar, that, when combined with another 3 carbon sugar, makes glucose.
DRAW DIAGRAM (lecture 7)
What is the purpose of cellulose in the plant cell
Major component of cell wall. It forms microfibrils which are a component of both primary and secondary cell walls.
What are the two phases of plant cell walls?
Phase one: microfibrils
Phase two: matrix (pectin polysaccharides and hemicellulose polysaccharides)
What is in the matrix of a plant cell?
Hemicellulose (large group of polysaccharides)
Pectin (negatively charged polysaccharides that bind water)
What controls the extensibility of the plant cell wall?
Extensin cross-linking reduces extensibility and increases strength. It controls how much a cell can expand, it is rigid in old cells
Describe the synthesis of the primary cell wall?
- Cellulose microfibrils at the plasma membrane
- Polysaccharides in the Golgi are transported to the wall vesicles
- Cell wall proteins from the rER, vesicles fuse to the plasma membrane.
Describe constitutive exocytosis
Releases extracellular matrix proteins
What are the cellulose-producing rosettes?
Proteins that move parallel to the cortical (close to the outside) microtubules. They determine where the cellulose microfibrils are laid down as the cell develops.
What determines the shape of a cell?
Where the microtubules are laid down, at different angles to give strength.
What are the cell wall functions in terms of cell shape?
Provides structural support.
Prevents excessive water uptake.
How do the orientation of microfibrils influence cell morphology?
When they are random the cell will expand equally in all directions
When they are at right angles on the long axis, the cell will expand longitudinally (square).
What provides structural support in the cell?
Protoplast being pushed against the cell wall to control rigidity.
How does the cell prevent excessive water uptake?
The protoplast expands when water enters the cell and pushes against the cell wall, the cell wall limits the volume of water that can be taken up.
What is the purpose of the secondary cell wall?
Not all plants have a secondary cell wall. It provides more structural support than the primary cell wall. Only produced after the growth has stopped.
What is the secondary cell wall made up of?
Lignin.
What are plasmodesmata?
Intercellular connections that enable cell to cell communication. Allows free exchange of small molecules but prevents organelle movements.
Describe the inside vs. the outside of the cell.
Outside (extracellular matrix of glycoproteins)
Inside (Cytoskeleton, support and mobility)
Describe the function of a cytoskeleton
Helps maintain cell shape. Highly dynamic and provides stability (has the ability to change)
What is the structure of the cytoskeleton? (3)
Microtubules, microfilaments, intermediate filaments.
Describe microtubules in the cytoskeleton
Resist compression, help maintain cell shape, composed of tubulin subunits, radiate from a centrosome.
Describe how microtubules provides cell motility
Flagella move the cell in snake-like motions, cilia move in rowing-like motion.
Describe intermediate filaments in the cytoskeleton.
Various types of proteins supercoiled into cables. They are permanent cellular structures.
They maintain cell shape and anchor organelles.
What are the 3 types of cell junctions
Tight, gap, desmosomes
Describe tight junctions
Middle seal, form a continous seal. Prevents movement of fluid.
Describe desmosomes
Anchoring junction. Strong, connected by intermediate filaments.
Describe gap junctions
Ions and small molecules can pass cell to cell.
What are most extracellular matrix proteins?
Glycoproteins
What are the most abundant ECM glycoprotein?
Collagen
What is the purpose of a proteoglycan in ECM
Trap water which subsequently retains tissue shape.
What is the purpose of integrins in the ECM?
Providing a communication link
Where are ribosomes found?
Attached to the rough ER (bound)
In the cytoplasm (free)
What is the function of ribsomes?
Making proteins
What is the structure of the nucleus?
Nuclear envelope
Nuclear pores
Contains DNA
Nucleolus
What is the structure of the nuclear envelope?
Inner and outer membrane with perinuclear space between. Nuclear laminar
What is the nuclear lamina
Lining of inner nuclear envelope, composed of intermediate filaments. It maintains the shape of the nucleus.
What happens if the nuclear lamina is defective?
Nuclei are unable to retain a spherical shape and this limits the ability of the affected cells to divide
What is a nuclear pore?
Channels that control the movement of molecules in and out of the nucleus
What are the two types of movement between the nucleus and cytoplasm?
Nucleus to cytoplasm is tRNA and mRNA
Cytoplasm to nucleus is control signals, building blocks, and energy
What is the nucleolus
Responsible for making RNA and ribosomal subunits
Describe DNA within the nucleus
Interact with histones to form beads called nucleosomes. Further interaction with histones causes the fibres to coil and form metaphase chromosomes
What is a karyotype?
Chromosomes displayed in pairs
What is euchromatin and heterochromatin?
Euchromatin contains genes being used by the cell (less dense to be able to access)
heterochromatin more dense and contains genes that are not being used.
What was Chargaff’s Discovery?
DNA could be genetic material, amounts of A and T (C,G) were the same yet differed between species
What did the X-ray diffraction discover?
DNA was a helical structure, it is double-stranded with perpendicular bases.
Which bases are made from Pyrindines?
C and T
Which bases are made from Purines?
A and G
How are nucleotide monomers formed?
With phosphodiester bonds
How are DNA strand orientated?
Anti-parralell
How many hydrogen bonds are between T and A?
2
How many hydrogen bonds between C and G?
3
What is the Watson-Crick model of DNA?
Double Stranded helical structure
Sugar-phosphate backbone on the outside
Bases on the inside
Stabilised by hydrogen bonds
Two polynucleotide strands orientated in opposite directions.
What kind of replication does DNA go through?
Semi-conservative replication
Which way does the parental template synthesise?
3’ - 5’ direction
What does semi-discontinuous mean for replication?
There is a leading and lagging strand
What way is the lagging strand synthesised?
In the 5’ - 3’ direction in Okazaki Fragments
What is Primase?
An enzyme that makes an RNA primer to start DNA polymerisation
What is a locus?
Position of a gene.
What is the purpose of cell divison?
Growth, repair, and developmnt
Describe the cell cycle
A cell spends most of its life in interphase, during the G1 phase, there is growth. In S phase, DNA is replicated.
Describe Prophase (mitosis)
Chromosomes condense, and sister chromatids stick to each other
Describe Prometaphase
Sister chromatids attach to the microtubules.
Describe Metaphase (mitosis)
Sister chromatids line up. Centromeres line up
Describe Anaphase (mitosis)
Microtubules shorten, ripping the sister chromatids apart.
Describe Telophase and Cytokinesis (mitosis)
Separation is complete and nuclear envelope is forming
What does mitosis produce?
Identical daughter cells
Why is meiosis important?
Because our gametes would be 2n and our embryos would be 4n.
What happens in interphase of meiosis?
Homologous diploid chromosomes in parent cell are duplicated into sister chromatids.
What happens in meiosis I?
Homologous chromosomes are separated, producing 4 haploid cells with duplicated chromosomes
What happens in meiosis II?
Sister chromatids are seperated and 4 haploid cells with unreplicated chromosomes are produced.
What happens in Prophase I?
Homologous chromosomes synapse and crossing over between non-sister chromatids occurs at the chiasmata.
What is a centromere?
Where the sister chromatids are held together
What happens in Metaphase I
Homologous chromosomes line by the chiasmata on the metaphase plate
What happens in Anaphase I?
Homologous chromosomes seperate and sister chromatids remain attached.
What happens in Telophase I and Cytokinesis?
Haploid cells with duplicated chromosomes are produced.
What happens in Anaphase II?
The sister chromatids seperate
What is the outcome of meiosis?
4 genetically different daughter cells with n amount of chromosomes
What causes down syndrome?
Aneuploidy, abnormal amount of chromosome 21. Nondisjunction or failure of chromosomes to separate during meiosis.
What is Klinefelter Syndrome
XXY
What is polyploidy?
Possession of multiple sets of chromosomes
What is Turner Syndrome?
XO
What are the 4 types of chromosomal aberrations?
Deletion, Inversion, duplication, and translocation
What is the cause of familial downsyndrome?
Translocation of chromosome 21 onto 14.
What is a Barr body?
Condensed (inactive) X chromosomes, XY will have 0, XX will have 1, and XXX will have 2.
What leads the progressive addition of new nucleotides?
DNA polymerase III
What marks the starting point for nucleotide addition?
Primase enzyme making RNA primer
What unwinds to gives two parental templates?
Helicase
What releases tension generated by the unwinding of the DNA helix
Topoisomerase rejoining NDA strands.
What prevents unwound single-stranded DNA from reforming and protecting it from degradation?
Singles-stranded DNA binding protein
What removes RNA primer and fills the gap with NDA nucleotides?
DNA polymerase I
What joins the end of newly synthesised fragments?
DNA ligase
What is Exonuclase?
Nuclease that removes DNA errors during DNA replication. Only the base is removed.
What is endonuclease?
Nuclease that repairs errors after replication, removing it and then the polymerase makes new DNA.
What is PCR?
Polymerase Chain Reaction. In vitro method of making DNA for medical applications.
What is the function of polymerase I?
Removes RNA primers and replaces the gap with DNA nucleotides.
