Topic 2: Cells Flashcards
What is Cell Theory?
- Cell is the smallest independent unit of life
- All living things are made up of one or more cells
- Cells are the basic unit of structure and function in organisms
- All cells are derived from pre-exisiting cells
What is the function of the cell membrane? What is the structure of the cell membrane?
Controls movement of substances into & out of the cell (selectively permeable)
Hydrophilic Head, Hydrophobic Tails
What is the ‘Fluid Mosaic Model’?
A mosaic of protein molecules embedded in a phospholipid bilayer.
What is the function of Cholesterol in the cell membrane? How does temperature effect Cholesterol?
Maintains properties of phospholipid bilayer
High Temp: Prevents Bi-layer from becoming fluid
Low Temp: Prevents Bi-layer from becoming solid
What are the properties of Prokaryotic Cells?
- No Nucleus or membrane-bound organelles
- Contain Ribosomes
- One Circular Chromosome + Plasmids
- Contain Cell Wall - Different Chemistry to that of eukaryotes
What are the properties of Eukaryotic Cells?
- Contain membrane-bound organelles
- Contain Ribosomes
- Only plants & fungi have cell walls
What is the function of the Nucleus in Eukaryotic cells?
- Contains chromosomes (most of cell’s genetic info)
- Double membrane with nuclear pores
- Contains nucleolus (region where rRNA is produced)
- Outer membrane connects to Rough ER
What is the function of the Mitochondria in Eukaryotic cells?
- Site of final stages of aerobic respiration
- Independently grows & reproduces within cell
- Double membrane (inner is folded)
- Own circular DNA & Ribosomes
What is the function of the Chloroplasts in Eukaryotic cells?
- Site of photosynthesis (occurs in inner membrane)
- Own circular DNA & Ribosomes
- Divides and grows independently
*Inner membrane is highly folded to increase SA
What is the function of the Endoplasmic Reticulum in Eukaryotic cells?
- Network of membranous tubules & sacs
- Rough ER: main site of protein synthesis
- Smooth ER: Diverse metabolic processes (depending on cell type), specific enzymes synthesise lipids
What is the function of the Golgi Body (Apparatus) in Eukaryotic cells?
- made of flattened membranous sacs
- site of collection from ER
- Function: modifies, packages & excretes molecules via exocytosis
What is the function of the vacuoles in Eukaryotic cells?
- fluid filled sac surrounded by a membrane
- Function: stores nutrients & provides structural support
Animal cells: numerous small vacuoles
Plant cells: large central vacuole
What is the function of vesicles?
- Composed of phospholipids
- Function: Involved in transport of molecules via exocytosis and endocytosis
What is the function of lysosomes in Eukaryotic cells?
- Specialised vesicles which contain digestive enzymes
- Function: Breakdown of biomolecules (carbohydrates, lipids, nucleic acids)
What is the function of the cytoskeleton in Eukaryotic cells?
- Network of protein fibres
- Provides support and structure to the cell
- Involved in the movement of organelles & chromosomes
What are the uses of energy in cells?
- Synthesis of substances (proteins, lipids. nucleic acids)
- Transportation of materials (active transport, endocytosis, exocytosis)
- Movement of organelles
What is photosynthesis? Where does photosynthesis occur in eukaryotic and prokaryotic cells?
Process of converting light energy into chemical energy (enzyme catalysed reaction)
Eukaryotes: highly folded inner membrane of the chloroplast
Prokaryotes: cytosol
What is chemical equation of photosynthesis?
6CO2 + 6H20 ——-> C6H12O6 + 6O2
What is aerobic respiration? Where does aerobic respiration occur in eukaryotic and prokaryotic cells?
Enzyme catalysed reaction
Eukaryotes: Begins in the cytosol, final stages occurs in highly folded inner membrane of mitochondria
Prokaryotes: Cytosol
What is chemical equation of aerobic respiration?
C6H12O6 + 6O2 ——> 6CO2 + 6H20
What are the benefits of step by step metabolism?
- Controlled Heat Release
- Many steps - gives cell numerous ways to control pathway
- Each step produces useful intermediate compounds
- Amount of energy released can be easily captured by ATP
What is fermentation (anaerobic respiration)? Where does it occur in cells?
Process of converting chemical energy into heat energy (no oxygen)
Location: Cytosol ONLY
*Produces less ATP molecules
Which type of cells produce lactic acid fermentation? What is the chemical equation of lactic acid fermentation?
Cell type: Animal Cells (People)
C6H12O6 ——> 2C3H6O3
Which type of cells produce alcohol fermentation? What is the chemical equation of alcohol fermentation?
Cell type: Plant/yeast cells
C6H12O6 ——-> 2C2H50H + 2CO2
How does the breakdown of glucose provide energy (ATP)?
Adds third inorganic phosphate (Pi) to ADP (Adenosine Diphosphate), forming ATP
ADP + Pi —–> ATP
How does the breakdown of ATP provide energy for cellular processes?
Bond between second and third phosphate breaks (releases energy - can be used to facilitate cellular processes)
ATP —–> ADP + Pi
Why is ATP used as the energy currency in cells?
- Release of third inorganic phosphate are not toxic to the cell
- ATP can easily be regenerated from ADP
- Regulates Heat Loss
- Provides ideal amount of energy for cellular processes
What is diffusion?
- Net movement of particles from a place of HIGH to LOW concentration (no input of energy required)
- Occurs with or without a membrane
- Materials diffuse down its conc. gradient to reach equilibrium
*Water is small enough to diffuse through phospholipid bilayer
What is osmosis?
Net movement of water from LOW solute conc. to HIGH solute conc. (no input of energy)
*Occurs when there is a membrane
*Aquaporins - increase rate of movement
What makes a solution Hypertonic? What happens to the cell as a result of this?
- High solute conc. outside cell, less solute conc. inside cell
- Water diffuses out - Cell shrivels
What makes a solution Hypotonic? What happens to the cell as a result of this?
- Low solute conc. outside cell, high solute conc. inside cell
- Water diffuses in (cell swells/bursts)
*cell bursts only in animal cells
What makes a solution Isotonic?
Inside solute conc. = Outside solute conc.
What is facilitated diffusion?
Used to transport molecules that cannot easily diffuse across phospholipid bilayer (molecules pass through carrier/channel proteins)
*No input of energy
*Down conc. gradient (High to Low)
What are the factors that affect rate of diffusion across the cell membrane?
- Concentration Gradient - Larger conc. gradient = faster rate of diffusion
- Temperature - High temp = more kinetic energy (faster rate of diffusion)
- Surface Area - Greater SA = faster rate of diffusion
- Type of molecule - Hydrophobic diffuse easier than hydrophilic and ions
- Size of molecule - Large molecules cannot diffuse through membrane
What is Active Transport?
Transport of molecules which requires input of energy
* Goes against concentration gradient
What is exocytosis?
Excretes molecules into extracellular environment
*Requires input of energy
What is endocytosis?
Importation of molecules
*Requires input of energy
What is Binary Fission? And What are the steps involved?
Cell Division in prokaryotes
1. Circular chromosome is copied
2. Each chromosome attaches to the cell membrane (different ends)
3. Cell extends - pulling the two chromosomes apart
4. Cell divides into two daughter cells
What are the properties of mitosis?
- Cell division in somatic cells
- Forms 2 daughter cells
- Daughter cells have identical genetic info to each other and parent cell
- Daughter cells are DIPLOID (full set of chromosomes)
What are the properties of meiosis?
- Cell division in germ-line cells (gametes)
- Produces 4 daughter cells
- Daughter cells are genetically unique
- Daughter cells are HAPLOID (half no. of chromosomes)
What are the steps involved in Mitosis?
Interphase
Prophase
Metaphase
Anaphase
Telophase
What happens in Interphase?
- Cell growth
- DNA replication
- General metabolic activity
What happens in Prophase?
- Chromosomes condense
- Nuclear membrane is broken down
- Spindle fibres form
What happens in Metaphase?
- Chromosomes align on metaphase plate
- Spindle fibres attach to chromosomes
What happens in Anaphase?
- Sister chromatids are pulled apart by spindle fibres
- Cell elongates
What happens in Telophase?
- Chromosomes decondense
- Nuclear membrane begins to form
What are the phases in the cell cycle? What happens in each phase?
G1 Phase - Replication of organelles
S Phase - Synthesis of DNA
G2 Phase - Preparation for cell division
M Phase - Mitotic division
What happens to a cell if it fails to pass through a checkpoint in the cell cycle?
Enters GO Phase (Cannot divide)
How do internal factors regulate the cell cycle?
- Chromosomes not attached to cytoskeleton
- DNA is damaged
- Sufficient ATP/Glucose available
- Intracellular molecules (CDK —-> MPF)
How do external factors regulate the cell cycle?
- Specific signal molecules (growth factors)
- Density dependent inhibition - Too crowded - cells cannot divide
- Anchorage dependent inhibition - Must be attached to a surface in order to divide
What is cancer?
- uncontrolled cell division
- cancerous cells DO NOT respond to internal/external factors to pass checkpoints
*Loss of control over cell cycle
What are carcinogens?
Factors that can cause mutations in DNA that are involved in regulation of cell cycle:
- Mutagenic chemicals
- Ionising radiation
- Some viruses
What is cell culturing? What are the potential applications of cell culturing?
Growing cells outside their natural environment
Applications:
- Testing novel medicines
- Creating clones
- Testing for mutagenic substances
What are the requirements to successfully culture cells?
- Sterile environment
- Suitable pH
- Constant temperature
- Oxygen availability
- Nutrient availability
- Growth factors
What is mitosis used for in humans?
Growth and Repair
What is meiosis used for in humans?
Reproduction
What is the haploid number (n)?
Half number of chromosomes
Humans have HAPLOID no. = 23
What is the diploid number (2n)?
Full set of chromosomes
Humans have DIPLOID no. = 46
What happens in Meiosis I and II?
- IPMATPMAT
- Meiosis I - Homologous chromosome pairs separate into different cells
- Meiosis II - Each chromosome separates its chromatids into different cells (4 haploid cells produced)
What happens in Prophase 1:
- Chromosomes condense
- nuclear membrane dissolves
- non-sister chromatids exchange DNA (Crossing Over*)
What happens in Metaphase 1:
- Chromosomes align on metaphase plate
- Spindle fibres attach to chromosomes
- Random/Independent assortment*
What happens in Anaphase 1:
- Spindle fibres pull apart chromosomes
- Cell elongates
What happens in Telophase 1:
- Chromosomes decondense
- Nuclear membrane forms
What happens in Prophase 2:
- Chromosomes condense
- Cell membrane breaks down
What happens in Metaphase 2:
- Chromosomes align metaphase plate
What happens in Anaphase 2:
- Non-sister chromatids are pulled apart
What happens in Telophase 2:
- Chromosomes decondense
- Nuclear membrane reforms
How does meiosis increase genetic variation?
Independent/Random assortment: chromosomes arrange independently of others (Metaphase I)
Crossing over: non-sister chromatids exchange DNA (Prophase I)
Random fertilisation: billions of combos as to how egg can be fertilised
