Cell Theory
State three key features of this theory
Cells are the units of structure and function in all organisms; a cell is the smallest independent unit of life; new cells arise from pre-existing cells; cells contain DNA which is passed onto daughter cells; cells require and use energy.
State the word AND balanced chemical equation of fermentation in animals
glucose -> lactic acid + energy
C6H12O6 -> 2C3H6O3 + energy
State the name of the process by which water moves across a semi-permeable membrane.
Osmosis
Explain why the amount of DNA in a cell doubles prior to cell division
When the cell divides, it produce two genetically identical daughter cells.
The amount of DNA must be doubled prior to cell division, to ensure each of the daughter cells receives an entire (identical) copy of the genetic information.
State three conditions necessary for successful cell culturing
Suitable T, sterile conditions, optimum pH, presence of nutrients, presence of growth factors, suitable oxygen concentration and suitable nutrient growth medium
Describe the structure of the cell membrane according to the fluid mosaic model
Cell membrane is composed of a bi-layer of phospholipids with proteins and other macromolecules embedded; the phospholipids are able to move about within the membrane and hence have fluid-like qualities; the proteins embedded give the membrane a mosaic-like appearance.
Why is there less energy released through the breakdown of glucose under anaerobic conditions?
Because in aerobic respiration, glucose is almost completely broken down (to carbon dioxide and water) releasing a large proportion of the energy locked in its chemical bonds. However, under anaerobic conditions, glucose is only partially broken down (to lactic acid in animals and ethanol in yeast, plants and bacteria) to release a smaller quantity of its energy.
State the name of the process by which ions are moved across the cell membrane against their concentration gradient
Active transport
State the name of the non-dividing phase of the cell cycle in eukaryotic cells
Interphase
State two potential limitations of cell culturing
Large costs
Time consuming
Potential contamination of cultures with other species (i.e. bacteria in human cell culturing)
Describe three structural differences between plant and animals cells
Plant cells contain a cell wall, chloroplasts and a large vacuole (animal cell don't)
State three reasons why cells require energy
movement (mot cells must be able to move or change shape which requires energy), synthesis (a new proteins, DNA, lipids, hormones etc) and maintaining a stable intracellular environment (the cell achieves this through active transport which requires energy)
Describe the difference between simple diffusion and facilitated diffusion
Simple diffusion – movement of small, lipid-soluble substances directly across the cell membrane down its concentration gradient.
Facilitated diffusion – movement of substances, such as ions, across the cell membrane through transport proteins (also down its concentration gradient).
State one possible effect on chromosomes of preventing the successful assembly of spindle fibres during mitosis
Chromosomes will not line up correctly.
Sister chromatids will not separate
Explain the importance of genetic variation for a species
Increased genetic variation increases the chances of a species surviving in a changing environment or changing selection pressures. Some individuals may die, but a few may possess the genes enabling them to survive and reproduce, thus preserving the species.
Compare the shape and location of chromosomes in prokaryotic and eukaryotic cells.
Prokaryotic cells contain a single circular chromosome, whereas eukaryotic cells contain multiple linear chromosomes; in prokaryotic cells, the chromosome is found in the cytosol, whereas in eukaryotic cells the chromosome is found in the nucleus (DNA also found in the mitochondria and chloroplasts)
Explain how the energy stored in ATP is released for use in cells
ATP is converted to ADP and phosphate.
The breaking of the bond between the last two phosphates releases energy that can be used for cellular processes
State two features of passive transport and two of active transport
The movement of a substance down the concentration gradient (from an area of high concentration to an area of low concentration);Does not require energy.
The movement of a substance against the concentration gradient (from an area of low concentration to high concentration);Requires energy, supplied by ATP.
State the type of cell division that gives rise to body cells in organisms.
Mitosis
State the four sources of variation in sexually reproducing organisms
Mutation
Crossing over
Independent assortment
Random fertilisation
State the function of these organelles: lysosome, vacuole, chloroplast, mitochondrion, and endoplasmic reticulum.
Lysosome-Breakdown of substances such as food vacuoles, damaged organelles and harmful bacteria; vacuole- Storage of water, salts, sugars, amino acids. Also important for shape retention (in plant cells); chloroplast- Site of photosynthesis, whereby light energy is transformed into chemical energy to form glucose; mitochodrion- Site of the latter stages of aerobic respiration, whereby glucose is broken down to release energy;endoplasmic reticulum- Rough ER: membrane synthesis and contains ribosomes – hence the site of protein synthesis. Smooth ER: site of detox of drugs, poisons, alcohol.
Explain how the process of aerobic respiration enables ATP to be formed from ADP
Aerobic respiration is the process by which glucose is broken down to release energy.
This energy is used to combine ADP and free phosphate (Pi) to form ATP.
Describe how a large molecule, such as a protein, could leave a cell.
Large molecule, such as a protein, is packaged into a vesicle at the Golgi body and sent towards the cell membrane.
The vesicle fuses with the cell membrane, expelling its contents into the extracellular environment
State two energy-using processes that occur in cell division
Production of spindle fibres
Separation of sister chromatids (by the mitotic spindle)
Production/synthesis of new membrane
Synthesis of DNA (prior to cell division)
Synthesis of proteins (such as cyclin) required for cell division (or for the production of new daughter cells
Explain how hormones regulate cell division in eukaryotic cells
Hormone is released by a signal cell and attaches to specific cell membrane receptors (containing a complementary 3D shape to the hormone) on a target cell.
Binding eventually leads to the processes of transcription and translation within the cell, which produces a gene product (protein) that stimulates (or inhibits) cell division.
Also, nutrient dependene, anchorage dependence, density dependence