Cells- Joseph Felton Flashcards
Recall the structure and explain what is meant by a eukaryotic cell and the defining characteristics of a eukaryotic cell?
A eukaryotic cell has a membrane-bound nucleus and organelles.
Explain the role of cell-surface membranes within eukaryotic cells?
A permeable layer which controls entry and exit of substances.
Explain the role of the nucleus within eukaryotic cells?
The nucleus contains the hereditary material and controls the cell’s activities.
Explain the role of the mitochondria within eukaryotic cells?
Site of aerobic respiration, responsible for ATP production.
Explain the role of the Golgi apparatus in eukaryotic cells?
A stack of membranes, creates glycoproteins, modifies and transports lipids and modified proteins via exocytosis.
Explain the role of vesicles within eukaryotic cells?
Vesicles transport lipids and glycoproteins from the Golgi apparatus to the cell-surface membrane where they are released to the outside of the cell via exocytosis.
Explain the role of lysosomes in eukaryotic cells?
Lysosomes are vesicles that contain lysozymes which hydrolyse cell walls of bacteria.
Explain the role of rough and smooth ER in eukaryotic cells?
RER-provides large surface area for protein synthesis and contains ribosomes.
smooth ER- lacks ribosomes, synthesise, store and transport carbs and lipids.
Explain the role of chloroplasts in eukaryotic cells?
Carry out photosynthesis, contain stacks of thylakoid discs called grana. In thylakoids is photosynthetic pigment called chlorophyll.
Explain the role of the cell wall in eukaryotic cells?
Provides mechanical strength for the plant as a whole, also prevents cell from bursting under pressure via osmosis.
Explain the role of the cell vacuole in eukaryotic cells?
Fluid-filled sac containing minerals, acts as a temporary food store, can make cells turgid.
Identify examples of specialised eukaryotic cells and explain common adaptations that cells have to particular functions?
A sperm cell will have a large number of mitochondria to produce Large amounts of ATP for fast movement, phagocytes will have a large number of lysosomes to effectively combat pathogens.
Describe the organisation of cells into tissues, organs and organ systems?
Cells aggregate into tissues. Tissues aggregate into organs, organs aggregate into organ systems.
Describe structural differences between prokaryotic and eukaryotic cells?
Eukaryotic cells have a distinct nucleus and DNA that is associated with proteins, also membrane-bounded organelles. Prokaryotic cells have no nucleus or protein-associated DNA, no membrane-bound organelles.
Explain the purpose of plasmids?
Possesses genes and enzymes that break down antibiotics.
Explain the purpose of capsules?
Protects bacteria from other cells, and helps bacteria stick together for protection.
Explain the purpose of flagella?
Allows movement for bacterium and viruses.
Describe the structure of virus particles?
Capsid, attachment proteins, enzyme, matrix, lipid envelope, RNA (genetic material)
Explain the role of the capsid?
A protein coat that encloses RNA.
Explain the role of attachment proteins?
Allows virus to identify and attach to a host’s cells.
Relate the structure of a virus to its replication within cells?
Attachment proteins allow the identification and attachment to a host’s cells. Enzyme allows the virus to convert its own RNA into DNA for host’s cell, Capsid fuses with cell-surface membrane.
Describe how a light microscope works?
Shines a bright light through a cross section of a thin specimen.
Describe how electron microscopy works?
TEM-A beam of electrons is focussed onto a thin specimen and the beam passes through and is absorbed by different parts of specimen.
SEM- Directs a beam of electrons on to the surface and then passes the beam back and forth, scattering of electrons causes an image to be produced.
Limitations and benefits of both forms of microscopy?
ADV- light microscope cheap and allows basic structures to be seen, electron microscopy produces cell ultrastructure.
DADV-light microscopy produces poor magnification, electron microscopy very expensive and sample must be viewed in vacuum.
What is magnification?
How many times bigger the image is than the actual object.
What is resolution?
The process of reducing or separating something into constituent parts or components.
What is cell fractionation?
Where cells are broken up and the different organelles are separated.
Describe the solution that the sample is placed in?
Cold- to reduce enzyme activity
Isotonic- prevent osmotic loss or gain
Buffered- maintain pH
What happens during homogenisation?
Cells are broken up by a homogeniser releasing the organelles from the cell. Homogenate then filtered removing debris and whole cells.
What happens during ultracentrifugation?
Filtrate placed in centrifuge and spun at low speeds, heaviest organelles removed, supernatant removed and spun faster removing lighter organelles.
Explain the role of the ribosomes in eukaryotic cells?
Contain ribosomal RNA and protein and are the site of protein synthesis.
Explain what the cell cycle is?
Cell cycle is the process of events that leads to the production of two daughter cells from one parent cell.
Identify the stages of the cell cycle?
Prophase, metaphase, anaphase, telophase.
What is interphase?
When DNA replication occurs.
What happens during prophase?
Chromosomes become visible and nucleolus dissolves, spindle fibres develop from centrioles.
What happens during metaphase?
Spindle fibres attach to centromeres of chromosomes and arrange them along the equator of the cell.
What happens during anaphase?
Centromeres divide into two and the spindle fibres pull chromatids to opposite poles of the cell, energy provided by mitochondria.
What happens during telophase?
Chromosomes reach the ends of their poles and disperse into chromatin, spindle apparatus dissolves. Nucleolus and nuclear envelope re-form.
What happens during cytokinesis?
Cytoplasm divides into two cells.
Describe uncontrolled cell division and explain how it can lead to the formation of tumours and cancers?
Caused by damage to genes that regulate mitosis leading to formation of a group of abnormal cells called a tumour, malignant tumours are cancerous.
Explain the processes within the cell cycle which are disrupted and which lead to cancer?
DNA replication in interphase becomes disrupted by mutations of the genes. Leads to formation of abnormal cells.
Explain how cancer treatments often work to inhibit stages of the cell cycle?
Chemotherapy involves preventing DNA replication and interfering with spindle fibre formation during metaphase.
Explain what binary fission is and describe how it occurs in prokaryotic cells?
Plasmids and circular DNA replicate, both copies attach to the membrane, membrane grows between two DNA molecules and pinches inward.
Explain how viruses are not classified as being living organisms?
They cannot undergo cell division and instead replicate within a host’s cell.
Describe the sequence of events by which viruses replicate?
They attach to their host’s cell via attachment proteins, capsid fuses with membrane of cell, viral RNA injected into nucleus, Cell produces viral components via metabolic processes.
Explain why viruses are so difficult to treat and develop medicines against?
Viruses hide themselves within host’s cells and replicate, antibiotics won’t target host’s cells.
Describe the fluid mosaic model of cell membranes?
Fluid- phospholipids can move allowing membrane to constantly change shape.
Mosaic- protein embedment varies in shape and size.
Explain the role and importance of phospholipids in cell membranes?
Allow lipid-soluble substances to enter and leave cell, Prevent water-soluble substances entering and leaving the cell.
Explain the role and importance of proteins in cell membranes?
Provide structural support, channel and carrier proteins allow facilitated diffusion, act as hormone receptors.
Explain the role and importance of cholesterol in cell membranes?
Prevent leakage of water and dissolved ions from the cell, make membrane less fluid at high temperatures.
Explain the role and importance of glycolipids in cell membranes?
Act as recognition sites, help maintain stability of membrane.
What are glycolipids?
Carbohydrate covalently bonded to a lipid.
Explain the role and importance of glycoproteins in cell membranes?
Act as recognition sites, allow cells to recognise each other.
What are glycoproteins?
Carbohydrate chain attached to extrinsic proteins.
Describe and explain the movement of water across partially permeable membranes by osmosis?
Water will move by osmosis from a region of high water potential to a region of less water potential.
