Topic 2 -everything I don’t understand Flashcards
Describe the structure and function of the cell surface membrane
Structure:
Fluid mosaic phospholipid bilayer with intrinsic and extrinsic proteins that are embedded.
Function:
Isolate cytoplasm from extra cell cellular environment
Selectively permeable to regulate transport of substances
Involved in cell signal and recognition
What is the role of cholesterol glycoproteins and glycolipids embedded in the cell surface membrane?
Cholesterol: steroid molecule connects phospholipids together and reduces fluidity.
Glycoproteins: cell signalling cell recognition and binding cells together
Glycolipids: cell signalling and recognition .
What is the structure and function of Golgi apparatus?
Structure: flattened cisternae- series of membrane bound sacs.
Function: modifies proteins and lipids packages molecules into vesicles for secretion or transport within the cell.
Describe structure and function of the endoplasmic reticulum
Structure: cisternae network of tubules & flattened extends from cell membranes through cytoplasm.
Function:
– RER: many ribosomes attached for protein synthesis and transport.
– SER: lipid synthesis
What is role with the cap on viral particles?
– Protects nucleic acid from degration by restrict endonucleases.
– Surface site enable viral particles to bind and enter the cell or inject the genetic material.
State the role of attachment proteins on a viral particle
Enable viral particle to bind to complementary sites on host cell.
What happens during interphase?
G1 phase: cell grows synthesis proteins and carries out functions.
S phase: DNA is replicated
G2 phase: cell continues to grow and prepare for mitosis
What happens during prophase of mitosis?
Chromosomes condense: the chromatin condenses into visible chromosomes.
Nuclear envelope breaks down: the membrane around the nucleus starts to disappear.
Spindle fibres form: these structures made of microtubules begin to form and extend from the centrioles.
What happens during metaphase of mitosis?
Chromosomes align: the condensed chromosomes lineup along the equator of the cell.
Spindle fibres attached: the spindle fibres form the centrioles attached the central mirrors of the chromosomes.
What happens during anaphase of mitosis?
Sister chromatids separate: the spindle fibres pull the cystic chromatids towards opposite poles of the cell.
Centromeres divide: the centromeres that held the sister climbed together split.
What happens during telophase of mitosis?
Chromosomes de-condense separated chromosomes begin to unwind back into chromatin.
Nuclear envelope reforms: two new nuclear envelopes form around each set of chromosomes at opposite poles.
Spindle fibres disassembled: the spindle apparatus breaks down.
Explain binary fission.
- DNA replication: the single circular DNA molecule is copied.
- Cell elongation: the cell grows and the two DNA copies move to opposite ends of the cell.
- Cytokinesis: the cell cell membrane pinches inwards dividing the cell into two.
- Two cells: the result is two genetically identical cells.
Why are viruses classified as non-living?
They are acellular: no cytoplasm no metabolism and cannot self replicate.
Outline how viruses replicate
- Attachment proteins attached to receptors on host cell membrane.
- Envelope viruses fuse with cell membrane or move in via endocytosis and release DNA/RNA into cytoplasm or inject it.
- Host cell uses viral genetic information to synthesise new viral proteins.
- Components of new viral particles assemble.
How do new viral particles leave the host cell?
Bud off and use cell membrane to form envelope.
Cause lysis of host cell
Explain the functions of extrinsic and intrinsic proteins in membranes
Extrinsic:
– Binding sites
– Antigens
– bind cells together
– Involved in cell signalling
Intrinsic:
– Electron carriers
– Channel proteins
– Carrier proteins
Define osmosis
Watered diffuses across the semi permeable membrane from a high area of water potential to low area of water potential until equilibrium is reached.
What is the definition of facilitated diffusion?
The passive transport of molecules or ions across a membrane through protein channels or carriers without the use of energy this process occurs down the concentration gradient.
Explain how channel proteins and carry a proteins work
Channel: hydrophilic channels buying two specific ions = one side of the protein closes on the other side opens.
Carrier: binds two complementary molecule = confirmational change releases molecule on other side of membrane in facilitated diffusion passive process; in active transport requires energy from ATP hydrolysis.
Define active transport
The movement of molecules or ions against their concentration gradient from an area of lower concentration to higher concentration using energy (ATP) and a specific carrier protein in the cell membrane.
Compare and contrast active transport and facilitated diffusion
– Both may involve carrier proteins
– Active transport requires energy from ATP hydrolysis; facilitated diffusion is a passive process.
– Facilitated diffusion may also involve proteins.
Define co transport
The coupled movement of two substances across a membrane where one moves down its concentration gradient to help the other move against its concentration gradient.
Explain how co-transport is involved in the absorption of glucose/amino acids in the small intestine
- Sodium actively transported out of the epithelial cells and into the bloodstream.
- Sodium concentration is lower in epithelial cells than lumen of gut.
- Transport of glucose/amino acids from lumen to epithelial cells is coupled to facilitated diffusion of sodium down electro chemical gradient.
What is an antigen?
A foreign molecule that triggers an immune response specifically the production of antibodies.
Outline the process of the cell mediated response
- Phagocytes present pathogens antigens
- Activation of T cells: helper T cells recognise antigens and become activated.
- Helper T cells divide creating psychotoxic T cells and memory cells.
- Cytotoxic T cells destroy infected cells.
- Memory cells: some cells remain to respond faster if the pathogen returns.
Outlining the process of the humoral response
- Complimentary T lymphocytes bind to foreign antigen on antigen presenting T cells.
- Releasing cytokines that stimulate clonal expansion of complementary B lymphocytes.
- B cells differentiate into plasma cells.
- Plasma cells secrete antibodies with complementary variable region to antigen.
explain the principles of vaccination
- Vaccine contains dead/inactive form of a pathogen or antigen.
- Triggers primary immune response
- Memory cells are produced and remain in the bloodstream, so secondary response is rapid and produces higher concentration of antibodies.
- Pathogen is destroyed before it causes symptoms.
Describe the structure of HIV
lipid envelope: derived from host cell
Capsid: surrounds the viral RNA and enzymes.
RNA
Reverse transcriptase: an enzyme that converts the viral RNA into DNA once inside the host cell.
How does HIV result in AID?
- Attachment proteins bind to CD4 on T cells.
- HIV particles replicate inside T cells, killing or damaging them.
- AIDS develops when there are too few T cells for the immune system to function.
- Individuals cannot destroy other pathogens and sufferers from secondary diseases.
Explain the ELISA test
- Antigens bind to the bottom of the test plate.
- Antibodies in sample bind to antigen.
- Secondary antibody attached binds to primary antibodies from the sample.
- Add substrate for enzyme.
