3.2: Cells Keywords Flashcards
Magnification
The number of times bigger the image/drawing is compared to the object/real size
Resolution
The minimum distance needed to differentiate between 2 adjacent objects
Micrometer
1x10^-6m
Nanometer
1x10^-9m
Light microscope
- A type of microscope which has a condenser, objective lens and eyepiece lens
- Light is passed through the thin specimen an up through the objective and eyepiece lenses to the eye
Electron microscope
- Beams of electrons are used to visualize structures in a vacuum
- Electrons have a smaller wavelength than light so electron microscopes have a higher resolution than light microscopes
Scanning electron microscope
A type of electron microscope which bounces beams of electrons off the surface of an object to develop a 3D image of the specimen (no need therefore for thin sections).
Transmission electron microscope
A type of electron microscope which passes a beam of electrons through a very thin section of specimen (which often has been stained with heavy metals to show up the fine internal structures)
Cell fractionation
The process where cells are broken up and the different organelles they contain are separated out
Homogenation
The first stage of cell fractionation when cells are broken up by a homogeniser (blender) and organelles are released from the cell
Ultracentrifugation
The second stage of cell fractionation when the fragments in filtered homogenate are separated in a machine called a centrifuge
Graticule
A series of lines on a microscope which can be used to calculate the size of objects
Eukaryote
- A cell that has a membrane-bound nucleus and chromosomes
- The cell also possesses a variety of other membrane-bound organelles, such as mitochondria and endoplasmic reticulum
Organelle
A part of a cell
Nucleus
Organelle which contains the hereditary material (DNA) and codes for the synthesis of proteins in cytoplasm
Mitochondria
Organelle where energy is released in aerobic respiration
Chloroplast
Organelle that is the site of photosynthesis
Rough endoplasmic reticulum (RER)
- Organelle which provides a large surface area for the synthesis of proteins and glycoproteins
- Proteins are transported here to be synthesised on the ribosomes
Smooth endoplasmic reticulum (SER)
Organelle where lipids and carbohydrates are synthesised, stored and transported
Golgi
- Organelle that contains a stack of membranes that make up flattened sacs (cisternae)
- Glycoproteins are synthesised, lipids are transported, modified and stored, proteins are packaged and lysosomes formed
Lysosome
- Organelle formed when the vesicles produced by the Golgi apparatus contain enzymes
- They are where unwanted materials & worn-out organelles are digested
Ribsome
- Organelle made of rRNA and protein
- Protein synthesis occurs here
Cell wall
- Organelle which provides mechanical strength to prevent the cell bursting under the pressure created by the osmotic entry of water
- Made of cellulose in plants and chitin in fungi
Vacuole
- Organelle which contains a solution of mineral salts, sugars, amino acids, wastes and sometimes pigments
- Support herbaceous plants by making cells turgid, may provide a temporary food store and if contain pigments, they may colour petals to attract pollinating insects
Tissue
A group of cells that work together to perform a specific function
Organ
A group of tissues that work together to perform a specific function
Organ system
A group of organs that work together to perform a specific function
Prokaryote
A cell of an organism belonging to the kingdom Prokaryote that is characterised by lacking a nucleus and membrane-bound organelles e.g. bacteria
Bacteria
A prokaryote
Plasmid
Small circular loops of DNA which contain genes that bacteria can have
Flagellum
Part of a bacterial cell which helps the bacteria to move
Virus
- Acellular, non-living particles that are smaller than bacteria
- Contain DNA or RNA but can only multiply inside living host cells
Capsid
A protein coat which encloses the nucleic acid in a virus
Attachment protein
The capsid can have these which are essential to allow to the virus to identify and attach to a host cell
Mitosis
The type of nuclear division in which the daughter cells have the same number of chromosomes as the parent cell
Daughter cell
The cells that produced by cell division
Chromatid
One of the two strands of a chromosome that are joined together by a single centromere prior to cell divisin
Centromere
The place where the two copies of DNA after replication are joined together
Interphase
The period of the cell cycle when the cell is not dividing
Prophase
- The first stage of mitosis when the chromosomes become visible and when spindle fibres develop
- The nucleolus disappears and the nuclear envelope breaks down
Metaphase
The second stage of mitosis when the chromosomes arrange themselves across the equator of the cell
Anaphase
The third stage of mitosis when the centromeres divide into two and the spindle fibres pull the individual chromatids making up the chromosome apart to their respective, opposite poles of the cell.
Telophase
- The fourth stage of mitosis when chromosomes reach their respective poles and become longer and thinner, finally disappearing altogether, leaving only widely spread chromatin
- The spindle fibres disintegrate and the nuclear envelope and nucleolus re-form
Cytokinesis
When the cytoplasm divides
Spindle fibres
These form the spindle apparatus which are responsible for pulling the chromatids to separate ends of the cell
Centrioles
Where the spindle fibres develop from in animal cells
Equator
Where the chromosomes arrange themselves during metaphase
Binary fission
The process by which cell division occurs in prokaryotic cells
Cancer
A group of diseases caused by a growth disorder of cells as a result of damage to the genes that regulate mitosis and the cell cycle which results in uncontrolled growth and division of cells
Tumour
A group of abnormal cells which develops and constantly expands in size
Plasma membrane
- Membranes consisting of a phospholipid bilayer found around and within all cells
- The cell-surface membrane is the plasma membrane that surrounds cells
Phospholipid
- Triglyceride in which one of the three fatty acid molecules is replaced by a phosphate molecule
- Phospholipids are important in the structure an functioning of plasma membranes
Bilayer
A membrane consisting of two layers of phospholipids
Protein channel
A protein completely spanning the phospholipid bilayer which form water-filled tubes to allow water-soluble ions to diffuse across the membrane
Carrier protein
A protein completely spanning the phospholipid bilayer which bind to ions or molecules then change shape in order to move these molecules across the membrane
Glycoprotein
- Carbohydrate chains attached to a protein (often extrinsic) which are part of the cell surface membrane
- They act as recognition sites, help cells to attach to one another and allows cells to recognise one another
Glycolipid
- A carbohydrate covalently bonded with a lipid
- They act as recognition sites, help maintain stability of the membrane and help cells attach to one another
Cholesterol
- Lipid that is an important component of cell-surface membranes because it adds strength
- Excess in the blood can lead to atheroma
Permeability
- How permeable a substance is depends on the size, polarity and charge of the molecule
- If it is small, non-polar and fat soluble it is very permeable and can pass through the cell membrane.
Fluid mosaic model
- The arrangement of the various molecules of the cell-surface membrane
- Fluid because the individual phospholipid molecules can move relative to one another and mosaic because the proteins vary in shape, size and pattern
Diffusion
- The net movement of molecules (or ions) from a region of high concentration to a region of low concentration
- It is passive
Facilitated diffusion
- Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances (normally large, polar or charged molecules) across plasma membrane
Osmosis
- The passage of water from a region where there is a higher water potential to a region where there is a lower water potential through a partially permeable membrane
Water potential
- The pressure created by water molecules
- It is the measure of the extent to which a solution gives out water
- The greater the number of water molecules present, the higher (less negative) the water potential
- Pure water has a water potential of zero
Isotonic
A solution which has the same water potential as the cell within it
Active transport
- Movement of a substance from a region where it is in a low concentration to a region where it is in a high concentration
- The process requires the expenditure of metabolic energy in the form of ATP.
Co-transport
- The transport of one substance coupled with the transport of another substance across a plasma membrane in the same direction through the same protein carrier
Pathogen
A microorganism that causes disease
Self
The body’s own cells and molecules
Foreign (non-self)
Not body’s own cells and molecules
Antigen
A molecule that triggers an immune response by lymphocytes
Lymphocyte
- Type of white blood cell responsible for the immune response
- They become activated in the presence of antigens
- There are two types: B lymphocytes and T lymphocytes
Phagocyte
Type of white blood cell which carries out a non-specific immune response and ingests and breaks down pathogens by phagocytosis
Phagocytosis
Mechanism by which phagocytes engulf particles to form a vesicle or a vacuole
Lysosome
Contain enzymes called lysozymes which they release into the phagosome and hydrolyses the bacterium
Phagosome
- A vesicle formed as the bacterium is engulfed by the phagocyte
- Lysosome releases their lysozymes into the phagosome
Antigen-presentation
When an antigen-presenting cell e.g. phagocyte displays foreign antigens on their own cell-surface membrane
Cell-mediated immuntiy
The type of response when T lymphocytes respond to antigens that are presented on a body cell
T Cells
Cells which mature in the thymus and are associated with cell-mediated immunity
Clonal selection
- As the receptor on a helper T cell attaches to the antigen this activates the T cell to divide rapidly by mitosis and form a clone of genetically identical cells
- These cloned T cells stimulate B cells to divide and form a clone of identical B cells all of which produce the antibody that is specific to the foreign antigen
TH Cells (helper T cells)
- Contain receptors which respond to a single antigen
- Many different types of T cell, each one responds to a different antigen
TC Cells (cytotoxic T cells)
Kill abnormal cells and body cells that are infected by pathogens by producing a protein called perforin which makes holes in the cell-surface membrane
Humoral immunity
The type of response which involves B lymphocytes and antibodies
B cells
Each type of B cell produces a specific antibody that responds to one specific antigen
Plasma B cells
When the B cell is activated to divide by mitosis, it gives a clone of plasma cells which produce and secrete the specific antibody that exactly fits the antigen on the pathogen’s surface
Antibody
A protein with specific binding sites produced by B cells in response to the presence of appropriate antigen
Memory B cells
Some B cells develop into memory cells which can respond to future infections by the same pathogen by dividing rapidly and developing into plasma cells that produce antibodies as part of the secondary response
Monoclonal antibodies
Antibodies produced by a single clone of cells
Primary response
Caused by initial response to the antigen which involves the production of antibodies and memory cells
Secondary response
- Caused by second exposure to the antigen
- Memory cells are responsible for this response - they divide rapidly and develop into plasma cells (which secrete many antibodies quickly) and more memory cells
Passive immunity
- Resistance to disease that is acquired from the introduction of antibodies from another individual, rather than an individual’s own immune system e.g. across the placenta or in the mother’s milk
- It is usually short lived
Active immunity
Resistance to disease resulting from the activities of an individual’s own immune system whereby an antigen induces plasma cells to produce antibodies.
Natural immunity
A type of active immunity resulting from an individual becoming infected with a disease under normal circumstances
Artificial immunity
- A type of active immunity resulting from vaccination
- It involves inducing an immune response in an individual without them suffering symptoms of the disease
Vaccination
The introduction of a vaccine containing appropriate disease antigens into the body, by injection or mouth, in order to induce artificial immunity
Herd immunity
Arises when a sufficiently large proportion of the population has been vaccinated which makes it difficult for a pathogen to spread within that population
Antigenic variability
Pathogen may mutate frequently so that its antigens change suddenly rather than gradually which means vaccines become ineffective because the new antigens on the pathogen are no longer recognized by the immune system
HIV
- Human immunodeficiency virus which causes the disease acquired immune deficiency syndrome (AIDS)
- It has a lipid envelope, attachment proteins, a capsid and two single strands or RNA and enzymes
Reverse transcriptase
An enzyme in HIV which enables the production of DNA from RNA
Retrovirus
A group of viruses which have the ability to make DNA from RNA because they have reverse transcriptase
mRNA
A single stranded polynucleotide found in HIV.
AIDS
The disease caused by HIV.
ELISA test
Enzyme linked immunosorbent assay which uses antibodies to detect the presence and quantity of a protein in a sample
Antibiotic
A substance produced by living organisms that can destroy or inhibit the growth of microorganisms
