Topic 2 - Cells Flashcards

Question

What is an electron microscope?

Answer 1

- A beam of electrons is condensed to create the image. Electromagnets are used to condense the beam. - Higher resolving power as electrons have a short wavelength. - Black and white images - Sample must be in a vacuum and therefore nonliving.

Answer 2

Light microscopes have a poor resolution due to the long wavelength of light. Small organelles in a cell are not visible using an optical microscope.

Answer 3

Can view living samples and can be examined and a colour image as obtained.

Answer 4

- samples must be in a vacuum so they cannot be living - The image is black-and-white - The sample must be complexly stained. - creates a 2-D image

Answer 5

Extremely thin specimens are stained and placed in a vacuum. An electron gun produces a beam of electrons that passes through the specimen. some parts absorb the electrons and appear dark. The image produced is 2-D and shows detailed images on the internal structure of the cell.

Answer 6

The specimens do not need to be thin as the electrons are not transmitting through. Instead electrons are beamed onto the surface and the electrons are scattered in different ways depending on the contours. This produces a 3-D image.

Answer 7

Image size = actual size x magnification

Answer 8

- to isolate different organelles so they can be studied - This enables individual organelle structures and functions to be studied.

Answer 9

- homogenisation: cells are broken to release the contents and organelles are then separated. The sales must be prepared in a cold, isotonic and buffered solution. -ultracentrifugation: put a sample in the centrifuge and spin at different speeds, separating the organelles according to their densities.

Answer 10

– Cold: to reduce enzyme activity. When the cell breaks open enzymes are released, which could damage the organelles. – Buffered: the solution has a pH buffer to prevent damage to organelles. – Isotonic: must be the same water potential to prevent osmosis as this could cause the organelles to shrivel or burst.

Answer 11

– The centrifuge spins and the centrifugal forces causes pellets of the most dense organelles to form at the bottom. - The centrifuge is first spun at a low speed and the process is repeated at increasing fast speeds – Each time the supernatant is removed, leaving behind a pellet of organelles – The supernatural is spun again to remove the next pellet organelles.

Answer 12

Nuclei, chloroplasts, mitochondria, lysosomes, endoplasmic reticulum and ribosomes

Answer 13

– Eukaryotic: cells enter the cell cycle and divide by mitosis or meiosis. – Prokaryotic: binary fission – Viruses: replicate inside of the wholesale they invade by injecting the nucleic acid into the cell to replicate the virus particles.

Answer 14

Interphase, nuclear division and cytokinesis.

Answer 15

The longest stage in the cell cycle. Interphase is when the organelles double, the cells grow and then DNA replicates.

Answer 16

Can be either mitosis creating two identical diploid cells; or meiosis creating genetically different haploid cells. Mitosis creates cells with identical DNA for growth and repair, whereas meiosis create gametes.

Answer 17

The final stage it is the division of the cytoplasm to create two cells.

Answer 18

Chromosomes condensed and become visible.

Answer 19

Chromosomes align along the equator of the cell. The spindle fibres released from the polls now attached to the centromeres and chromatid.

Answer 20

Spinal fibres retract and pull the centromeres and chromatids to opposite poles. Causing the Centromere to divide into pulling apart the chromatids.

Answer 21

Chromosomes become long and thinner spindle fibres, disintegrate, and nucleus starts to reform. Cytoplasm splits into to create the two genetically identical cells.

Answer 22

Mitotic index = the number of cells in mitosis/the number of cells x 100.

Answer 23

1. Replication of circular DNA and of plasmids. 2. Division of the cytoplasm to produce two cells each with a single copy of the circular DNA and a variable number of plasmids.

Answer 24

- Fluid-mosaic model: due to the mixture and movement of the phospholipids proteins, glycoproteins and glycolipids. - All of these molecules arranged within the phospholipid bilayer create the partially permeable membrane that is the cell surface membrane.

Answer 25

Form tubes that will fill with water to enable water soluble ions to diffuse.

Answer 26

They bind with others and larger molecules such as glucose and amino acid and change shape to transport them to the other side of the membrane.

Answer 27

The net movement of molecules from a high area of concentration to an area of lower concentration until equilibrium is reached and it does not require ATP.

Answer 28

Passive process, but proteins are used to transport molecules. The movement of ions and polar molecules which cannot simply diffuse can be transported across membranes by facilitated diffusion using protein channels and carrier proteins.

Answer 29

Osmosis is the movement of water from an area of higher water potentials to an area of lower water potential across a partially permeable membrane.

Answer 30

Isotonic – the water potential is the same in the solution and the cell within the solution. Hypotonic – the water potential of a solution is more positive than the cell. Hypertonic – when the water potential of a solution is more negative than the cell.

Answer 31

1. Transport is to carry a proteins spanning the cell membrane. 2. Molecule binds to a receptor complimentary in shape on the protein. 3. ATP vines to the carrier protein from the inside of the cell and is hydrolysed into ADP + Pi. 4. This causes the carrier protein to change shape and release the molecule to the other side. 5. The phosphate ion is then released and the protein returns to its original shape.

Answer 32

The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

Answer 33

– Sodium ions are actively transported out of the epithelial cell into the blood. – Sodium ions can then diffuse from the lumen down their concentration gradient into the epithelial cell. – The protein sodium ions diffuse through is a co-transporter protein so either glucose or amino acids also attacked and are transported into the epithelial cell cell against the concentration gradient.

Answer 34

– An increase in surface area to volume ratio – An increase in the number of protein channels and carry a molecules in their membranes.

Answer 35

Identify the presence of pathogens and potentially harmful non-self substances in the body to destroy them.

Answer 36

Each type of cell has specific antigens on its surface that identify it. These molecules are usually proteins as their tertiary structure enables lots of unique identifiable shapes to be made.

Answer 37

– toxins – Pathogens – Cells from other organisms – Abnormal body cells.

Answer 38

A molecule usually a protein that triggers an immune response by production of antibodies when detected by the body.

Answer 39

The transport of two different molecules or ions across a membrane through the same protein carrier. Any previous immunity to the pathogen through infection is no longer effective as the memory cells in the blood will have a memory of the old antigen shape. This is known as antigens variability.

Answer 40

- Pathogens DNA can mutate frequently. If a mutation occurs in the gene which codes for the antigen then the shape of the antigen will change. - Any previous immunity is lost as the memory cells in the blood will have a memory of the old antigen shape.

Answer 41

The influenza virus mutate and changes its antigens very quickly and this is why a new flu vaccine has to be created each year.

Answer 42

Chemical and physical barriers such as the skin and stomach acid.

Answer 43

Phagocytes - form a non-specific response. Lymphocytes - a specific response.

Answer 44

A macrophage that carries out phagocytosis. They are found in the blood and in tissue.

Answer 45

Any non-self cell that is detected will trigger the same response to destroy it.

Answer 46

1. Phagocytes are in the blood and tissue and any chemicals or debris released by pathogens or abnormal cells attract the phagocytes and they will move towards these cells. 2. There are many receptor binding points on the surface of the phagocytes. They were attached to chemicals or antigens on the pathogen via these receptors. 3. The phagocytes changes shape to move around and engulf the pathogen. 4. Once the pathogen is contained within a phagosome vesicle. 5. A lysosome within the phagocyte will refuse with the phagosome and release its contents. 6. The lysosome enzyme is released into the phagosome. This is a lytic enzyme which hydrolyses the pathogen. 7. This destroys the pathogen. 8. The soluble products are absorbed and used by the phagocyte.

Answer 47

– Lymphocytes are white blood cells involved in the specific immune response. – All lymphocytes are made in the bone marrow but t cells mature in the thymus. – The cell mediated response is the response involving t cells and body cells.

Answer 48

Because T cells respond to the antigens on the surface of cells.

Answer 49

Any cell that presents a non-self antigen on their surface: infected body cells will present the viral antigens on their surface. A macrophage which has engulfed and destroyed a pathogen will present the antigens on their surface. Cells of a transplanted organ will have different shaped antigens on their surface compared to your self-cell antigens. Cancer cells will have an abnormal shape compared to self -cell antigens.

Answer 50

1. Once a pathogen has been engulfed and destroyed by a phagocyte, the antigens are positioned on the cell surface. This is now called an antigen presenting cell. 2. Helper T cells have receptors on their surface which can attach the antigens on antigen presenting cells. 3. Once attached this activates the helper T cells to divide by mitosis to replicate and make large numbers of clones. 4. Cloned helper T cells differentiate into different cells.

Answer 51

– Some remain as helper T cells and activate B lymphocytes. – Some simulate macrophages to perform more phagocytosis. – Become memory cells for that shaped antigen. – Some become cytotoxic T cells.

Answer 52

They destroy abnormal or infected cells. They release a protein called perforin which embeds in the cell surface membrane and makes a pore so that any substances can enter or leave for cell.

Answer 53

– Lymphocytes are white blood cells involved in the specific immune response. – All lymphocytes are made in the bone marrow and B cells mature there too. – The humoral response is the response involving B cells and antibodies. Antibodies are soluble and transport in bodily fluids. (Humour) is an old term for bodily fluids hence the name humoral response.

Answer 54

– There are approximately 10 million different B cells which have antibodies on their surface complementary to 10,000,000 different antigens. – Antigens in the blood collide with their complementary antibody on a B cell. The B cell takes in the antigen by endocytosis and then presents it on its cell surface membrane. – When the B cell collides with a helper T cell receptor this activates the cell to go through clonal expansion and differentiation. – B cells undergo mitosis to make large numbers of cells these differentiate into plasma cells or memory B cells. – Plasma cells make antibodies. – B. Memory cells can divide rapidly into plasma cells, when reinfected with the same pathogen to make large numbers of antibodies rapidly.

Answer 55

Memory B cells can live for decades in your body, whereas plasma cells are short-lived. Do not make antibodies rather they will divide by mitosis and make plasma cells rapidly if they collide with an antigen they have previously encountered. This results in large numbers of antibodies being produced so rapidly that the pathogen is destroyed before any symptoms can occur.

Answer 56

– They have a quaternary structure (4 polypeptide chains). – They have a variable region which is the part of the antibody that binds to the antigen. – They have a constant region

Answer 57

Antibodies are flexible and combined to multiple antigens to clump them together. This makes it easier for phagocytes to locate and destroy the pathogens.

Answer 58

– Antibodies are introduced into the body. – The pathogen doesn’t enter the body so plasma cells and memory cells are not made. – No long-term immunity.

Answer 59

– Immunity created by your own immune system following exposure to the pathogen or its antigen. – natural, active immunity: following infection and the creation of the bodies, own antibodies and memory cells. – artificial active immunity: following the introduction of a weak version of the pathogen or antigens via a vaccine.

Answer 60

– Small amounts of weekend or dead pathogen or antigens are introduced in the mouth or by injection. – Exposure to the antigens activates the cell to go through clonal expansion and differentiation. – B cells undergo mitosis to make large numbers of cells these differentiate into plasma cells or memory B cells. – Plasma cells make antibodies. – B Memory cells can divide rapidly into plasma cells when reinfected with the same pathogen to make large numbers of antibodies rapidly.

Answer 61

If enough of the population of vaccinated, the pathogen cannot spread easily amongst the population. This provides protection for those who are not vaccinated.

Answer 62

Core = genetic material (RNA) and the enzyme reverse transcriptase, which are needed for viral replication. Capsid = outer protein coat. Envelope = extra outer layer made out of membrane taken from the host cell membrane. Protein attachments = on the exterior of the envelope to enable the virus to attach to the host helper T cell.

Answer 63

– HIV is transported around in the blood until it attaches to a CD4 for protein on the helper T cell. – The HIV protein capsule then fuses with the helper t cell membrane, enabling that RNA and enzyme from HIV to enter. – The HIV enzyme reverse transcript copies the viral RNA into a DNA copy moves to the cell nucleus. This is why it is called a retrovirus. – Here mRNA is transcribed and the helper T cell starts to create viral proteins to make new viral particles.

Answer 64

With the help of T cells being destroyed by the virus the host cell is unable to produce an adequate immune response to other pathogens and its left vulnerable to infections and cancer.

Answer 65

– A monoclonal antibody is a single type of antibody that can be isolated and cloned. – Antibodies are proteins which have binding sites complementary in shape to certain antigens.

Answer 66

– Medical treatment. – Medical diagnosis. – Pregnancy test.

Answer 67

Some cancer can be treated using monoclonal antibodies which are assigned with a binding site complimentary in shape to the antigens on the outside of of cancer cells. The antibodies are given to the cancer patient and attached the cancer cells. Well, the antibodies are bound to the cancer antigens this prevents chemicals binding to the cancer cells which enable uncontrolled cell division. Therefore, the monoclonal antibodies prevent the cancer cells growing, and as they are designed to only attach the cancer cells they do not cause harm to other normal cells.

Answer 68

Cancer can also be treated with monoclonal antibodies complementary in shape to the antigens on the outside of the cancer cells which have drugs attached to them. This cancer drug is therefore delivered directly to the cancer cells and kill them. This reduces the harmful side effects that traditional chemotherapy and radiotherapy can produce. This is often referred to as ‘bullet drugs’.

Answer 69

There is use of two antibodies: – first mobile antibody complimentary to the antigen being tested for and has a coloured dye attached. – A second antibody complimentary in shape to the antigen is immobilised in the test. – a third antibody is immobilised and is complimentary in shape the first antibody.

Answer 70

Creating monoclonal antibodies requires mice to produce the antibodies and tumour cells which lead to ethical debate as to whether this use of animals is justified to enable the better treatment of cancers in humans and detect disease.

Topic 2 - Cells Flashcards

(94 cards)