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Cells Flashcards

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1
Q

What is the structure and function of the vacuole?

A

Fluid filled sacs bounded by a single member (tonoplast) which stores minerals, sugars, amino acids and sometimes pigments.
They support herbaceous plants to make turgid and act as temporary food stores.

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2
Q

What is the structure and function of the Ribosomes?

A

Small cytoplasmic granules found in cells made by the nucleolus made of 2 sub-units.
It is the site of protein synthesis which is when cells produce proteins from amino acids.

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3
Q

What is the structure and function of the Chloroplasts?

A

Organelles found in leavs containing a double membrane called an envelope and stroma containing enzymes. It also consists of thylakoids which are sacs containing chlorophyll which is the site of photosynthesis. These are stacked into grana to increase surface area.
They harvest sunlight for photosynthesis.

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4
Q

What is the structure and function of the
Endoplasmic Reticulum?

A

Membrane passages spread through the cytoplasm to transport materials. It contains a network of tubules and flattened sacs called cisternae.
Rough ER- have ribosomes for protein synthesis
Smoot ER- no ribosomes transport lipids and carbs

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5
Q

What is the structure and function of the Lysosomes?

A

Vesicles containing enzymes called lyzozomes to break down material and dead cells and digest worn out organelles.

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6
Q

What is the structure and function of the Golgi Body (apparatus)?

A

Series of fluid filled, flatterned sacs with vesicles surrounding.
It processes and packages proteins and lipids while producing lysosomes

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7
Q

What is the structure and function of the Nucleus?

A

Control centre of the cell containing an organisms hereditary material and produces RNA and ribosomes.
Chromosmes- protein bound linear DNA
Nuclear Pores- allow passage of larger molecules
Nucleoplasm- granular, jelly-like material making up the bulk of a nucleus
Nuclear Envelope- Double membrane surrounding nucleus which is continuous with the ER

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8
Q

What is the structure and function of the Cell Wall?

A

Rigid outer layer keeping the cell strong
Eukaryotes- microfibrils of cellulose
Algae- glycoproteins
Fungi- Chitin

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9
Q

What is the structure and function of the Mitochondria?

A

Site of aerobic respiration to produce ATP
Double membrane controls what goes in and out.
Cristae- Folds in the inner membrane to increase the surface are for enzyme attachment used in respiration
Matrix- fluid containing enzymes

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10
Q

What organelles are present in Prokaryotic Cells?

A

Plasmids- circular strands of DNA that have genes that aid survival
Circular DNA- holds genetic information
Capsule- Extra layer of protection to maintain shape and prevent dehydration
Flagella- helps movement (locomotion)
Pilli- Hair like structures which attach to other bacteria
Mesosomes- infoldings in the inner membrane which contain enzymes for respiration
cell wall and membrane

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11
Q

What is the difference between Magnification and Resolution?

A

Magnification-The number of times larger an image is compared with the real size.

Resolution- ability to distinguish between two separate points, if two points cant be resolved, they will be seen as one.

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12
Q

What is a light microscope and what are the advantages and disadvantages of one?

A

Use glass lenses to capture small objects. The resulving power of a light microscope is 0.2um, so if two objects are less than 0.2um, they will be seen as one.
- quick a nd simple to prepare
- naturally coloured
- living tissue
- cheaper

  • only magnify uo to 1500x
  • limited resolution
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13
Q

What is an electron microscope and the advantages and disadvantages of one?

A

Electron microscopes are used to look at objects objects that are 0.2um apart by using a beam of electrons in a vacuum environment.
- vaccum means that living organisms cant be assessed
- complex staining processes are required
- specimins have to be very thin

  • higher resolution to see smaller specimins.
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14
Q

What is the difference between Transmission and Scanning Electron microscopes?

A

TEM- a beam of electrons passes through a thin section of a specimen. Areas that absorb the electrons appear darker on the electron micrograph that is produced.

SEM- in a scanning electron microscope a beam of electrons passes across the surface and scatter. The pattern of scattering builds up a 3D image depending on the contours of the specimen

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15
Q

What is cell fractionation?

A

The process in which different parts and organelles of a cell are separated so can be studied in detail.

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16
Q

What is homogenization and what is needed?

A

Homogenization is the process of breaking open cell membranes and walls to release organelles using a homogenizer.
The sample must be:
- Ice Cold- stop lytic enzyme activity
- PH buffered- prevents damage to organelles
- isotonic- prevent osmotic lysis

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17
Q

Why do we filter the solution after homogenizing?

A

Removes cellular debris so our samples dont end up impure

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18
Q

Talk about the process of differential centrifugation.

A
  1. Spin the homogenate at a low speed to seperate a pellet of the densest organism (nuclei)
  2. This forms a pellet of the organelle and a supernatent including the rest
  3. Remove the pellet and centifuge at a higher speed to obtain the next densest organelle
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19
Q

What is the order of organelles from most to least dense?

A

Nuclei
mitochnodria/ chloroplasts
Golgi/ ER
ribosomes

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20
Q

Why are virus’ non-living?

A
  • No nucleus, plasma membrane, cytoplasm or ribosomes
  • Arent made of cells.
  • Can’t reproduce independently
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21
Q

Talk about the structure of virus’

A

Capsid- A protein coat containing genetic material in the form of DNA or RNA

Attachment proteins (glycoproteins- Attached to capsid, help viruses to recognize and bind to cells in the host.

Genetic Material (DNA or RNA)- Contains instructions for making new copies of the virus (only inside living host cells)

Lipid Envelope- Made from fatty lipid molecules taken from cells in the host → only in some

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22
Q

Talk about how virus’ reproduce.

A

Viruses depend on a host cell to infect and reproduce, when found outside of host cells, viruses exist as a protein coat or capsid, sometimes in a membrane. It encloses either a DNA or RNA which codes for the virus elements.

  1. Attachment- The Virus attaches to the surface of the host cell
  2. Entry- Viral genetic info enters host cell
  3. Replication- Viral DNA/RNA replicates and new viral proteins are made forming new capsids.
  4. Assembly- New viral particles are assembled
  5. Release- Host cell lyses (bursts) leaving newly made viruses
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23
Q

Talk about interphase.

A

Period during which the cell is not dividing, however DNA is replicating. It is split into 3 phases:
1. G1 PHASE: Cell growth- Cell increases in size, produce RNA, synthesize proteins and organelles increase in numbers.
2. S PHASE: DNA replication- Increase DNA number from 2N to 4N to create 46 pairs
3. G2 PHASE: Preparation for mitosis- cells continue to grow and produce proteins and make microtubules.

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24
Q

What is the G0 phase?

A

sometimes when no cell division is needed (for example neuron cells), they just stay in G0 phase

25
Q

What are the other phases of mitosis?

A

PROPHASE: Chromosomes condense (thicken), Nucleolus disappears and nuclear envelope disintegrates, poles start to produce spindles.

METAPHASE: Chromosomes line up in the Centre of the cell, spinals form and spinal fibres attach to chromosomes.

ANAPHASE: The spinal fibres contract and the chromatids are pulled toward poles.

TELOPHASE: Chromosomes reach poles and become indistinct, nuclear envelope reforms and nucleolus, spindles disintegrate

CYTOKENISIS- splitting of cytoplasm

26
Q

What is the process of binary fission?

A

The process by which prokaryotic cells divide.

1.The circular DNA in the cells replicates and both copies attach to the cell membrane.
Plasmids also replicate.

2.The cell membrane then begins to grow between the two DNA molecules and begins to pinch
inwards, dividing the cytoplasm in two.

  1. A new cell wall forms between the two DNA molecules dividing the original cell. The identical daughter cells each have a single copy of the circular DNA and a variable number of copies of the plasmids.
27
Q

What are the components of the fluid mosaic model?

A

Phospholipid bilayer
Cholestreol
Glycolipids
Glycoproteins
Proteins (intrinsic and Extrinsic)

28
Q

Talk about the phospholipid Bilayer.

A

Individual phospholipids which are a triglyceride consisting of 2 fatty acids and a phosphate group. The hydrophilic heads face outwards and the hydrophobic tails point inwards. This allows lipid soluble molecules to pass through but not water soluble molecules.

29
Q

Talk about Cholesterol.

A

Strengthen the membranes to reduce lateral movement of other molecules to make the membrane less fluid at high temperatures and prevent leakages

30
Q

Talk about Glycolipids

A

carbohydrates covalently bonded to lipids in the membrane. The carb extends to act as a cell surface receptor and maintain stability.

31
Q

Talk about glycoproteins

A

Carbohydrate attached to extrinsic proteins act as cell surface receptors help cells attach to each other (forming tissues) and self recognition (ie lymphocytes)

32
Q

Talk about the proteins found in the model.

A

Interspersed throughout the surface of the membrane (intrinsic proteins) or on the surface (extrinsic. some give mechanical support or cell receptors for things like hormones. Others completely span the bilayer creating protein channels allowing water soluble ions to diffuse across. others are carrier proteins which bind to molecules and change shape to move them accross

33
Q

Define Diffusion

A

Movement of small, non-polar molecules from an area of high concentration to an area of low concentration. They move directly through the bilayer.

34
Q

Talk about facilitated diffusion

A

Large, charged ions and polar molecules that don’t diffuse easily require a channel protein.

  • Protein Channels, Water filled hydrophilic channels that allow water soluble ions to pass through. They open in the presence of a specific ion.
  • Carrier Proteins, When a specific molecule like glucose which is specific to the protein, it binds to the protein and change shape to allow them through.
35
Q

Talk about osmosis.

A

Movement of water from an area of high water potential to an area of low water potential through a partially permeable membrane

36
Q

What is water potential?

A

The preassure created by water potential, measured in kilopascals
In standard conditions of temperature (37) and preassure (100kPa), pure water has a water potential of 0kPa.

  • adding a solute lowers the potential
  • the water potential of a solute must always be lower than 0
37
Q

What is the difference between hypotonic, hypertonic and isotonic?

A

Hypotonic- Lower solute concentration, more water, less solute.

Hypertonic- High solute concentration, more solute, less water.

Isotonic- Same solute concentration

38
Q

What is active transport and its process?

A

Movement of substances like ions from a low to high concentration against the concentration gradient with the help of ATP and carrier proteins through a partially permeable membrane.

  1. Ion binds to the carrier protein
  2. ATP binds to protein and splits into ADP and a Phosphate Ion.
  3. The protein changes shape allowing the ion to move accross
  4. The phosphate ion is released and the protein changes back to the original shape
39
Q

What is the immune system and what does it detect?

A

The immune system is made up of specialised cells that respind to foreign objects and protect an individual from harm. The cells detect:
Toxins- harmful substances produced by pathogens, detected by immune cells
Cells from other organisms- Immune cells csn detect the presence of cells from other organisms of the same species, ie, an organ transplant
Pathogens- Microorganisms which cause disease
Abnormal Body Cells- Ie. cancerous cells

40
Q

What are antigens

A

molecules that are present on the cell surface membrane if all cells that elicit an immune response if they are foreign. Every cell has a specific antigen that binds to complementary receptors

41
Q

What is the immune response and the two types?

A

The immune system responds to antigens which are the protein layer around a pathogen which have a specific structure which is unique to each cell.

Non-Specific- Non-specific immune responses are innate, immediate, the same for all pathogens and act as a physical barrier. Its less effective

Specific- The specific Immune response is antigen specific and produces responses specific to one pathogen only .

42
Q

What is the process of the non-specific immune response?

A

PHAGOCYTOSIS-
1. When pathogens enter the body, they release attractants to bring phagocytes closer- chemotaxis
2. Phagocytes have several receptors on their surface that recognize and attach to the chemicals on pathogens
3. They engulf the pathogen into itself and form a vesicle known as a phagosome
4. Lysosomes fuse with the phagosome
5. Enzymes called lysozymes destroy the ingested bacteria via hydrolysis of their cell walls.
6. The soluble products are absorbed into the cytoplasm

43
Q

What is the difference between B and T cells?

A

B cells: These lymphocytes produce antibodies that recognize and bind to specific antigens on pathogens, marking them for destruction by other cells of the immune system. Involved in the humoral response

T cells: They move to the thymus gland where they mature and are involved in cell mediated response. There are two types of T cells involved in the specific immune response. Helper T cells help activate B cells and other immune cells, while cytotoxic T cells directly kill infected cells.

44
Q

Talk about the Cell-Mediated response.

A

In the cell mediated response, phagocytes engulf pathogens causing them to ingest and process them eventually becoming an antigen presenting cell which is where the invading pathogens antigen is presented on the surface of the WBC’s membrane. Examples include cancer cells, phagocytes, body cells, transplanted cells or viral infected cells. Helper T cells receptors bind to the complementary antigens on the APC’s which activate T cells to rapidly divide via mitosis. These clones can have different functions like: stimulating B cells to produce antibodies, stimulate phagocytosis, become memory cells or cytotoxic T cells (punch holes in infected cells using the chemical perforin to destroy them.

45
Q

Talk about the Humoral Response.

A

The surface antigens of invading pathogens are taken up by a B cell which processes them and presents them in its surface. Helper T cells attach to the processed antigens activating the B cell causing it to divide by mitosis to give a clone of plasma cells. These plasma cells produce the specific antibody that is complementary to the antigens on the patheogens surface.The antibody attaches to antigens on the pathogen and destroys them, this is the primary immune response.

Some B cells develop into memory cells which can respond to future infections by the same patheogen by dividing rapidly and developing into plasma cells that produce antibodies, this is the secondary immune response.

46
Q

Talk about Memory Cells

A

Memory Cells- cells which replicate themselves when exposed to an invading pathogen and remain in the lymph nodes for decades searching for the same antigen resulting in much faster immune response should the individual be infected by the same pathogen again.

So during the second exposure to the antigen, memory B cells are present. These respond to the pathogens infection faster by rapidly dividing bby mitosis to make genetically identical plasma cells in larger quantities, this is called clonal expansion Therefore more complementary antigens can be produced at a faster rate to destroy the pathogens.

47
Q

What are Antibodies?

A

Antibodies are protein chains forming a Y shape structure which is complementary to only a signle antigen. They work by forming an antigen antibodu complex which serves as markers for phagocytes to destroy attached cells. They clump cells together making it easier for phagocytes to find (agglutination)

48
Q

Talk about the two types of Antigen Variability.

A

Antigenic Shift- occurs when a virus undergos sudden change in genetic makeup creating a completely new strain. It occurs when a non-human virus enters a host and combines with a human virus. This way memory cells dont detect the altered antigens so its no longer effectve

Antigenic Drift- occurs when a virus undergoes a gradual change in genetic makeup causing a different but somewhat similar generic makeup to present. Drift occurs when a virus undergoes gradual mutatuons which overtime can lead to the creation of a new virus.

49
Q

What is Immunity and the two types?

A

Immunity is the ability of an organism to resist infection.
Passive Immunity- Produced by the introducion of antibodies into individuals from an outside source. No dircect contact to the patheogen or its antigen is necessary to induce immunity. As the antibodies are not being produced by the individuals themselves, the antobodies arent replaced when broken down so its short lasting. Examples incude: The Mothers Placenta or milk as a transfer od antivodies, anti-venom or infected antibodies.

Active Immunity- Produced by stimulating the production of antibodies by individuals own immune system causing the formation of memory cells. Needs the exposure to a pathogen. Has a lag time however is long-term. Examples include: Natural infection and vaccination

50
Q

Talk about Vaccination.

A

Vaccination is the introduction of the appropriate disease antigens in the form of dead or inactive pathogens into the body by injections. The intention is to stimulate an immune response to form memory cells to allow a greater and more immediate response to a future infection, The result is in the future if a person gets infected again, antibodies can be produced rapidly to overcome the infection quickly.

When a sufficiently large proportion of the population have been vaccinated, it is called Herd Immunity. Pathogens are passed from one person to another when in close contact, however if a large amount of the population is immune, it is more difficult for a pathogen to spread. This is good as babies and young children can be protected as they cannot be vaccinated due to their immune system not being developed fully.

51
Q

What is the ethics behind vaccination?

A
  • The production and testing of vaccines may be done on animals
  • The risks of the vaccine (ie side effects) have to be balanced with benefits
  • Has to be tested on humans
  • Expensive
  • Should they be compulsory?
52
Q

What are monoclonal antibodies?

A

Monoclonal antibodies are made from b lymphocytes which are unspecified. they bind to antigens in the samew w\y as naturally produced antibodies. Due to there being many different types of antigens, each B cell will produce a different complementary antibody. It is therefore medically useful to be able to produce many clones of a single type of antibody

53
Q

Uses of monoclonal antibodies?

A
  • Direct Therapy- Monoclonal antibodies which are specific to antigens found on the surface of cancerous cells can be used to target and then destroy the cells as part of an immune response
  • Indirect Therapy- Drugs can be attached to monoclonal antibodieslike a cytotoxic drug. The antibody isb then used to direct the drug toward the cells displaying a particular antigen
  • Diagnosis- Particular antigens are targeted by antibodies to measure levels of that antigen in the body
  • Pregnancy- Monoclonal antibodies in home pregnancy tests are specific to the hormone human chrionic gonadotrophin (hCG) in the urine sample:
54
Q

What is HIV?

A

Human Immunodeficiency Virus is a patheogen that can lead to the disease acquired Immune Dificiency Syndrome (AIDS) It contains:

55
Q

Talk about the replication of HIV.

A
  1. GP120 binds to the protein CD4 found on T-helper cells.
  2. The capsid fuses with the cell surface membrane and the RNA and reverse transcriptase enters the cell.
  3. The reverse transcriptase converts RNA into DNA
  4. Newly made DNA is moved into the nucleus and inserted into the cells DNA
  5. The HIV DNA creates mRNA (messenger RNA) with the help of viral enzymes, which contains the instructions for making new viral proteins and RNA.
  6. The mRNa passes out of the nucleus through a nuclear pore and uses the cells protein synthesis mechanisms to make HIV
  7. These break away forming new HIV particles
56
Q

How does HIV cause AIDS?

A

HIV causes AIDS by killing ot interfering eith the normal functioning of helper T cells decreasing the number of them. This means the immune system cannot stimulate B cells to produce antibodies and memory cells may become infected or destroyed. As a result, the body is unable to produce adequate immune response and becomes susceptible to other infections and cancers.

57
Q

What is the ELISA test?

A

Enzyme linked immunosorbant assay. It uses antibodies to detect the presence of a protein in a sample and the quantity. This is used to detect HIV and the pathogens of diseases.

58
Q

Talk about antibiotics.

A

In bacterial cells, water constantly enters via osmosis, this entry of water would normally cause the cell to burst but it doesnt due to the tough murein walls. Antibiotics like penicillin inhibit certain enzymes required for the synthesis and assembly of peptide cross linkages which weakens the walls making them unable to withstand preassure, killing the cells

Viruses rely on host cells, therefore lack metabolic pathways and cell structures. Antibiotics are ineffective as there are no metabolic mechanisms or structures for them to disrupt. They also have a protein coat so dont have sites where antibiotics can work

Biology (4 decks)

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