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topic 2 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

nucleus

A

-has a double membrane called the nuclear envelope.
-the nuclear envelope contains around 3000 nuclear pores that enable molecules to enter and leave the nucleus.
-the nucleus contains a substance called chromatin found within chromosomes and consists of DNA and protein.
-chromatin packages long DNA molecules into more compact, denser structures.
-the nucleus also has a nucleolus which is the site of ribosome production.

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2
Q

cell membrane

A

-surrounds the cell and lets substances in and out.
-contains proteins involved in transport across the membrane and cell recognition.

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3
Q

mitochondria

A

-the site of aerobic respiration and synthesises ATP
-bound by a double membrane called the envelope
-its inner membrane is folded to form projections called cristae with a fluid matrix inside containing all the enzymes needed for respiration

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4
Q

golgi apparatus

A

-a series of fluid filled, flattened and curved sacs with vesicles surrounding the edges.
-it processes and packages proteins and lipids.
-it also produces lysosomes

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5
Q

lysosome

A

-vesicles containing digestive enzymes to digest obsolete organelles
-bound by a single membrane
-can take in substances through endocytosis and remove and eliminate substances through exocytosis

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6
Q

ribosomes

A

-composed of two sub-units.
-they are either free in the cytoplasm or attached to the rough endoplasmic reticulum
-the site of protein synthesis
-they read RNA and string amino acids together to form polypeptides which fold to make proteins

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7
Q

rough endoplasmic reticulum

A

-a series of flattened sacs enclosed by a membrane with ribosomes on the surface.
-it folds and processes proteins made on the ribosomes
-membrane is folded to form cisternae

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8
Q

smooth endoplasmic reticulum

A

-a system of membrane-bound sacs.
-produces and processes lipids
-membrane is folded to form cisternae

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9
Q

cell fractionation

A

the process in which different parts and organelles of a cell are separated so they can be studied in detail. the separated is based on the different sizes of the organelles.

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10
Q

differential centrifugation

A
  1. the tissue is blended in a homogeniser to form a fluid called the homogenate. the tube filled with the homogenate is placed in a centrifuge and spun at a slow speed.
  2. the heaviest organelles (e.g. nuclei) are forced to the bottom where a thin sediment called the pellet forms
  3. the fluid sitting on top of the pellet is called the supernatant. it is removed, transferred to another tube and spun at a slightly faster speed. the pellet that forms contains the next heaviest organelles (e.g. chloroplasts and mitochondria).
    4 this process continues so that each time the speed is increased, the next heaviest organelles is sedimented and separated out (internal membranes/ pieces of plasma membrane, then ribosomes).
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11
Q

why is the homogenate placed in a cold, buffered solution of the same water potential?

A

-to prevent the organelles from bursting under osmotic pressure (w.p.)
-to deactivate any enzymes from breaking down organelles (cold)
-so the pH doesn’t fluctuate and to prevent denaturation of proteins (buffered)

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12
Q

what is the role of mitosis and the cell cycle?

A

-to produce identical daughter cells for growth and asexual reproduction
-the cells produced are genetically identical and so there is no genetic variation

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13
Q

why is mitosis important?

A

-for growth as all cells produced are identical so organisms can grow using mitosis
-for repair as all cells produced are identical so can replace dead tissues using mitosis
-for reproduction as some single celled organisms such as yeast reproduce by mitosis

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14
Q

what are the 3 stages of the cell cycle

A

mitosis - cell division that produces identical daughter cells. it is made of 4 stages, prophase, metaphase, anaphase and telophase.
interphase - chromosomes undergo DNA replication
cytokinesis - the cytoplasm divides, producing two daughter cells

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15
Q

describe each stage of mitosis

A

prophase- nuclear envelope breaks down, chromosomes condense
metaphase- the chromosomes line up in the center of the cell
anaphase- the centromere divides and spindle fibres separate the chromatids and pull them to opposite sides of the cell.
telophase - nuclear membrane reforms, chromosomes decondense. cytoplasm begins to divide

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16
Q

describe binary fission

A

plasmids and circular DNA in cells replicates
the cytoplasm divides
a new cell wall forms between the 2 DNA molecules.
two identical daughter cells from, each having a single copy of the circular DNA and a variable number of copies of the plasmids.

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17
Q

why don’t viruses undergo cell division

A

they are non-living
they inject their nucleic acids into another cell and the infected host cell replicates the virus particles

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18
Q

describe the basic structure of all cell membranes

A

-partially permeable
-composed of a sea of phospholipids with protein molecules between the phospholipid molecules
-fluid mosaic model- fluidity of membrane and mosaic arrangement of proteins

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19
Q

function of the membrane

A

-controlling the movement of substances in and out of the cell/organelle.
-contains receptors for other molecules such as hormones
-enables adjacent cells to stick together

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20
Q

describe the phospholipid bilayer

A

-hydrophilic heads point outwards and the hydrophobic tails point inwards.
-allows very small molecules and lipid soluble molecules to pass through the membrane but not water soluble/ polar molecules
-means the membrane is flexible and self-sealing

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21
Q

what other components are in the membrane

A

-proteins
-cholesterol
-glycolipids
-glycoproteins

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22
Q

describe proteins in the membrane

A

-may be integrated throughout the membrane (intrinsic) or on the surface (extrinsic)
-carrier proteins are a type of intrinsic protein which allows substances to cross the membrane
-proteins aid movement across the membrane, provide mechanical support and act in conjunction with glycolipids as receptors

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23
Q

describe cholesterol in the membrane

A

-makes the membrane more rigid and reduces the lateral movement of the phospholipids.
-prevents the leakage of water and dissolved ions from the cell as it is very hydrophobic

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24
Q

describe glycolipids in the membrane

A
  • acts as cell surface receptors for certain molecules.
    -allows cells to adhere to one another to form tissues
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25
Q

describe glycoproteins in the membrane

A

-act as cell surface receptors and neurotransmitters
-allows cells to recognise to recognise each other and adhere to one another to form tissues

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26
Q

describe diffusion

A

-the passive movement of small, non-polar, lipid soluble molecules (e.g. CO2 and O2) from an area of high to low concentration. the molecules diffuse directly through the phospholipid bilayer.

27
Q

describe facilitated diffusion

A

-requires a channel protein in the cell membrane to transport polar, water soluble and charged molecules across the membrane.

28
Q

describe osmosis

A

-the diffusion of water molecules from an area of high to low water potential through a partially permeable membrane.

29
Q

describe active transport

A

-all types of molecules can be transported through carrier proteins
-area of low to high concentration
-requires energy in the form of ATP

30
Q

describe endocytosis and exocytosis

A

-transports large particles
-the large particles are enclosed in vesicles made from the cell surface membrane and transported into the cell in endocytosis.
-in exocytosis, vesicles containing large particles are fused with the cell surface membrane and released from the cell

31
Q

describe co-transport

A

uses ions to move substances in and out of cells
e.g. in the epithelial cells of the ileum, sodium and potassium ions are pumped out of the epithelial cells by active transport into the blood, leaving a lower concentration in the cell. this causes these ions to move in from the lumen by facilitated diffusion which at the same time brings glucose and amino acids into the cell. These then diffuse from a high concentration in the epithelial cell to a low concentration in the blood.

32
Q

factors that increase rate of reaction

A

-increased surface area
-decreased diffusion distance
-steeper diffusion gradient
-increased temperature

33
Q

compare viruses and bacteria

A

-bacteria are prokaryotic cells - their genetic information is stored in the form of circular strand of DNA
-viruses consist of nucleic acid enclosed in a protein coat. their genetic material can take the form of DNA or RNA
-bacteria do not need a host whereas viruses cannot survive without them
-viruses are significantly smaller than bacteria
-bacteria have a cell membrane, cell wall, cytoplasm and other organelles whereas viruses have no such organelles.

34
Q

define antibodies

A

proteins that recognise and bind to specific antigens

35
Q

define antigens

A

foreign substances that stimulate the production of antibodies.

36
Q

specific molecules on cell surfaces that enable the immune system to identify:

A

-pathogens
-cells from other organisms of the same species
-abnormal body cells (e.g. cancer cells)
-toxins

37
Q

define the immune system

A

-a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens

38
Q

examples of non specific responses

A

inflammation
lysozyme action
phagocytosis

39
Q

describe phagocytosis

A

-pathogens release chemical products that the phagocyte is attracted to so it moves towards the pathogen
-the receptors on the phagocyte attach to chemicals on the surface on the pathogen
-the phagocyte engulfs the pathogen forming a phagosome
-the phagocytes fuses with a lysosome which releases lysozymes which hydrolyses the pathogen
-the hydrolysis products of the pathogen are absorbed by the phagocyte
-the antigens on the pathogen are presented on the surface of the phagocyte
-the phagocyte becomes an APC which activates an immune response if there is a foreign antigen

40
Q

what is the specific immune response

A

-antigen specific
-produces responses specific to one type of pathogen only

41
Q

which cells are involved in which response

A

-B cells - humoural response (matures in the bone marrow)
-T cells - cell-mediated response (matures in the thymus gland)

42
Q

describe humoural immunity

A

-when antigens collide with their complementary antibody on a B cell, the B cell takes in the antigen and presents it on its cell surface membrane
-this B cell collides with a helper T cells receptor, which activates the B cell to undergo mitosis to create large numbers of cells
-these cells differentiate through clonal selection into either memory B cells or plasma cells
-plasma cells produce antibodies
-memory B cells can divide rapidly into a large number of plasma cells when the body is re-infected with the same pathogen to make large amounts of antibodies rapidly

43
Q

what is active immunity

A

-immunity created by your own immune system following exposure to the pathogen or its antigen

44
Q

describe the structure of antibodies

A

-made of 4 polypeptide chains forming a Y shaped structure
-chains are held together by disulfide bridges
-variable region is different in every antibody as the shape is specific to the antigen that it binds to
-the hinge region allows flexibility in binding
-the constant region binds to receptors on cells
-they form antigen-antibody complexes which act as markers for phagocytes to destroy the pathogen they are attached to

45
Q

what is agglutination

A

-as antibodies have 2 binding sites, they can clump cells together making them easier for phagocytes to find

46
Q

describe cell-mediated immunity

A

-they respond to antigens presented by APCs or by the body’s own infected cells
-helper T cells have receptors on their surface that can attach to the antigens on APCs
-once the helper T cell is attached, it becomes activated and undergoes mitosis to produce many clones of itself with identical receptors
-these cloned helper T cells differentiate into:
-memory T cells that enable a rapid response to future infections of the same pathogen
-remain as helper T cells that stimulate B lymphocyte production which is important in humoral immunity
-stimulate macrophages to perform more phagocytosis
-become cytotoxic T cells which kill infected cells by making perforin, a protein that causes damage to the cell’s surface membrane

47
Q

what is passive immunity

A

-antibodies are introduced to the body
-the pathogen doesn’t enter the body so plasma cells and memory cells are not made
-there is no long term immunity
-e.g., antibodies passed to a foetus through the placenta or through breast milk to a baby

48
Q

examples of natural and artificial active immunity

A

natural immunity- when the body creates its own antibodies and memory cells following an infection
artificial immunity- when a weakened strain of the pathogen or antigen is introduced to the body via a vaccine

49
Q

how do vaccines work

A

-small amounts of weakened or dead pathogen is introduced to the body
-this activates the B cell to undergo mitosis to create large numbers of cells
-these cells differentiate through clonal selection into either memory B cells or plasma cells
-plasma cells produce antibodies
-memory B cells can divide rapidly into a large number of plasma cells when the body is re-infected with the same pathogen to make large amounts of antibodies rapidly

50
Q

what is herd immunity

A

-if enough of the population are vaccinated, the pathogen cannot spread easily amongst the population
-provides protection for those who cannot get a vaccine

51
Q

why are viruses difficult to destroy

A

-they replicate inside cells so difficult to destroy them without harming host cells
-viruses have different structures and replicate in a different way to bacteria so can’t be destroyed by antibiotics

52
Q

describe the structure of HIV

A

core- contains RNA and the enzyme reverse transcriptase which are needed for viral replication
capsid- outer protein coat
envelope- extra outer layer made from the host’s membrane
protein attachments- on the exterior of the envelope to enable the virus to attach to the host’s helper T cells

53
Q

descibe HIV replication

A

-attachment protein on HIV attaches to a receptor on a helper T cell
-HIV capsid fuses with helper T cell membrane so RNA and reverse transcriptase can enter the helper T cell’s cytoplasm
-reverse transcriptase makes a complementary strand of DNA from the viral RNA template
-the viral DNA moves to the host’s nucleus where it becomes integrated with the host’s DNA
-this causes helper T cells to create viral proteins to make new viral particles
-this causes the helper T cells to die

54
Q

describe how AIDS can develop

A

-gradually the virus reduces the number of helper T cells in the immune system
-B cells are no longer activated
-no antibodies are produced
-this decreases the body’s ability to fight off infections, eventually leading to AIDS

55
Q

what are monoclonal antibodies

A

-are antibodies which are specific to a certain antigen.

56
Q

what can monoclonal antibodies be used for

A

-medical diagnosis
-medical treatment
-pregnancy tests

57
Q

how can cancer be treated directly with monoclonal antibodies

A

-the monoclonal antibodies can be designed with a binding site complementary in shape to the antigens on the outside of cancer cells
-the antibodies are introduced to the body and bind to the cancer antigens
-this prevents chemicals that cause uncontrolled cell division from binding
-therefore, monoclonal antibodies prevent cancer cells from growing and don’t harm body cells as they are specific only to cancer cells

58
Q

how can cancer be treated indirectly with monoclonal antibodies

A

-the monoclonal antibodies can be designed with a binding site complementary in shape to the antigens on the outside of cancer cells and they have drugs attached to them
-the cancer drugs are delivered directly to the cancer cells and kill them
-reduces the harmful side effects of chemotherapy and radiotherapy

59
Q

ethical considerations of vaccines

A
  • Production and testing of vaccines may be done on animals
  • The risks of the vaccine need to be balanced with the benefits
  • The vaccine must be tested on humans first to determine toxicity
  • Vaccinations are very expensive
60
Q

describe how an ELISA test works

A

-add test sample to beaker
-wash to remove any unbound test sample
-add antibody complementary in shape to antigen being tested for
-wash to remove any unbound antibody
-add second antibody complementary in shape to the first antibody so it binds to it. the second antibody has an enzyme attached to it
-wash to remove any unbound antibody
-the substrate for the enzyme which is colourless is added. it produces coloured products in the presence of the enzyme
-if a color is produced, the antigen is present. the higher the intensity of the colour, the greater the quantity present

61
Q

ethical issues of monoclonal antibodies

A

-requires mice to produce the antibodies and tumour cells, may not be justified

62
Q

how to make a temporary mount

A

-add a drop of water to slide
-place thin section of tissue on slide
-stain e.g. iodine
-lower coverslip with mounted needle

63
Q

describe how a transmission electron works

A

-electrons pass through the specimen
-denser parts absorb more electrons
-denser parts appear darker
-electrons have a short wavelength so resolution is higher

64
Q

limitations of transmission electron microscope

A

-can’t look at living material - must be in a vacuum
-specimen must be very thin
-only 2D images

Biology (9 decks)

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