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AS BIO - BIOLOGICAL MOLECULES > CELLS > Flashcards

CELLS Flashcards

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1
Q

what are all living organisms made of

A

cells that have the same basic features in common

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2
Q

what feature about cells suggests that all living things have evolved from the same common ancestor

A

the fact that cells have the same basic feature in common

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3
Q

what are the 2 main types of organisms

A

eukaryotes and prokaryotes

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4
Q

what are prokaryotic organisms made of

A

prokaryotic cells

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5
Q

are prokaryotic organisms multi or uni cellular

A

unicellular - single celled organisms

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6
Q

what are eukaryotic organisms made of

A

eukaryotic cells

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7
Q

what do both types of cells contain

A

organelles

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8
Q

compare eukaryotic cells and prokaryotic cells in terms of complexity

A

eukaryotic cells are more complex
prokaryotes are more small and simple

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9
Q

describe organelles

A

parts of cells
each organelle has a specific function

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10
Q

what type of microscope can you use to see an organelle and its internal structure

A

electron microscope

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11
Q

describe eukaryotic cells

A

bit more complicated than prokaryotic cells

have more organelles than prokaryotic cells

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12
Q

give 4 examples of eukaryotic cells

A
  • animal cells
  • plant cells
  • algal cells
  • fungal cells
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13
Q

name all the organelles found in an animal cell (EUKARYOTIC)

A

cell surface plasma membrane
ribosome
cytoplasm
mitochondria

nucleus
nucleolus
nuclear envelope

rough endoplasmic reticulum
smooth endoplasmic reticulum

lysosome

golgi apparatus

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14
Q

name the organelles in a plant cell

A

all the same as animal cell, expect they have 3 extra which is written down below

cellulose cell wall with plasmodesmata - channels for the exchange of substances between adjacent cells

vacuole - fluid filled compartment

chloroplasts - organelles involved in photosynthesis

therefore all the organelles in a plant cell are :

cell surface plasma membrane
ribosome
cytoplasm
mitochondria
cellulose cell wall with plasmodesmata
vacuole
chloroplasts

nucleus
nucleolus
nuclear envelope

rough endoplasmic reticulum
smooth endoplasmic reticulum

lysosome

golgi apparatus

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15
Q

name the organelles in an algal cell

A

cell surface plasma membrane
ribosome
cytoplasm
mitochondria
cellulose cell wall
vacuole
chloroplasts

nucleus
nucleolus
nuclear envelope

rough endoplasmic reticulum
smooth endoplasmic reticulum

golgi apparatus

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16
Q

name the differences/potential differences between a plant cell and an algal cell

A

algae can be unicellular, chlorella, or multicellular, seaweed

shape and size of chloroplasts are different in algal cells, compared to plant cells, ex an algal cell can have 1 large chloroplast compared to many small chloroplasts in a plant cell

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17
Q

name the organelles in fungal cells

A

cell surface plasma membrane
ribosome
cytoplasm
mitochondria
chitin cell wall
vacuole

nucleus
nucleolus
nuclear envelope

rough endoplasmic reticulum
smooth endoplasmic reticulum

golgi apparatus

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18
Q

describe the appearance and function of the cell surface membrane

A

appearance
- inside the cell wall of other cells, mainly made of lipids and protein

function
- regulates the movement of substances in and out of the cell
- has receptor molecules on it which allow it to respond to chemicals like hormones

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19
Q

describe the appearance and function of the nucleus

A

appearance
- large organelle
- surrounded by a nuclear envelope which contains many pores
- contains chromosomes
- contains a nucleolus

function
- controls cells activities by controlling the transcription of the DNA
- DNA contains instructions to make proteins
- pores in the nucleus allow substances, like RNA to move between the nucleus and cytoplasm
- nucleolus makes ribosomes

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20
Q

describe the appearance and function of the mitochondrion

A

appearance
- oval shaped
- double membrane
- inner membrane folded to form cristae
- inside contains the matrix which contains enzymes involved in respiration

function
- site of aerobic respiration, which produces ATP
- found in large numbers in cells which are very active and require lots of energy, ex - sperm cells

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21
Q

describe the appearance and function of the chloroplast

A

appearance
- small + flat
- found in plant and algal cells
- surrounded by a double membrane
- has membranes inside called thylakoid membranes
- thylakoid membranes are stacked to form grana
- grant are linked together by lamella, which are thin flat pieces of thylakoid membrane

function
- site of photosynthesis
- some parts of photosynthesis are in the grana and others in the stroma

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22
Q

describe the appearance and function of the golgi apparatus

A

appearance
- group of fluid filled membrane bound flattened sacs
- vesicles seen at the edges of the sacs

function
- processes + packages new lipids and proteins
- makes lysosomes

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23
Q

describe the appearance and function of the golgi vesicle

A

appearance
- small fluid filled sac in cytoplasm
- surrounded by membrane and produced by golgi apparatus

function
- stores lipids and proteins made by golgi apparatus and transports them out the cell VIA cell surface membrane

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24
Q

describe the appearance and function of the lysosome

A

appearance
- round organelle
- surrounded by a membrane
- no clear internal structure

function
- contains hydrolytic enzymes, kept separate from the cytoplasm by surrounding membrane
- enzymes can be used to digest invading cells or break down worn out components of the cell

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25
Q

describe the appearance and function of the ribosome

A

appearance
- very small organelle
- floats free in cytoplasm OR attached to RER
- made of proteins and RNA
- NOT surrounded by membrane

function
- site of protein synthesis

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26
Q

describe the appearance and function of the RER

A

appearance
- system of membranes enclosing a fluid filled space
- surface is covered with ribosomes

function
- folds and processes proteins that have been made at ribosomes

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27
Q

describe the appearance and function of the SER

A

appearance
- similar to RER, but no ribosomes

function
- synethesises and processes lipids

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28
Q

describe the appearance and function of the cell wall

A

appearance
- rigid structure that surrounds cells in plants, algae and fungi
- in plants and algae its mainly made of cellulose
- in fungi its made of chitin

function
- supports cells and prevents them from changing shape

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29
Q

describe the appearance and function of the cell vacuole

A

appearance
- membrane bound organelle
- found in cytoplasm
- contains cell sap, a weak solution of sugar and salts
- membrane surrounding it is called a ‘tonoplast’

function
- helps to maintain pressure inside cell
- keeps cell rigid
- stops plant from wilting
- involved in isolating unwanted chemicals in the cell

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30
Q

what process do cells go through to be able to carry out their specific functions

A

specialisation

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31
Q

what feature of the cell helps it carry out its function

A

its shape

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32
Q

describe how epithelial cells are specialised to carry out their functions

A

in the small intestine and are adapted to absorb food efficently

  • walls of small intestine have lots of villi (finger like projections) = increase SA for absorption
  • villi have folds called microvilli = further increase SA
  • lots of mitochondria = provide energy for transport of digested food molecules into cell
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33
Q

describe how red blood cells are specialised to carry out their functions

A

adapted to carry oxygen around the body

no nucleus = more room for haemoglobin, which carries oxygen

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34
Q

describe how sperm cells are specialised to carry out their functions

A

have to propel themselves to an egg

have lots of mitochondria to provide energy to travel

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35
Q

describe cell organisation

A

specialised cells -> tissues
tissues -> organs
organs -> organ system

tissues = group of cells working together to perform a certain function

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36
Q

describe cell organisation in epithelial cells

A

epithelial cells -> epithelial tissue

epithelial tissue, muscular tissue and glandular tissue work together to form the stomach, which is an organ

stomach is part of the digestive system - organ system made of all organs involved in digestion and absorption of food, includes small and large intestine and liver

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37
Q

are prokaryotes single or multi cellular

A

they are single celled organisms

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38
Q

give an example of a prokaryote

A

bacteria like E. Coli

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39
Q

what is the cell wall of a prokaryote made of

A

murein

glycoprotein, protein with carbohydrate attached

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40
Q

describe the appearance and function of the flagellum

A

appearance
- long hair like structure
- not all prokaryotes have one, some have multiple

function
- makes prokaryotes move

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41
Q

describe the appearance and function of the nucleus in a prokaryote

A
  • dont have a nucleus
  • DNA floats free in the cytoplasm
  • circular DNA presents as one long coiled up strand
  • DNA not attached to any histone proteins
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42
Q

describe the appearance and function of the plasmids in a prokaryote

A

appearance
- small loops of DNA that aren’t part of the main circular DNA molecule
- not present in all prokaryotes, while some have multiple

function
- contain genes for things like antibiotic resistance
- can be passed between prokaryotes

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43
Q

describe the appearance and function of the slime capsule

A

appearance
- capsule around the cell wall
- made of secreted slime
- only some have it

function
- helps to protect the bacteria from attack by cells of immune system

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44
Q

describe the size of prokaryotes

A
  • extremely small
  • less than 2 hm in diameter - 0.002 mm
  • eukaryotes can be up to 50x bigger
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45
Q

how do prokaryotes replicate

A

binary fission

cell replicates and makes 2 copies of its genetic material, before splitting into 2 daughter cells

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46
Q

describe the process of binary fission

A
  • circular DNA and plasmid/s replicate
  • main DNA loop only replicated once
  • plasmid/s can be replicated many times
  • cells gets bigger
  • DNA moved to opposite poles/ends of the cell
  • cytoplasm begins to divide
  • new cell walls begin to form
  • cytoplasm divides and 2 daughter cells are produced
  • each daughter cell has 1 copy of the circular DNA but a variable number of copies of the plasmids
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47
Q

describe viruses

A
  • aceullar = not cells
  • nucleic acids surrounded by protein
  • not alive
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48
Q

give examples of viruses

A

HIV, causes AIDS
influenza, causes the flu
rhinoviruses, causes colds

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49
Q

how do viruses enter the body

A

invade and reproduce inside the cells of organisms

the cells they invade and reproduce in are called HOST CELLS

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50
Q

name the features of the basic structure of a virus

A

core of genetic material, either DNA or RNA (the nucleic acid)

attachment proteins

capsid/protein coat

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51
Q

describe the size of a virus

A

even smaller than bacteria

0.1 hm across

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52
Q

what is the calculation for magnification

A

magnification = size of image / size of real object

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53
Q

what is resolution

A

how well a microscope can distinguish between 2 points that are close together

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54
Q

describe the functions of a light microscope

A
  • use light to form an image
  • max resolution : 0.2 hm
  • cant use a microscope to see organelles smaller than 0.2 hm : ribosomes, both ER, lysosomes
  • may be able to see mitochondria, but not in perfect detail
  • can see nucleus
  • max magnification : x1500
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55
Q

describe the functions of an electron microscope

A
  • use electrons to form an image
  • have a higher resolution than optical microscopes, therefore gives a more detailed image
  • max resolution : 0.0002 hm
  • max magnification : x1500000
  • produce black and white images, but this can be turned into coloured by a computer
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56
Q

what are the 2 types of electron microscope

A

transmission electron microscope - TEM

scanning electron microscope - SEM

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57
Q

describe the function of TEM’s

A
  • use electromagnets to focus a beam of electrons, which is then transmitted through the specimen
  • denser parts of the specimen absorb more electrons and therefore those parts look darker on the image produced
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58
Q

describe the function of SEM’s

A
  • scan a beam of electrons across the specimen
  • knocks off electrons from the specimen, these are gathered in a cathode ray tube to form an image
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59
Q

name the pros of using a TEM

A
  • gives high resolution images, so shows small objects
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60
Q

name the cons of using a TEM

A
  • can be only used on thin specimens
  • can only be used on non-living specimens
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61
Q

name the pros of using a SEM

A
  • can be used on thick specimens
  • can produce 3D images
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62
Q

name the cons of using a SEM

A
  • gives lower resolution than images from TEMs
  • can only be used on non-living specimens
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63
Q

name the steps involved in preparing a microscope slide

A
  • start by pipetting a small drop of water onto the centre of the slide
  • use tweezers to place a thin section of the specimen on top of the water drop
  • add a drop of stain, used to highlight objects in a cell
  • add the cover slip, do this by standing the slip upright on the side next to the water droplet and then carefully tilt and lower it so it covers the specimen
  • when trying to add the cover slip, try not to get any air bubbles underneath as they obstruct the view of the specimen
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64
Q

give examples of stains and what objects they highlight

A

eosin - makes cytoplasm show

iodine in potassium iodide solution - used to stain starch grains in plant cells

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65
Q

describe microscope artefacts

A

they are things that you can see down at the microscope, they are not a part of the cell/speciment looked at

usually made during the preparation of the specimen and should not be there

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66
Q

give examples of microscope artefacts

A
  • dust
  • air bubbles
  • fingerprints
  • inaccuracies caused by squashing and staining the sample
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67
Q

which microscope are artefacts most common in and why

A

electron micrographs

because specimens need a lot of preparation before you can view them under a microscope

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68
Q

how did the first scientists differentiate between artefacts and organelles, using electron microscopes

A

by repeatedly preparing specimens in different ways

if an object could be seen with one preparation technique, but not another, it was more likely to be an artefact than an organelle

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69
Q

describe the homogenisation step of cell fractionation

A
  • homogenisation = breaking up the cells
  • can be done in different ways, ex - vibrating the cells OR grinding up the cells in a blender
  • this breaks up the plasma membrane and releases the organelles into solution
  • the solution must be kept ice cold : reduces activity of enzymes which break down organelles
  • solution must be isotonic : should have the same concentration of chemicals as the cells being broken down BECAUSE it prevents damage to organelles through osmosis
  • solution must be buffered : to maintain pH
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70
Q

describe the filtration step of cell fractionation

A
  • involves getting rid of the big bits
  • homogenised cell solution is filtered through a gauze to separate any large cell debris, ex connective tissue, from the organelles
  • organelles are much smaller than the debris, so they pass through the gauze
71
Q

describe the ultracentrifugation step of cell fractionation

A
  • involves separating the organelles
  • cell fragments are poured into a tube
  • tube is put into a centrifuge, a machine that separates material by spinning
  • initially, it is spun at a low speed
  • the heaviest organelles, like nuclei, get flung to the bottom of the tube by the centrifuge : these form a thick sediment at the bottom called the PELLET
  • the SUPERNATANT contains the rest of the organelles suspended in the fluid
  • the supernatant is drained off and poured into another tube and spun in the centrifuge at a higher speed
  • heaviest organelles form a pellet at the bottom of the tube
  • the supernatant containing the rest of the organelles are drained off and poured into another tube and spun at an even higher speed
  • this process continues to repeat at a higher and higher until all organelles are separated
  • Mach time the pellet at the bottom is made of lighter and lighter organelles
  • order of organelles being separated : nuclei, mitochondria, lysosomes, ER, ribosomes
    order of organelles being separated in plants : nuclei, chloroplasts, mitochondria, lysosomes, ER, ribosomes
72
Q

why do we undergo cell division

A
  • for growth and replacement of damaged tissue
73
Q

what is the name of cell division that produces 2 genetically identical daughter cells

A

mitosis

74
Q

do all the cells in a multicellular organisms keep their ability to divide

A

no

75
Q

the cells that are available to divide, what process do they follow

A

the cell cycle

76
Q

what is the end product of the cell cycle

A

2 genetically daughter cells are produced

77
Q

name the phases in the interphase

A

gap phase 1/ G1
synthesis
gap phase 2/ G2

78
Q

describe what happens in gap phase 1

A
  • the cell grows
  • new organelles and proteins are made
79
Q

describe what happens in the synthesis phase

A
  • cell replicates its DNA
  • cell is ready to divide by mitosis
80
Q

describe what happens in gap phase 2

A
  • cell keeps growing
  • proteins needed for cell division are made
81
Q

what is the other part of the cell cycle

A

mitosis

82
Q

describe interphase

A
  • cell carries out normal functions, but also prepares to double its genetic content
  • cells DNA is unravelled and replicated = genetic content is doubled
  • organelles are replicated, so there are spare ones
  • ATP content s increased, as ATP provides the energy for cell division to take place
83
Q

what are the 2 types of cell division

A

mitosis AND meiosis

84
Q

describe the basics of the process of mitosis as a whole

A
  • form of cell division that occurs during the cell cycle
  • parent cell divides to produce 2 genetically identical daughter cells
  • needed for the growth of multicellular organisms AND to repair damaged tissues
  • actually one continous process, but its described as being split up into prophase, metaphase, anaphase and telophase PMAT
85
Q

describe the structure of chromosomes in mitosis

A
  • made of 2 strands joined together in the middle by a CENTROMERE
  • one strand = chromatid
  • 2 strands on the same chromosome = sister chromatid
86
Q

describe the what happens in prophase

A
  • chromosomes condense = get shorter + fatter
  • centrioles = tiny bundles of protein, start moving to opposite ends of the cell AND they form a network of protein fibres across the cell called THE SPINDLE
  • nuclear envelope, membrane around the nucleus, breaks down AND chromosomes lie free in the cytoplasm
87
Q

describe the what happens in metaphase

A
  • chromosomes line up along the spindle equator, in the middle of the cell
  • the chromosomes become attached to the spindle by their centromere

metaphase = middle = equator

88
Q

describe the what happens in anaphase

A
  • centromeres divide, separating the sister chromatids
  • spindles contract which pulls the chromatids to opposite poles (ends) of the spindle
  • chromatids appear v shaped

summary - sister chromatids move to opposite poles of the spindle due to the centromeres dividing and spindle contracting

anaphase = ‘aaaaaa’ = sound of sister chromatids separating

89
Q

describe the what happens in telophase

A
  • chromatids reach the opposite poles on the spindle
  • chromatids uncoil and become long and thin again = called chromosomes again
  • nuclear envelope forms around each group of chromosomes = 2 nuclei
  • division of the cytoplasm, cytokinesis, finishes (started in anaphase)
  • now 2 daughter cells that are genetically identical to the original parent cell and to each other
  • mitosis is finished and each daughter cell starts interphase to get ready for another round of mitosis
  • Telophase = cyTokinesis
90
Q

describe how cancer takes place and how that involves mitosis

A
  • mitosis and the cell cycle are controlled by genes and when enough division of cells takes place, they stop
  • if there is a mutation in the gene, the cells can grow out of control AND these cells will keep on dividing to make more and more cells, forming a TUMOUR
  • cancer = a tumour which invades surrounding tissue
91
Q

describe the action of cancer treatments

A
  • some treatments for cancer are designed to control the rate of cell division in tumour cells by disrupting the cell cycle = kills the tumour cells
  • these treatments are unable to differentiate between the tumour cells and the normal cells, so they kill the normal cells that are dividing
  • tumour cells divide more frequently than normal cells, so the treatments are more likely to kill tumour cells
92
Q

give 2 examples of cancer treatments that target the cell cycle

A
  • chemotherapy targets the G1 phase
  • chemo prevents the synthesis of enzymes needed for DNA replication
  • if these aren’t produced, the cell is unable to enter the S phase
  • this disrupts the cell cycle, and the cell kills itself
  • radiation and some drugs are able to damage DNA
  • DNA in the cell is checked for damage at multiple points in the cell cycle
  • if severe damage is detected, the cell will kill itself = preventing further tumour growth
93
Q

describe the function of membranes

A
  • cell membranes are the boundaries of cells
  • all cells are surrounded by membranes
  • in eukaryotic cells, many of the organelles are surrounded by membranes
94
Q

describe the function of cell surface membranes

A
  • surround cells
  • barrier between the cell and its environment, controlling which substances enter and leave the cell
  • they are partially permeable, they let some molecules through but not others
  • substances can move across the cell surface membrane by diffusion, osmosis, active transport
  • sometimes the cell surface membrane is called the plasma membrane
95
Q

describe the function of membrane within cells

A
  • membranes around organelles divide the cell into different compartments = act as barrier between organelle and the cytoplasm
  • also partially permeable and control what substances enter and leave the organelle
96
Q

give examples of membranes within cells and their purpose

A
  • substances needed for respiration, like enzymes, are kept together inside a mitochondrion by the membrane surrounding the mitochondrion
  • RNA leaves the nucleus via the nuclear membrane/nuclear envelope
  • DNA is too large to pass through the partially permeable membrane, so it remains in the nucleus
97
Q

describe the structure of membranes

A
  • basic structure of all cell membranes is pretty much the same
  • they are composed of lipids, mainly phospholipids, proteins and carbohydrates
98
Q

describe the structure of the fluid mosaic model

A
  • 1972 = ‘fluid mosaic model’ suggested to describe the arrangement of molecules in the membrane
  • in the model phospholipid molecules form a continuous double layer - bilayer
  • the bilayer was fluid because the phospholipids are constantly moving
  • proteins are scattered through the bilayer, like tiles in a mosaic
  • include channel and carrier proteins, these allow large molecules and ions to pass through the membrane
  • receptor proteins on the cell surface membrane allow the cell to detect chemicals released from other cells
  • the chemicals signal to the cell to respond in some way, ex : insulin (hormone) binds to receptor proteins on liver cells, which tells the cells to absorb glucose
  • some proteins are able to move sideways through the bilayer, while others are in a fixed position
  • some proteins have a carbohydrate attached = glycoproteins
  • some lipids have a carbohydrate attached = glycolipids
  • cholesterol molecules are also present within the bilayer
99
Q

describe the structure and function of phospholipids

A
  • phospholipids molecules form a barrier to dissolved substances
  • they have a ‘head’ and a ‘tail’
  • head = hydrophilic = attracts water
  • tail = hydrophobic = repels water
  • molecules automatically arrange themselves into a bilayer
  • heads face out towards water on both sides of the membrane
  • centre of the bilayer is hydrophobic so the membrane doesn’t allow water soluble substances, ex - ions and polar molecules, to diffuse through
  • small, non polar substances, ex - carbon dioxide, and water can diffuse through the membrane
100
Q

describe the structure and function of cholesterol

A
  • gives membrane stability
  • type of lipid that is present in all cell membranes, except bacterial cell membranes
  • fits between the phospholipids
  • binds to the hydrophobic tails of the phospholipids, causing them to pack more closely together
  • restricts the movement of the phospholipids, making the membrane less fluid and more rigid
  • cholesterol helps to maintain the shape of animal cells (as they dont have cell walls)
  • important for cells that aren’t supported by other cells, ex - red blood cells which float free in the blood
  • also has hydrophobic regions, so its able to create a further barrier to polar substances moving through the membrane
101
Q

are cell membranes affected by temperature or not

A

yes, they are

affects how much the phospholipids in the bilayer can move = affects membrane structure and permeability

102
Q

how do temperatures below 0 degrees celsius affect the membrane

A
  • phospholipids dont have much energy, so they cant move much
  • packed closely together and the membrane is rigid
  • channel and carrier proteins in the membrane denature = increases the permeability of the membrane
  • ice crystals may form and pierce the membrane, making it highly permeable when it thaws
103
Q

how do temperatures between 0-45 degrees celsius affect the membrane

A
  • phospholipids can move around and aren’t as tightly packed together
  • membrane = partially permeable
  • as temp increases, the phospholipids move more as they have more energy = increases permeability of the membrane
104
Q

how do temperatures above 45 degrees celsius affect the membrane

A
  • phospholipid bilayer starts to melt = membrane becomes more permeable
  • water in cell expands, putting pressure on the membrane
  • channel and carrier proteins in the membrane denature = cant control what enters or leaves the cell = increasing permeability of the membrane
105
Q

what are the 2 types of diffusion

A

simple diffusion and facilitated diffusion

106
Q

define diffusion

A

the net movement of particles (molecules or ions) from an area of HIGHER concentration to LOWER concentration

107
Q

do molecules diffuse both ways and what does this have to do with the net movement

A

they do move both ways

the net movement will be to the area lower concentration

108
Q

when does diffusion stop

A

until the particles are evenly distributed throughout the liquid or gas

109
Q

what is the concentration gradient

A

the path from an area of higher concentration to an area of lower concentration

110
Q

do particles diffuse up or down a concentration gradient

A

down the concentration gradient

111
Q

is diffusion a passive or active process

A

it is a passive process, meaning no energy is required for it to take place

112
Q

can particles diffuse across a cell membrane or not

A

they can, as long as they can move freely through the membrane

113
Q

define simple diffusion

A

when molecules can diffuse directly through a cell membrane

114
Q

give an example of simple diffusion

A

oxygen and carbon dioxide can diffuse easily through cell membranes

they can do this because they are SMALL and NON POLAR

small = so they can pass through spaces between the phospholipids

non polar = makes them SOLUBLE in lipids, so they can DISSOLVE in the hydrophobic bilayer

115
Q

what are the factors affecting the rate of diffusion

A
  • the concentration gradient
  • the thickness of the exchange surface
  • the surface area
116
Q

how does the concentration gradient affect the rate of diffusion

A

higher the conc gradient = faster the rate of diffusion

as diffusion takes place, the diff in conc between the 2 sides of the membrane decreases UNTIL it reaches an equilibrium = diffusion slows down over time

117
Q

how does the thickness of the exchange surface affect the rate of diffusion

A

the thinner the exchange surface = the faster the rate of diffusion

the thiner the exchange surface = the shorter the distance the particles have to travel

118
Q

how does the surface area affect the rate of diffusion

A

the larger the surface area = the faster the rate of diffusion

ex of SA would be the SA of the cell surface membrane

119
Q

give an example of how specialised cells are adapted to increase their rate of diffusion

A

ex of specialised cells - epithelial cells in the small intestine

they have MICROVILLI, which are projections formed by the cell surface membrane folding up on itself = increases the cells SURFACE AREA

larger SA = more particles can be exchanged in the same amount of time = increases rate of diffusion

120
Q

why does facilitated diffusion take place

A

as some larger molecules would diffuse very slowly through the phospholipid bilayer as they are very big in size

charged particles would diffuse slowly because the centre of the bilayer is HYDROPHOBIC and they WATER SOLUBLE

121
Q

give examples of molecules that are too large to undergo simple diffusion easily

A
  • amino acids
  • glucose
122
Q

give examples of molecules that are charged and therefore unable to undergo simple diffusion easily

A
  • ions
  • polar molecules
123
Q

what is used to speed up the diffusion for large and polar molecules in FACILITATED DIFFUSION

A

the large or charged particles diffuse through CARRIER or CHANNEL proteins in the cell membrane = facilitated diffusion

124
Q

what are the similarities between simple and facilitated diffusion in terms of concentration gradient and if energy is required for the process

A

moves particles down a concentration gradient = from a higher to lower concentration

it is a passive process = doesn’t require energy

125
Q

what type of protein is used to move large molecules across the membrane

A

a carrier protein

126
Q

describe the action of a carrier protein when moving a large molecule across a membrane

A
  • moves large molecules across a membrane, down their concentration gradient
  • a large molecule attaches to a carrier protein in the membrane
  • the protein changes shape
  • the molecule is released on the opposite side of the membrane
127
Q

what type of protein is used to move polar molecules/ charged particles across the membrane

A

channel proteins

128
Q

describe the action of a channel protein when moving a charged molecule across a membrane

A

the channel proteins form pores in the membrane for the charged particles to diffuse through/ down their concentration gradient

different channel proteins facilitate the diffusion of different charged particles

129
Q

name the factors that affect the rate of facilitated diffusion

A
  • the concentration gradient
  • the number of channel or carrier proteins
130
Q

how does the concentration gradient affect the rate of facilitated diffusion

A

the higher the conc gradient = the faster the rate of facilitated diffusion, until a certain point

when equilibrium is reached, the rate of facilitated diffusion will level off

131
Q

how does the number of channel or carrier proteins affect the rate of facilitated diffusion

A

once all the proteins are in use, facilitated diffusion cant happen any faster EVEN if the concentration gradient is increased

the higher the number of channel or carrier proteins in the cell membrane, the faster the rate of facilitated diffusion

132
Q

give an example of channel proteins that allow the diffusion of water

A

aquaporins

they are special channel proteins that allow the facilitated diffusion of water through cell membranes

some kidney cells are adapted to have lots of aquaporins

the aquaporins allow the cells to reabsorb a lot of the water that would have otherwise been excreted by the body, through urination

133
Q

define osmosis

A

the diffusion of water molecules across a partially permeable membrane from an area of higher WP to an area of lower WP

134
Q

define WP/water potential

A

the likelihood/potential of water molecules to diffuse out to into a solution

135
Q

can water molecules and large solutes molecules diffuse easily through the cell membrane

A

water molecules can because they are small and can diffuse easily through the cell membrane

large solutes are unable to

136
Q

what is the WP of pure water

A

0

137
Q

what is the effect on WP when you add solutes to pure water

A

it lowers the WP

138
Q

generally, what would the WP of any solution be

A

negative

139
Q

what does it mean if the WP for a solution is very negative

A

it means the solution contains a high concentration of solutes

more negative the WP = stronger the concentration of solutes in the solution

140
Q

define isotonic

A

if 2 solutions have the same WP

141
Q

describe how cells in an isotonic solution behave

A

they wont lose or gain any water , there is no net movement of water molecules BECAUSE there is no net movement of water molecules BECAUSE there is NO difference in WP between the CELL and the SURROUNDING SOLUTION

142
Q

define hypotonic

A

solutions with a higher WP compared with the inside of the cell

143
Q

describe how cells in an hypotonic solution behave

A

it will swell as water moves into the cell via osmosis

144
Q

define hypertonic

A

a solution that has a lower WP than the cell

145
Q

describe how cells in an hypertonic solution behave

A

the cell may shrink as water moves of the cell via osmosis

146
Q

name the factors that affect the rate of osmosis

A
  • WP gradient
  • thickness of the exchange surface
  • SA of the exchange surface
147
Q

how does the WP gradient affect the rate of osmosis

A

the higher the WP gradient, the faster the rate of osmosis

as osmosis takes place, the difference in WP on either side of the membrane decreases, so the rate of osmosis levels off over time

148
Q

how does the thickness of the exchange surface affect the rate of osmosis

A

the thinner the exchange surface, the faster the rate of osmosis

149
Q

how does the SA of the exchange surface affect the rate of osmosis

A

the larger the SA, the faster the rate of osmosis

150
Q

name the basics of active transport

A
  • active process = uses energy to move molecules and ions across plasma membranes
  • usually against the conc gradient
  • carrier proteins and co-transporters are involved in active transport
151
Q

describe the role of carrier proteins in active transport

A
  • a molecule attaches to the carrier protein
  • protein changes shape, which moves the molecule across the membrane = releases it on the other side
152
Q

describe the differences between AT and FD

A
  • AT moves solutes from a low concentration to a high concentration, compared to FD which always moves from a high to a low concentration
  • AT requires energy while FD doesn’t
153
Q

describe the process of AT with carrier proteins, specifically with ATP

A
  • ATP is a common source of energy in the cell and its needed for AT
  • ATP undergoes a hydrolysis reaction, splitting into ADP and Pi = releases energy so solutes can be transported
154
Q

describe the role of co-transporters in AT

A
  • co-transporters are a type of carrier protein
  • they bind 2 molecules at the same time
  • the conc gradient of one of the molecules is used to move the other molecule against its own conc gradient, ex : the co-transport of glucose
155
Q

describe the co-transport and absorption of glucose

A
  • glucose is absorbed into the bloodstream in the small intestine
  • in the mammalian ileum, final part of a mammals small intestine, the conc of glucose is too low for glucose to diffuse out INTO the blood
  • glucose is absorbed from the lumen (middle of the ileum) by co-transport
  • step 1
  • Na+ ions are actively transported out of the epithelial cells in the ileum INTO the blood, by the sodium potassium pump
  • creates a conc gradient, now a HIGHER conc of sodium ions in the LUMEN than in the CELL
  • step 2
  • causes Na+ ions to diffuse from the LUMEN into the EPITHELIAL CELL, down the concentration gradient via the sodium-glucose co transporter proteins
  • the co transported carries glucose into the cell along with Na+
  • results in the concentration of glucose in the cell increasing
  • step 3
  • glucose diffuses out of the cell, into the BLOOD, down its concentration gradient through a protein channel by facilitated diffusion
156
Q

name the factors affecting the rate of active transport

A
  • speed of individual carrier proteins
  • number of carrier proteins present
  • rate of respiration in the cell and availability of ATP
157
Q

how does the speed of individual carrier proteins affect the rate of AT

A

the faster they work, the faster the rate of AT

158
Q

how does the number of carrier proteins present affect the rate of AT

A

the more proteins there are, the faster the rate of active transport

159
Q

how does the rate of respiration in the cell and availability of ATP affect the rate of AT

A

if respiration is inhibited, AT can’t take place

respiration produces ATP, which is needed for AT as AT is an active process

160
Q

define antigen

A
  • molecules, usually proteins, that can generate an immune response when detected the body
  • usually found on the surface of cells, including all your body cells
  • antigens that aren’t normally found in the body are referred to as ‘foreign antigens’ - these antigens are the ones the immune system usually responds to
  • antigens allow the immune system : pathogens, abnormal body cells, toxins and cell from other individuals of the same species
161
Q

describe the role of antigens on the cell surface membrane

A
  • cell surface membrane contains proteins that act as antigens
  • these antigens allow the immune system to tell the difference between the bodys healthy cells (self cells) and ‘foreign invaders’
162
Q

what are pathogens

A
  • organisms that cause disease
  • all pathogens have antigens on their surface - these are identified as foreign by cells in the immune system and this leads to the immune response to destroy the pathogen
163
Q

give examples of pathogens

A
  • bacteria
  • viruses
  • fungi
164
Q

what are abnormal body cells

A
  • cancerous or pathogen infected cells
  • have abnormal antigens on their surface, these trigger an immune response
165
Q

what are toxins

A
  • posions
  • molecules, NOT cells
  • some toxins are produced by bacteria
  • ex : clostridium botulinum (bacteria) releases a protein toxin which affects the nervous system, causing the system of botulism
  • the immune system is able to respond to toxins and the pathogens that release them
166
Q

what are cells from other individuals of the same species

A
  • when you receive cells from another person, those cells will have some different antigens to your own cells
  • this would be done through an organ transplant or blood transfusion
  • the foreign antigens trigger an immune response, this leads to the rejection of transplanted organs if the drugs aren’t taken to suppress the recipients immune system (anti-rejection meds)
  • for blood transfusions, the most important antigens are the ABO blood group antigens
  • if the blood contains A or B antigens that aren’t recognised by the recipients immune system, they WILL generate a immune response
167
Q

in which case will cells from other individuals of the same species NOT have different antigens

A

if the donor is genetically identical to you

168
Q

what is the first step of the immune response

A

phagocytosis

169
Q

what is a phagocyte

A
  • a type of white blood cell
  • it carries out phagocytosis, the engulfment of pathogens
  • found in the blood and in tissues
  • they are the first cells to respond to an immune system trigger in the body
170
Q

give an example of a phagocyte

A

a macrophage

171
Q

describe how phagocytosis takes place

A
  • a phagocyte recognises the foreign antigen on a pathogen
  • cytoplasm of the phagocyte moves around the pathogen, engulfing it
  • the pathogen is now contained in a phagocytic vacuole (bubble) in the cytoplasm of the phagocyte
  • a lysosome, an organelle which contains lysozymes, fuses with the phagocytic vacuole
  • the lysozymes break down the pathogen
  • the phagocyte presents the pathogens antigens, it sticks the antigens on its surface to activate other immune system cells
  • the phagocyte is now acting an antigen presenting cell
172
Q

what is a t cell

A
  • also called a t lymphocyte
  • another type of white blood cell
  • has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes : this activates the t cell
  • different types of t cells respond in different ways
173
Q
A

AS BIO - BIOLOGICAL MOLECULES (2 decks)

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