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THE MITOCHONDRIA IS THE POWERHOUSE OF THE CELL > 1 — cell biology > Flashcards

1 — cell biology Flashcards

1
Q

explain how changes to the cell cycle can result in tumour formation (4)

A
  • cell cycle is repeated sequence of cytokinesis, interphase, mitosis I to form new cells which repeat the cycle
  • cyclins control the cycle/ ensure the cell moves on to the next stage of the cycle when it is appropriate
  • extra cells produced when they are needed
  • tumour formation is the mix up of controlled cell division
  • repeated mitosis
  • due to mutations in oncogenes
  • carcinogens cause mutations
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2
Q

outline the sequence of events that occurs during mitosis (5)

A
  • supercoiling of chromosomes
  • breakup of nuclear membrane
  • growth of spindle fibres
  • attachment of spindle fibres to centromeres
  • chromosomes line up at the equator
  • division of centromeres
  • sister chromatids move to opposite poles
  • reformation of nuclear membranes around chromosomes at each pole
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3
Q

distinguish between the structure of chromosomes in prokaryotes and eukaryotes (2)

A
  • prokaryotes usually have one chromosome while eukaryotes have numerous chromosomes
  • prokaryotes have a circular chromosome while eukaryotes have linear ones
  • eukaryotes’ chromosomes are associated its histones/ proteins but prokaryotes/ eubacteria have naked dna
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4
Q

explain cairn’s technique to measure the length of the DNA molecule (2)

A
  • cairns grew e. coli in radioactive thymine containing tritium
  • contents of cell put of photographic film
    measured the length of the DNA molecule and photographed it
  • could show the new strands were all labelled with thymine
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5
Q

outline reasons for the therapeutic use of stem cells (3)

A
  • unspecialised stem cells can divide along different pathways
  • stem cells are accessible as they come from the umbilical cord blood
  • stem cells can regenerate damaged tissues in people
  • e.g. leukaemia — hematopoietic stem cells (HSC) are harvested from the bone marrow, chemotherapy and radiotherapy is used to destroy the diseased white blood cells, new white blood cells need to be replaced with healthy cells, HSC are transplanted back into the bone marrow, HSC differentiate to form new healthy white blood cells
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6
Q

outline the significance of surface area to volume ratio in the limitation of cell size (4)

A
  • surface area of the cell affects the rate of material exchange
  • when the cell increases in size, so does its chemical activity
  • more substances need to be taken in and more waste products need to be excreted
  • as the volume of the cell increases, so does the surface area, however not to the same extent
    metabolic rate will exceed the rate of exchange
  • cell divide when maximum size is reached
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7
Q

describe transport across cell membrane by osmosis (4)

A
  • form of diffusion
  • osmosis is the movement of water molecules
    across a semi permeable membrane
  • from a region of low solute concentration to a region of high solute concentration
  • passive transport mechanism
  • channel proteins/ aquaporins are used
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8
Q

identify structures in eukaryotic cells that are not present in prokaryotic cells (4)

A
  • nucleus/ nuclear membrane
  • membrane bound organelles
  • mitochondria
  • rough ER
  • lysosomes
  • large ribosomes
  • linear chromosomes
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9
Q

outline how depolarisation of the membrane of an axon occurs (2)

A
  • local depolarisation causes voltage rate channels to open
  • altering membrane permeability to sodium ions, Na+ diffuses into the cytoplasm
  • membrane potential changes from negative to positive
  • a threshold potential is reached an an action potential is generated
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10
Q

outline the structures in prokaryotic cells that are not present in a human cell (3)

A
  • cell wall
  • flagella
  • 70s ribosomes
  • nucleotide
  • plasmids
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11
Q

state 2 structural similarities between mitochondria and chloroplasts (2)

A
  • 70s ribosomes
  • double membrane
  • electron transport chains
  • enzymes in stroma and matrix
  • large area of internal membrane — cristae and thylakoids
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12
Q

compare and contrast mitochondria and chloroplasts in terms of the substrates they use and the products they produce

A
  • ATP produced by both
  • oxygen produced by chloroplasts and used by mitochondria
  • carbon dioxide produced by mitochondria and used by chloroplasts
  • carbon compounds built up in chloroplast and broken down in mitochondria
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13
Q

outline cell theory (2)

A
  • cells can only arise from preexisting cells
  • living organisms are composed of cells
  • organisms consisting of only 1 cell carry out all functions of life in that cell
  • although most organisms conform to cell theory, there are exceptions
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14
Q

outline the functions of rough endoplasmic reticulum and golgi apparatus (3)

A
  • ribosomes on RER synthesise proteins
  • proteins from RER for secretion
  • golgi alters proteins
  • vesicles budded off golgi transport proteins to plasma membrane
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15
Q

explain how hydrophobic and hydrophilic properties contribute to the arrangement of molecules in a membrane (7)

A
  • hydrophilic is attracted to water and hydrophilic is not attracted to water
  • hydrophilic phosphate and hydrophobic hydrocarbon in phospholipids
    phospholipid bilayer in water
  • hydrophilic heads face outwards
  • hydrophobic tails face inwards
  • cholesterol is mainly hydrophobic so its located among phospholipids
  • some amino acids are hydrophilic and some are hydrophobic
  • hydrophobic amino acids in phospholipid bilayer
    hydrophilic amino acids are on the membrane surface
  • integral proteins are embedded in membranes due to hydrophobic properties
  • peripheral proteins are on the membrane surface due to being entirely hydrophilic
  • pore of channel proteins is hydrophilic
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16
Q

outline the reasons for differences between the proteomes of cells within a multicellular organism (4)

A
  • all the genome is the same in all the cells of an organism
  • the genome instructs the production of proteins
  • the proteome is all the proteins produced by a cell
  • the proteome varies with the function of the cell
    specific genes are expressed
  • according to a required function
17
Q

discuss the cell theory and its limitations (7)

A
  • cell theory is the accepted explanation of life
  • organisms are composed of one or more cells
  • cells are the basic units of life
  • cells can only come from pre-existing cells
  • spontaneous generation of life has been disproven
  • striated muscle cells contain many nuclei while most eukaryotic cells have one nucleus
  • giant algae have complex single cell structure
    aseptate fungal hyphae are tube like structures contain no cell membranes between the many nuclei
  • viruses have some characteristics of living organisms but are not cells
  • if all cells come from pre-existing cells, where did the first one come from
18
Q

discuss alternative models of membrane structure including evidence for or against each model (8)

A
  • early evidence showed membranes are partially permeable and organic solvents penetrate faster than water
  • suggests they have non polar regions
  • chemical analysis showed membranes consist mainly of proteins and lipids
  • layer of phospholipids spread over water, orientate themselves into monolayer with non polar tails out of water and polar heads in water surface
  • when shaken with water form micelles with tails inwards away from water
  • davison danielle model proposed phospholipid bilayer coated with protein molecules on both surfaces
  • evidence from electron microscopy supported davison danielle model
  • three layered structure
  • model could not account for hydrophobic proteins
  • fluorescent labelling later used to investigate membrane structure
  • led to fluid mosaic model of protein molecules floating in fluid lipid bilayer
  • shows particles partially and sometimes right through lipid bilayer
  • indicates peripheral and integral proteins present
19
Q

describe the processes involved in absorbing different nutrients across the membrane of villus epithelium cells lining the small intestine (4)

A
  • simple diffusion of nutrients along a concentration gradient
  • e.g. fatty acids
  • facilitated diffusion of nutrients involves movement through channel proteins
  • e.g. fructose
  • active transport of nutrients against a concentration gradient
  • e.g. ions
  • endocytosis
  • e.g. cholesterol in lipoprotein particles
20
Q

describe the origin of eukaryotic cells according to the endosymbiotic theory (4)

A
  • mitochondria and chloroplasts are similar to prokaryotes
  • host cell took in another cell by endocytosis
    but did not digest the cell
  • chloroplasts and mitochondria were once independent organisms
  • dna in chloroplast/ mitochondria
  • division of chloroplast/ mitochondria
  • double membrane around chloroplast/ mitochondria
  • 70s ribosomes in chloroplast/ mitochondria
21
Q

outline mitosis (4)

A
  • mitosis is the division of a nucleus to produce two genetically identical daughter nuclei
  • consists of four phases — prophase, metaphase, anaphase, telophase
  • cytokinesis occurs after mitosis
  • interphase is the metabolically active phase between cell divisons
  • the interphase consists of the s phase, G1 and G2
  • DNA replicates in S phase
22
Q

describe how pasteur’s experiments provided convincing evidence to falsify the concept of spontaneous generation

A
  • spontaneous generation is life appearing from nothing
  • broth in flasks
  • broth sterilised to kill microbes
  • no clouding in flasks of boiled broth
  • after necks of flasks snapped, boiled broth became cloudy
  • because microbes from the air contaminated the boiled broth
  • curved necks allowed exposure to air but prevented microbes
23
Q

discuss the advantages and disadvantages of the use of adult stem cells (3)

A
  • can differentiate
  • can be used to repair tissues
  • fewer ethical objections than embryonic stem cells
  • adult source not killed
  • adults can give consent for use of their stem cells
  • no rejection problems
  • less chance of cancer developing
  • most tissues in adults contain some stem cells
  • difficult to find in adult body
  • very few available
  • differentiates into fewer cell types than embryonic cells
24
Q

explain how the cell cycle is controlled (4)

A
  • cell cycle is a sequence of stages
  • controlled by cyclins
  • levels of cyclins fluctuate during the cell cycle
    conditions inside as well as outside the cell affect regulation
  • four cyclins to enter different stages of the cell cycle
  • cyclin bind to kinases and activate them
  • kinases phosphorylate other proteins
  • phosphorylated proteins perform specific functions in the cell cycle
25
Q

outline the effects of putting plant tissue in a hypertonic solution (4)

A
  • hypertonic solution has more solutes
  • water moves out of the cells
  • water moves from lower solute concentration to higher solute concentration
  • pressure inside cell drops
  • volume of cytoplasm drops
26
Q

describe the organelles and other structures in animal cells that are visible in electron micrographs (7)

A
  • plasma membrane is thin layer forming outer boundary
  • cytoplasm fills space between membrane and nucleus
  • nucleus enclosed in nuclear membrane
    chromosomes inside the nucleus
  • mitochondria with cristae
  • 80s ribosomes seen as dots free in cytoplasm
  • endoplasmic reticulum is a network interconnected tubes
  • golgi apparatus with stack of sacs
  • vesicles which are small membrane sacs
  • lysosome which contains enzymes
27
Q

explain how vesicles are used by cells to move materials (5)

A
  • fluidity of membranes allows vesicles to bud off membranes
  • materials taken into cells by endocytosis
  • e.g. phagocytes engulf pathogens
  • materials released from cells by
  • e.g. neurotransmitter released at synapses
  • movement or transport of materials within cells
  • e.g. movement of proteins from the rough ER to the golgi
28
Q

outline the processes occurring during interphase in the cell cycle (4)

A
  • growth in cell size
  • division of mitochondria/ production of more organelles
  • replication of DNA
  • transcription of genes
  • protein synthesis
  • cell respiration
29
Q

explain how plant cells originated by endosymbiosis (5)

A
  • host cell toon in bacteria
  • taken in by endocytosis
  • not digested
  • mutualistic relationship
  • aerobically respiring bacterium engulfed
  • evolved into mitochondria
  • photosynthetic bacterium engulfed
  • evolved into chloroplasts
  • chloroplasts have double membrane due to endocytosis

THE MITOCHONDRIA IS THE POWERHOUSE OF THE CELL (12 decks)

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