2A & 3A Cells and Transport Flashcards
name 3 similarities and 3 differences between prokaryotic and eukaryotic cells
similarities:
- both have ribosomes
- both have cell surface (plasma) membranes
- both have cytoplasm
differences:
- prokaryotic DNA in plasmids and cytoplasm whereas eukaryotic DNA in nucleus
- eukaryotes have membrane-bound organelles whereas prokaryotes do not
- eukaryotes are larger
- prokaryotes have plasmids
magnification
size of image / size of real object
tissue
- group of similar cells
- that are specially adapted
- to work together to carry out particular function
what kind of cell does MITOSIS produce
genetically identical daughter cells
what is mitosis needed for?
- growth
- repairing damaged tissues
- asexual reproduction
what does the cell cycle consist of?
- INTERPHASE -> period of cell growth and DNA replication (G1 -> SYNTHESIS ->G2)
- MITOSIS
what happens during INTERPHASE?
- G1 -> cell grows and new proteins made
- SYNTHESIS -> cell unravels and replicates its DNA ready to divide by mitosis
- G2 -> cell keeps growing and proteins needed for cell division are made
-> ATP content increased
cell’s organelles also replicated so to has spares
order of stages in mitosis
P ussy like BMAT but for pussies
M edical
A dmissions
T est
- PROPHASE
- METAPHASE
- ANAPHASE
- TELOPHASE
what happens in PROPHASE?
- chromosomes condense -> get shorter and fatter
- centrioles (bundles of proteins) moving to opposite ends of cell -> makes network of protein fibres = SPINDLE
- nuclear envelope breaks down and chromosomes lie free in cytoplasm
what happens in METAPHASE?
- chromosomes (each with 2 chromatids) line up along middle of cell
- and become attached to spindle by centromere
what happens in ANAPHASE?
- centromeres divide -> separating each pair of sister chromatids
- spindles contract -> pulling sister chromatids to opposite ends of spindle
- makes chromatids appear v-shaped
what happens in TELOPHASE?
- chromatids reach opposite ends on spindle
- uncoil and become long and thin (chromosomes again!)
- nuclear envelope forms around each group of chromosomes so there are 2 nuclei
- cytoplasm divides -> now 2 genetically identical daughter cells!
what is cholesterol?
component of cell membrane that allows whole thing to be fluid / rigid depending on temp
diffusion (passive)
net movement of particles from area of high conc.->low. conc.
passive process -> no ATP needed
active transport
movement of molecules / ions across SEMI-PERMEABLE MEMBRANE from low->high conc. using ATP and carrier proteins
receptors
molecules (could be proteins) in cell membrane that recognise other molecules that can enter cell
glycoproteins
act as cell receptor on surface membrane
functions of proteins in cell membrane?
transport
communication
intrinsic proteins
= integral
- embedded in MEMBRANE
- with PRECISE ARRANGEMENT DETERMINED by …
- their HYDROPHILIC and HYDROPHOBIC regions
extrinsic proteins
= peripheral
found on the outer or inner surface of the membrane
why is cholesterol important in cell surface membrane?
increases fluidity of membrane at low temp. stops it becoming too RIGID
-> as cholesterol stops phospholipid tails packing too closely together
how does relationship between cholesterol and phospholipid tails affect cell membrane?
interactions stabilise cell membrane at higher temp. by stopping membrane from becoming too FLUID
state 2 factors that affect permeability of cell membranes
- temp
- alcohol conc (ethanol)
how is beetroot used to measure permeability of cell membranes?
(3 marks)
high permeability = more red (betalains) pigment leaks out into surrounding sol in given amount of time
colorimeter used to determine absorbance hence conc of pigment
outline procedure to investigate effect of temp on permeability of cell membrane
- cut beetroot into 8 identical cubes with scalpel (no skin) -> put in distilled water overnight to remove any dye released when cut
- wash and blot dry with filter paper
- place each cube in 8 diff test tubes with 10cm³ distilled water
- place each test tube into 8 diff water baths ranging from 0-70 ℃. leave for 30 mins
- filter each sol out into cuvette and read absorbance using colorimeter
what are the safety hazards in testing effect of ethanol on membrane permeability?
- ethanol is an IRRITANT and FLAMMABLE
-> keep away from naked flames and wear goggles - keep sharp scalpel away from fingers
- handle hot water with care
explain effect of temp on membrane permeabilty
(3 marks)
-
increasing temp = increase in membrane permeability
-> high temp DENATURE some membrane proteins
-> creates gaps in membrane for molecules to pass through -
decreasing temp = decreases Eᵏ of phospholipids -> so they pack tighter together
-> restricts movement of molecules across membrane
what is the effect of increasing ethanol conc on membrane permeability?
increasing ethanol conc = increased membrane permeability
-> as ethanol ruptures membrane to form gaps for molecules to pass through
how does low s.a : vol ratio affect transport of molecules?
low s.a : vol ratio = further distance molecules need to travel to reach all parts of organism
- diffusion alone isnt sufficient so SPECIALISED GAS EXCH. SURFACES required
name 3 features of efficient gas exchange surface
- large s.a -> eg folded membranes in mitochondria
- short distance -> walls of capillaries
- steep conc grad maintained by BLOOD SUPPLY / VENTILATION eg alveoli
what is Ficks Law?
large s.a = larger diff in conc
shorter diffusion distance = faster rate of diffusion
rate of diffusion ∝ ( s.a x conc diff ) ÷ membrane thickness
where in plants can cells undergoing mitosis be found?
meristem tissue at shoot and root tips
what is the mitotic index?
ratio of
cells undergoing mitosis : total no. of cells in sample
outline procedure to prepare root tip slide
(abbrieviated version)
- warm 2 cm³ 1M HCl to 60℃ in water bath
- cut 1-2 cm root tip of garlic and add to HCl -> leave for 5 mins
- remove from HCl and wash with cold distilled water
- dry and place on slide
- macarate with mounted needle to spread out cells
- add 1 drop stain to make chromosomes visible and observe
mitotic index calculation
do q’s on this
no. cells with visible chromosomes
÷
no. cells in sample
state hazards and precautions for reagents in observing stages of mitosis practical
HCl -> corrosive, avoid contact with skin
Toluidine Blue O stain -> irritant, avoid contact with skin
scalpel -> cut away from fingers
why is the root tip placed in hot HCl?
(stages of mitosis practical)
HCl dissolves MIDDLE LAMELLAE in order to break up cellulose cell wall
this allows STAIN to PERMEATE and TIP to be SQUASHED more easily
describe how the lungs are adapted for rapid gas exchange
- lots of alveoli = larger s.a for diffusion to occur across
- alveolar epithelium and capillary epithelium are one cell thick -> short diffusion pathway
- all alveoli have good blood supply from capillaries
-> constantly take away O₂ and bring more CO₂
= maintains conc gradient - breathing in and out refreshes air in alveoli -> keeps conc grad high
organ system
group of different organs that work together to carry out a particular function
osmosis
net movement of free water molecules across partially permeable membrane from area of high to low conc
facilitated diffusion
- diffusion of larger molecules (eg glucose, a.a) and charged particles (ions) via carrier / channel proteins in cell membrane
as these molecules / ions cannot diffuse directly through bilayer
endocytosis
cells taking in substances that are too large to be taken into cell via carrier proteins
- cell surrounds substance with section of its cell membrane
- membrane pinches off to form vesicle inside cell containing ingested substance
exocytosis
movement of substances leaving cell
as some substances (eg. dig enzyme, hormones, lipids) made by cell
- vesicles containing substances pinch off from sacs of golgi apparatus and move towards cell membrane
- vesicles fuse with cell membrane and release contents outside cell
describe how a carrier protein operates
move larger molecules in / out of cell
diff carrier proteins facilitate diffusion of diff molecules
- large molecule attaches to carrier protein in membrane
- protein changes shape …
- … releasing molecule on opposite side of membrabne
describe how a channel protein operates
channel proteins form pores in membrane for charged particles to diffuse through (down conc grad)
which organelles in eukaryotes have double membranes?
- mitochondria
- nucleus (nuclear envelope)
- (chloroplasts) for plants only
describe the nucleus and its function in eukaryotic cells
- large organelle surrounded by nuclear envelope (double membrane) …
- … with pores (gaps) -> allow substances eg RNA to move from nucleus->cytoplasm
- contains chromatin (made from DNA and proteins)
- contains nucleolus -> makes ribosomes
describe the lysosome and its function in eukaryotic cells
round organelle surrounded by membrane
-> contains dig enzymes which can …
- eat invading cells
- eat worn out bits of cell
where are ribosomes in eukaryotic cells and what are they made of?
- cytoplasm
- attached to rER
made of proteins and RNA
NO MEMBRANE
describe the rER and its function in eukaryotic cells
- system of membranes enclosing fluid-filled space
- surface covered in ribosomes
- folds and processes proteins that have been made at ribosomes
describe the sER and its function in eukaryotic cells
- system of membranes enclosing fluid-filled space
- but NO RIBOSOMES
- synthesises and processes lipids
describe the Golgi apparatus and its function in eukaryotic cells
- group of fluid-filled membrane-bound, flattened sacs
- has vesicles at edges of sacs
- processes and packages new lipids and proteins
- makes lysosomes
describe the mitochondria and their function in eukaryotic cells
- double membrane with inner one folded to form cristae
- inside is matrix -> contains enzymes involved in respiration
- site of aerobic respiration -> where ATP produced
describe the centrioles and their function is eukaryotic cells
- small hollow cyclinders made of mictrotubules (tiny protein cyclinders)
- in all animal cells but also some plant cells
- involved in separation of chromosomes during cell division
describe how organelles in eukaryotic cells allow protein transport within cells
- proteins made in ribosomes
- ribosomes on rER make proteins that are excreted / attached to cell membrane
- free ribosomes in cytoplasm make proteins that stay in cytoplasm
- new proteins made at rER are folded and processed (eg. sugar chains added) in rER
- rER packages proteins in vesicles
- then transported to golgi in vesicles
- at golgi: proteins undergo further processing (eg. sugar chains trimmed / more added AND prosthetic groups added eg. iron in haemoglobin)
- proteins enter more vesicles to be transported around cell
-> eg. extracellular enzymes (eg. dig enzymes) move to cell surface to be secreted
describe the DNA in prokaryotic cells
- circular DNA:
->one long coiled up strand (bacterial chromosome in bacteria cell)
-> not attached to any histone proteins
-> floats free in cytoplasm
- plasmids:
-> small loops of DNA
-> contains genes for eg. antibiotic resistance
-> can be passed between prokaryotes
describe mesosomes in prokaryotic cells
inwards folds in plasma membrane
could be used in cellular processes or just artifact in cells
some prokaryotes have pili. describe their function in these cells
help prokaryote stick to other cells
-> used in transfer of genetic material between cells
describe the function of cell wall in prokaryotic cells
supports cell and prevents it changing shape
made from polymer murein (glycoprotein: protein with carb attached)
describe the function of the capsule in prokaryotic (eg. bacterial) cells
made of secreted slime
helps protect bacteria from attack by cells of immune system
organ
group of different tissues that work together to perform a particular function
give one diff between a tissue and an organ
tissues made of one type of cell
organ made of diff tissues
active transport
- uses ATP to move molecules / ions from low->high conc (against conc grad) …
- across plasma membranes
- using carrier proteins
active transport requires ATP.
Describe where this ATP comes from in animals
- ATP produced from respiration
- acts as immediate source of energy in cell
- when ATP is hydrolysed: broken down into ADP + Pi …
- releasing energy …
- which is used to move molecule against conc gradient
suggest what would happen if phospholipid bilayer had no cholesterol
cholesterol controls rigidy/fluidity
too fluid = unstable, cell would burst under osmotic Pa
too rigid = brittle
rate of diffusion
using Ficks Law
Permeability constant x s.a
x (conc difference ÷ thickness of membrane)
