ch1: kili, fili and pili Flashcards
outline the cell theory (2)
living things are composed of 1+ cells
cells are the basic unit of life
cells come from pre-existing cells
outline the therapeutic use of stem cells (5)
stem cells retain their capacity to divide
unspecialised: multi/pluri/totipotent
form a variety of tissues/organs → repair/replace damaged ones
during differentiation: some genes are expressed while some are suppressed
used in medical research: embryonic stem cells can cure Stargardt’s disease
outline the use of human embryonic stem cells to treat Stargardt’s disease (2)
eye genetic disorder
stem cells can differentiate into healthy retinal cells
injecting stem cells into the eye can restore vision in animal and human trials
discuss the advantages and disadvantages of the use of adult stem cells (3)
advantages:
can differentiate: repair/regenerate tissues/organs
fewer ethical objections than with embryonic stem cells
adults can give informed consent for use of their stem cells
adult source is not killed
disadvantages:
difficult to obtain in adult body bc very few available
some adult tissues contain few to none stem cells
adult stem cells differentiate into fewer cell types than embryonic cells
explain the importance of surface area to volume ratio as a factor limiting cell size (7)
V ↑ → ratio of SA to V ↓
rate of substance crossing the membrane depends on SA:
food/oxygen enter
waste leave
larger cell → ↑ metabolic activity
↑ food and oxygen required
↑ waste produced
↑ diffusion time
eventually surface area can no longer serve the requirements of the cell
size of the cell is reduced and kept within size limits
critical ratio stimulates mitosis
why are specimens stained? (1)
most cell structures are colourless → clearer observation
reasons for using cover slip on specimen (2)
flatten specimen for better focusing
prevent specimen from drying
prevent objective from touching mounting solution
distinguish between prokaryotic cells and eukaryotic cells (6)
google docs
draw a prokaryotic cell (5)
google docs
draw a human eukaryotic cell (5)
google docs
draw a plant cell (5)
google docs
state the function of a flagella (1)
movement of the bacterial cell
state the functions of pili (2)
connect bacterial cells → transfer of genetic material
adhesion to another cell/surface
state the functions of the naked DNA in prokaryotic cells (2)
located in the nucleoid region: nucleoid initiates binary fission
controls cell structure and function
state the functions of a plasmid (2)
confer luxury functions
e.g. antibiotic resistance
state the functions of a capsule (2)
protects cell
promotes adherence
state the function of ribosomes (1)
site of synthesis of proteins released to cytoplasm
state the functions of a plasma membrane (2)
carries out active transport
controls entry and exit of substances
state the function of cytoplasm (1)
contains enzymes that carry out metabolism
state the function of lysosomes (1)
digestive enzymes break down food
state the function of the Golgi apparatus (1)
collection, packaging, modification and distribution of proteins
state the functions of cell walls (3)
protects the cell from damage
prevents the cell from bursting
provide rigidity and support
state the function of a rough endoplasmic reticulum (1)
synthesis and transport of proteins
state the function of centrosomes (1)
pair of centrioles at right angles → assembly of microtubules → cell division
state the functions of a large central vacuole (1)
provide turgidity and support
suggest how microscopic images of plasma membranes led to Davson-Danielli model of membrane structure (2)
protein lipid sandwich
appears as 2 black lines
proteins stained black
phospholipids unstained
explain how properties of phospholipids help to maintain the structure of cell membranes (8)
phospholipid consisting of head + 2 tails
head: glycerol + phosphate
hydrophilic: attracted to water
tails: fatty acid chains
hydrophobic: not attracted to water but each other
leads to the formation of double layer in water → stability
heads are outer & attracted to water
tails in the middle & attracted to each other
attraction of non-polar tails to each other → in fluid state
allows vesicles to form or fuse with membrane
non-polar amino acid side chains attracted to hydrophobic tails
why is the structure of the cell membrane fluid and mosaic? (2)
fluid: phospholipid and protein molecules can move laterally
mosaic: diff kinds of protein molecules interspersed among phospholipid molecules in mosaic pattern
draw a labelled diagram to show the fluid mosaic structure of a plasma membrane (5)
google docs
outline how molecules move across a membrane by simple diffusion (2)
membranes are permeable allowing diffusion
diffusion = passive movement of particles from high to low conc
continues until conc are equal across the membrane
no use ATP
compare simple diffusion with facilitated diffusion as mechanisms to transport solutes across membranes (5)
google docs
explain passive transport and active transport across membranes (8)
large and polar molecules cannot cross the hydrophobic membrane freely
google docs
define osmolarity (1)
measurement of solute concentration of a solution
outline the effects of putting plant tissue in a hypertonic solution (4)
hypertonic solution has higher solute concentration than the tissue
water moves out of the cells by osmosis from lower solute conc to higher solute conc
cell becomes flaccid and plasmolysed
describe how the structure of the membrane allows the formation of vesicles (2)
phospholipid bilayer makes membrane fluid → allows change of shape
cholesterol affects membrane fluidity: provides firmness and integrity and prevents it from becoming overly fluid
phospholipid tails
weak bonding
kinks prevent close packing
explain how vesicles are used to transport materials secreted by a cell (8)
proteins synthesised by ribosomes + rER
proteins are bound by vesicles
vesicles bud off from rER → transport proteins to Golgi apparatus → fuse with Golgi apparatus membranes
Golgi modifies proteins as they move along in vesicles
secretory vesicles bud off in trans Golgi → move across the cytoplasm → fuse with plasma membrane
exocytosis: release proteins outside the cell
rER + vesicle + plasma membrane have phospholipid bilayer structure
cells use vesicles to secrete substances
e.g. hormones + digestive enzyme
can contain cell products other than proteins
describe the process of endocytosis (5)
2 phospholipid layers form a pit to enclose a target particle → edges fuse back → make vesicle
fluidity of membrane permits movement
inner phospholipid layer of original membrane → outer phospholipid layer of vesicle
outer phospholipid layer of original membrane → inner phospholipid layer of vesicle
vesicle moves into cytoplasm
changes in membrane shape require ATP
e.g. pinocytosis + phagocytosis
outline four different functions of membrane proteins (4)
binding site for hormone/neurotransmitter cell-to-cell communication channels for facilitated diffusion pumps for active transport cell adhesion enzymes embedded in the membrane electron transport
explain the endosymbiotic theory (5)
symbiosis occurs when 2 different species benefit from living and working together
endosymbiosis: 1 organism living inside the other
there is evidence that mitochondria and chloroplasts were once primitive free-living bacterial cells: DNA loop binary fission double membrane 70s ribosomes
a large host cell & the bacteria ingested through endocytosis become dependent on one another for survival → permanent relationship
smaller cell was provided food and protection by the larger cell
mitochondria would supply energy through aerobic respiration for the larger cell
chloroplast would supply food through photosynthesis for the larger cell
millions of years of evolution → mitochondria and chloroplasts have become more specialised → cannot live outside the cell
describe Pasteur’s experiment of spontaneous generation (4)
he prepared a nutrient broth
placed equal amounts of the broth into 2 long-necked flasks:
one flask with a straight neck
one bent to form an “S” shape
boiled the broth in both flasks to kill any living matter → sterile
flasks sit at room temperature + exposed to the air
broth in the straight-neck flask was discoloured and cloudy:
organisms in the air were able to fall unobstructed → contaminate the broth
broth in the curved-neck flask had not changed:
trapped organisms in its curved neck → prevent them from reaching the broth
describe the events that occur during the cell cycle/mitosis (9)
interphase:
G1: cell grows + organelles duplicate
S: DNA replication
G2: chromosomes begin condensing + prep for cell division
mitosis:
prophase:
chromosomes condense by supercoiling → sister chromatids visible
nuclear membrane breaks down
prophase + metaphase: spindle microtubules grow from poles to equator
metaphase:
spindle microtubules attach to the centromeres
chromosomes line up at equator
anaphase:
centromeres split
sister chromatids separate → dragged to opposite poles by the shortening of spindle microtubules
telophase:
spindle microtubules disappear
nuclear membrane reforms around chromosomes → decondense
cytokinesis: cytoplasm divides → 2 daughter cells with identical nuclei
plant: cell plate form between nuclei
explain how the cell cycle is controlled (5)
cell cycle = G1, S, G2, mitosis
levels of cyclins fluctuate during the cell cycle
4 cyclins enter different stages in cell cycle → sequence of stages controlled by cyclins
cyclins bind to kinases → activate cyclin-dependent kinases
kinases phosphorylate other proteins
phosphorylated proteins perform specific functions in the cell cycle
conditions inside + outside cell affect regulation
list processes that involve mitosis (2)
growth (through increasing cell number)
embryonic development
tissue production/repair
asexual reproduction
