Topic 1- Cells Flashcards
what can organisms be?
prokaryotes or eukaryotes
what are all living things made of
cells
examples of prokaryotes
bacteria
examples of eukaryotes
animal and plant cells
what’s a eukaryote
an organism that is made up of a eukaryotic cell
what’s a prokaryote
a prokaryotic cell (a single celled organism)
what are the different parts of cells called
sub cellular structures
what’s the nucleus?
contains genetic material that controls the activities of a cell
what’s the cytoplasm
gel like substance where most of the chemical reactions happen
contains enzymes that control these chemical reactions
what’s the cell membrane
holds the cell together and controls what goes in and out
what’s the mitochondria
where most of the reactions for aerobic respiration happen
respiration transfers energy that the cell needs to work
what are ribosomes
where proteins are made
what do plant cells have
all the animal cell parts plus
rigid cell wall
permanent vacuole
chloroplasts
what does an animal cell have
nucleus cytoplasm cell membrane mitochondria ribosomes
what does a cell wall do
made of cellulose
supports the cell and strengthens it
what’s the permanent vacuole
contains cell sap, a weak solution of sugar and salts
what’s chloroplasts
where photosynthesis occurs, which makes food for the plant
contain chlorophyll which absorbs light for photosynthesis
what type of cells are bacteria
prokaryotes
what does a bacteria cell contain?
cytoplasm cell membrane cell wall strand of DNA that floats in the cytoplasm rings of DNA (plasmids)
what don’t the bacteria cells have
chloroplasts or mitochondria or nucleus
what’s differentiation
the process by which a cell changes to become specialised for its job
What happens when the cells change
develop different sub cellular structures and turn into different types of cells which allows them to carry out specific functions
When does most differentiation occur
as an organism develops
What are the cells that differentiate in mature animals mainly used for
Repairing and replacing cells such as skin or blood cells
Give five specialised cells and what they’re specialised for
sperm- reproduction nerve- rapid signaling muscle- contraction root hair- absorbing water and minerals phloem and xylem- transporting substances
describe a sperm cells function
to get the male dna to the female dna
adaptations of a sperm cell
long tail
streamlined head to help swim to egg
lots of mitochondria to provide energy
enzymes in head to digest through the egg cell membrane
function of nerve cell
To carry electrical signals from one part of the body to another
adaptations with nerve cell
Long to cover more distance
branched connections at their end to connect to other nerve cells and form a network throughout the body
Muscle cell function
contract quickly
Adaptations of muscle cell
Long so they have space to contract
contain lots of mitochondria to generate the energy needed for contraction
Root hair cell function
Cells on the surface of plant roots which grow into long hairs that stick out into the soil
Adaptation of root hair cell
large surface area for absorbing water and mineral irons from the soil
thin walls to allow easy movement of water
Function of phloem and xylem cells
they form phloem and xylem tubes which transport substances such as food and water around plants
to form the tubes the cells are long and joined end to end
adaptations of phloem and xylem cells
Xylem cells are hollow in the centre and phloem cells have very few sub cellular structures so that stuff can flow through them
What do chromosomes contain
Genetic information
What does the nucleus contain
Your genetic material in the form of cromosones
What are chromosomes
coiled up lengths of DNA molecules
What does each chromosome carry
A large number of genes
what do genes do
different genes control the development of different characteristics for example hair colour
How many chromosomes does the body have
Two copies of each chromosome
one from the organisms mother and one from its father so humans have two copies of chromosomes one and two copies of chromosome two etc
23 pairs of chromosomes in total
What’s the stage of the cell cycle where the cell divides called
Mitosis
What’s the cell cycle
where body cells in multicellular organisms divide to produce new cells as part of a series of stages
What does mitosis do
Grow or replace cells that have been damaged
describe the growth and DNA replication part of the cell cycle
1) in a cell thats not dividing the DNA is spread out in long strings
2) cell grows and increases the amount of sub cellular structures such as mitochondria and ribosomes
3) it’s duplicate the DNA so there is one copy for each new cell
the DNA is copied and forms X shaped chromosomes
each arm of the cromosome is an exact duplicate of the other
Describe the mitosis part of the cell cycle
1) the chromosomes line up at the centre of the cell and cell fibres pull them apart
the two arms of each chromosome go to opposite ends of the cell
2) membranes form around each of the sets of chromosomes
these become the nuclei of the two new cells
the nucleus has divided
3) The cytoplasm and cell membrane divides the new daughter cells are produced and contain exactly the same DNA
what’s binary fission
where prokaryotic cells can reproduce using a type of simple cell division called binary fission
what happens in binary fission
the cell splits in two
describe the steps of binary fission
1) circular DNa and plasmids replicate
2) cell gets bigger and circular DnA strands move to the opposite ‘poles’ (ends of cell)
3) cytoplasm begins to divide and new cell walls begin to form
4) cytoplasm divides and two daughter cells are produced
5) each daughter cell has one copy of the circular DNA bit can have a variable number of copies of the plasmids
conditions for bacteria to divide?
warm
lots of nutrients
if conditions are unfavourable what happens to the cells
they stop dividing and eventually begin to die
what’s the mean division time
the average amount of time it takes for one bacterial cell to divide into two
if you know the mean division time of a cell what can you work out?
how many times it has divided in a certain amount of time and so the number of cells it has produced in that time
how do you find the mean number of divisions
divide total time that bacteria are producing cells by mean division time
how do you find the number of cells
put 2 to the power of how many divisions
where is bacteria grown
in a culture medium
what does a culture medium contain
carbohydrates
minerals
proteins
vitamins
what can the culture medium be?
nutrient broth solution or solid agar jelly
when bacteria is grown on agar plates what will it form?
visible colonies on the surface of the jelly or it will spread out to give an even covering of bacteria
how do you make an agar plate
hot agar jelly is poured into shallow round plastic dishes called PETRI DISHES
what’s an inoculating loop
inoculating loops transfer microorganisms to the culture medium
what else can be used other than an inoculating loop
sterile dropping pippete and spreader
what happens after inoculating loops transfer microorganisms
the microorganisms multiply
why are microorganisms not kept higher than 25 degrees
because harmful pathogens are more likely to grow above this temp
when are cultures incubated at high temps
industrial conditions
how can you test the action of antibiotics or antiseptics in cultures of bacteria
1) place paper discs soaked in different concentrations/types of antibiotics on an agar plate that has an even covering of bacteria
LEAVE SPACE BETWEEN DISCS
2) antibiotic diffuses into jelly antibiotic-resistant bacteria will continue to grow around discs, but NON RESISTANT STRAINS WILL DIE
a clear area will be left where bacteria has died- inhibition zone
3) use a control, non antibiotic soaked disc (soaked in sterile water instead)
4) leave plate for 48 hours at 25 degrees
5) larger inhibition zone= more effective antibiotic
whats a clear area will be left where bacteria has died called?
inhibition zone
what can contamination do
result i. growth of pathogens
to avoid uncontaminated cultures, you MUST?…
use sterilised petri dishes, by heating at high temps
pass inoculating loop through flame to kill unwanted microorganisms
lid of dish lightly taped on to stop microorganisms from air getting in
dish stored upside down to stop drops of condensation falling onto agar surface
equation for area of inhibition zone
area= pi r squared
what can the area equation be used for
area of colony
size of inhibition zone
what’s differentiation
the process by which a cell changes to become specialised for its job
what type of cells are stem cells
undifferentiated
what can stem cells do
divide to produce lots more undifferentiated cells
they can differentiate into different types of cells depending on what instructions they’re given
where are stem cells found
early human embryos
what do stem cells have the potential to do
turn into any kind of cell at all
where are adult stem cells found
bone marrow
what can bone marrow stem cells do
turn into only certain types of cells such as blood cells
what can all stem cells be used for
they can be grown in the lab to produce clones
made to differentiate into specialised cells to use in medicine or research
what can stem cells do to cure disease
bone marrow- replace faulty blood cells
embryonic- insulin producing cells, nerve cells
what’s therapeutic cloning
where an embryo could be made to have the same genetic information as the patient
this means that some cells produced from it would also contain the same genes and so wouldn’t be rejected by patient’s body if used to replace faulty cells
stem cell risks
becoming contaminated with virus which could be passed on to patient
arguments against and for stem cells
-Potential human life
+curing existing patients who are suffering is more important than the rights of embryos
+embryos used are unwonted ones which would probably just be destroyed
-scientist should find other sources of stem cells
In some countries stem cell research is…
BANNED
Where arestem cells found in plants
meristems
what happens to cells in the meristem tissues
They can differentiate into any type of plant cell
Plant stem cells can be used to produce what
clones of plants (rare species and disease resistant)
what’s diffusion
the spreading out of particles from an area of higher concentration to an area of lower concentration
where does diffusion happen
in solutions and gases because the particles in these are free to move about randomly
whats the conc gradient
the difference in concentration
the bigger the conc gradient…
the faster the diffusion rate
the higher the temp…
the faster the diffusuion rate because particles will have more energy
what sort of substances move in and out of cells by diffusuion
dissolved
what does the cell membrane do in diffusion
let stuff in and out
what molecules can diffuse through cell membranes
small molecules such as oxygen, glucose, amino acids and water
what molecules can’t fit through the membrane
starch and proteins
if there are a lot more particles on one side of the membrane…
theres a net (overall) movement from that side
the larger the surface area of the membrane…
the faster the diffusion rate because more particles can pass through at once
what is osmosis
the movement of water particles across a partially permeable membrane from a region of higher water concentration to an region of lower water concentration
whats a partially permeable membrane
a membrane with very small holes in it, so only water can pass through, beacause the molecules are very small
what way do water molecules travel through the membrane
randomly, both ways
whats the net flow of osmosis
where because there are more water molecules on one side than on the other, theres a steady flow of water into the region with fewer water molecules (the stronger sugar solution). this means the water gets more dilute
what is the water trying to do in osmosis
dilute the strong sugar solution and even up the conc on each side of the membrane
describe the potato practical
1) cut up potato evenly
2) put each one in beakers with different sugar solutions
3) one should be pure water, then 1 mol/dm3, 0.2 mol/dm3, 0.4mol/dm3 etc
4) measure mass of each potato cylinder
5) leave potato in sugar solutions for 24hours or so
6) dry the cylinders and measure mass agai
if the cylinders of potato have increased mass…
they have drawn in water by osmosis
if the cylinders of potato have increased mass…
they have drawn out water by osmosis
dependent variable of potato experiment
chip mass
independent variable of potato experiment
conc of sugar solution
control variables of potato experiment
volume of solution, temp, time, type of sugar etc
potential errors in potato experiment
excess water gives higher mass- not fully dried cylinders of potato
conc of sugar changes-water evaporates from beakers
whats active transport
where substances are absorbed against a conc gradient, from lower to higher conc, using energy
what do root hair cells take in
minerals and water
what are the branches of roots covered in
microscopic hairs
what do microscopic hairs do to the plant
give them a large surface area for absorbing water and mineral ions from the soil
what do plants need minerals for
healthy growth
the conc of minerals is higher in the root hair cells than…
the soil around them , so diffusion cant be used to take up minerals from the soil
what does active transport allow plants to do
absorb minerals from a very dilute solution, against the conc gradient
what does active transport need to work
energy
where else does active transport happen
in the gut when there is a lower conc of nutrients in the gut but a higher conc of nutrients in the blood
when else does active transport happen in humans
when glucose can be taken into the bloodstream when its conc in the blood is already higher than in the gut. It can then be transported to cells, where it is used for respiration
organisms exchange substances with their…
environment
what do cells use to take in substances that they need and to get rid of waste products
diffusion
the larger an organism is, the smaller the…
SA is compared to its volume
SA equation
length x width
volume equation
length x width x height
to simplify the ratio, what do you do
divide both sides of the ratio by the volume
whats the sa: v ratio like in single celled organisms
large sa compared to their volumbe,
so gases and dissolved substances can diffuse directly into or out of the cell across the cell membrane
enough substances can be exchanged across the membrane to supply the volume of the cell
whats the sa: v ratio like in multicellular organisms
small sa compared to volume, so not enough substances can diffuse from their outside surface to supply their entire volume. This means they need an exchange surface to allow enough of the necessary substances to pass through
how are exchange surfaces adapted to maximise effectiveness
thin membrane- substances only have short distance to diffuse
large SA- lots of substances can diffuse at once
in animals, have lots of blood vessels- to get stuff in and out of body quickly
gas exchange surfaces in animals (eg.alveoli) are ventilated- are moves in and out
what is the job of the lungs
to transfer oxygen to the blood and remove waste carbon dioxide from it
what are the alveoli specialised for
to maximise the diffusion of O2 and CO2
adaptations of alveoli
enormous SA
moist lining- dissolving gases
Thin walls
good blood supply
where are the villi?
the inside of the small intestine
what do villi do?
they increase the SA in a big way so that digested food is absorbed much more quickly into the blood
what do villi have
a single layer of surface cells
a very good blood supply to assist quick absorption
The top and bottom of the leaf are covered with what
a layer of very thin cells called epidermal cells and they form epidermal tissue
Epidermis adaptations
- At the top of the leaf are the upper epidermis and at the bottom are the lower epidermis
- The epidermis protects the surface of the leaf
- The upper epidermis is transparent and allows light to pass through to the photosynthetic cells below
Waxy cuticle
- The upper epidermis is covered with a thin layer of oily material called the waxy cuticle
- The waxy cuticle reduces the evaporation of water form the leaf and helps it from drying out
Stomata
- Allow carbon dioxide to enter the leaf and oxygen to leave
- Help control the amount of water vapour that can pass out of the leaf
- On either side, there are guard cells
Palisade mesophyll has what?
palisade cells
what do palisade cells have lots of
chloroplasts
chlorophyll does what
which absorbs the light energy needed for photosynthesis
The spongy mesophyll is full of what
air spaces
what do air spaces in spongy mesophyll allow
carbon dioxide to diffuse from the stomata through the spongy mesophyll to the palisade cells
what diffuses from the palisade cells through the spongy mesophyll to the stomata
oxygen and water vapour
what does xylem tissue do
transports water from the roots to the stem and leaves
what else does the xylem do
xylem also transports dissolved minerals ions. These include magnesium which is used to make chlorophyll
what does the phloem do
• Transports dissolved sugars produced by photosynthesis from the leaves to the rest of the plant
what are sugars transported by phloem used for?
sugars can be used immediately, for example glucose and respiration. Or they can be stored, for example starch.
translocation definition?
• The movement of sugars and other molecules through phloem tissue
wheres meristem tissue found
growing tips eg shoots and roots
what does meristem tissue contain
• Contains stem cells, which can differentiate into different types of plant tissue
whats the underneath of the leaf
an exchange surface
what diffuses into the leaf then into the cells for photosynthesis?
CO2
what does CO2 use to diffuse in
stomata
wheres water vapour lost from in the leaf
stomata
what do guard cells do
close the stomata if the plant is losing too much water
what does the flattened shape of the leaf do
it means the area of the exchange ssuface is increased so its more effective
whats another exchange surface in the leaves formed by
walls of the leaf cells
what do the walls of the cells inside the leaf do
the air spaces inside the leaf increase the area of the surface so more chance for CO2 to get into the cells
where does water evaporate from the leaf
the cells
by what process does water vapour leave the leaf
diffusion, theres more inside the leaf than there is outside the leaf
whats the gas exchange surface in a fish
gills
how does water enter and exit the fish
enters through mouth
exits through gills
what happens to oxygen and CO2 in the fish
oxygen diffuses from water -> blood in gills
CO2 diffuses from the blood -> water
what are gills made of
gill filaments, which make a big surface area for exchange of gases
what are gill filaments covered in
lots of tiny structures called lamellae, increasing the SA
the lamelllae have lots of what?
lots of blood capilaries to speed up diffusion
what do the fish cells have to minimise the distance gas has to difuse?
thin surface layer
how is a large conc gradient maintained between water and blood in fish
blood flows through lamellae in one direction and water flows over in the opposite direction
describe the conc of oxygen in water (fish)
its always higher than the blood, so as much oxygen as possible diffuses from the water in the blood
formula for magnification
magnification = image size divided by real size
