cell biology (seneca) Flashcards
Eukaryotic cells are found in
plants, animals, fungi and protists (single-celled organisms that don’t fit other categories).
what are protists?
Eukaryotic single celled cells that are not plants, animals, fungi
Eukaryotic are —- micrometres in size.
10 - 100
Prokaryotic cells are —– micrometres in size.
0.1 - 5.0
prokaryotes are
Bacteria
what is the micrometer unit
µm
Some prokaryotic cells contain small rings of DNA called …
plasmids.
Plasmids can ——- and move between …
- replicate
- cells so that genetic information can be shared.
Prokaryotic cells do not have a (n)…
nucleus (where DNA is stored).
Most of prokaryotic cells genetic material is stored in a ——- in the …
single DNA loop
cytoplasm (watery jelly that fills the cell).
Prokaryotic cells do NOT contain (m)…
mitochondria (where respiration takes place) or chloroplasts (where photosynthesis takes place).
The cell membrane is ——— permeable
selectively
Something that is selectively permeable can …
control which substances move through it.
To multiply numbers in standard form:
- Multiply the leading numbers.
- Add the powers.
- Change into the correct format.
To divide numbers in standard form:
- Divide the leading numbers.
- Subtract the powers.
- Change into the correct format
1 µm = — m
0.000001m
1 nm = —- m
0.000000001 m
An animal cell contains the following sub-cellular structures:
- Cell membrane
- Nucleus
- Ribosomes
- Mitochondria
- Cytoplasm
The nucleus contains …
chromosomes (which contain the cell’s genetic material).
Ribosomes are responsible for …
synthesising (making) proteins.
Mitochondria is where …
aerobic respiration takes place.
Cytoplasm is a ———————- where…
jelly-like fluid that fills the cell.
most of the cell’s chemical reactions take place.
An animal cell contains a ———————– membrane.
partially permeable
As well as the sub-cellular structures that animal cells have, a typical plant cell has a few more:
- Permanent vacuole
- Chloroplasts
- Cell wall
A permanent vacuole is a …
fluid-filled sac that stores water.
Permanent vacuole is enclosed in a …
membrane (a wall that substances can pass through).
Permanent vacuole can make up as much as — of a plant cell’s volume.
90%
Chloroplasts contain ———, which is needed for the process of …
chlorophyll
photosynthesis.
The cell wall ———- and is made of …
surrounds the cell
cellulose.
The cell wall —— the structural strength of the cell.
increases
When cells differentiate, they acquire ——-
different sub-cellular structures.
Many plant cells can differentiate —————
This means that plants are …
throughout their lives.
always able to create new tissues.
Most animal cells differentiate —– on in their development.
early
In mature animals, cells mostly ——————————- to replace cells and repair tissues that are already present.
New tissues are rarely created by …
divide (one cell splits to create two cells)
cell differentiation
The cytoplasm is where …
most of the cell’s chemical reactions take place
Plasmids are …
small rings of DNA.
Some bacteria have (f) …
flagella.
Flagella are …
whip-like structures used for movement.
Plasmids can replicate (have copies made) and move …
between cells so that genetic information can be shared.
Prokaryotic cells do NOT contain …
nucleus, mitochondria (where respiration takes place) or chloroplasts (where photosynthesis takes place).
Cell differentiation is the process where …
a cell develops new sub-cellular structures (structures inside a cell) to let it perform a specific function.
Differentiation happens primarily during an organism’s …
development.
The ————– is used for the cell’s motion. This allows sperm cells to travel towards the egg cell.
flagellum (‘tail’)
The —— contains the sperm cell’s nucleus. The nucleus carries one half of an organism’s genetic material.
‘head’
Sperm combines with the …
egg cell’s half of genetic material to fertilise the egg cell.
The middle section of the sperm is filled with …
mitochondria to provide the sperm with the energy it needs to travel a long distance to reach the egg cell.
Digestive enzymes are found at the tip of the head of sperm cells in the …
acrosomes.
Sperm cells spin their tails in a ——— to move themselves towards their target - the egg.
corkscrew motion
Nerve cells (or neurones) are specialised to …
transmit electrical messages around the body
What is an axon
Part of the cell that electrical signals travel along.
Nerve cells have a ——— axon. This increases …
long
the distance that electrical signals can travel.
A sheath made of a material called myelin surrounds the axon of the nerve cell. This stops the electrical nerve signals leaking out of the nerve cell.
This increases …
the speed of transmission (travel) of electrical signals.
A sheath made of a material called ——- surrounds the axon of the nerve cell. This stops the electrical nerve signals leaking out of the nerve cell.
This increases the speed of transmission (travel) of electrical signals.
myelin
A sheath made of a material called myelin surrounds the axon of the nerve cell. This stops the …
This increases the speed of transmission (travel) of electrical signals.
electrical nerve signals leaking out of the nerve cell.
What are dendrites?
Branches of a nerve cell.
Several dendrites spread outwards from the cell body to…
transfer electrical messages to other neurons
Signals are transmitted across gaps between nerve cells. What are these gaps called?
Synapses
Muscle cells are specialised (perform a specific function). They can produce …
force and motion.
- within the cell can 2. , allowing the muscle to move.
- Protein fibres
- contract
A muscle cell contains lots of —————- to generate lots of energy for motion.
mitochondria
Root hair cells are specialised (to perform a specific function). Their structure allows the plant to 1. . They also allow a plant to …
- absorb more water
take in the minerals it needs to survive.
Root hair cells cells are located underground.
This means that they do not contain …
chloroplasts (there is no light for photosynthesis).
Root hair cells have long projections that ——————- that the plant can use to absorb water and minerals.
increase the surface area
The xylem is specialised to …
transport water up the stem of a plant and into the leaves.
Xylem vessels are made up of a …
series of connected dead xylem cells.
The end walls of the dead xylem cells are …
broken to allow water to move through
—— (a substance) strengthens the cell walls of xylem cells.
Lignin
Lignin (a substance) ———————— of xylem cells.
strengthens the cell walls
The phloem is specialised to —————————————-. Phloem vessels are made up of columns of living cells.
transport food products to parts of the plant where they are needed
The phloem is specialised to transport food products to parts of the plant where they are needed. Phloem vessels are made up of …
columns of living cells.
The end walls of ———- contain small holes to allow food products to move up and down the phloem vessels throughout the plant.
phloem cells
The end walls of phloem cells contain small holes to allow …
food products to move up and down the phloem vessels throughout the plant.
When using microscopes, two variables matter the most: …
magnification and resolution.
Magnification tells us …
how many times larger an image seen through a microscope is compared to the real object.
Resolution is the …
ability to distinguish between (tell apart) two or more objects that are close together.
Magnification =
image size ÷ actual size
A light microscope passes ———— and creates a magnified image using lenses.
light through a specimen.
Light microscopes allowed bacteria to be seen for the first time. They also allowed us to see ————
However, we still could not tell …
plant cells and animal cells as separate
lots of sub-cellular (within the cell) structures apart.
The electron microscope was first used in …
1933
Electron microscopes work in a similar way to light microscopes. However, ———- are passed through the specimen instead of light.
electrons
Electron can now resolve distances of 1nm (better resolution) with magnifications of …
×500,000.
The high level of detail of electron microscopes allowed scientists to see …
They also allowed scientists to study how …
sub-cellular structures more clearly.
structures such as mitochondria, chloroplasts and ribosomes function.
The first light microscope was made using two lenses towards the end of the —- century.
16th
What are the steps for using a light microscope
Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide.
Add a few drops of a suitable stain/dye (e.g. iodine).
Place a coverslip on top of the tissue and place the slide onto the microscope stage.
Use the objective lens with the lowest magnification, and focus on the sample.
Increase the magnification and refocus to see different features of the cell.
Microorganisms can be grown as colonies on an …
agar gel plate.
Microorganisms can be grown within a solution of a …
nutrient broth
Microorganisms can be grown within a solution of a nutrient broth.
This contains …
carbohydrates as an energy source, minerals and sometimes other chemicals.
Microorganisms can be grown in mediums that contain everything that a bacteria needs to survive. How many types of mediums are there? What are these mediums?
2
Agar gel plates
Nutrients broth
When growing cultures of bacteria, we provide conditions that are good for lots of different types of bacteria to grow. If bacteria that are not being investigated grow, then our investigation has been …
contaminated
When culturing bacteria, As well as jeopardising the results of the investigation, contamination is 1., potentially 2.
1.a serious health and safety risk as it lets other
- harmful bacteria grow.
Potential sources of contamination are:
- Skin
- Air
- Soil
- Water
For investigations into antibiotics to be useful, the cultures must be …
pure (do not contain bacteria that are not being investigated).
To prevent contamination (from skin, air, soil, or water), aseptic (free from contamination) techniques are used on all apparatus. These techniques kill and prevents the entry of unwanted bacteria. They involve:
- flames
- boiling
- lids
- temperature
——————————- must be passed through a flame for sterilisation (removes bacteria).
Inoculation loops (tools used to transfer bacteria)
Inoculation loops (tools used to transfer bacteria) must be passed through a —— for sterilisation (removes bacteria).
flame
Solutions and agar must be ———- for sterilisation.
boiled
To stop air from getting into the Petri dish, the lid must be 1. when using the inoculating loop to add bacteria to the agar.
This lid should be taped on and the dish should be stored 2. to prevent 3.
- rapidly taken off and put back on
- upside down
- condensation forming on the lid and then dripping onto the agar.
In schools, the maximum temperature at which cultures should be incubated (stored) is 1.
This extra precaution reduces the risk of 2.
- harmful bacteria growing.
- 25 degrees Celsius
Bacteria multiply through …
simple cell division (binary fission), in which one cell divides to produce two cells.
The average time for how often the bacteria divide is called …
the mean division time of that population.
A future population of bacteria can be estimated by …
multiplying the current population by two for every mean division time (time it takes for the bacteria to divide) that passes.
Divisions can happen as fast as every ———— when the conditions are ideal.
20 minutes
To calculate the future population of bacteria, (equation) …
we multiply the current population by 2 to the power of (time passed ÷ mean division time).
Chromosomes are typically found in ——— in body cells.
pairs
Each chromosome carries a …
large number of genes.
Chromosomes are made from ———— and can be found in the …
-molecules of DNA
-nucleus of a eukaryotic cells
Chromosomes are made up of many different genes that …
encode (produce) many different proteins.
Each chromosome contains a large number of genes. Each gene tells the cell how to …
make a specific protein
In the Initial growth stage, extra ————————- are produced.
ribosomes, mitochondria and other sub-cellular structures
In mitosis, the cell’s chromosomes (which are made of DNA) are …
replicated (copied) so that
there are two sets of the cell’s chromosomes.
In mitosis, The two sets of chromosomes are ————————-
Then, the nucleus divides into two.
pulled to opposite ends of the cell poles by cell fibres.
In mitosis, The two sets of chromosomes are pulled to opposite ends of the cell.
Then, the …
nucleus divides into two.
During cell division, the ———————— are divided resulting in the production of two identical cells.
cytoplasm and cell membranes
During cell division, the cytoplasm and cell membranes are ———resulting in …
-divided
-the production of two identical cells.
The stages of the cell cycle:
Initial growth
Mitosis
Cell division
Mitosis (type of cell division) is part of the cell cycle. During mitosis: The two sets of chromosomes copied during the initial growth stage are …
pulled to opposite ends of the cell.
Mitosis (type of cell division) is part of the cell cycle. During mitosis: The nucleus is divided into …
two
Mitosis ensures that both daughter cells have the …
same chromosomes as each other and the parent cell.
Mitosis ensures that both daughter cells have the same chromosomes as each other and the parent cell.
This is important for processes that require —————————-
For example, the …
identical cells to be produced.
growth and repair of tissues and asexual reproduction.
In mitosis, what are copied during the initial growth stage and then pulled to opposite ends of the cell?
Chromosomes
In the cell cycle, what process occurs before chromosomes duplicate?
Cell growth and the duplication of sub-cellular structures
Humans have — pairs of chromosomes in their body cells
23
In human adults, stem cells can be found in …
- bone marrow
- embryos
- teeth
Adult stem cells differentiate into ——- cell types than stem cells in embryos.
fewer
Adult stem cells differentiate into fewer cell types than stem cells in embryos. They are used …
to replace dying cells and damaged tissues.
Plant stem cells are found in the …
meristem tissue.
Plant stem cells can differentiate into all types of plant cell ————————-. This allows plants to …
- throughout the life of the plant
- grow for their whole lives.
The stem cells in embryos can differentiate into———, to …
- most cell types
- produce all of the cell types that will make up the organism.
Stem cells are …
undifferentiated cells that haven’t yet specialised to do a specific function.
Stem cells are un-differentiated. This means that …
they haven’t yet specialised to do a specific function.
Stem cells can be used for many different medical, scientific and commercial purposes:
- Stem cell treatments
- Plant clones
- Therapeutic cloning
Stem cells may be able to —————————
For example, stem cells may replace the damaged cells that cause diabetes or paralysis.
replace damaged cells in the body.
Stem cells may be able to replace damaged cells in the body.
For example, …
stem cells may replace the damaged cells that cause diabetes or paralysis.
Plant stem cells can help us quickly and cheaply produce ——— plants.
cloned
Plant stem cells can help us quickly and cheaply produce cloned plants.
This could help …
to protect rare plant species from extinction and create large populations of plants with special features, such as disease resistance.
Therapeutic cloning is a process that …
produces an embryo with genes that are identical to the patient’s.
Stem cells taken from this embryo will have the same DNA as the patient. This means that …
This is ideal for use in stem cell medical treatments.
the patient’s body will not reject the stem cells or body cells made from the embryo’s stem cells.
Stem cells taken from this embryo will have the same DNA as the patient. This means that the patient’s body will not reject the stem cells or body cells made from the embryo’s stem cells.
This is ideal for use in …
stem cell medical treatments.
Using stem cells in medical treatment can have some downsides:
- Viral infections
- Ethical beliefs
Stem cell transplantation could transfer …
viral infections
Some people disagree with using stem cells on ethical or religious grounds:
They believe that life begins at conception, which means that the embryo is alive.
Therefore, they view the use of embryonic stem cells as ‘killing’ an embryo.
Diffusion is the …
net movement of particles from an area of higher concentration to an area of lower concentration.
Diffusion describes the movement of particles in what states?
fluids (liquids and gases).
Substances can move ———————— via diffusion.
in and out of cells across cell membranes
The rate of diffusion can speed up or slow down based on the following factors:
-Temperature
-Membrane surface area
- Concentration gradient
The ——- the temperature, the faster the rate of diffusion.
higher
The ——- the surface area of the membrane that a substance is diffusing through (e.g. the membrane around a cell), the faster the rate of diffusion.
larger
The concentration gradient is linked to the …
difference in concentration between two areas
The —- the difference in concentration between two areas, the greater the concentration gradient and the faster the rate of diffusion.
bigger
Small organisms normally have higher surface area to volume ratios than large organisms. This means that diffusion can happen through a ————————. This makes diffusion useful for transporting molecules through a small organism.
large area in small organisms
In animals, if a gas is exchanged, the surface is 1. to maintain a 2.
- ventilated (through breathing)
- high concentration gradient and increase the rate of exchange.
A thin membrane reduces …
the diffusion distance.
A large surface area allows…
more of a substance to diffuse at the same time.
Where substances are exchanged through blood in animals, exchange surfaces are densely packed with blood vessels: These blood vessels replenish the blood supply to maintain a …
high concentration gradient by bringing in new blood as diffusion starts to even out the concentrations.
Where substances are exchanged through blood in animals, exchange surfaces are densely packed with …
blood vessels
Exchange surfaces are surfaces that …
are adapted to maximise the efficiency of gas and solute (a substance dissolved in a liquid) exchange across them
The small intestine is adapted for …
exchanging nutrients between digested food in the small intestine and the blood.
The lungs are adapted for …
exchanging carbon dioxide and oxygen between the blood and air.
The gills are adapted for …
exchanging oxygen that is dissolved in water, with the carbon dioxide in a fish’s bloodstream.
Roots are adapted for
taking up both water and minerals from the soil around them.
Leaves are adapted for …
exchanging carbon dioxide and oxygen between the leaves and the surrounding air.
lungs have a very large surface area to allow …
maximum diffusion of oxygen into your blood, and carbon dioxide into the air.
Osmosis is the …
diffusion of water across a partially permeable membrane from a dilute solution (high concentration of water/high water potential) to a concentrated solution (low concentration of water/low water potential).
A partially permeable membrane allows 1. through, but 2.
- water
- won’t let larger molecules dissolved in water pass through.
When there are lots of water molecules (in a dilute solution) on one side of a partially permeable membrane, but not many on the other side (in a concentrated solution), water will move from the…
dilute to the concentrated solution.
Water will move to make the concentrations the ————— of the membrane.
same on both sides
It is important to remember that water molecules will ———————————————-, but the net (overall) movement of water will be from the dilute solution to a concentrated solution.
move through the membrane in both directions
What specialised plant cell is uses osmosis to absorb water?
root hair cell
in osmosis, water moves to where there are —— water molecules.
fewer
———– allows sugar molecules, which are needed for cell respiration, to be absorbed from the gut and into the blood from the gut, even when the sugar concentration of the blood is higher.
Active transport
Active transport allows sugar molecules, which are needed for cell respiration, to be absorbed from the …
gut and into the blood from the gut, even when the sugar concentration of the blood is higher.
Active transport in the root hairs of plants means that plants are able to absorb mineral ions that are necessary for healthy growth, even though the …
concentration of minerals is usually lower in the soil than in the root hair.
———— in the root hairs of plants means that plants are able to absorb mineral ions that are necessary for healthy growth, even though the concentration of minerals is usually lower in the soil than in the root hair.
Active transport
In root hair cell, The mineral ions are transported from the soil where the concentration of mineral ions is 1. , to the root hair cell where the concentration of mineral ions is 2.
- low
- high
Diffusion describes when there is a …
net movement of particles from an area where their concentration is higher to an area where their concentration is lower.
Osmosis is a specific type of diffusion in which only…
water molecules move
Osmosis requires a …
partially permeable membrane.
Active transport is the …
net movement of particles against a concentration gradient.
This means that ——– is needed for active transport to happen.
energy
what are examples of passive transport?
- osmosis
- diffusion
Passive transport 1. require 2.
- does not
- energy
Chromosomes are…
Coiled up lengths of DNA molecules.
