B1 - Cell Biology Flashcards
What are the 2 types of cells for organisms?
Eukaryotes - complex, such as animal and plant cells
Prokaryotes - smaller and simpler, such as bacteria
Name all the subcellular structures in an animal cell and their functions
Nucleus - contains the genetic material, controls activities of the cell
Cytoplasm - gel -like substance where most chemical reactions occur, controlled by enzymes
Cell membrane - hold the cell together and controls what goes in and out
Mitochondria - THE POWERHOUSE OF THE CELL (ha) most reactions for aerobic respiration takes place. Respiration transfers energy that the cell needs to work
Ribosomes - where protein synthesis occurs
What are the extra subcellular structures in a plant cell that isn’t in an animal cell? (as plant cells contain all in animal cells too)
Rigid cell wall - it supports and strengthens the cell. Made from cellulose
Permanent vacuole - contains cell sap (a weak solution of sugar and salts)
Chloroplasts - where photosynthesis occurs, made green by chlorophyll to absorb the light needed from photosynthesis
Complete the sentence:
Bacterial cells are…
much smaller compare to eukaryotes
What don’t bacteria have?
Chloroplasts or mitochondria
What do bacterial cells have instead of a nucleus?
A single circular srand of DNA that freely floats in thne cytoplasm. They may also contain one or more small rings of DNA called plasmids
What are the subcellular structures in bacterial cells?
Cytoplasm, Cell membrane, a cell wall, single circular strand of DNA and possibly plasmids
If you get asked to estimate the area of a subcellular structure, what do you do?
Treat it as a regular shape - if its a rectangle, area = length x width
Give 2 differences between prokaryotic and eukaryotic cells
1 - Prokaryotic cells are smaller than eukaryotic cells
2 - Prokaryotic cells don’t have mitochondria but eukaryotic cells do
3 - Prokaryotic cells don’t have a true nucleus but eukaryotic cells do
3 - Prokaryotic cells have circular DNA but eukaryotic cells don’t
Give the formula to calculate the image size
magnification x real size
What are the 2 microscopes called? What are the advantages and disadvantages of each?
Light microscopes + cheaper, portable
Electron microscopes + high resolution, higher magnification - only works with dead specimens
The cons of each are just the opposite of the other
How many micrometres in a millimetre?
1000µm = 1mm
Give the formula to calculate the real size
image size/ magnification
How many mm in a cm?
10mm = 1cm
How many micrometres in a centimetre?
10,000µm = 1cm
Give the formula for magnification
image size/ real size
How does a light microscope work?
They use light and lenses to form an image of a specimen and magnify it. They allow us to see individual cells and large subcellular structures (like nuclei)
How do electron microscopes work?
They use electrons to form an image, rather than light
How do you prepare a slide for a light microscope to view onion cells? Rearrange these instructions:
1) Using the tweezers, put the tissue into the water on the slide.
2) Cut an onion into layers, using tweezers to peel off some epidermal tissue from the bottom of one of the layers
3) Add a drop of iodine solution
4) Place a cover slip on top, trying not to get air bubbles there (as it obscures the view)
5) Add a drop of water to the centre of a clean slide
5) Add a drop of water to the centre of a clean slide
2) Cut an onion into layers, using tweezers to peel off some epidermal tissue from the bottom of one of the layers
1) Using the tweezers, put the tissue into the water on the slide
3) Add a drop of iodine solution
4) Place a cover slip on top, trying not to get air bubbles there (as it obscures the view)
Why is iodine solution needed on a slide to see cells in a light microscope?
Because iodine solution is a stain, which highlight objects by adding colour to them
Where do you clip the slide?
a) The eyepiece
b) The light
c) The stage
d) The ring
c) The stage
What are the parts in an onion cell?
The nucleus, the cell wall, the cytoplasm, the cell membrane
When drawing the observations of a microscpe, what should you consider?
Drawing it neatly with a sharp pencil with clear, unbroken lines
Include a title
Drawn in proportion (not cell walls inside nuclei for example)
Label it
Label the magnification size and the real length
No colouring or shading
What does cell differentiation mean?
The process by which a cell changes to become specialised for its job
What are stem cells?
Undifferentiated cells
What is the difference between animal and plant cells in terms of basic differentiation?
In most animal cells, the ability to differentiate is lost at an early stage, after they become specialised. However, lots of plant cells don’t ever lose this ability
Complete the sentence:
The cells that differentiate in in mature animal are mainly used for…
Repairing and replacing cells such as skin or blood cells
Give 5 examples of specialised cells
Sperm cells Nerve cells Muscle cells Root hair cells Phloem and Xylem cells
How are nerve cells specialised to complete their role?
Their main aim is rapid signalling, so they are long (to cover more distance as it takes longer to travel through the synapses that join the nerve cells). They also have branched connections at their ends to connect to other nerve cells, forming a network throughout the body
Muscle cells are specialised for contraction. True or false?
True - they are long (so they have enough space to contract) and lots of mitochondria so they have the necessary energy to contract
This cell is specialised by being streamlined, with lots of mitochondria and a long end. What cell is this?
Sperm cells. Also, they have enzymes in its head to digest through the egg cell membrane
Root hair cells are specialised in which of the following ways?
a) A thin cell wall so substances can easily transport in and out
b) Grow on the surface of plant roots so they can grow into long hairs that can reach further and get more minerals needed from the soil
c) Has a large surface area for absorbing water and mineral ions
d) Have lots of chloroplasts so they can conduct enough photosynthesis to get energy needed for active transport
b) Grow on the surface of plant roots so they can grow into long hairs that can reach further and get more minerals needed from the soil
c) Has a large surface area for absorbing water and mineral ions
It cannot photosynthesise, as it is underground
In what ways are phloem cells and xylem cells adapted?
They form tubes (as they are long and joined end to end), able to transport food and water around plants
How are xylem cells different to phloem cells?
Xylem cells are hollow in the centre so minerals can flow through it
Phloem cells have very few subcellular structures so minerals can flow through it
What are chromosomes, what do they contain, and how many are in a human cell?
Chromosomes are coiled up lengths of DNA molecules, they contain genetic information (they are contained in the nucleus), with 23 pairs in a human cell
Fill the blanks:
Each chromosome carries a large number of _____. Different _____ control the ___________ of different _______________, such as hair colour
Genes
Genes
Development
Characteristics
What does the cell cycle do?
Makes new cells for growth, development and repair
Body cells in multicellular organisms divide to produce new cells as part of the cell cycle. True or false?
True
What are the two stages of the cell cycle?
1) Growth & DNA replication
2) Mitosis (the smallest part)
Give the stages of mitosis
1) The mitochondria is doubled and put into x shaped pairs. They are EXACT duplicates
2) The chromosomes line up at the centre of the cell and cell fibres pull them apart. Each half of the chromosomes goes to opposite ends of the cells
3) Membranes form around each of the sets of chromosomes. These become the nuclei of the 2 new cells
4) The cell membrane and the cytoplasm divide
The parent cell has now become 2 daughter cells, which are all identical
What type of cell is undifferentiated, therefore able to change into ANY type of cell?
Embryonic stem cells (stem cells from an embryo)
Where can stem cells be found in adults?
In the bone marrow, however it is more limited as it can only become certain types of cells (such as blood cells)
How can stem cells (from adults) cure diseases?
Stem cells transferred from a healthy person can replace failing blood cells in another patient.
What does therapeutic cloning mean?
An embryo can be made to have the same genetic info as the patient, so the new stem cells wouldn’t be rejected by the patient’s body
Give one risk of using stem cells in medicine
Stem cells grown in a lab may become contaminated with a virus, and if passed on to a patient it will only make them worse.
Give the ethical reasons for (+) and against (-) of stem cell research
+ Curing existing patients who are suffering is more important than an embryo
+ Embryos used are often unwanted anyway and from a fertility clinic, so they would otherwise be destroyed
- Some religions believe that human life begins in an embryo, so they are actively destroying a being not just a thing
- Human embryos shouldn’t be used as each is a potential human life
Stem cell research is banned in the UK. True or false?
False - it is legal but it has very strict guidelines. It is banned in some countries though
How can stem cells be used to preserve a rare plant species? (2 marks)
Copies of the plant can be made from taking stem cells from the meristem of the plant (1)
and growing them into new, genetically identical plants (clones) (2)
Where are the meristems in a plant?
Parts of the plant where growth occurs. Stem cells are found there
Why would a farmer want to use stem cells to grow crops of genetically identical plants?
They would have desired features for the farmer, such as disease resistance
What is diffusion?
It is the net movement of particles from an area of high concentration (of that particle) to an area of lower concentration
Why does diffusion occur in solutions and gases?
Because they are free to move about randomly
Fill the gaps:
The bigger the _____________ ________, the ______ the rate of diffusion. Also, high ___________ increases the rate of diffusion too as the particles have ____ ______ so move more.
concentration gradient
faster
temperature
more energy
How do dissolved substances move in an out of cells?
By diffusing through the cell membrane
Why don’t big molecules diffuse?
Starch and proteins are too large to diffuse through the cell membrane. Diffusion only works with small particles such as amino acids, oxygen (for respiration) glucose
How will surface area affect the rate of reaction of diffusion
The larger the surface area, the faster it is because more particles can pass through at once
Give the good definition of osmosis
Osmosis is the net movement of water across a partially permeable membrane from a region of high water concentration to a lower concentration of water
What does net flow mean?
The total amount of something going somewhere.
With osmosis and diffusion, the particles all actually move both ways, but it is the NET MOVEMENT that counts
What is the experiment of osmosis?
A vegetable chopped up, one put in salt water, one put in pure water. Potato in highest concentration of salt water weighs less at end because water inside potato go “less water out, must be friends” and leaves spud alone… Potato in pure water weighs more because there is less water in the potato, so more water goes in to have a party and be COUCH POTATOES
Remember to calculate difference in mass, the original potatoes don’t have to weigh the same, the difference is what counts and that doesn’t change
What are the potential errors in the osmosis experiment? How can you reduce the effect of these errors/ make it more reproducible?
Some potato cylinders may not have been fully dried, so the excess water would give a higher mass.
If some of the water evaporated from the beakers, the salt water concentrations would change, so the results would not be accurate.
Repeating the experiment and calculating the mean percentage change for each concentration
Active transport means what?
When substances have to be absorbed against the concentration gradient (a lower to a higher concentration of that particle)
Active transport helps the root hair cell take in what?
Minerals from the soil
Which of these require energy? Where is this energy from?
a) Osmosis
b) Active transport
c) Diffusion
b) Active transport (uphill - low to high concentration)
it comes from respiration
Where else is active transport used and how?
It is used in the gut when there is a low concentration of nutrients (glucose and amino acids) in the gut compared the higher concentration of nutrients in the blood. However, when the concentration gradient is fine, the nutrients will diffuse into the bloodstream
What is urea? How is this related to diffusion?
A waste product produced from the breakdown of proteins. This diffuses from cells into the blood plasma for removal in the body by the kidneys
Complete the sentence:
How easy it is for an organism to exchange substances with its environment depends on the organism’s…
Surface area to volume ratio (SA:V)
The larger an organism is, the smaller its surface area is compared to its volume. True or false?
True - in a 1cm cube, the surface area would be 6, the volume only 1
In a 2 by 4 by 4 cuboid, the surface area is 64 but the volume is 32
What do multicellular organisms need?
Exchange surfaces for efficient diffusion, as the surface area is smaller compared to their volume
How are exchange surfaces adapted to maximise effectiveness?
They have a thin membrane, so substances only need to diffuse across a short space
They have a large surface area, so more substances can diffuse at once
In animals, exchange surfaces have lots of blood vessels to get substances in and out of the blood quickly
Gas exchange surfaces in animals (such as alveoli) are often ventilated too - air moves in and out
Where does gas exchange occur? What is this organs job and how is it done?
In the lungs - their job is to transfer oxygen to the blood and remove waste CO2 from it. In order to do this, the lungs contain millions of little air sacks called alveoli where gas exchange takes place.
Red is deoxygenated blood
Blue is oxygenated blood
True or false?
False - red is oxygenated, blue is deoxygenated
How do these qualities of the alveoli improve its perfomance?
a) An enormous surface area (75m²)
b) A moist lining
c) Very thin walls
d) A good blood supply
a) more space for gas transfer
b) for dissolving gases
c) easy diffusion
d) that is where the gases come and go from, so there needs to be a lot for easy access of the gases for the alveoli
What are the villi?
They are inside the small intestine (looking kinda like sea anenimies filled with a network of capillaries) and they are tiny. They increase the surface area so that digested food is absorbed much more quickly in the blood
What are some qualities of the villi?
They have a single layer of surface cells (probably easy diffusion)
The have a very good blood supply to assist quick absorption
How does diffusion help in leaves?
Carbon dioxide diffuses into the air spaces within the leaf, then it diffuses into the cells where photosynthesis occurs. The leaf’s structure is adapted so this can happen easily
Where is the main exchange surface on a leaf?
On the underneath of it, and it is covered in stomata which the CO2 can diffuse through, and oxygen (produced during photosynthesis) & water vapour diffuse out
The area of the main exchange surface in a leaf is increased how?
By the leaf being flat
What are the walls of the cells inside the leaf?
Another exchange surface - the air spaces in the leaf increases the area of this surface so there’s more chance for CO2 to get into the cells
Fill the blanks:
Water vapour __________ from the cells inside the ____. Then it escapes by _________ because there’s more air ______ the leaf compared to _______ the leaf
evaporates leaf diffusion inside outside
Why do gills have a large surface area?
For gas exchange - the gills are the gas exchange surface in a fish
How do fish take in oxygen?
Water (with oxygen) is drunk by the fish and passes out through its gills. As this happens, oxygen diffuses out of the water into the blood in the gills and CO2 diffuses from the blood of the gills into the water
What are gills made from and how does this help gas exchange?
Lots of thin plates called gill filaments, which give a big surface area for gas exchange.
The gill filaments are made of lots of tiny structures called lamellae, increasing the surface area even more (they also have lots of capillaries to speed up diffusion, and a thin surface layer of cells to minimise the distance of diffusion)
The concentration of oxygen in the water is always higher/lower than that in the blood, so as much oxygen as possible diffuses from the water into the blood
Higher
How do gills help maintain the large concentration gradient between the water and the blood?
Blood flows through the lamellae (tiny structures in the gills) in one direction and water flows over in the opposite direction.
