B1 - Cell Biology

what is are eukaryotic cells?

they are complex cells and contain a nucleus. organisms made up of these are call eukaryotes

what are prokaryotic cells?

PRO = NO

they are simpler and smaller cells and they do not contain a nucleus. organism made up of these is call a prokaryote.

what are the sub-cellular structures that plant and animals cells have with their functions?

• nucleus - contains genetic material that controls the activities of the cell

• cytoplasm - gel like substance where most of the chemical reactions occur

• cell membrane - holds the cell together and controls what goes in and out

• mitochondria - where most aerobic respiration takes place which provides energy

• ribosomes - were proteins are made

what are the sub-cellular structures that are only in plant cells and their function?

• cell wall - made of cellulose and it supports and strengthens the cell

• permanent vacuole - contains cell sap

• chloroplasts - where photosynthesis occurs to provide food for the plant. It also contains …

• chlorophyll - a green substance that absorbs the light needed for photosynthesis

what are the subcellular structures of a bacteria cell?

• Cytoplasm

• cell membrane

• cell wall

• single circular strand of DNA

• plasmids - small rings of DNA

which microscope gives a higher resolution and magnification?

electron microscope

how do you calculate magnification?

image size ➗ real size

what is the method to prepare your slide?

1. add a drop of water in the middle of your slide

2. cut up an onion and separate the layers, then use tweezers to peel off some epidermal tissue

3. using tweezers place the epidermal tissue into the water on the slide

4. add a drop of iodine solution so that the stains highlight the subcellular structures

5. place a cover slip on top.

what are the rules to drawing your observations from a microscope?

• draw in pencil

• don’t shade it in

• add labels

what is differentiation?

the process by which a cell changes to become specialised for its job

when do cells differentiate?

most occur as an organism is developing

• animal cells lose the ability to differentiate at a young age ( the cells that do differentiate in mature cells are mainly used for repair and replacement).

• plant cells don’t ever lose the ability

what are some examples of specialised cells?

1. sperm cells are specialised for reproduction - it has a long tail and a streamline head to help it swim and a lot of mitochondria for energy to reach the egg.

2. Nerve cells are specialised for rapid signalling - they are long to cover more distance and have branched connections at the ends connect to over nerve cell and form a network

3. muscle cells are specialised for contraction - they are long and contain lots of mitochondria so that they have room to contract and generate lots of energy

4. Root hair cells to absorb water and minerals - big surface area to allow more absorbtion to occur

5. Phloem and Xylem cells for transporting substances - xylem tubes are hallow and phloem tubes have very few subcellular structure so that food and water can be carried round the plant

what does the nucleus contain?

genetic material in the form of chromosomes which are coiled up lengths of DNA.

how many chromosomes are in a human body?

23 pairs, 46 all together

what is mitosis

1. the cell grows and increases the amount of subcellular structures

2. it then duplicates its DNA

3. the chromosomes are lined up at the centre of the cell and the cell fibres pull them apart

4. two arms of each chromosomes go to opposite sides of the cell

5. the membrane forms around each of the sets of chromosomes and divides the nucleus

6. the cytoplasm and cell membrane divides creating two identical daughter cells.

what is special about embryonic stem cells?

they can differentiate into an y type of cell.

where are stem cells found?

• in early human stem cells

• adults in bone marrow but can’ turn into any type of cell (blood cells)

• in plants - the meristem

how can stem cells be used to cure diseases?

• adult stem cells transferred from the bone marrow from a healthy person can replace faulty blood cells in the patient that receives them.

• stem cells from embryos and bone marrow can be grown in a lab to produce clones ( genetically identical cells ) and made to deffrentiate into specialised cells to be used in medicine or research.

why are some people opposed to using stem cell research?

• people believe that embryos are possible human lives so they shouldn’t be experimented on.

• existing suffering patients are more important.

• there is a risk of infection.

what can plant stem be used for?

during there whole life they can defrentiate

• to produce clones of whole plants quickly and cheaply.

• to grow more plants of rare species.

• to grow crops of identical plants but they have desired features (e.g disease resistant)

what is diffusion?

the gradual movement of particles from an area of high concentration to an area with lower concentration.

why does diffusion occur in gases and solutions?

because the particles are free to move about randomly.

what factors affect the rate of diffusion?

• bigger concentration = faster rate

• higher temperature = higher rate because they have more energy.

• bigger surface are = faster rate

how does the cell membrane use diffusion?

only small molecules like oxygen (needed for respiration), glucose ,animo acids to diffuse through the cell membrane but not big molecules like starch and protein.

what is osmosis?

the net movement of water molecules across a partially permeable membrane from a higher water concentration to a lower water concentration.

what is a partially permeable membrane?

a membrane with very small wholes so only tiny molecules can pass through them.

describe the net movement of water molecules.

because there are more water molecules on one side there’s a steady net flow of water into the region with a fewer water molecules. This means that the stronger sugar solution becomes more dilute.

what is the method for observing the effects of sugar solutions on plant tissues?

1. cut up a potato into identical cylinders and fill about 5 beakers with different sugar solutions from 0mol/dm3 to 1mol/dm3

2. measure the mass of each cylinder and place one in each cylinder and leave them for 24 hours.

3. then take them out and pat them dry to get rid of any excess water and measure there masses again.

4. calculate the change in mass for each cylinder and then the percentage change in mass.

5. repeat steps 1-4 about 3 times and calculate an average mean in mass.

what is active transport?

the movement of substances from a low concentration to a high concentration. (this requires energy as it goes against the concentration gradient.

what is the function of root hair cells?

they have a large surface area to absorb more mineral ions and water.

why can’t root hair cells use diffusion?

because root hair cells tend to have a higher concentration inside the cell than in the soil, so it uses active transport.

how does active transport use active transport?

it allows them to absorb minerals against the concentration gradient so active transport needs energy from respiration to make it work.

how do our bodies use active transport?

when there is a low concentration of nutrients in the gut then there is blood. Active transport allows nutrients to be taken into the blood, despite the concentration gradient being the wrong way, so that glucose can be transported to cells for respiration.

give an example of how cells use diffusion to take in substances they need and get rid of waste products.

oxygen and carbon dioxide are transferred between cells and the environment during gas exchange

what does exchange rate depend on ?

how easy it is for an organism to exchange substances depends on their surface area to volume ratio.

why do multicellular organisms need exchanging surfaces?

they have a smaller SA compared to volume, meaning they need an exchange surface for diffusion.

exchange surfaces are adapted to minimise…

• thin membrane= short distance to diffuse

• large surface area = lots of substances can diffuse at once

• lots of blood vessels = to get substances in and out of the blood quicker

how does gas exchange occur in the lungs?

The alveoli have an enormous surface area, moist lining very thin walls and a capillary surrounding them to maximise diffusion.

how does the villi help gas exchange in the small intestine?

They increase the surface area so that digested foods can get into the blood quicker.