B1 - Cell Biology

Created by

Sophie Hamilton-Mills

Cards (44)

What are the two types of cell?
E ukaryotic
P rokaryotic
What are examples of eukaryotic cells?
P lant
A nimal
What is an example of a prokaryotic cell?
Bacterial
What is a prokaryote?
A single celled organism
What subcellular structures do animal cells have and what are their functions?
N ucleus - contains genetic material and controls the activities of the cell.
C ytoplasm - most chemical reactions here and contains enzymes
C ell M embrane - holds cell together and controls what goes in and out.
M itochondria - reactions for aerobic respiration which transfers energy the cell needs.
R ibosomes - where protein synthesis takes place.
What subcellular structures do plant cells have that animal cells don't and what are their functions?
C ell W all - made of cellulose and supports and strengthens the cell.
V acuole - contains cell sap (solution of sugar and salts).
C hloroplasts - where photosynthesis happens and contains chlorophyll which absorbs the light needed.
How are bacterial cells different to plant and animal cells?
They do not have chloroplasts or mitochondria.
They don't have a true nucleus and instead have a singular circular strand of DNA.
They can also have small rings of DNA called plasmids.
What do microscopes do?
Let us see things we can't see with the naked eye.
What is a light microscope?
Use light and lenses to form an image and magnify it.
They let us see individual cells and large subcellular structures like the nucleus.
What is an electron microscope? 
Use electrons instead of light to form an image.
They have a much higher magnification than light microscopes.
They also have a higher resolution which creates a sharper image.
They allow us to see smaller structures like mitochondria and ribosomes.
How do you calculate magnification?
Magnification = Image size / Object size
What is a slide?
A strip of clear glass or plastic onto which the specimen is mounted.
How do you prepare a slide to view onion cells?
> Add a drop of water onto the middle of a clean slide.
> Cut up an onion and use some tweezers to peel off some epidermal tissue.
> Place the tissue into the water.
> Add a drop of iodine.
> Place a coverslip on top by carefully tilting and lowering it.
Why is iodine solution used when viewing onion cells?
It is a stain.
It highlights objects in a cell by adding colour to them.
Why are coverslips lowered carefully onto the slide?
It stops air bubbles getting underneath which could obstruct the view of the specimen.
How do you use a light microscope to view a specimen?
> Clip the prepared slide onto the stage.
> Used the lowest powered objective lens.
> Use the coarse adjustment knob to move the stage up.
> Look down the eyepiece and use the coarse adjustment knob to focus the image.
> Adjust the focus with the fine adjustment knob to produce a clear image.
> Use a higher powered objective lens to have a greater magnification.
What is differentiation?
The process by which a cell changes to become specialised for its job.
How are sperm cells specialised for reproduction?
> Long tail and streamlined head - swim to egg.
> Lots of mitochondria - provides energy needed.
> Enzymes held in the acrosome - digest through egg cell membrane.
How are nerve cells specialised for rapid signalling?
> They are long - cover more distance.
> They have branched connections - connect to other nerve cells in a network.
How are muscle cells specialised for contraction?
> They are long - have space to contract.
> Lots of mitochondria - generate energy needed for contraction.
How are root hair cells specialised for absorbing water and minerals?
> Large surface area - absorb more water and minerals from the soil.
How are phloem and xylem cells specialised for transporting substances?
> Joined end to end - form long tubes.
> Xylem cells are hollow and phloem cells have few subcellular structures - stuff can flow through them.
What are chromosomes?
Coiled up lengths of DNA molecules in the nucleus which carry genes.
These control the development of different characteristics.
How many chromosomes does each human cell contain?
23 pairs.
One from each parent.
What is mitosis?
The stage of the cell cycle where the cell divides.
What do multicellular organisms use mitosis for?
Growing or replacing cells that have been damaged.
What is the cell cycle?
> Number of subcellular structures are increased.
> DNA is then duplicated so that each new X shaped chromosome has two copies of the DNA.
> Chromosomes line up down the centre of the cell and the cell fibres pull them apart.
> Membranes form around the chromosomes which forms the nuclei.
> The cytoplasm and the cell membrane then divide.
> This produces two identical daughter cells.
What is binary fission?
> Circular DNA and the plasmids replicate.
> The cell gets bigger and the circular DNA strands move to opposite poles of the cell.
> The cytoplasm begins to divide and new cell walls form.
> The cytoplasm then fully divides and two daughter cells are produced.
> These have the same circular DNA strand but variable copies of the plasmids.
What conditions do bacteria need to reproduce?
A warm environment.
Lots of nutrients.
What is the mean division time?
The average amount of time it takes for one bacterial cell to divide in two.
What are stem cells?
Undifferentiated cells that can differentiate into different types of cells depending on the instructions given.
What are embryonic stem cells?
Found in early human embryos.
They can turn into any type of cell.
What are adult stem cells?
Only found in certain places like bone marrow.
They can only turn into certain types of cells like blood cells.
What is diffusion?
The spreading out of particles from an area of higher concentration to an area of lower concentration.
What increases the diffusion rate?
Having a larger concentration gradient.
A higher temperature as the particles have more energy.
How do cell membranes filter substances?
They let dissolved substances in and out by diffusion.
Only small molecules like oxygen, glucose, amino acids and water can fit through.
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.
What is active transport?
The movement of particles from a lower concentration to a higher concentration using energy from respiration.
Why is active transport needed in plants?
Root hair cells absorb mineral ions and water from the soil.
To absorb all the nutrients, plants use active transport as well as diffusion.
How are exchange surfaces adapted to maximise effectiveness?
> Thin membrane - substances have a short distance to diffuse.
> Large surface area - more substances can diffuse at once.
> Lots of blood vessels - maintains a steep concentration gradient as substances are taken away.
> Gas exchange surfaces are often ventilated.