B1: Cells Flashcards
What is magnification?
How much bigger a sample appears to be under the microscope than it is in real life.
What is resolution?
The ability to distinguish between two points on an image- the amount of detail.
What is the difference between an electron microscope and a light microscope?
Electron: greater magnification, higher resolution, can study cells in finer detail meaning it can understand more cell structures, expensive, require the specimen to be dead.
How do you calculate total magnification?
Total magnification= magnification of eyepiece lense x magnification of objective lense
How do you calculate magnification?
Magnification= image size / actual size
What is an organelle?
Specialized structures within a living cell that perform a function.
What is the method for using a microscope?
- Put the slide on the stage and turn the nose piece to select the lowest power, the end of the objective lense needs to almost touch the slide.
2.Turn the coarse adjustment knob to move the lense towards the slide. Look from the side not through the eyepiece. - Look through the eyepiece and turn the coarse adjustment knob to move the objective lense away from the stage until a imagine of the cells form.
4.Turn the fine adjustment knob to focus the image so it is clear to see. - Switch to a higher power lense and refocus using the adjustment knobs.
- Make a clear, labelled drawing of the cells and write the magnification underneath a label the parts of the cell you can see.
How do you use onion cells when using a microscope?
Peel one thin layer of onion and place it on the slide. Add one drop of iodine and place a coverslip over the top. Remove an excess iodine.
What is a eukaryote?
An organism consisting of cells where the genetic material is DNA in the form of chromosomes contained in a nucleus.
What is the DNA in a prokaryotic cell called?
Plasmids
What structures do prokaryotic cells have?
Cell membrane, DNA, Cytoplasm
How do you convert from mm to micrometres to nanometres?
mm - x1000 - micrometre - x1000 - nanometres
What is bigger a eukaryotic cell or a prokaryotic cell?
Eukaryotic cell
What is differentiation?
The process in which cells, tissue, and organs acquire specialized features, especially during embryonic development.
What is a nerve cells job and how is it adapted to do this?
Job: to carry electrical signals around the body
Adaptations: long, form networks, branched connections
What is a sperm cells job and how is it adapted to do this?
Job: fertilize an egg cell, get male DNA to the female DNA
Adaptations: lots of mitochondria, produced in large numbers, small and long tail to swim
What is a muscle cells job and how is it adapted to do this?
Job: to contract easily
Adaptations: lots of space to contract, lots of mitochondria
What is a root hair cells job and how is it adapted to do this?
Job: to absorb water minerals
Adaptations: big long hairs to stick into the soil, large surface area, no chloroplasts
What is a xylem cells job and how is it adapted to do this?
Job: transports water and ions
Adaptations: hollow in the center
What is a phloem cells job and how is it adapted to do this?
Job: transports glucose
Adaptations: small sieves
What is a stem cell?
An undifferentiated cell that has not yet changed and become a specialised cell.
What are the two cells that can make specialised cells?
Adult and embryonic
Where are adult stem cells found?
Bone marrow
Where are embryonic stem cells found?
The embryo- IVF donation
What is the difference between adult stem cells and embryonic stem cells?
Embryonic can make any possible specialised cell. Adult can only make specific specialised cells (types of blood cells).
Why would someone agree and disagree with stem cell research?
Agree: curing people- more important the the right of embryos, they are unwanted embryos left in fertility clinics
Disagree: embryos are human life, scientists should find other stem cells.
Three advantages from embryonic stem cells?
- these stem cells can develop into most other cells
- it divides every 30 minutes
- low chance of the patient’s body rejecting the cells
Three advantages from adult stem cells?
- it’s cheaper than embryonic
- adults can give their own permission for their bone marrow to be collected
- is is considered a safe procedure
What is the plant stem cell called and where are they found?
Meristem tissue is found in the roots and shoots.
What is the use of meristem stem cells?
Can be used to make clones of plants quickly and cheaply.
How many chromosomes are in most human body cells?
46
How many chromosomes do sperm and egg cells have?
23
What is DNA?
A molecule in cells that contains genetic information.
Name these from biggest to smallest:
Cell, genes, nucleus, chromosome, DNA
Cell, nucleus, chromosomes, DNA, genes
What is mitosis?
The cell cycle where a cell reproduces itself by splitting to form two identical daughter cells.
When is mitosis used?
Growth, repair and replace.
What happens during mitosis?
- The cell has to grow and increase the amount of subcellular structures.
- It then duplicated the DNA so there is a copy of each chromosome.
- Each chromosome lines up in the centre of the cell and cell fibres pull them apart- two arms of each chromosome go to opposite ends.
- Membrane form and these become the nuclei of the two cells.
- The cytoplasm and cell membrane divide.
What are the three stage of the cell cycle?
Stage 1: cell growth- organelles increases
Stage 2: copies of chromosomes
Stage 3: cell divides -cytoplasm and cell membrane
What is diffusion?
The movement of particles from an area of high concentration to an area of low concentration.
What factors effects the rate of diffusion?
Temperature, shorter diffusion pathway, larger surface area, concentration
How are alveoli adapted to make gas exchange very efficient?
- very thin- one cell thick
- good blood supply
- large surface area
What are the gases diffused in gas exchange?
Carbon dioxide and oxygen
How are villi adapted to absorb nutrients?
- very thin
- large surface area
- good blood supply
Why is it important to keep removing the food molecules that have entered the villi?
To provide energy for growth and repair.
To maintain the concentration gradient so diffusion is maximised.
How are plants adapted for quick gas exchange?
- thin leaves
- large surface area
How do you calculate the surface area: volume ratio?
surface area / volume
What is osmosis?
The movement of water to an area of high concentration to low concentration through a partially permeable membrane.
How will the rate of osmosis change if the concentration gradient is greater?
It will increase.
What is the method for the osmosis practical?
- cut three potato cylinders of the same diameter and trim the cylinders so that they are all the same length (about 3 cm).
- accurately measure and record the length and mass of each potato cylinder.
- measure out 10 cm3 of the 1 M sugar solution and place into the first boiling tube (labelled 1 M sugar), measure out 10 cm3 of 0.5 M sugar solution and place into the second boiling tube (labelled 0.5 M sugar), and measure out 10 cm3 of the distilled water into the third boiling tube (labelled water).
- add one potato cylinder to each tube (make sure you know which one is which in terms of the
length and mass and record your lengths and masses in a table such as the one below. - leave the potato cylinders in the boiling tubes overnight in the test tube rack.
6 . remove the cylinders from the boiling tubes and carefully blot them dry with the paper towels and re-measure the length and mass of each cylinder (make sure you know which is which).
What is active transport?
The movement of particles from an area of low concentration to and area of high concentration through a partially permeable membrane and this requires energy from respiration.
