1. Cells Flashcards
How has greater resolution of electron microscopes increased our understand of cell structures?
Electron microscopes use a beam of electrons to allow us to see structures that can be as close as a 10000th of a micrometer, meaning we can see more detail of a structure and better understand how it might function
How do you calculate magnification ?
Magnification : size of image divided by size of real object using a scale bar
Explain the function of the cell membrane
Controls entry and exit of substances from the cell
Explain the function of chromosomes
Thread-like structures composed of DNA that carry genes
Explain the function of the nuclear membrane
Enclosed the genetic material inside the nucleus
Explain the function of the cytoplasm
Site of chemical reactions in the cell
Explain the function of the nucleus
Control centre of the cell
Explain the function of the mitochondria
Structures in the cell responsible for releasing energy during respiration
Draw an animal cell
Nucleus
Cell membrane
Mitochondria
Cytoplasm
Explain the function of the Cellulose cell wall
Provides strength and shape to the cell
Explain the function of of chloroplasts
Contain the green pigment, chlorophyll to absorb light for photosynthesis
Explain the function of the permanent vacuole
Stores water, salt and sugars
Draw a plant cell
Cell wall Cell membrane (inside cell wall) Vacuole Cytoplasm Mitochondria Chloroplasts Nucleus
Name four differences between the bacterial cells and other cells
- they do not contain a nucleus
- they have 1 large circular chromosome and extra small rings of DNA (plasmids)
- they have a cell which isn’t made of cellulose
- they are much smaller compared to plant and animal cells
What happens to the area you see as magnification increases?
The area of the field of view decreases and the resolution of the image isn’t as clear
How do you calculate the actual size?
Actual size = image size divided by magnification
What are stem cells?
A group of unspecialised cells which have the ability to divide to produce more stem cells and become any type of cell required by the body
Where are stem cells found on a plant?
The meristems at the apices of roots and stems. Many if these cells retain the ability to divide and so can be used in cloning techniques
Name one ethical concern for the use of adult bone marrow
Theoretically the technology could allow humans to be cloned
Name 3 limitations for adult bone marrow stem cells
Not all cell types can be produced, only specific types of blood cell
Cells have a limited life span
Cells can be hard to grow
Name ethical concerns for the use of stem cells in medicine (3)
- Harvesting of the cells may result in the abortion of the embryo
- Theoretically humans could be cloned
- Creation of embryos artificially for the sole purpose of generating stem cells and then killing them raises similar debates to abortion of embryos
Give an example of when stem cells may be used
With leukaemia patients, a bone marrow transplant containing donor stem cells can be given after chemotherapy to replace the white blood cells and bone marrow that was destroyed
Define diffusion
Diffusion is the random molecular movement of molecules from a region of high concentration to a region of lower concentration alone a concentration gradient
Give three examples of diffusion in biology
- gas exchange in the lungs
- gas exchange in leaves during photosynthesis
- absorption of digested food molecules in the gut
When does a rapid rate of diffusion occur?
A rapid rate of diffusion is allowed when the temperature is warm, the difference in concentration is greater and the surface area is high
List the levels of organisation
Cell - tissue - organ - organ system - organism
Explain why as organisms increase in size they have more difficultly exchanging and transporting substances
As an organisms size increases, it’s surface area to volume radio decreases
Name two systems that make exchange and transport more efficient
- The respiratory system
- The circulatory system
Where can stem cells be harvested from in an animal ?
Stem cells have be harvested from the embryonic umbilical chord or bone marrow (adult)
Why is it important to use the fine focus knob?
Using other knobs focuses the image in and out top quickly and it is difficult to adjust with precision
What structures do plant cells have that others don’t? (3)
- Cellulose Cell Wall
- Large Permanent vacuole
- chloroplasts
Describe what Leukaemia is and how stem cells are used to treat it: (4)
- Leukaemia is a form of cancer affecting white blood cells.
- White blood cl so are unable to function correctly and so diseases cannot be fought off
- Treatment involves the patients unhealthy white blood cells and bone marrow being destroyed by chemo and radiotherapy
- The patient is then given a bone marrow transplant that contains donor stem cells
Risks of treating patients with stem cells vor Leukaemia : (3)
- Patients can be left with no immunity and therefore susceptible to infection
- This leads to patients being treated in highly specialised medical units and have limited contact with family / friends
- The donated stem cells could divide in an uncontrolled way producing tumours and unwanted cells types
Why do plant cells tend to have a more fixed shape and rigid structure than animal cells ?
The cell wall of the plant cell makes it rigid
The more active a cell the more mitochondria. Which types of cells have the largest numbers of mitochondria ?(3)
- Muscle
- Liver
- Sperm
What are the advantages of cells having cell organelles ?
It isolated cells that might be damaging
Why are Ring shapes sometimes observed on cells in the microscope ?
Air bubbles have been trapped in the coverslide
Name the steps to calculate magnification of a leaf cell
Measure bar in mm = 20mm
- Convert mm to micrometer
( 20 x 1000 = 20000 micrometers ) - divide measured length by the printed measurement
( 20000 divided by 5 = x 4000)
Why must the onion tissue used only be 1 cell thick?
- Onion cells more than 1 cell thick would overlap and the cells wouldn’t be clear to see under the microscope
How is a Petri dish sterilised ?
Heat up to a temperature above the water
Why is iodine and methylene blue used in the onion practical ?
They stain the starch granules and make them visible
Risks of using stem cells in Leukaemia treatment (3)
- Patients can be left with no immunity during the process making them susceptible to infection
- Patients May have to be treated in highly specialised medical units and have limited contact with family/friends
- Donated stem cells could divide in an uncontrollable way producing tumours
Two structure in the bacterial cells that contain DNA
- In the form of a circular chromosome in the cytoplasm
- In the plasmids
Describe making a slide (6)
- Forceps are used to peel the thin, transparent layer of epidermis cells
- Epidermis cells are then placed on a microscope slide with a few drops of Iodine solution or methylene blue
- These chemicals stain the cells and make certain parts more obvious
- A coverslide is then lowered onto the onion epidermis using a mounted needle or forceps
- Lower coverslip one end first as this helps to prevent trapping air bubbles
- Coverslip prevents the cell drying out
Factors affecting diffusion
- Concentration gradient
- Temperature
- surface area
Why does being multi-called not contribute to efficient exchange of substances ?
The body cells are closely packed together which increases volume but not surface area
Stem cells two important abilities (2)
- to continue dividing by cell division to produce more stem cells
- to differentiate into a wide variety of specialised cell types
