B1 Flashcards
What are the two types of cells?
Eukaryotic and Prokaryotic
What are the differences between eukaryotic and prokaryotic cells?
- Prokaryotic cells are smaller
- Eukaryotic cells contain membrane bound-organelles and a nucleus
What is the prokaryotic cell wall composed of?
Peptidoglycan
How is genetic information stored in a prokaryotic cell?
Found free within the cytoplasm as:
- Chromosomal DNA
- Plasmid DNA
What are plasmids?
Small, circular loops of DNA found free in the cytoplasm they carry genes that provide a genetic advantage
What is order of magnitude?
A power to the base 10 used to quantify and compare size
What is a centimetre?
1 x 10-2
What is a millimetre?
1 x10-3
What is a micrometer?
1 x 10-6
What is a nanometre?
1 x10-9
Other than storing genetic information what is the function of the nucleus?
Controls cellular activities
Describe the structure of the cytoplasm
- Fluid component of the cell
- Contains organelles, enzymes and dissolved ions and nutrients.
What is the function of the cytoplasm?
- Site of cellular reactions
- Transport medium
What is the function of the cell membrane?
Controls the entry and exit of materials into and out of the cell
What is the function of mitochondria?
Site of later stages of aerobic respiration
What is the function on ribosomes?
Protein synthesis
What is a plant wall made of?
Cellulose
What is the function of the plant cell wall?
- Provides strength
- Prevents the cell bursting when water enters
What dies the permanent vacuole contain?
Cell sap (a solution of salts, sugars and organic acids)
What is the function of the permanent vacuole?
Supports the cell, maintaining its turgidity
What is the function of chloroplasts?
Site of photosynthesis
Describe how sperm cells in animals are adapted to their function?
- Haploid nucleus: contains genetic information
- Tail: enables movement
- Mitochondria: provide energy for tail movement
- Acrosome: constrains enzymes that digest the egg cell membrane
Describe how nerve cells in animals are adapted to their function?
- Long axon: allows electrical impulses to be transmitted all over the body from the central nervous system
- Dendrites: from the cell body connect to and receive impulses from other nerve cells, muscles and glands
- Myelin sheath: insulates the axon and speeds up the transmission of impulses along the nerve cell
Describe how muscle cells in animals are adapted to their function?
- Arrangement of protein filaments: allows them to slide over each other to produce muscle contraction
- Mitochondria: to provide energy for muscle contraction
- Merged cells in skeletal muscle: allow muscle fibre contraction in unison
Describe how root hair cells in plants are adapted to their function?
- Large surface area: to absorb nutrients and water form surrounding soil
- Thin walls that do not restrict water absorption
Describe how xylem cells in plants are adapted to their function?
- No upper or lower margins between cells: to provide a continuous route for water to flow
- Thick, woolly side walls: strengthen their structure and prevent collapse
Describe how phloem cells in plants are adapted to their function?
- Serve plates: let dissolve amino acids and sugars be transported up and down the stem
- Companion cells: provide energy needed for active transport of substances along the phloem
What is cell differentiation?
The process by which cells become specialised
Why is cell differentiation important?
Allows production of different tissues and organs that perform various vital function in the human body
At what point in their life cycle do most animal cells differentiate?
Early in their life cycle
For how long do plant cells retain the ability to differentiate?
Throughout their entire life cycle
What is the purpose of cell division in mature animals?
Repair and replacement of cells
What changes does a cell go through as it differentiates?
Become specialised through acquisition of different sub-cellular structures to enable a specific function to be performed by the cell
Define magnification?
The number of times bugger an image appears compare to the size of the real object
Define resolution?
The smallest distance between two objects that can be distinguished
How does a light microscope work?
Passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed
What are the advantages of light microscopes?
- Inexpensive
- Easy to use
- Portable
- Observe both dead and living specimens
What is the disadvantage of light microscopes?
Limited resolution
How does an electron microscope work?
It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible light, producing an image
Name the two types of electron microscopes?
- Transmission electron microscope
- Scanning electron microscope
What is the advantage of electron microscope?
Greater magnification and resolution
Why do electron microscopes have a greater magnification and resolution?
They use a beam of electrons which has a shorter wavelength than photons of light
How have electron microscopes enabled scientists to develop their understanding of cells?
- Allow small sub-cellular structures
- Enable scientists to develop more curate explanations about how cell structure relates to function
What are the disadvantages of electron microscopes?
- Expensive
- Large so less portable
- Require training to use
- Only dead specimens can be observed
How can magnification be calculated?
Magnification= Size of image/size of real object
What nutrients make up a nutrient broth solution?
All nutrients required for bacteria to grow including nitrogen for protein synthesis, carbohydrates for energy and other minerals
What are chromosomes made up of?
Chromosomes consist of DNA molecules combined with proteins. They contain genes which provide the instructions for protein synthesis.
What is a gene?
A section of DNA which code for a protein
How many chromosomes are found in the nucleus of human body cells?
46
How many chromosomes are found in the nucleus of gametes?
23
How are chromosomes arranged in the nucleus of a body cell?
Arranged in pairs - 46 chromosomes form 23 pairs
What are the three main stages of the cell cycle?
- Replication of DNA and synthesis of organelles
- Mitosis
- Division of cell
Why is mitosis important?
- Produces identical cells which all have the same genetic information
- Produces additional cells for growth and repair
Describe the first stage of the cell cycle?
Longest stage- cells grow and increase in mass, replicate DNA and synthesise more organelles
Describe the second stage of the cell cycle?
Each chromosomes in a pair is pulled to opposite poles of the cell, then the nucleus divides
Describe the third stage of the cell cycle?
The cytoplasm and cell membrane divide - two identical daughter cells are produced
What is a stem cell?
An unspecialised cell which is capable of differentiating into other cell types and of self-renewal
What is the function of stem cells in embryos?
Embryonic stem cells can replicate themselves and differentiate into many other types of cells.
They may be able to treat conditions such as paralysis and diabetes by diving to replace damaged cells
What is the function of stem cells in adult bone marrow?
Adult stem cells can differentiate into several cell types to replace dead or damaged tissues.
What is the function of stem cells n plant meristems?
Meristem stem cells retain the ability to differentiate into any type of plant cell throughout their lifespan - they can differentiate into any cell which is required by the plant.
What is therapeutic cloning?
A cloning method where an embryo is produced with the same genetic makeup as the patient the stem cells which originate from the embryo will not be rejected by the patients immune system, so it can be used to treat certain conditions.
What are the advantages of cling plants using meristem stem cells?
- Can prevent rare plants from becoming extinct
- Can produce large numbers of plants with a favourable characteristic
- Can produce identical plants for research
What are issue that are associated with the use of embryonic stem cells?
- Ethical/ religious objection
- Development of stem cell therapies is slow, expensive and difficult
- Adult stem cells infected with viruses could transfer infections
- If donor stem cells do not have similar genetic makeup and immune response could be triggered
What is diffusion?
The net movement of particles from an area of higher concentration to an area of lower concentration
What three main factors affect the rate of diffusion?
- Concentration gradient: large gradient, faster diffusion
- Temperature: higher temp, faster diffusion
- Surface area: larger surface area faster diffusion
Give examples of substances transported by diffusion in the lungs and the kidney?
- Lungs: oxygen diffuses into the blood form the lungs and carbon dioxide diffuses into the lungs from the blood, both down their concentration gradient
- Kidney: urea diffuses from cells into blood plasma so it can be excreted in urine
How are single-celled organisms adapted for diffusion?
They have a large surface area to volume ratio
How is surface area to volume calculated?
Surface area = Number of sides x (side length x side width)
Volume = length x width x depth
Ration = surface area:volume
What four factors increase the effectiveness of a gas exchange surface
- Large surface area
- Thin membrane
- Efficient blood supply
- Ventiliation
What is osmosis?
The movement of water form a dilute solution to a concentrated solution through a partially permeable membrane
What is meant when a solution is isotonic to a cell?
The concentrations of the external and internal solution are the same
What is meant when a solution is hypertonic to a cell?
The concentration of the external solution is higher than that of the internal solution
What is meant when a solution is hypotonic to a cell?
The concentration of the external solution is lower than that of the internal solution
How do plant leaves and stems remain rigid?
Turf or pressure - water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall
How do plant root hair cells use active transport?
Root hair cells use active transport to take up mineral ions from a more dilute solution in soils. Ions such as magnesium and nitrates are required for healthy growth
How is active transport used to absorb the products of digestion?
Active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood. Glucose is then transported to the tissues where it can be used in respiration.
