Topic 1: Cell Biology Flashcards
What microscope has the highest magnification?
Electron microscope
What microscope is used in schools?
Light microscope
What is the formula for magnification?
Magnification= image size/real size
What are studied using microscopes?
Cells
What are eukaryotes?
Organisms made up of eukaryotic cells
What are prokaryotes?
A prokaryotic cell
What is the function of the nucleus?
Contains genetic material of the cell
What is the function of the mitochondria?
Where aerobic respiration takes place
What is the function of the cytoplasm?
Where chemical reactions happen
What is the function of the cell membrane?
Controls what goes in and out of the cell
What is the function of the ribosomes?
Where proteins are made
What is the function of the cell wall?
Supports the cell/strengthens it
What is the function of the permanent vacuole?
Contains cell sap
What is the function of the chloroplasts?
Where photosynthesis occurs
What are bacteria?
Prokaryotes
What do bacteria cells not have?
A ‘true’ nucleus only a single circular strand of DNA in the cytoplasm, chloroplasts or mitochondria
What are the rings of DNA called?
Plasmids
What is the process of differentiation?
Differentiation is the process by which a cell changes to become specialised for it’s job
What is the function of a sperm cell?
To get male DNA to the female DNA
How are sperm cells specialised?
- long tail to help swim to the egg
- lots of mitochondria to provide energy needed
- carries enzymes in head to digest through egg cell membrane
What is the function of nerve cells?
To carry electrical signals from one part of the body to another
How are nerve cells specialised?
- long so can cover long distances
- branched connections to connect to other nerve cells and form a network around the body
What is the function of muscle cells?
To contract quickly
How are muscle cells specialised?
- long so have space to contract
- lots of mitochondria to generate energy needed for contraction
What is the function of root hair cells?
Absorb water and minerals
How are root hair cells specialised?
- long hairs that stick into soil which gives plant big surface area for absorbing water and mineral ions from soil
What is the function of phloem and xylem cells?
xylem- transports water around the plant
phloem- transports food and minerals around plant
How are phloem and xylem cells specialised?
- cells joined end to end to make the tubes
- phloem cells have very few subcellular structures, so stuff can flow through them
Where are stem cells found?
In early human embryos
What can embryonic stem cells do?
Turn into ANY type of cell
What could stem cells do?
May be able to cure many diseases
Why are some people against stem cell research?
some people feel it’s potential human life
How do stem cells produce identical plants?
- stem cells found in meristems
- cells in meristems can differentiate into any type of cell
- stem cells can be used to produce clones
- prevent a species being wiped out
- grow crops for farmers
What do chromosomes contain?
Genetic information
Where are chromosomes found?
In the nucleus
What do chromosomes do?
Carries large number of genes, different genes control different characteristics
How many copies of chromosomes does everyone have?
Two copies, one from the mother and one from the father, we have 23 pairs of chromosomes
What does the cell cycle do?
Makes cells for growth, development and repair
What is mitosis?
The stage in the cell cycle when the cell divides
What is the 2nd stage of the cell cycle?
Growth and DNA replication
What happens at the end of the cell cycle?
Results in 2 new cells identical to the original cell, same number of chromosomes
What is growth and DNA replication?
- In a cell that’s not dividing, DNA splits out into long strings
- Before it divides, the cell has to grow and increase the number of subcellular structures
- DNA is duplicated and is copied into chromosomes, each ‘arm’ is a duplicate copy
Describe mitosis
- chromosomes line up and cell fibres pull them apart
- membranes form around each set of chromosomes, these become nuclei of the two new cells- nucleus divided
- cytoplasm and cell membrane divide
- two new daughter cells are produced, exactly the same DNA and identical
Define diffusion
the spreading out of particles from an area of high concentration to an area of low concentration
What factors affect diffusion rate?
- bigger concentration gradient: faster diffusion rate
- higher temperature: faster diffusion rate (particles have more energy)
How do dissolved substances move in and out of cells?
by diffusion
What can only diffuse through cell membranes?
Very small molecules such as oxygen, glucose, amino acids and water
How does the surface area of the membrane affect diffusion rate?
The larger the surface area of the membrane, the faster the diffusion rate because more particles can pass through at once
What is the definition of osmosis?
Osmosis is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of a lower water concentration
Why is osmosis a different type of diffusion?
movement of water particles from an area of higher water concentration to an area of lower water concentration
How do root hairs take in minerals and water?
- each branch of root covered in millions of microscopic hairs
- gives plant large surface area for absorbing water + mineral ions from soil
Why do plants need mineral ions?
For healthy growth
Why can’t root hair cells use diffusion to take up minerals from the soil?
concentration of minerals usually higher in the root hair cells than in the soil around them
How do root hair cells take up minerals?
Using active transport
What is active transport?
the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.
What does active transport allow?
allows the plant to absorb minerals from a very dilute solution, against a concentration gradient- essential for growth
What does active transport need to work?
energy from respiration
Why do humans need active transport?
it is used in the gut when lower concentration of nutrients in gut but higher concentration of nutrients in blood
How does active transport in humans work?
- when lower concentration of nutrients in gut compared to blood
- means concentration gradient is wrong way
- use active transport
- allows nutrients to be taken in the blood despite fact concentration gradient is wrong way
What are some examples of exchanging substances?
- oxygen and carbon dioxide transferred between cells and the environment during gas exchange
- in humans, urea diffuses from cells into blood plasma for removal of the body by the kidneys
Why do organisms need to exchange substances?
to get rid of waste products
Why do multicellular organisms need exchange surfaces?
they have smaller surface area compared to their volume- not enough substances can diffuse from their outside surface to supply their entire volume- need some sort of exchange surface for efficient diffusion
How have exchange surfaces adapted to maximise effectiveness?
- thin membrane: substances only have short distance to diffuse
- large surface area : lots of substance can diffuse at once
- lots of blood vessels: (animals) to get stuff into and out of the blood quickly
- gas exchange surfaces: (animals) often ventilated- air moves in and out
How does gas exchange happen in the lungs?
- lungs transfer oxygen to the blood and remove CO2 from it
- lungs contain millions of alveoli where gas exchange takes place
- alveoli are specialised: an enormous surface area, good blood supply, very thin walls, moist lining for dissolving gases
