B1 And B2 Flashcards
Eukaryotic cells
Complex - includes all animal and plant cells
Prokaryotic cells
- Simpler and smaller
- Single celled organisms
Nucleus
Contains genetic material that controls the cell
Cytoplasm
Where most reactions happen. Enzymes control the reaction
Cell membrane
Controls what comes in and out
Mitochondria
Where most reactions for aerobic respiration occur
Ribosomes
Where proteins are made
Rigid cell wall
- only in plant
- made of cellulose
- supports and strengthens the cell
Permanent vacuole
- only in plants
- contains cell sap (weak solution of sugar and salts)
Chloroplasts
- only in plants
- where photosynthesis occurs (makes food for the plants)
- contains a green substance called Chlorophyll
Plasmids
- (Not in plant or animal but in bacterial cells)
- small rings of DNA
Bacterial cell contains… (5)
- cytoplasm
- cell wall
- cell membrane
- (optional) plasmids
- single circular strand that floats freely in the cytoplasm
Bacterial cells are…
Prokaryotes
Light microscopes use…
Light
Electron microscopes use…
Electrons - better than light microscopes
Magnification formula
Magnification = image size / real size
How many μm in 1mm?
1000
Differentiation
When a cell changes to become specialised for its job
Stem cells
Undifferentiated cells
Sperm cell. (4)
- reproduction
- long tail and streamline
- lots of mitochondria
- carries enzymes
Nerve cell. (4)
- rapid signalling
- carries electrical signals around the body
- long to cover more distance
- branched connections to form a network across the body
Muscles cells. (3)
- contracts quickly (function)
- long to have space to contract
- lots of mitochondria to generate the energy needed
Root hair cells. (3)
- absorbing water and minerals
- on the surface of plant roots
- big Surface Area to absorb water and minerals
Phloem cells (4)
- transportation
- forms Phloem tubes which transport food and water
- long and join end to end
- few sub-cellular structure so stuff can go through
Xylem cells (4)
- transportation
- forms xylem cells
- long and joined end to end
- hollow
What contains your chromosomes?
Nucleus
Chromosomes are coiled up lengths of…
DNA Molecules
Amount of chromosomes in a human cell
23 pairs (total 46)
Stage 1 of the cell cycle?
Growth and DNA replication
Stage 2 of the cell cycle?
Mitosis
Stage 3 of the cell cycle?
Cytokenisis
What happens during stage 1 of the cell cycle? (3)
- DNA is spread into long strings
- cells increases amount of sub-cellular structure
- duplicates its DNA forming X-shaped chromosomes
What happens during stage 2 of the cell cycle? (2)
- the chromosomes line up at the centre of the cell
- cell fibres pull them apart
What happens during stage 3 of the cell cycle? (3)
- inner membrane forms around the new set of chromosomes
- the cytoplasm and cell membrane divides
- forms two new daughter cells
Stem cells that cannot turn into any cell type
Adult stem cells
Positives of stem cell research (3)
- cure diseases by transferring healthy cells to a patient
- replace faulty cells
- therapeutic cloning makes the embryo have the same genetic info as the patient meaning it wouldn’t get rejected
Negatives of stem cell research. (2)
- human embryos are a potential life threat
- cells grown in labs could get contaminated
Where are stem cells found in the plant?
The meristems
Meristems
Part of the plant where growth occurs
Cells in meristem tissues can differentiate. True of false?
True
Advantages of using stem cells in plants. (2)
- produce clones of whole plants quickly (for endangered plants)
- grow more plants
- make crops with desirable features (eg. Disease resistant)
Osmosis definition
Osmosis is the moment of water molecules through a partially permeable membrane from a region of higher water concentration to an area of lower water concentration
Active transport
Substance that need to be absorbed against a concentration gradient
Example of active transport
- plants need minerals for health growth
- the concentration of minerals is usually higher in the root hair cell than in the soil around it
- so they need to absorb minerals against the concentration gradient
Active transport doesn’t need energy. True of False?
False - needs energy from respiration to make it work
Larger Surface Area means you can absorb more substances at once. True of False?
True
How do you find out how easy it is for an organism to exchange substance?
Surface Area : Volume Ratio
Ways in which exchanging surfaces are adapted to maximise effectiveness. (4)
(Both) - thin membrane = short distance to diffuse
(Both) - big Surface Area = lots of substances can diffuse at once
(Animal) - lots of blood vessels = gets things in and out of blood quickly
(Animal) - gas exchange surfaces are ventilated = air moves in and out
