Year 9 Term 1 Flashcards
Prokaryotic cells
Much smaller than eukaryotic cells and are unicellular, with no nucleus e.g bacteria an blue-green algae
Nucleus
Controls the activity of the cell
Cytoplasm
In which most of the chemical reactions take place which are controlled by enzymes
Cell membrane
Controls the passage of substances in and out of the cell
Mitochondria
Where most energy is released in respiration
Ribosomes
Where protein synthesis takes place
Chloroplasts
Absorb light energy for photonsynthesis
Permanent vacuole
Filled with sap
Cell wall
Physical barrier protects against damage and osmotic lysis
Capsule
Protection and helps bacteria to adhere to each other
Cell-surfaced membrane
Permeable barrier controls entry and exit of chemicals
Chromosomal dna
Genetic information for replication of the cell
Plasmid
Process genes which aid the survival of bacteria
Flagellum
Small whip-like tail for propulsion
How big is a prokaryotic cell
Between 2 and 8 micrometers
Stem cells
Single cells that can replicate themselves and differentiate into many cell types
Eukaryotic cells
Cells which contain a true nucleus and other organelles which are enclosed within membranes e.g plant and animal cells
Where are stem cells found in animals
In the umbilical cord, in bone marrow in adults,
Where are stem cells found in animals
In the meristems of plants
What are meristems and where are they found
They are found in the roots and shoots of a plant and they have the ability to divide over and over again to produce stem cells. The cells can continues to divide and grow taller and wider throughout its life
How does growth happen in animals and plants
In animals it’s by increasing the number of cells but in plants it’s cell enlargements
Cell differentiation in animals and plants
In animals most cells lose the ability to differentiate at an early stage and in plants many cells can differentiate
Mitosis
Cell division in eukaryotic cells. The cell divides to produce 2 new identical copies
cancer
Cancer cells must arise due to mutations in genes that control cell growth (mitosis), this leads to uncontrolled cell growth and results in a tumour
diffusion
Random movement of particles from an area of high concentration to an area of low concentration i.e down a concentration gradient. Diffusion continues until particles are at an even concentration
Where does diffusion take place
Lungs
Leaf
placenta
What factors affect the rate of diffusion
Temperature
Concentration gradient
Surface area
Thickness of diffusion pathway
An example of a short diffusion pathway
alveoli
osmosis
The diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules
What is it called when an animal cell swells and bursts
lysis
What is it called when an animal cell shrivels
crenation
Why doesn’t a plant cell burst
Because it has a cell wall which prevents the cell from bursting
What happens when a plant cell is placed in a concentrated solution
The water molecules will leave the cell and the cell membrane will pull away from the cell wall and is said to be plasmolysed
What happens when a plant cell is placed in a dilute solution
The water molecules will enter the cell from outside and the cell will fill up with water but won’t burst, the cell is said to be turgid
Active transport
Cell use active transport to transport substances across a partially permeable membrane against it’s concentration gradient i.e low to high using carrier protein and energy from respiration
Where does this happen in living systems
Glucose can be reabsorbed into the kidney tumbles by active transport
Plants rely on active transport to obtain minerals through root hair cells.
magnification
The number of times larger an image is compared with the real size of the object
What is the equation for magnification
Size of image (I) / actual size of specimen (A)
Key trick
Always measure your image in mm and most of the time the actual size of specimen is in micrometres
