B2.1 Flashcards
What is diffusion?
Net overall movement of gas particles from a region of high concentration to a region of low concentration across
Moves down a concentration gradient
Continues until the concentration gradient is zero
Where does diffusion occur in the body?
All cells need glucose and oxygen for respiration so the boood transports these around your body
They diffuse into the cells that need them
What factors affect rate of diffusion?
Distance - takes particles less time to travel a shorter distance so rate of diffusion increases
Concentration gradient - steeper concentration gradient, the greater the net movement
Surface area - increase SA allows more space for diffusion so more particles can move in a period of time
What is osmosis?
Net movement of water molecules across a selectively permeable membrane down a water potential gradient
What happens to plant cells with different WP gradient?
Cell becomes turgid if water enters it as it has a lower WP
Cell remains same if it has the same WP
Cell become flaccid if it loses water and eventually becomes a plasmolyse cell after cell contents collapse away
Where does osmosis occur in animal cells?
Cell placed in a solution that is more dilute will swell and may burst, called lysis
Cell placed in more concentrated solution will lose water, and crenates
What is active transport?
Allows cells to move substances from an area of low to high concentration
As the particles move against their concentration gradient energy must be transferred
What are the 3 key features of active transport?
1) particles are transported against a concentration gradient
2) ATP is required
3) process makes use of carrier proteins in the cell membrane
What are carrier proteins?
They span across the width of the cell membrane
A particular molecule that the cell requires will bind to the carrier protein
Energy is transferred from an energy transfer to the protein so it can change shape of rotate
The molecule is then transported to the cell and rotates or changes shape again
What is mitosis?
The process in which body cells to divide to produce two genetically identical daughter cells
Why does mitosis occur?
Replace worn out cells, repair damaged tissue and enable organism to increase in size
What are the 4 stages of the cell cycle?
DNA replication
Movement of chromosomes
Cytokinesis
Growth of the daughter cell
How is DNA replicated?
The chromosomes need to be copied so:
- the DNA molecule unzips forming two separate strands
- free nucleotides in the nucleus line up against each of the strand with their complementary bases
- this forms DNA base pairings
- when the whole strand is complete there is an identical copy of the DNA
How do the chromosomes move?
- chromosome line up across the centre of the cell
- the two identical copies of each chromosome are pulled apart by cell fibres to opposite ends of the cell
- each end now contains a full set of identical chromosomes
- to new nuclei are formed
What is cytokinesis?
The cell membrane pinches inwards to separate the now two daughter cells
The daughter cells will then grow independently and follow the cell cycle
What is cell differentiation?
The cells become specialised to perform particular jobs
The structure changes so it is better adapted to perform its function
How are sperm specialised?
To transfer genetic material from the male to the ovum. Its adaptions include:
- flagellum (tail) which propels the sperm to the ovum
- lots of mitochondria for respiration so ATP can be produced for the flagellum to move
- acrosome, stores digestive enzymes which break down the outer layers of the ovum to allow the sperm to transfer and incorporate its genetic material
How are fat cells specialised?
To store fat
Enables an animal to survive when food is short, provides insulation and a protective layer around organisms such as the heart
- have a small layer of cytoplasm surrounding a fat reservoir
How is a red blood cell specialised?
Transport oxygen around the body:
- biconcave disc, increases SA to volume ratio speeds up diffusion of oxygen into the cell and CO2 out of it
- packed with haemoglobin, binds to oxygen to form oxyhaemoglobin
- no nucleus, more space for haemoglobin
How are ciliated cells specialised?
The cilia sweeps mucus from lungs produced by goblet cells and any bacteria is swallowed and killed in the tomach
How are palisade cells specialised?
Carry out photosynthesis
Near the surface of the leaves and full of chloroplasts
What are stem cells?
Undifferentiated cells that divide by mitosis and form cells that differentiate and become specialised
Can develop into any type of specialised cell
Used during development, growth, repair
What are the two types of stem cells?
Embryonic - found in embryos, divide by mitosis to produce all the cells needed to make an organism. Can differentiate into all cell types
Adult - found in various body tissues (brain,bone marrow, skin, liver). Can differentiate into some different types of cells but not as many. There are blood stem cells in the bone marrow
Where are stem cells in plants?
The meristems and shoot tips continue to grow throughout a plants life
Where are stem cells found?
Plant meristems
Have very thin walls, small vacuoles and no chloroplasts
- can make stem thicker
