B2 - Scaling Up Flashcards
What is diffusion?
The net (overall) movement of particles from a region of high concentration to a region of low concentration.
Do the particles in diffusion move down or against a concentration gradient?
Down
What factors affect the rate of diffusion?
1) distance
2) concentration gradient
3) surface area
How do you increase the rate of diffusion?
1) decrease the distance the particles need to move
2) increase the concentration gradient
3) increase the surface area
What is osmosis?
The diffusion of water molecules across a selectively permeable membrane
What is the water potential?
The concentration of free water molecules
What type of water has the highest possible water potential?
Pure water
Does osmosis move down or against a concentration gradient?
Down
What happens to a plant cell if the surroundings are a less concentrated solution than cell contents?
1) it takes up water by osmosis
2) the pressure in the cell increases
3) the cell becomes firm or turgid
What happens to a plant cell if the surroundings have the same concentration as the cell contents?
1) there is no net movement of water
2) the cell remains the same
What happens to a plant cell if the surroundings are a more concentrated solution than cell contents?
1) it loses water by osmosis
2) the pressure in the cell decreases
3) the cell becomes flaccid (soft)
4) the cell contents collapse away from the cell wall
5) the cell becomes plasmolysed
What happens to an animal cell if the surroundings are a less concentrated solution than cell contents?
1) it takes up water
2) swells and may burst
3) undergoes lysis
What happens to an animal cell if the surroundings have the same concentration as cell contents?
1) there is no net movement of water
2) the cell remains the same
What happens to an animal cell if the surroundings are a more concentrated solution than cell contents?
1) loses water by osmosis
2) cell becomes crenated (it crinkles)
Does active transport move down or against a concentration gradient?
Against
What are the three key features of active transport?
1) particles are transported (pumped) against a concentration gradient
2) ATP is required
3) the process makes use of carrier proteins in the cell membrane
What do cells that carry out a lot of active transport contain many of?
Mitochondria
What does the rate of active transport depend on?
The rate of respiration to produce the required ATP
What do carrier proteins do?
Transports molecules into the cell
When is active transport used?
Whenever a substance needs to be moved against a concentration gradient
Give examples of when active transport is used.
1) digestion - in the small intestine carbohydrates are broken down into glucose. Glucose is actively transported into the bloodstream through the villi
2) nerve cells - a carrier protein actively pumps sodium ions out of the cell. At the same time potassium ions are pumped back in. The sodium potassium pump plays an important role in creating nerve impulses
3) plants - plants use active transport to take in minerals from the soil
Why do body cells divide?
1) to replace worn out cells
2) to repair damaged tissue
3) to enable the organism to increase in size
What is mitosis?
The process in which body cells divide
What does mitosis produce?
Two identical daughter cells
What is the process of cell growth and division called?
Cell cycle
What are the four stages in the cell cycle?
1) DNA replication
2) movement of chromosomes
3) cytokenesis
4) growth of the daughter cells
How is DNA replicated?
1) the DNA molecule ‘unzips’ forming two separate strands
2) the DNA bases on each strand are exposed
3) free nucleotides in the nucleus line up against each of the strand following the rule of complementary base pairing
4) this forms DNA base pairs
5) when the whole strand is complete, there are two identical molecules of DNA
How do chromosomes move?
1) the chromosomes line up across the centre of the cell
2) the two identical copies of each chromosome, formed when the DNA replicated, separate and move to opposite ends of the cell
3) each end now contains a full set of identical chromsosomes
4) two new nuclei then form
How are sperm cells specialised?
To transfer genetic material from to the ovum (egg)
What do the flagellums on sperm cells do?
Whips from side to side to propel the sperm to the ovum
Why do sperm cells have lots of mitochondria?
Respiration occurs in mitochondria, and the reactions of respiration transfer energy from chemical stores so that the flagellum can move
What do the acrosome in sperm cells do?
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
How are red blood cells specialised?
To transport oxygen around the body
What are the three main adaptations of re blood cells?
1) biconcave discs - they are pushed in on both sides to form a biconcave shape, which increases the surface are to volume ratio, speeding up the diffusion of oxygen into the cell and carbon dioxide out of the cell
2) packed full of haemoglobin - this protein binds to oxygen to form oxyhaemoglobin, which is bright red
3) no nucleus - this means that there is space to contain more haemoglobin molecules
What do goblet cells produce?
Sticky mucus
