1 - Key Concept in Biology Flashcards
(36 cards)
Is a plant cell a prokaryotic cell or a eukaryotic cell?
A eukaryotic cell
In which sub-cellular structures do most of the reactions of aerobic respiration take place?
Mitochondria
Describe the main similarities and differences between a bacterial cell and a plant cell.
Similarities: e.g. both have a cell membrane, a cell wall and a cytoplasm.
Differences: e.g. plant cells have chloroplasts and mitochondria but bacteria do not. Plant cells also have a true nucleus, whereas bacteria have a single circular strand of DNA that floats freely in the cytoplasm. Bacterial cells may also contain small rings of DNA called plasmids
What is the purpose of the fine adjustment knob on a light microscope?
It’s used to focus the lens until a clear image of what’s on the slide appears
True or false? Electron microscopes have a smaller magnification than light microscopes, but they have a higher resolution than light microscopes
False
Electron microscopes have both a higher resolution and a higher magnification than light microscopes.
How has electron microscopy increased biologists’ understanding of cells?
Electron microscopes let us study cells in much finer detail than light microscopes. This has enabled biologists to see and understand more sub-cellular structures, such as ribosomes and plasmids, and the internal structures of mitochondria and chloroplasts.
A specimen is 100 μm wide. Calculate the width of the image of the specimen under a magnification of x200
Give your answer in mm
Use the equation: magnification = image size/real size
20mm
Image size = magnification x real size
= 200 x 100 μm = 20000μm
=20000μm / 1000 = 20mm
Which cells in plants are specialised for absorbing water and minerals from the soil?
root hair cells
What is the function of a sperm cell?
To transport male DNA to the female DNA in eggs for reproduction
What is the function of xylem cells? How are xylem cells specialised for this function?
Xylem cells function to transport water and minerals up plants. They are specialised for their function because the cells are long and are joined end to end, forming hollow tubes. This means that substances can flow through them.
What is the function of a nerve cell? How is a nerve cell adapted for its function?
A nerve cell carries electrical impulses from one part of the body to another. The cell is long and has branched connections at its ends to connect to other nerve cells and form a network throughout the body. This allows for rapid signalling.
Exocrine acinar cells function to produce lots of digestive enzymes, which are then secreted from the pancreas. Suggest one way that these cells may be specialised for their function.
E.g. the exocrine acinar cells may contain a large number of ribosomes for the synthesis of digestive enzymes
Name a gas molecule that can diffuse through cell membranes.
E.g. oxygen and carbon dioxide
How does the concentration gradient affect the rate of diffusion?
The bigger the concentration gradient, the faster the rate of diffusion.
Oxygen diffuses from the blood stream into muscles,. During exercise, oxygen is used up in the muscles faster than when a person is at rest. Suggest how the rate of oxygen diffusion might differ when a person is running compared to when they are sitting down.
The diffusion rate will be greater when the person is running compared to when the person is sitting down. This is because there will be a lower concentration of oxygen in the muscles, meaning there will be a greater concentration gradient and so a faster rate of diffusion
What type of membrane is needed for osmosis to happen?
A partially permeable membrane
True or false? Oxygen entering the blood from the lungs is an example of osmosis
False.
This happens by diffusion. Osmosis involves the movement of water.
Lois has two potato cylinders. The fluid inside the potato cell has a concentration of 0.3 mol/dm^3. She weighs the two cylinders and places one into a beaker of pure water and the other into a beaker of 0.1 mol/dm^3 glucose solution. After 24 hours, she removes the cylinders, dries them, and measures their final mass. Explain how the mass of each potato cylinder will have changed after 24 hours.
The mass of the cylinder in pure water will have increased because the water will have moved by osmosis from an area of higher water concentration to an area of lower water concentration. The mass of the cylinder in the glucose solution will have decreased, as water will have moved by osmosis from an area of higher water concentration to an area of lower water concentration
When plants lose water, they start to wilt. Explain why most plants will wilt if the soil they are growing in is flooded with salty sea water.
The sea water has a high concentration of salt, so the water concentration in the soil will be lower than that in the plant. This means water would move by osmosis from the plant to the soil, causing the plant to lose water and wilt.
What is active transport?
The movement of substances from a lower concentration to a higher concentration, using energy from respiration
Give one difference between active transport and osmosis
Active transport needs energy
Osmosis is used to move water only
Active transport moves substances from a lower concentration to a higher concentration, whereas osmosis moves water from a higher to a lower water concentration
Explain why root hair cells need to use active transport to take in minerals
The concentration of minerals is usually higher in the root hair cells than in the soil, so root hair cells can’t absorb minerals using diffusion
In humans, glucose is absorbed into the bloodstream from the gut. Why is active transport important for this process?
Sometimes the concentration of glucose in the gut is lower than the concentration of glucose in the blood, so cells must use active transport to absorb glucose into bloodstream.
How do enzymes affect the rate of a reaction?
Enzymes increase the rate of a reaction
