Structure and functions in living organisms Flashcards
What is the role of the nucleus?
-controls the activities of the cell
What is the cytoplasm?
- a jelly-like fluid that fills the cell.
- It is where most of the cell’s chemical reactions take place.
What is the cell membrane?
- surrounds the cells, a thin layer on the surface
- forms a boundary between the cytoplasm and the outside
- partially permeable =selectively permeable
What is the cell wall?
- found outside the cell membrane
- made of cellulose (in plants)
What are mitochondria?
- site of aerobic respiration in eukaryotic cells. Aerobic respiration (process which uses sugar and oxygen to release energy) releases energy in the mitochondria.
What are chloroplasts?
-absorb light energy and make food via photosynthesis
What are ribosomes?
-organelles that are responsible for synthesising (making) proteins.
What is the vacuole?
-filled with cell sap(storage area)
Where are Eukaryotic cells found and how big are they?
- plants, animals, fungi and protoctists (single-celled organisms that don’t fit other categories).
- 10-100 micro meters in size.
Give an example of a Prokaryote.
-bacteria, they are multi cellular
What parts of cells do plants have that animals don’t?
-vacuole, chloroplasts, cell wall (made of cellulose)
What is the cell wall in fungi made of?
-chitin
How do fungi feed?
-secreting digestive enzymes and absorbing broken down decaying matter), and often store carbohydrates as glycogen.
Is fungi uni or multi cellular?
-both
What are enzymes?
-biological catalysts; they speed up lots of the reactions that happen in cells, such as those involved in respiration.
What is tissue?
-groups of similar cells that act together to perform a similar function.
What is epithelial tissue?
-lines the stomach.
What is muscular tissue?
- tissue that can contract to bring about force and motion.
- moves the contents of the stomach around during digestion.
What is the function of glandular tissue?
-produces digestive juices that break down the stomach’s contents.
What does the liver produce?
-bile
What do glands produce?
-Glands (e.g. pancreas and salivary glands) produce digestive juices.
What is the role of the small intestine?
-digests food and absorbs soluble (can be dissolved) food molecules.
What is the role of the large intestine?
-absorbs water molecules from the remaining undigested food. This allows it to produce faeces.
What is a permanent vacuole?
- found in plants
- a fluid-filled sac that stores water.
- It is enclosed in a membrane
What allows a sperm cell to penetrate an egg cell?
-acrosome at the tip of the head contains
digestive enzymes needed to penetrate (break into) an egg cell.
What is an axon?
- part of the cell where electrical signals travel along
- nerve cells have long axons
What is the substance that strengthens the cells walls of xylem cells?
-lignin
What are the steps for a light microscope experiment?
- Put a thin sample of tissue (e.g. onion epidermis) onto a microscope slide
- Add a few drops of a suitable stain
- Place a coverslip on top of the tissue and place the slide onto the microscope stage.
- Use the objective lens with the lowest magnification, and focus on the sample.
- Increase the magnification and refocus to see different features of the cell.
Define diffusion.
- the net movement of particles from an area of high concentration to an area of lower concentration.
- Substances can move in and out of cells across cell membranes via diffusion
What factors affect the rate of diffusion? (4)
- The higher the temperature, the faster the rate of diffusion.
- The greater the distance a substance has to diffuse across, the more time taken.
- the bigger the difference in concentration between two areas, the greater the concentration gradient and the faster the rate of diffusion
- The larger the surface area of the membrane that a substance is diffusing through (e.g. the membrane around a cell), the faster the rate of diffusion.
What is the formula for volume to surface area ratio?
-Surface area to volume ratio = surface area ÷ volume
Define osmosis.
-the diffusion of water across a partially permeable membrane from a dilute solution (high concentration of water) to a concentrated solution (low concentration of water).
What is an experiment for osmosis?
- Cut discs of raw potato and measure their mass.
- Put discs in different concentrations of sugar or salt solution.
- After 30 minutes, measure the mass of each disc again.
Formula for calculating % change in mass
(final mass-initial mass)/initial mass x 100
What does active transport do in humans?
- allows sugar molecules, which are needed for cell respiration, to be absorbed into the blood from the gut
- there is a lower concentration of sugar molecules in the lumen compared to the cell
What does active transport in the root hair cell in a plant do?
- allows plants to absorb mineral ions, which are necessary for healthy growth
- there is a lower concentration of mineral ions in the soil compared to the cell
What is active transport?
-moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient)
What does active transport require and how does it get it?
- energy from respiration
- from the mitochondria in the cell
What is passive transport?
- diffusion and osmosis
- means they don’t require energy
What features make the lungs a good exchange service?
- large surface area to volume ratio
- there is a small diffusion difference
- they have a steep concentration gradient because the lungs have a good blood supply and are well ventilated.
What are lipids and what are they made up of?
- fats and oils, make up cell membranes
- made up of carbon hydrogen and oxygen
- made up of fatty acids and glycerol
What are Carbohydrates made of and what are they used for?
- carbon, hydrogen and oxygen
- stored as energy
What are proteins made up of and what do they do?
- carbon, hydrogen, oxygen, nitrogen, sulfur
- amino acids
- give structural support and may have important roles in chemical reactions
Which 2 types of proteins have active sites?
- antibodies and enzymes
- these are areas of the protein that have to be a specific shape for the protein to function properly.
How do you test for starch in a leaf?
- add iodine solution.
- It will turn blue-black if starch is present.
How do you test for lipids?
- add ethanol and water and shake.
- If lipids are present, a white emulsion (cloudy liquid) will form.
How do you test for glucose?
- add Benedict’s reagent and heat for about two minutes.
- It will turn any of green, yellow or red if sugar is present.
- The colour depends on the concentration.
How do you test for proteins?
- add Biuret solution.
- It will turn mauve or purple if proteins are present.
What is the function of enzymes?
-speed up a reaction, known as a biological catalyst
How does temp affect rate of enzyme action?
- increasing temp initially speeds up action
- Enzymes have an optimum temperature. Once this temperature is reached, the activity decreases.
- Past a certain temperature, the active site changes shape, and the enzyme is denatured (loses its catalytic activity).
How does pH affect rate of enzyme action?
- have an optimum pH (measure of acidity).
- If the pH changes away from the optimum pH, then the enzyme activity decreases.
- If the pH is too low or too high, then the enzyme is denatured and will not function.
What does amylase do?
-an enzyme that breaks down starch
How does light intensity affect the rate of photosynthesis?
- more energy is provided.
- if the light intensity is increased above a certain threshold, the rate of photosynthesis will not increase because another factor (such as temperature) is limiting the rate of the reaction.
What factors affect the rate of photosynthesis?
- light intensity
- carbon dioxide concentration
- chlorophyll concentration
- temperature (until 45)
How do you test the rate of photosynthesis?
- using pondweed and a lamp
- change the distance between the lamp and the pondweed and count the number of bubbles produced.
- In this experiment, light intensity is the independent variable and the number of bubbles is the dependent variable.
When testing for stored starch in leaves, why are they first soaked in ethanol?
- removes the chlorophyll from leaves, turning them white.
- This makes it easy to see which parts of the leaf turn dark blue when iodine is added.
What is the difference between accuracy, reliability, and validity?
- accuracy=how close a measured value is to its true value.
- reliability=the ability of an experiment to produce consistent results.
- validity=how appropriate an experimental method is at achieving the aim of an experiment
How can you increase reliability?
-repeat experiment
What is the role of the waxy cuticle?
-covers the upper and lower epidermis and creates a water proof barrier over the surface of the leaf, reducing water loss
What is the role of the guard cells?
-in the lower epidermis of the leaf, close in certain conditions to reduce water los
Visking tubing experiment for osmosis.
- fix some visking tubing over the end of a thistle funnel
- pour sugar solution down the glass tube into the thistle funnel
- put thistle funnel into glass beaker of water, measure where sugar solution comes up to on the glass tube
- leave overnight and measure where the water level is
