Science B1 Definitions Flashcards
What is the definition for active transport
The movement of substances from a more dilute solution to a more concentrated solution (against a concentration gradient) with the use of energy from respiration.
What is cell differentiation
Cell differentiation: The process where a cell becomes specialised to its function.
What is the function of a cell membrane
Cell membrane: A partially permeable barrier that surrounds the cell.
Function of cell wals
Cell wall: An outer layer made of cellulose that strengthens plant cells.
What are chromosomes
Chromosomes: DNA structures that are found in the nucleus which are made up of genes.
What is the use of chlorplast
Chloroplast: An organelle which is the site of photosynthesis.
What is diffusion
Diffusion: The spreading out of the particles of any substance in solution, or particles of a
gas, resulting in a net movement from an area of higher concentration to an area of lower
concentration
What are eukaryotic cells
Eukaryotic cell: A type of cell found in plants and animals that contains a nucleus.
Function of mitrochondria
Mitochondria: An organelle which is the site of respiration.
What is the nucleus
Nucleus: An organelle found in most eukaryotic cells that contains the genetic material of the
cell and controls the activities of the cell.
What is osmosis
Osmosis: The diffusion of water from a dilute solution to a concentrated solution through a
partially permeable membrane.
What is a plasmid
Plasmid: Loops of DNA found in the cytoplasm of prokaryotic cells.
What are prokaryotic cells
Prokaryotic cell: A type of cell found in bacteria that does not contain a nucleus.
What are specialised cells
Specialised cells: Cells that are adapted to perform a specific function.
What are stem cells
Stem cell: An undifferentiated cell that can divide to produce many specialised cells of the
same type.
Surface area
Surface area to volume ratio (SA:V): The size of the object compared with the amount of
area where it contacts its environment.
What is the cell cycle
The cell cycle: A series of stages preparing the cell for division.
What are the different organelle in eukaryotic cells
Animal and plant cells are eukaryotic. They have a: ● Cell membrane ● Cytoplasm ● Nucleus containing DNA
What organelles are in a bacterial cell
Bacterial cells are prokaryotic and are much smaller. They have a: ● Cell wall ● Cell membrane ● Cytoplasm ● Single circular strand of DNA and plasmids (small rings of DNA found in the cytoplasm)
what is use nee for a Nucleus in a animal an plant cell.
it Contains DNA coding for a particular protein needed to build new cells an is Enclosed in a nuclear membrane.
What is the need for cytoplasm ina animal and plant cell
● Liquid substance in which chemical reactions occur. ● Contains enzymes (biological catalysts, i.e. proteins that speed up the rate of reaction). ● Organelles are found in it
Why do we need cell membrane in a eukaryotic cell
Cell membrane ● Controls what enters and leaves the cell Mitochondria ● Where aerobic respiration reactions occur, providing energy for the cell Ribosomes ● Where protein synthesis occurs. ● Found on a structure called the rough endoplasmic reticulum.
Use of chloplast in a plant cell
● Where photosynthesis takes place, providing food for the plant ● Contains chlorophyll pigment (which makes it green) which harvests the light needed for photosynthesis. Permanent vacuole ● Contains cell sap ● Found within the cytoplasm ● Improves cell’s rigidity Cell wall (also present in algal cells) ● Made from cellulose ● Provides strength to the cell
What are the Organelle found in a prokaryotic cell
Bacterial cells are prokaryotic, so do not share as many similarities in the type of organelles as animal and plant cells do. Cell wall Made of a different compound (peptidogylcan) Single circular strand of DNA As they have no nucleus, this floats in the cytoplasm Plasmids Small rings of DNA. Cytoplasm ● Liquid substance in which chemical reactions occur. ● Contains enzymes (biological catalysts, i.e. proteins that speed up the rate of reaction). ● Organelles are found in it. Cell membrane ● Controls what enters and leaves the cell
What is cell specification
Cells specialise by undergoing differentiation: a process that involves the cell gaining new sub-cellular structures in order for it to be suited to its role. Cells can either differentiate once early on or have the ability to differentiate their whole life (these are called stem cells). In animals, most cells only differentiate once, but in plants many cells retain the ability.
Example of cell specification in animal cells
Sperm cells: specialised to carry the male’s DNA to the egg cell (ovum) for successful reproduction ● Streamlined head and long tail to aid swimming ● Many mitochondria (where respiration happens) which supply the energy to allow the cell to move ● The acrosome (top of the head) has digestive enzymes which break down the outer layers of membrane of the egg cell
Examples of cell specification in a animal cell
Nerve cells: specialised to transmit electrical signals quickly from one place in the body to another ● The axon is long, enabling the impulses to be carried along long distances ● Having lots of extensions from the cell body (called dendrites) means branched connections can form with other nerve cells ● The nerve endings have many mitochondria which supply the energy to make special transmitter chemicals called neurotransmitters. These allow the impulse to be passed from one cell to another.
Example of specification in animal cell
Muscle cells: specialised to contract quickly to move bones (striated muscle) or simply to squeeze (smooth muscle, e.g found in blood vessels so blood pressure can be varied), therefore causing movement ● Special proteins (myosin and actin) slide over each other, causing the muscle to contract ● Lots of mitochondria to provide energy from respiration for contraction ● They can store a chemical called glycogen that is used in respiration by mitochondria
Examples of cell specification in plant cells
Root hair cells: specialised to take up water by osmosis and mineral ions by active transport from the soil as they are found in the tips of roots ● Have a large surface area due to root hairs, meaning more water can move in ● The large permanent vacuole affects the speed of movement of water from the soil to the cell ● Mitochondria to provide energy from respiration for the active transport of mineral ions into the root hair cell
Example of cell specification in plant cells
Phloem cells: specialised to carry the products of photosynthesis (food) to all parts of the plants ● Cell walls of each cell form structures called sieve plates when they break down, allowing the movement of substances from cell to cell ● Despite losing many sub-cellular structures, the energy these cells need to be alive is supplied by the mitochondria of the companion cells.
What is the process of cell differentiation in a animal cell
In animals, almost all cells differentiate at an early stage and then lose this ability. Most specialised cells can make more of the same cell by undergoing mitosis (the process that involves a cell dividing to produce 2 identical cells). Others such as red blood cells (which lose their nucleus) cannot divide and are replaced by adult stem cells (which retain their ability to undergo differentiation). In mature animals, cell division mostly only happens to repair or replace damaged cells, as they undergo little growth.
What is the process of cell differentiation in a plant cell
In plants, many types of cells retain the ability to differentiate throughout life. They only differentiate when they reach their final position in the plant, but they can still re-differentiate when it is moved to another position.
How do you calculate magnification
magnification Common calculations: 1. Magnification of a light microscope: magnification of the eyepiece lens x magnification of the objective lens 2. Size of an object: size of image/magnification = size of object (this formula can be rearranged to obtain the other values, make sure you are in the same units!)
Chromosomes
chromosomes - The nucleus contains your genetic information. ● This is found in the form of chromosomes, which contain coils of DNA. ● A gene is a short section of DNA that codes for a protein and as a result controls a characteristic- therefore each chromosome carries many genes. ● There are 23 pairs of chromosomes in each cell of the body, as you inherit one from your mother and one from your father - resulting in 46 chromosomes in total in each cell. ● Sex cells (gametes) are the exception: there are half the number of chromosomes, resulting in 23 chromosomes in total in each gamete cell.
What is the cell cycle
The cell cycle is a series of steps that the cell has to undergo in order to divide. Mitosis is a step in this cycle- the stage when the cell divides.
What is stage 1 in mitosis
Stage 1 (Interphase): In this stage the cell grows, organelles (such as ribosome and mitochondria) grow and increase in number, the synthesis of proteins occurs, DNA is replicated (forming the characteristic ‘X’ shape) and energy stores are increased Stage 2 (Mitosis): The chromosomes line up at the equator of the cell and cell fibres pull each chromosome of the ‘X’ to either side of the cell. Stage 3 (Cytokinesis): Two identical daughter cells form when the cytoplasm and cell membranes divide
What is stage 2 in mitosis
Stage 2 (Mitosis): The chromosomes line up at the equator of the cell and cell fibres pull each chromosome of the ‘X’ to either side of the cell.
What is stage 3 in mitosis
Stage 3 (Cytokinesis): Two identical daughter cells form when the cytoplasm and cell membranes divide
Why is cell division important
Cell division by mitosis in multicellular organisms is important in their growth and development, and when replacing damaged cells. Mitosis is also a vital part of asexual reproduction, as this type of reproduction only involves one organism, so to produce offspring it simply replicates its own cells.
Stem cells
Embryonic stem cells ● Form when an egg and sperm cell fuse to form a zygote ● They can differentiate into any type of cell in the body ● Scientists can clone these cells (though culturing them) and direct them to differentiate into almost any cell in the body ● These could potentially be used to replace insulin-producing cells in those suffering from diabetes, new neural cells for diseases such as Alzheimer’s, or nerve cells for those paralysed with spinal cord injuries
Function of adult stem cell
. Adult stem cells ● If found in bone marrow they can form many types of cells including blood cells
What is diffusion
The definition of diffusion in the specification is ‘the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement from an area of higher concentration to an area of lower concentration’. When many particles are close together they collide with each other more often, resulting in them moving around and becoming mixed with the other particles in the area. It is passive as no energy is required.
Diffusion
Substances can move over cell membranes via diffusion, into and out of cells. The molecules have to be small in order to be able to move across- for example oxygen, glucose, amino acids and water, but starch and proteins cannot. Examples of where this takes place in the body: ● Oxygen moves through the membranes of structures in the lung called alveoli into the red blood cells, and is carried to cells across the body for respiration. Carbon dioxide (the waste product of respiration) moves from the red blood cells into the lungs to be exhaled. These movements of gases is called gas exchange. ● Urea (a waste product) moves from the liver cells into the blood plasma to be transported to the kidney for excretion
What are the factors and effect of diffusion
factor - Concentration gradient (difference in concentrations) effect - The greater the difference in concentration, the faster the rate of diffusion. This is because more particles are randomly moving down the gradient than are moving against it.
What are the factors and effect of diffusion
factor - Temperature effect - The greater the temperature, the greater the movement of particles, resulting in more collisions and therefore a faster rate of diffusion.
Examples of diffusion
In the lungs, oxygen is transferred to the blood and carbon dioxide is transferred to the lungs. This takes place across the surface of millions of air sacs called alveoli, which are covered in tiny capillaries, which supply the blood.
Example of diffusion
The gills are where gas exchange takes place in fish. Water which has oxygen passes through the mouth and over the gills. Each gill has plates called gill filaments, and upon these are gill lamellae, which is where diffusion of oxygen into the blood and diffusion of carbon dioxide into the water takes place. Blood flows in one direction while water flows in the other.
Examples of diffusion
The roots of plants are adapted to take up water and mineral ions. Roots have root hair cells with large surface areas, which project into the soil.
Examples of diffusion
In the leaves of the plant there are many different tissues to aid with gas exchange. Carbon dioxide diffuses through stomata for photosynthesis, whilst oxygen and water vapour move out through them. The stomata are controlled by guard cells, which change the size of the stomata based on how much water the plant received (the guard cells swell with lots of water and make the stomata larger)
What is osmosis
osmosis - Water is able to move across cell membranes by osmosis- the movement of water from a less concentrated solution to a more concentrated one through a partially permeable membrane. A dilute solution of sugar has a high concentration of water (and therefore a high water potential). A concentrated solution of sugar has a low concentration of water (and therefore a low water potential). Water moves from a dilute solution to a concentrated solution because it moves from an area of high water potential to low water potential- down the concentration gradient. It is passive (does not use energy).
Osmosis
The cytoplasm of a cell contains salts and sugars, so therefore when a cell is placed in a dilute solution, water will move in. ● This situation can be modelled with a partially permeable membrane bag containing sugar molecules, with a glass tube placed in it with the top out of the water
Osmosis in animals
Osmosis in animals: ● If the external solution is more dilute (higher water potential), it will move into animal cells causing them to burst. ● On the other hand, if the external solution is more concentrated (lower water potential), excess water will leave the cell causing it to become shrivelled.
Osmosis in potatoes
Placing potato tubers (cylinders) in different concentrations of sugar solution results in different volumes of water moving in or out of the tubers. This affects its mass. By measuring the mass of the tuber before and after placing it in solution we can see whether the concentration of external solution or potato was higher, depending on whether it has got heavier or lighter. From this we can calculate the percentage change in mass (by dividing the change by the original mass) and plot on a graph.
What is active transport
Active transport is the movement of particles from an area where they are in lower concentration to an area where they are in higher concentration- against their concentration gradient. This is not passive as diffusion is, but requires energy from respiration, which is why it is called active.
Examples of active transport
In root hairs: ● They take up water and mineral ions (for healthy growth) from the soil ● Mineral ions are usually in higher concentrations in the cells, meaning diffusion cannot take place ● This requires energy from respiration to work
