1. Cells & Processes Flashcards
What are some examples of plant tissue?
1) Epidermal tissue - Covers the whole plant 2) Palisade mesophyll tissue - Where most photosynthesis happens in the leaf 3) Spongy mesophyll tissue - Contains air spaces to allow gases to diffuse in and out of cells in the leaf 4) Xylem and phloem - Transport water, mineral ions and sucrose around the plant
How are palisade cells adapted for photosynthesis?
- Packed with chloroplasts (more at top of cells so they are nearer to the light) - Tall shape increases SA down the side for absorbing CO2 from the air in the leaf - Thin shape means many can be fitted at top of leaf
Is stem cell research allowed in the UK?
Yes, as long as it follows strict guidelines. In some countries, however, it is banned.
Why do root hair cells need to use active transport to take up minerals?
There is usually a higher concentration of minerals in the cells than in the soil, meaning that active transport is needed to take up nutrients against the concentration gradient.
What determines the positioning of the xylem and phloem?
The xylem’s other function - support.
When is meiosis used?
In humans, only in reproductive organs.
How could embryonic stem cells be used to cure disease?
Scientists can extract stem cells from early embryos and grow them. Embryonic stem cells could be used to replace faulty cells in sick people (e.g. beating heart muscle cells for people with heart disease)
What is the function of the vacuole?
Contains cell sap, a weak solution of sugar and salts.
How does sexual reproduction cause variation?
When the gametes fuse, the fertilised egg contains a mixture of genes and therefore characteristics from each parent.
What is a gene?
A part of a chromosome.
What is net movement and why is it relevant to diffusion?
Net movement is the overall movement of molecules in diffusion. It is needed because molecules move both ways but there is more movement in one direction.
How many pairs of chromosomes does a human cell have?
23
What do animal cells contain?
1) Nucleus
2) Cytoplasm
3) Cell Membrane
4) Mitochondria
5) Ribosomes
What do people who are against stem cell research suggest should be done?
Scientists should concentrate more on finding and developing other sources of stem cells, so people could be helped without the use of embryos.
When does differentiation occur?
During the development of a multicellular organism.
What are root hair cells specialised for?
Absorbing water and minerals.
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of high water concentration to a region of low water concentration.
Specialised cells form what, which form what, which form what, etc. ?
Specialised cells form tissues, which form organs, which form organ systems.
When is mitosis used?
When plants or animals want to grow or replace cells that have been damaged.
Where does tissue fluid come from?
It is squeezed out of the blood capillaries.
Give 3 examples of how stem cells could be used to cure disease.
Making:
1) Beating heart muscle cells for people with heart disease
2) Insulin-producing cells for diabetics
3) Nerve cells for people paralysed by spinal injuries
What the two experiments that can be used to show osmosis?
1) Potato cylinders 2) Visking tubing
What are chemical carcinogens?
Chemicals that cause cancer.
What is meiosis?
When a cell divides twice to form four gametes with only 1 of each chromosome (i.e. Half the normal number)
What type of organism is yeast?
Microorganism (it is single-celled).
What is the function of the cytoplasm?
Gel-like substance where most of the chemical reactions happen. It contains enzymes which control these reactions.
How are adult stem cells already being used to cure disease?
- Some blood diseases (e.g. sickle cell anaemia) can be transplanted by bone marrow transplants.
- Bone marrow contains stem cells that can turn into new blood cells to replace the faulty old ones.
What happens when gametes join?
The gametes fuse at fertilisation. The resulting cell has a mixture of the mother’s and father’s genes. The cell divides by mitosis to form many cells. As the organism develops, these cells differentiate to make many kinds of specialised cells.
How can tumours can be caused?
- Chemicals
- Radiation
What is mitosis?
When a cell reproduces itself by SPLITTING to form two identical offspring with the same number of chromosomes as the original.
What happens when gametes join?
The gametes fuse at fertilisation. The resulting cell has a mixture of the mother’s and father’s genes. The cell divides by mitosis to form many cells. As the organism develops, these cells differentiate to make many kinds of specialised cells.
What is tissue fluid and what is it used for?
Water with oxygen, glucose and other things dissolved in it. It surrounds the cells in the body and supplies them with everything they need.
What is the function of the cell wall?
Supports the cell and strengthens it.
How many pairs of chromosomes does a human cell have?
23
How does ionising radiation cause cancer?
- Breaks molecules up into ions
- These ions interfere with normal reactions going on inside the cell
- They can cause the cell to start dividing uncontrollably, producing a tumour
What happens when tissue fluid is isotonic?
No net movement of water.
What are alleles?
Different versions of the same gene (e.g. Gene for blue eyes and gene for brown eyes)
Give an example of an experiment to show osmosis (visking tubing).
1) Tie a piece of wire around one end of some Visking tubing and put a glass tube in the other end. 2) Fix the tubing around the glass tube with wire. 3) Pour some sugar solution (hypertonic) down the glass tubing into the Visking tubing. 4) Put the Visking tubing into a beaker of pure water (hypotonic) and measure where the sugar solution comes up to on the glass tube. 5) Leave the tubing overnight then measure where the liquid is in the glass tubing. Water should be drawn into the Visking tubing by osmosis and this should force the liquid up the glass tube.
What is the difference between animal and plant cells?
Plant cells contain everything animal cells contain AND: - Cell wall - Permanent vacuole - Chloroplasts
What is the function of egg cells?
To carry the female DNA and to nourish the developing embryo.
When is active transport needed in the human body?
Taking glucose from low concentrations in the intestines and from low concentrations in the kidney tubules.
What does a larger SA : Volume ratio mean?
Substances move in and out of the organism faster.
Why are some people AGAINST stem cell research?
They think that human embryos shouldn’t be used for experiments since each one is a potential human life.
What is a chromosome?
A thread-like structure made of DNA.
At what rate does substance exchange happen in single-celled organisms and why?
Quick, because: - Substances only have to travel a short distance - Large SA : Volume ratio
What is a plasmid?
A circular structure of genetic material.
What happens to cells when a plant is well watered?
- They draw up water by osmosis and become swollen (turgid). - The contents of the cell push against the inelastic cell wall. This is called turgor pressure and helps to support plant tissues.
How do root hair cells take up minerals?
Using active transport.
In meiosis, what makes the resulting gametes different?
In the first division, each cell receives some of the mother’s and some of the father’s chromosomes.
What does the small intestine have for food absorption?
Villi
What is the function of the chloroplasts?
Where light is absorbed and photosynthesis happens.
Give 3 examples of plant organs.
Stems, roots, leaves
Are stem cells also found in adults?
Yes, but only in certain places, such as bone marrow. They aren’t as versatile as embryonic stem cells - they can only turn into certain cell types.
How is the cell structured in terms of genetics? (i.e. What contains what?)
Cell -> Nucleus -> Chromosome -> Gene -> Made of DNA
What do plant cells contain?
1) Nucleus 2) Cytoplasm 3) Cell Membrane 4) Mitochondria 5) Ribosomes 6) Cell Wall 7) Vacuole 8) Chloroplasts
What is the function of the ribosomes?
Where proteins are made.
What does hypotonic mean?
A solution which is less concentrated than another.
What is plasmolysis?
When a plant faces an extreme lack of water, in the cells the cytoplasm starts to shrink and the membrane pulls away from the cell wall. The cell is said to be plasmolysed.
Why are stem cells exciting for doctors and medical researchers?
They have the potential to turn into any kind of cell.
What are red blood cells adapted for?
Carrying oxygen
How does meiosis work?
- The cell duplicates its DNA. The arms of each chromosome are identical. 2. The chromosomes line up at the centre and are pulled apart. Each new cell has only one copy of each chromosome. 3. The chromosomes line up at the centre again and are pulled apart again. 4. Four gametes with only a single set of chromosomes are produced.
What is the structure of a leaf (in terms of tissues), from top to bottom?
Cuticle, Upper Epidermal Tissue, Palisade Mesophyll Tissue, Spongy Mesophyll Tissue, Lower Epidermal Tissue (+ Guard Cells), Cuticle (+ Stomata)
What is active transport?
The process by which substances are absorbed against a concentration gradient (i.e. from a lower to a higher concentration).
In meiosis, what makes the resulting gametes different?
In the first division, each cell receives some of the mother’s and some of the father’s chromosomes.
What do genes do?
Control the development of a characteristics (e.g. Hair colour)
What is the job of the lungs?
To get oxygen into the blood and remove waste CO2 from it.
What is the difference between gametes and normal cells?
Gametes have only one of each chromosome, while normal cells have two.
What is diffusion?
The movement of particles from an area of high concentration to an area of low concentration.
What is meiosis?
When a cell divides twice to form four gametes with only 1 of each chromosome (i.e. Half the normal number)
How do carcinogens cause cancer?
They interfere with normal cell functions, causing uncontrollable division, which forms a tumour.
What is therapeutic cloning?
- Another method of producing stem cells (instead of extracting from embryos or bone marrow)
- An embryo would be produced with the same genes as the patient
- Cells from the embryo would not be rejected by the patient’s body
- Currently being investigated
What is an organ?
A group of different tissues that work together to perform a certain function. For example, the stomach is made up of: - Muscular tissue - Glandular tissue - Epithelial tissue
What are root hair cells?
The cells on the surface of plant roots which grow into long hairs that stick stick out into the soil.
Where are the xylem and phloem in roots and why?
The roots have to resists being crushed, so the xylem is in the centre to give it strength.
Why do multicellular organisms not exchange substances through the outer membrane?
It is too slow because: - Some cells are deep in the body - Larger organisms have a small SA : Volume ratio
What are the 3 concentrations of tissue fluid?
Hypotonic, Hypertonic, Isotonic
What are alveoli?
Little air sacs where gas exchange happens. They are found in the lungs.
Where can stem cells be found?
In early human embryos.
What type of organism are bacteria?
Microorganism (they are single-celled).
How does the Surface Area : Volume ratio of small organisms compare to large organisms?
Small organisms have a larger SA : Volume ratio than large organisms.
How does water move from the tissue fluid to the cells?
Osmosis.
What happens when tissue fluid is hypertonic?
Water moves out of the cell.
What is a gene?
A part of a chromosome.
What happens to cells when a plant does not get enough water?
- They lose their turgor pressure and become flaccid. The plant starts to wilt.
Can some organisms use mitosis to reproduce?
Yes, for example, strawberry plants form runners like this.
What type of molecules can pass through cell membranes?
Small molecules (e.g. oxygen, glucose, amino acids, water)
Can some organisms use mitosis to reproduce?
Yes, for example, strawberry plants form runners like this.
What is the function of the nucleus?
Contains genetic material that controls the activities of the cell.
How are root hair cells adapted?
- Long thin shape -> Gives the plant a large SA for absorbing water and mineral ions.
What do yeast cells contain?
1) Nucleus 2) Cytoplasm 3) Cell Membrane 4) Cell Wall
What are sperm and egg cells specialised for?
Reproduction
Dissolved substances can move in and out of cells by…
Diffusion
What is a benign tumour?
- When the tumour grows until there is no more room.
- The cells stay where they are -> They don’t invade other tissues
- This type of tumour usually isn’t dangerous
What are stem cells?
Undifferentiated cells which can develop into different types of cell depending on what instructions they are given.
What is the cell wall made of in plants?
Cellulose.
How are guard cells adapted?
- Special kidney shape -> Opens and closes stomata - When plant has lots of water -> Guard cells go turgid and open the stomata, which allows gas exchange for photosynthesis - When plant has little water -> Guard cells go flaccid and close the stomata, which prevents water escaping - Thin inner walls and thick outer walls -> Allow opening and closing to work - Sensitive to light -> Close at night to save water - More stomata on underside of leaf -> Less water is lost
Why does tissue fluid have varying water concentrations?
So that water will move either in or out of the cell.
What does turgid mean?
Swollen.
What do bacterial cells lack?
A nucleus.
How are villi adapted to maximise food absorption?
- Single layer of surface cells - Constant blood supply
What is the alternative definition of osmosis?
Movement of water from a dilute to a more concentrated solution. (i.e. The water tries to even up the concentrations)
What does active transport require for it to happen?
Energy (from respiration).
What is a tissue?
A group of similar cells that work together to carry out a particular function. It can include more than one type of cell.
Give some examples of carcinogens.
Chemicals found in:
- Tobacco smoke
- Asbestos
These have been linked to lung cancer.
When is meiosis used?
In humans, only in reproductive organs.
What do lungs contain for gas exchange?
Alveoli
What causes cancer?
When cells divide abnormally and in an uncontrolled way, forming a tumour. This usually happens when normal cell division to replace cells in the body goes wrong.
What happens when tissue fluid is hypotonic?
Water moves into the cell.
What is a partially permeable membrane?
A membrane that allows small particles through it, but not large particles.
Give an example of an experiment to show diffusion.
Phenolphthalein is a pH indicator - it’s pink in alkaline solutions and colourless in acidic ones. 1) Make some agar jelly with phenolphthalein and sodium hydroxide, which will make it pink. 2) Using a scalpel, cut some cubes out and put them in some hydrochloric acid. 3) The cubes turn colourless eventually, showing that the acid has diffused into the jelly and neutralised the sodium hydroxide, turning the phenolphthalein colourless.
Give some examples of ionising radiation which causes cancer.
- UV
- X-rays
What does isotonic mean?
A solution which is equally concentrated to another.
Give three examples of tissue and what they do.
1) Muscular tissue - Contracts to move whatever it is attached to 2) Glandular tissue - Makes and secretes chemicals like enzymes and hormones. 3) Epithelial tissue - Covers some parts of the body (e.g. the inside of the gut)
What is mitosis?
When a cell reproduces itself by SPLITTING to form two identical offspring with the same number of chromosomes as the original.
What substance do chloroplasts contain?
Chlorophyll - a green substance which absorbs lights.
What do bacterial cells contain?
1) Cytoplasm 2) Cell Membrane 3) Cell Wall 4) Genetic Material 5) Plasmid
What are alleles?
Different versions of the same gene (e.g. Gene for blue eyes and gene for brown eyes)
What are guard cells adapted for?
Gas exchange and controlling water loss within a leaf
What is a malignant tumour?
- Where the tumour grows and can spread to healthy tissue
- Some cells can get into the bloodstream and circulate to other parts in the body
- Here, they can invade healthy tissues and form secondary tumours
- Dangerous and can be fatal
What does hypertonic mean?
A solution which is more concentrated than another.
How are sperm cells adapted?
- Long tail + streamlined head -> Helps it swim to egg - Lots of mitochondria -> Provide energy for swimming - Enzymes in head -> Digest through egg cell membrane
How are alveoli adapted to maximise diffusion?
- Large SA (about 75m2 in humans) - Moist lining for dissolving gases - Thin walls - Constant blood supply
How does mitosis work?
- Before dividing, the DNA is spread out in long strings. 2. The cell duplicates its DNA, forming X-shaped chromosomes, where each arm of the X is identical. 3. The chromosomes line up in the centre of the cell and cell fibres pull them apart. Each arm of the X is pulled to the opposite side of the cell. 4. Membranes form around each set of chromosomes. The become the nuclei of the new cells. 5. The cytoplasm divides.
What is the function of the cell membrane?
Holds the cell together and controls what goes in and out of the cell.
What must exchange surfaces be adapted to do?
Allow enough of the necessary substance to pass through.
How does mitosis work?
- Before dividing, the DNA is spread out in long strings. 2. The cell duplicates its DNA, forming X-shaped chromosomes, where each arm of the X is identical. 3. The chromosomes line up in the centre of the cell and cell fibres pull them apart. Each arm of the X is pulled to the opposite side of the cell. 4. Membranes form around each set of chromosomes. The become the nuclei of the new cells. 5. The cytoplasm divides.
What type of molecules cannot pass through cell membranes?
Large molecules (e.g. starch, proteins)
What is an organ system?
A group of organs working together to perform a particular function. For example, the digestive system is an organ system.
How do researchers get cultures of one specific cell from stem cells?
They control the differentiation of the stem cells by changing the environment they are grown in.
What is the difference between gametes and normal cells?
Gametes have only one of each chromosome, while normal cells have two.
What are palisade cells adapted for?
Photosynthesis
Why are some people FOR stem cell research?
- They think that curing patients who already exist and are suffering is more important than the rights of embryos.
- Embryos used in research are usually unwanted ones from fertility clinics which would probably be destroyed if not used for research.
What is a tumour?
A mass of cells, formed by abnormal and uncontrolled division of cells.
In plasmolysis, why doesn’t the plant totally lose its shape?
The inelastic cell wall keeps things in position.
What are villi?
Tiny hair-like projection in the small intestine, where they help with food absorption by increasing the SA.
How are red blood cells adapted?
- Concave shape -> Large SA for absorbing oxygen + Helps RBCs to pass smoothly through capillaries - Contain haemoglobin -> Allows oxygen to be absorbed - No nucleus -> More room for haemoglobin
How are egg cells adapted?
- Contain food reserves -> To feed the embryo - When sperm fuses with egg, the egg’s membrane changes its structure -> Stops more sperm getting in
What do genes do?
Control the development of a characteristics (e.g. Hair colour)
What affect does concentration gradient have on the rate of diffusion?
The higher the gradient, the faster the rate of diffusion.
When is the ability for cells to differentiate lost in plants and animals?
Most animal cells - At an early stage
Many plant cells - Never
What are specialised cells?
Cells which are specialised in order to allow them to carry out a specific function.
What do multicellular organisms use for substance exchange instead of the outer membrane?
Specialised exchange organs, each with a specialised exchange surface.
How does substance exchange work in single-celled organisms?
Substances can diffuse straight in and out of the cell.
What is differentiation?
The process by which cells become specialised.
When is mitosis used?
When plants or animals want to grow or replace cells that have been damaged.
How does meiosis work?
- The cell duplicates its DNA. The arms of each chromosome are identical. 2. The chromosomes line up at the centre and are pulled apart. Each new cell has only one copy of each chromosome. 3. The chromosomes line up at the centre again and are pulled apart again. 4. Four gametes with only a single set of chromosomes are produced.
In what substances does diffusion happen and why?
Solutions and gases - because the particles in these substances are free to move about randomly.
When is active transport used in the guts?
When there is a low concentration of nutrients in the gut, but a high concentration of nutrients in the blood.
What are all living things made of?
Cells
How are exchange surfaces adapted to maximise effectiveness?
- Thin -> Substances only have a short distance to travel - Large SA -> Lot of substance can diffuse at once Also, in animals: - Lots of blood vessels -> Quickly move substances in and out of the blood - Gas exchange surfaces are often ventilated
What does a nucleus contain?
Genetic material in the form of chromosomes.
Give an example of an experiment to show osmosis (potato cylinders).
1) Cut a potato into identical cylinders. 2) Fill one beaker with pure water and fill another with very concentrated sugar solution. 3) Measure the length of the cylinders and place a few in each beaker. 4) After half an hour, take the cylinders out and measure them. 5) The cylinders in pure water should swell up as they take in water, while the cylinders in the concentrated solution should shrink as water is drawn out. Dependent variable - cylinder length. Independent vartiable - concentration of sugar solution.
Do molecules flow both ways in diffusion?
Yes, molecules move randomly and therefore go both ways, not only from high to low concentration, but there is a net movement that way.
Where are palisade cells located?
Top of the leaf
What is the function of sperm cells?
To get the male DNA to the female DNA.
Where are the xylem and phloem in the stem and why?
Stems need to resist bending. The xylem forms a sort of scaffolding and the phloem is always around the outside of the stem.
What is the function of the mitochondria?
Where respiration reactions happen.
