CELL BIOLOGY Flashcards
Describe the characteristics of Prokaryotes
-Smaller than eukaryotes
- have a cytoplasm and a cell membrane and are surrounded by a cell wall
- the genetic material is not enclosed in a nucleus
- a single DNA loop and may be one or more small rings of DNA called plasmids
- are bacterial cells
Describe the characteristics of a eukaryotic cell
- they are plant and animal cells
- have cell membrane, cytoplasm and genetic material enclosed in a nucleus
What are the different parts of a cell called
Subcellular structures
Describe the functions of subcellular structures in an animal cell
NUCLEUS - contains genetic material that controls the activities of the cell
CYTOPLASM- gel-like substance where modt of the chemical reactions happen. It contains enzymes that control these chemical reactions
CELL MEMBRANE: holds the cell together and controls what goes in and out of the cell.
MITOCHONDRIA: these are where most of the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work
RIBOSOME: these are where proteins are made in the cell
Decribe the functions of the subcellular structures in a plant cell
CELL WALL: made of cellulose. Supports the cell and strengthens it.
PERMANENT VACUOLE: contains cell sap, a weak solution of sugar and salts.
CHLOROPLAST: where photosynthesis occurs, shich makes food for the plant. They dontain a green substance called chlorophyll, which absorbs the light needed for photosynthesis
Bacterial cells, what subcellular structures does it include
Cytoplasm
Cell membrane
Cell wall
May include one or more small rings of DNA called plasmids
What is the definition of resolution
Resolution is the ability to distinguish between two points, so a highee resolution gives a sharper image
What is magnification
How large the image is compared to its actual size
What do microscopes do?
Microscopes let us see things that we can’t see with the naked eye.
Why have microscopy techniques have developed over time?
Because technology and knowledge have improved.
Explain how electron microscopes has increased understanding of sub-cellular structures?
An electron microscope has much higher magnification and resolving power than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures.
What is an electron microscope?
Uses electrons instead of light to form an image.
How does a light microscope work
It uses light and lenses to form an image of a specimen and magnify it.
IAM TRIANGLE
Image size
Mag. actual size
1000um = ? Mm
1mm
What is differentiation?
Differentiation is the process by which a cell change to become specialised for its job
At what stage do most animal cells and plant cells differentiation
-Animal cells differentiate at an early stage
-Plant cells retain the ability to differentiate throughout life
Why is cell differentiation important.
As cells develop, they develop dfiferent subcellular structures and turn into different types of cells allowing them carry out specific functions
In mature animals what is cell division mainly
restricted to repair and replacement.
What is it when a cell becomes specialised cells?
As a cell differentiates it acquires different sub-cellular structures to enable it to carry out a certain function
Explain how sperm cells are specialised for reproduction
- Function of a sperm is basically to get the male DNA to the female DNA.
- It has a long tail and a streamlined head to help it swim to the egg
- lots of mitchondria providing energy.
- carries enzymes in its head to digest through the egg cell membrane
Explain how nerve cells are specialised for rapid signalling?
- function of nerve cells is to carry electrical signals from one part of the body to another
- long and have branched connections at their ends to connect to other nerve cells and form a network throughout the body
Explain how muscle cells are specialised for contraction
Function of muscle cell is to contract quickly.
- these cells are long ( have space to contract) and contain lots of mitochondria to generate the energy needed for contraction
Explain how root hair cells are specialised for ansorbing water and minerals
Root hair cells are cells on surfsce of plant roots, which grow into long “hairs” that stick out into the soil.
Explain how phloem and xylem cells are specialised to trnasporting substances
They form tubes, which transport substances such as food and water around plants.
- to form tubes, the cells are long and joined end to end.
- xylem cells are hollow in the centre and phloem cells have very few subcellular structures, so that stuff can flow through them
What are chromosomes
They are coiled up lengths of DNA molecules
Facts about chromosomes
- the nucleus of a cell contains chromosomes made of DNa molecules.
- each chromosome carries a large number of genes
- in body cells the chromosomes are normally found in pairs
- 23 pairs of chromosomes from a human cell
Describe the stages of the cell cycle
During the cell cycle the genetic material is doubled and then divided into two identical cells.
Before a cell can divide it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome.
In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides.
Finally the cytoplasm and cell membranes divide to form two identical cells.
What is the stage called in the cell cycle where cells divide
Mitosis
What does the end of the cell cycle result in
Two identical cells
What pulls the chromosomes apart in the mitosis stage
Cell fibres
How do prokaryotic cells replicate
By binary fission
Explain the steps in binary fission
1) circular DNA and plasmids replicate
2) cells get bigger and circular DNA strands move to opposite ‘poles’ of cell
3) cytoplasm begins to divide and new cell walls begin to form
4) cytoplasm divides and two identical daughter cels produced. Each daughter cells are produced. Each daughter cell has one cooy of the circular DNA, but can have a variable number of copies of the plasmids
Explain how you use mean division time to find the number of bacteria in a population
Num of. hr. X 60 = b
b divided by num of min in Question = c
2 to power of c
What is a stem cell
A stem cell is an undifferentiated cell of an organism which is capable of giving rise to many more cells of the same type, and from which certain other cells can arise from differentiation.
What is the function of stem cells from the human embryos
Stem cells from human embryos can be cloned and made to differentiate into most different types of human cells.
What is the function of adult stem cells
Stem cells from adult bone marrow can form many types of cells including blood cells.
They cant turn into any cell type, only certain ones
What is the function of stem cells in meristems in plants
Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant.
Explain how adult stem cells and embryonic stem cells can help cure disease
Medicine uses adult stem cells to cure deisease. (Example# stem cells transferred from bone marrow of healthy oerson can replace faulty blood cells in patient who recieves them
Embryonic stem cells used to replace faulty cells in sick people- you could make insulin-producing cells for people with disbetes, nerve cells for people paralysed by spinal injuries.
Explain what therapeutic cloning is
In therapeutic cloning an embryo is produced with the same genes as the patient. Stem cells from the embryo are not rejected by the patient’s body so they may be used for medical treatment.
Explain the potential risks for stem cells
The use of stem cells has potential risks such as transfer of viral infection, and some people have ethical or religious objections.
Explain why some people are against stem cell research
- people feel human embryos shouldn’t be used for experiments since each one is a potential human life
- people think curijg patients who are suffereing is more important than the rights of embryos
- they argue that embryos used in research are usually unwanted ones from fertility clinics which if they weren’t used for research, would probably be destroyed
- some feel scientists should concentrate more on finding and developing other sources of stem cells, without needing to use human embryos
Explain how stem cells from meristems in plants can be used to produce clones of plants
Stem cells from meristems in plants can be used to produce clones of plants quickly and economically.
• Rare species can be cloned to protect from extinction.
• Crop plants with special features such as disease resistance can be cloned to produce large numbers of identical plants for farmers.
What is diffusion
DIFFUSION is rhe SPREADING OUT of PARTICLES from an area of HIGHER CONCENTRATION to an area of LOWER CONCENTRATION
Substances may move into and out of cells across the cell membranes via
Diffusion
Diffusion can happen in both
Solutions and gases
If the concentration gradient is bigger, the rate of diffusion
INCREASES
GIVE THE THREE FACTORS THAT WOULD AFFECT THE RATE OF DIFFUSION
- The difference in concentrations
- the temperature
- the surface area of the membrane
Give some examples of substances tranported in and out of cells by diffusion
are oxygen and carbon dioxide in gas exchange, and of the waste product urea from cells into the blood plasma for excretion in the kidney.
What is osmosis
OSMOSIS is the MOVEMENT OF WATER MOLECULES across a PARTIALLY PERMEABLE MEMBRANE from a region of HIGHER WATER CONCENTRATION to a region of LOWER WATER CONCENTRATION
If a solution has a strong sugar level (concentrated) it will become ? via osmosis
It will become dilute as water travels to areas of lower water concentration
What is active transport?
Active transport moves substances from a more dilute solution to a more concentrated solution (against a concentration gradient). This requires energy from respiration.
“Hairs” on root hair cells give a large surface area for the absorbtion of water and mineral ions from the soil. Plants need these why?
For healthy growth
Is the concentration of mineral ions usually higher or lower in the root hair cells than in the soil. Which means?
Higher.
Which means they can’t use diffusion to take up minerals from the soil
What do root hair cells use so they can absorb mineral ions instead of diffusion as its against the concentration gradient
Active transport allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil, against the concentration gradient. Plants require ions for healthy growth.
Where else can active transport be used to allow substances to move to higher concentrations (against the gradient) ?
It also allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration. Sugar molecules are used for cell respiration.
a single-celled organism has a large surface area to volume ratio, explain what this allows for
This allows sufficient transport of molecules into and out of the cell to meet the needs of the organism.
What is the equation for finding surface area of a shape
Length x width of each side of the shape
What is the equation for volume
Length x width x height
A multi-cellular organism has a smallersurface area comoared to volume- explain what this means
Smaller surface area compared to volum meaning - Not enough substances can diffuse from their outside surfsce to suppoy their entire volume
In multicellular organisms, surfaces and organ systems are specialised for exchanging materials. This is to allow sufficient molecules to
be transported into and out of cells for the organism’s needs. The effectiveness of an exchange surface is increased by:
having a large surface area
• a membrane that is thin, to provide a short diffusion path
• (in animals) having an efficient blood supply
• (in animals, for gaseous exchange) being ventilated.
Explain how gas exchanhe happens in fhe lungs
The job of the lungs is to transfer oxygen to the
blood and to remove waste carbon dioxide from it.
To do this the lungs contain millions of little air sacs called alveoli where gas exchange takes place.
The alveoli are specialised to maximise the diffusion of O2,and CO2. They have:
An enormous surface area (about 75 m° in humans,
A moist lining for dissolving gases.
Very thin walls.
A good blood supply.
Explain how villi provide a really big surface area
1)
The inside of the small intestine is covered in millions and millions of these tiny little projections called villi.
2) They increase the surface area in a big way so that digested food is absorbed much more quickly into the blood.
Notice they have:
a sinple layer of surface cells,
a very good blood supply to assist quick absorption
Explain how the structure of leaves is adapted to let gases diffuse in and out of the cells
Carbon dioxide diffuses into the air spaces within the leaf, then it diffuses into the cells where photosynthesis happens.
The underneath of the leaf is an exchange surface. It’s covered in little holes called stomata which the carbon dioxide diffuses in through.
Oxygen (produced in photosynthesis) and water vapour also diffuse out through the stomata.
The flattened shape of the leaf increases the area of this exchange surface so that it’s more effective.
The walls of the cells inside the leaf form another exchange surface. The air spaces inside the leaf increase the area of this surface so there’s more chance for carbon dioxide to get into the cells.
The water vapour evaporates from the cells inside the leaf. Then it escapes by
diffusion because there’s a lot of it inside the leaf and less of it in the air outside
How does the stomata open and close
The size of the stomata are controlled by guard cells. These close the stomata if the plant is
losing water faster than it is being replaced by the roots. Without these guard cells the plant would soon wilt.
What are gills
The exchange surface for fish
Explain how water enters a fish and what happens to the oxygen and carbon dioxide from the water and blood
Water enters the fish through its mouth and passes put through the gills, As this happens, oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the bkood into the water
What is the role of gill filaments and what are they
Each gill is made of lots of thin plates called gill filaments which give a large sirfsce area for exchange of gases.
What are the fish gills covered in and what do they do
Fish gills are covered in lamellae, which increase the surface area even more
What do lamellae have to speed up diffusion
Lots of blood capillaries
What else do lamellae have that is not lots of blood capillaries
They have a thin surface layer of cells to minimise the distsnce that the gases have to diffuse
How is there a large concentration of oxygen between the wayer and the blood in a fish
Blood flows through the lamellae in one direction and water flows ovee in the opposite direction
What does it mean when the concentration of oxygen in the wayer is always jigher than in the blood (in terms of fish)
So as much oxygen as possibke diffuses from the eayse into the nlood
