B1 - Cell Biology Flashcards
What are both Animal and Plant cells?
Eukaryotes
What are Eukaryotic cells?
Cells that contain their genetic material (DNA) enclosed in a nucleus.
What are Features all Eukaryotic cells have?
Cell membrane
Cytoplasm
Nucleus
Genetic Material
What is a Prokaryotic Cell and Give an example?
In Prokaryotic cells, the genetic material (DNA) is not enclosed in a nucleus. e.g. Bacteria
What are the Differences between Prokaryotes and Eukaryotes?
- Prokaryotes do not have mitochondria
- Prokaryotic cells are smaller than Eukaryotes
- Prokaryotes divide using binary fission while Eukaryotes use Mitosis
Prokaryotes - Eukaryotes DNA is in a nucleus while Prokaryotes have DNA as a single molecule floating with additional plasmids
- Prokaryotes are surrounded by a cell wall while Eukaryotes are surrounded by cell wall in plants and fungi
What is the Formula for Magnification?
magnification = image size/real size
What does 1 order of magnitude mean?
10 Times
What is the function of the Nucleus?
Contains genetic material, including DNA, which controls the cell’s activities.
What is the Cytoplasm and its function?
A jelly-like material that contains dissolved nutrients and salts and structures called organelles. It is where many of the chemical reactions happen like respiration.
What is the cell membrane and its function?
Its structure is permeable to some substances but not to others.
It therefore controls the movement of substances in and out of the cell.
Why can’t we see Mitochondria or Ribosomes?
They are too small to be seen using a light microscope. They can only be seen using an Electron Microscope.
What is the Mitochondria and its function?
Organelles that contain the enzymes for respiration, and where most energy is released in respiration.
What is a Ribosome and what do they do?
Tiny structures where protein synthesis occurs.
Draw an Animal cell and label it
Draw and Label a Plant cell
What are the three additional structures plant cells have over animal cells?
Chloroplast
Cell wall
Permanent vacuole
What is a Chloroplast and it’s function?
Organelles that contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis. Contains the enzymes needed for photosynthesis.
What is a Cell wall and it’s function?
Made from cellulose fibres and strengthens the cell and supports the plant.
What is a permanent vacuole and its function?
Filled with cell sap to help keep the cell turgid.
Can Animal cells have a vacuole?
Animal cells may also have vacuoles, but these are small and temporary. In animals, they are commonly used to store or transport substances.
What does it mean if most animal and planat cells are specialised?
They have adaptations which help them to carry our their particular function.
When cells become specialised, scientists call that differentiation.
What is the job of the sperm cell?
How are they adapted to this?
Its job is to join with an ovum(egg cell). We call this Fertilisation. During Fertilisation the genetic information of the ovum and sperm combine.
- The head of the sperm contains the genetic material for fertilisation.
- The acrosome in the head contains enzymes so that the sperm can penetrate an egg.
- The middle piece is packed with mitochondria to release energy needed to swim and fertilise the egg.
- The tail enables the sperm to swim.
What is the job of the Nerve cell?
How is it adapted to it’s function?
The Nerve cell’s job is to send electrical impulses around the body.
- The nerve cell is extended, so that nerves can run to and from different parts of the body to the central nervous system.
- Dendrites increase the surface area so other nerve cell can connect more easily.
- The end of the Axon has synapses which are junctions that allow the impulse to pass from one nerve to another.
- The nerve cell is covered with a fatty sheath called Myelin, which insulates the nerve cell and speeds up the nerve impulse
What is the job of a muscle cell and how is it adapted to its function?
Their job is to contract
- Muscle cells contain filaments of protein that slide over each other to cause muscle contraction.
- They contain many well-developed mitochondria to provide the energy for muscle contraction.
- In skeletal muscle, the cells merge so that the muscle fibres contract in unison.
What is the job of a root hair cell and how is it adapted to its function?
Their job is to absorb water and dissolved minerals.
- It achieves this by having a increased surface area.
- It does not have chloroplasts as it is underground.
- It has thin walls so as not to restrict the movement of water.
What is the job of a xylem cell and how is it adapted to its function?
They form long tubes which carry water and dissolved minerals from the roots to the leaves.
They achieve this by:
- very thick walls containing lignin. This provides support to the plant. But because the cell walls are sealed with lignin this causes the xylem cells to die.
- There are no top and bottom walls between xylem vessels, so there is a continuous column of water running through them flowing more easily.
- They have no nucleus, cytoplasm, vacuole or chloroplasts which makes it easier for water and minerals to flow.
What is the job of a Phloem cell and how is it adapted to its function?
Phloem tubes carry dissolved sugars up and down the plant.
They have two different types of cells:
- Phloem cells which have no nucleus and only limited cytoplasm. The end walls of the vessel cells have pores called sieve plates which allow dissolved sugars to move cell interior.
- Each Phloem Vessel cell has a companion cell connected by pores. Adjacent to the sieve tubes they provide energy required to transport substances in the phloem
What is the problem with light microscopes?
- They have a limited magnification.
- They have a limited resolution which means we cannot see fine details.
What is resolution?
the shortest distance between two points on a specimen that can still be seen as two different points by the observer.
What is an Electron Microscope and its advantages?
Electron microscopes use a beam of electrons instead of light rays.
There are two types of electron microscope:
The scanning electron microscope (SEM) has a large field of view so can be used to examine the surface structure of specimens. SEMs are often used at lower magnifications.
The transmission electron microscope (TEM) is used to examine thin slices or sections of cells or tissues.
- Higher Magnification
- Higher Resolution
What is Binary Fission?
A form of cell division used by prokaryotes to reproduce which is a simple form of cell division.
The bacteria splits into two bacterial cells
This level of replication will depend on the availability of nutrients and other suitable conditions such as temperature.
How do you calculate the number of bacterium produced in a certain amount of time?
Example Question) Under ideal conditions, a type of bacterium divides every twenty minutes. Calculate the number of bacteria present after three hours.
3 Hours = 180 minutes
180/20 = 9 rounds
2^9 = 512 = Number of Bacteria
or 5.12*10^2
What do we find in the Nucleus
We find Chromosomes that carry genetic information in a molecule called DNA.
What is a Gene?
a small section of DNA on a chromosome, that codes for a particular sequence of amino acids , to make a specific protein .
How many Chromosomes does each body cell contain?
How many pairs of chromosomes do each human body cells contain?
Each body cell contains two of each chromosome. They are paired
Human body cells contain 23 pairs of Chromosome.
What is the Female and Male Chromosome?
Each human body cell contains 46 chromosomes. These can be arranged into 23 pairs.
Each chromosome in a pair carries the same types of genes. The 23rd pair are the sex chromosomes:
In females, the two chromosomes are identical in shape. There are two X chromosomes. Females are referred to as XX.
In males, one of the chromosomes is a different in shape. There is an X and also a Y chromosome. Males are referred to as XY
What is the Process of Mitosis?
For a multicellular organism to grow, cells must divide by mitosis to produce two new identical daughter cells
During mitosis, one chromosome from each set is pulled to each end of the cell, and a new nucleus forms around each group of chromosomes
After this, the cytoplasm and cell membranes divide in a process known as cytokinesis. This results in the formation of two genetically identical daughter cells
How do you calculate how many cells are in each stage of the cell cycle to estimate how long each stage of the cell cycle lasts
Where are stem cells found in plants and how is it different to Animals.
Cell division in plants occurs in regions called meristems.
Cells of the meristem can differentiate to produce all types of plant cells at any time during the life of the plant.
The main meristems are close to the tip of the shoot, and the tip of the root.
In a growing shoot, new cells are being produced continuously near the tip. As the cells become older, further away from the tip, they become differentiated – they enlarge and develop vacuoles
How do we clone plant from meristem cells?
Cells from meristems can be cloned. Meristematic cells are removed from a plant and grown in tissue culture. The cells are grown in a culture medium that contains agar – to provide support and water for the growing cells – along with nutrients and plant hormones to stimulate growth and cell division.
How and why can stem cells treat paralysis
What is Therapeutic cloning and how does it take place?
What are it’s advantages?
Therapeutic cloning could produce stem cells with the same genetic make-up as the patient.
The technique involves the transfer of the nucleus from a cell of the patient, to an egg cell whose nucleus has been removed.
Stem cells produced in this way could be transferred to the patient. Although human stem cells have been produced in this way, and used in research, there is no evidence that, as yet, they have been used to treat anyone.
Explain what diffusion is
Diffusion is the spreading out of the particles of any substance in solution, or particles of a gas, resulting in a net movement of particles from an area of higher concentration to an area of lower concentration. It is a passive process as it requires no energy.
This means:
Particles in a solution or a gas are always moving about randomly
If there happen to be more particles in one area/region, then there tends to be an overall (net) movement of particles from this region of higher concentration to a region where there are fewer particles (an area of lower concentration)
How does diffusion take place in living organisms?
All cells are surrounded by a cell membrane which separates the inside of the cell from its outside environment
Substances have to be able to diffuse through the cell membrane to enter or exit the cell unaided (there are other ways for substances to get in)
Not all substances are able to diffuse across the cell membrane which is why it is described as being ‘partially permeable’; some substances are able to enter or leave the cell whilst others aren’t
For example, oxygen and carbon dioxide can diffuse across the cell membrane during gas exchange whereas the carbohydrate starch cannot (it’s too big)
What are the three factors that affect the rate of diffusion and why?
- Temperature
- Surface Area
- Concentration gradient
How is the small intestine adapted for gas exchange?
Role in the body:
- Most absorption of digested food molecules into the bloodstream occurs across the wall of the small intestine.
How it’s adapted to its role:
- Huge surface area, produced by thousands of villi.
- Only one layer of epithelial cells covers the surface of each villus – this decreases diffusion distance
- Each villus has a good blood supply – this maintains a concentration gradient
How are the Alveoli adapted for gas exchange?
The alveolus is the gas exchange surface in humans
Role in the body:
- Gas exchange between air in the alveoli and the blood, to supply cells with oxygen for aerobic respiration and to remove carbon dioxide
How it’s adapted to its role:
- Millions of alveoli (singular: alveolus) which collectively provide a huge surface area this increases SA
- The wall of each alveolus is one cell thick, with a moist lining and excellent blood supply - this maintains a concentration gradient
- Extensive blood supply - ensuring oxygen rich blood is taken away from the lungs and carbon dioxide rich blood is taken to the lungs.
How are gills adapted to gas exchange?
-Each gill is made from lots of smaller plates called filaments, which themselves are covered in projections called lamellae – this increases SA
-Dense capillary network ensures a good blood supply which flows in the opposite direction to water passing through the gills – this maintains a concentration gradient
How are Roots adapted to gas exchange?
Role in the plant:
- To absorb water and mineral ions (such as magnesium and nitrate ions) from the soil and anchor the plant
How it’s adapted to its role:
- Mitochondria for active transport of mineral ions
- The surface of the roots are covered in root hair cells – this increases SA
- Thinner walls (due to shorter diffusion distance)
- Permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water potential gradient
- Remember that chloroplasts are not found in these cells – there’s no light for photosynthesis underground!
- The root network is highly branched - this increases SA
How is the Leaf adapted for gas exchange?
Role in the plant:
- The leaves contain most of a plant’s photosynthetic cells
- Photosynthesis requires efficient gas exchange between air surrounding the leaf and the photosynthetic cells, whilst minimising water loss
How it’s adapted to its role:
- Stomata are tiny openings that predominantly cover the lower side of the leaf, allowing air to circulate inside the leaf – this decreases diffusion distance for carbon dioxide and oxygen
- The lower layer of the leaf is made from spongy mesophyll cells which allow air to circulate inside the leaf
What is Osmosis?
Water moves from a high water to a low water concentration across a partially permeable membrane and down a concentration gradient
Osmosis is a just a special type of diffusion, so water molecules move about randomly just like any other particle that can diffuse
Water will always move from a more dilute solution to a more (solute) concentrated solution to even up the concentration of water molecules on each side of the membrane
What does dilute and concentrated mean?
What is the Effect of Osmosis on Plant Tissue
The movement of water by osmosis can easily be observed by placing two similar pieces of plant tissue into solutions with differing concentrations
If the plant tissue gains mass:
- *- Water must have moved into the plant tissue from the solution surrounding it by osmosis
- The solution surrounding the tissue is more dilute than the plant tissue (which is more concentrated)**
If plant tissue loses mass:
- *- Water must have moved out of the plant tissue into the solution surrounding it by osmosis
- The solution surrounding the tissue is more concentrated than the plant tissue (which is more dilute)**
If there is no overall change in mass:
- There has been no net movement of water as the concentration in both the plant tissue and the solution surrounding it must be equal
- Remember that water will still be moving into and out of the plant tissue, but there wouldn’t be any net movement in this case
What is Active Transport?
Diffusion and osmosis rely upon the passive transport of substances down concentration gradients, relying on the random movement of particles
However, cells also need to be able to transport substances across the cell membrane against a concentration gradient. This requires energy released by respiration
The energy from respiration is used by protein transport molecules embedded in the cell membrane to move substances into or out of the cell
Active transport moves substances from a more dilute solution to a more concentrated solution
What is Active Transport?
Diffusion and osmosis rely upon the passive transport of substances down concentration gradients, relying on the random movement of particles
However, cells also need to be able to transport substances across the cell membrane against a concentration gradient. This requires energy released by respiration
The energy from respiration is used by protein transport molecules embedded in the cell membrane to move substances into or out of the cell
Active transport moves substances from a more dilute solution to a more concentrated solution
Compare Transport Processes
