Topic 1 - Cell Biology Flashcards
nucleus function
Controls and regulates the activity of the cell and contains DNA
Cytoplasm function
-Gel like substance where Chemical reactions happen and holds everything in place
-Contains enzymes that control these rewctions
Cell surface membrane function
Keeps everything in the cell, and keeps unwanted things out. Let’s in nutrients.
Ribosomes function
Makes proteins
Mitochondria function
-Where most of the reactions for aerobic respiration take place
Organelles in an animal cell
-Nucleus
-Cell surface membrane
-Ribosomes
-Mitochondria
-Cytoplasm
Organelles in plant cells
-Vacuoles
-Chloroplasts (Made of chlorophyll)
-Cell wall (made of cellulose)
Chloroplasts function
Used for photosynthesis
Contains chlorophyll which absorbs light needed for photosynthesis
Cell wall function
Supports the cell and makes it strong
Made of cellulose
Vacuole function
Contains a cell sap which is a weak solution of sugar and salts
How are phloem and xylem cells specialised
-Transport substances such as food and water around plants
-To form these tubes the cells are long and joined end to end
-Xylem cells are hollow in the centre
-phloem cells have few sub cellular structure so things can flow through the,
White blood cell
-Fights bacteria, viruses and other invaders
-Destroy harmful substances and prevent illness
Root hair cells
-On the surface of plant roots which grow into long hairs that stick out into the soil
-Gives the plant a big surface area for absorbing water and mineral ions from the soil
What are adult stem cells
-We have stem cells in our body (e.g. bone marrow)
-Can only turn into certain cell types, such as blood crlls
Embryonic stem cells
-Come from a developing embryo (usually one that has been discarded after IVF)
-Can turn into any kind of cell at all
Arguments against stem cell research
-Drugs given to women to stimulate eggs are dangerous
-Embryonic stem cells are unstable and cause tumours
-Even at 3 days embryos are considered living things
-Organisms given stem cell therapy often develop problems
-Embryos are created purely for research
For stem cell research
-Diverts resources to treatments that really work
-Offers treatment to many incurable diseases
-No waiting lists for organ transplant ion
-Less lab animals and money will be wasted and money will be wasted testing new drugs
-Will offer a cure for many diseases such as diabetes and cancer
-Donated cells are identical so there are no problems with rejection
-A cell at 3 days is not a living thing as it only contains 150 cells
-Damaged or dead can grown and replaced
-Curing existing patients ailments is more important than the life of the embryo
What is diffusion
The net movement of particles from an area of high concentration to low concentration
How does concentration affect diffusion
Particles travel faster when there is a higher concentration
How does temperature affect diffusion
Particles travel faster when hotter
How does surface area affect diffusion
The larger surface area the greater rate of diffusion
Partially permeable meaning
somethings can get in/out
Diffusion - alveoli and blood
-Carbon dioxide is made during respiration which goes into the blood, which carries it to the lungs where it diffuses into the alveoli
-Oxygen is brought in through the lungs and diffuses into the blood which carries it to be used in cells in the body for respiration
Diffusion between skin and small blood vessel
-Oxygen diffuses through the thin skin into a small blood vessel. The oxygen then diffuses into the cells
-Carbon dioxide that is made in the cells goes into the blood and diffuses out the skin
Epithelial Tissue
-Epithelial cells are specialised because they need to be thin when lining your organs, so when activity happens there isn’t any friction.
-They line both external and internal parts of the body
-Can line organs and in tubes around the body (e.g. small intestine and stomach)
-Also found as part of the skin
Muscular tissues
-Soft tissue that makes muscles in animals that must be able to shorten or contact to make the body
Glandular tissue
Secretes things such as hormones. They make up glands for things such as sweat they rope-like and lumpy.
What is a tissue
A group of similar cells that carry out a specific function.
What are eukaryotic cells
They are complex cells and include all animal and plant cells
What are prokaryotic cells
Smaller and simpler cells (e.g. bacteria)
Features of a prokaryotic cell (bacteria)
-Cell membrane
-Cell wall
-No nucleus but a single strand of DNA that floats in the cytoplasm
-May contain small rings of DNA called plasmids
-Don’t have chloroplasts or mitochondria
-Cytoplasm
Features of an electron microscope
-Higher resolution
-Higher magnification
-Allows us to see smaller things in more detail such as internal structure of mitochondria and chloroplasts or ribosomes and plasmids
Formula for magnification
Magnification = image size / regular size
Difference between micrometers and millimetres
from micrometers to millimetres divide by 1000
How to prepare slides
-Add water in middle of a clean slide and cut up an onion and separate it into layers
-Use tweezers to pull off epidermal tissue from the bottom of one of the layers
-Place it into the water on the slide and add a drop of iodine solution which is a stain and highlights the object in a cell by adding a colour
-Place a cover slip on top by standing it upright on the slide next to the water and tilt and lower it so it covers the specimen
How to use the light microscope to look at your slide
-Clip it onto the stage and select the lowest powered objective lense
-Use the coarse adjustment knob to move it up to just below the objective lens.
-Look down the eyepiece and use the coarse adjustment knob until it is roughly in focus
-Ajust the focus with the fine adjustment knob until you get a clear image of the slide
What to do once you’ve viewed your onion with the microscope
-Draw what you see using a pencil with a sharp point and make sure it takes up at least half of the space available and that it is drawn with clean, unbroken lines
-Don’t include colouring or shading
-sub cellular structures should be drawn in proportion
-Out a title and write down the magnification, then label features
What is differentiation
-The process by which a cell changes to become specialised for its job.
-As they change they develop different sub cellular structures and turn into different types of cells allowing them to carry out specific functions
Difference between differentiation between plant and animal cells
-As an organism develops, after this in an animal cell loses this ability after becoming specialised.
-Plant cells often don’t lose this ability
What purpose do animal cells differentiate for
-Mainly for repairing and replacing cells such as skin or blood cells
Spermcells as specialised cells
-Function to get male DNA to female DNA
-long tail and streamlined head to help it swim to the egg
-Lots of mitochondria to provide the energy needed and carries enzymes in its head to digest through the egg cell membrane
Muscle cells as specialised cells
-A function is to contract quickly
-The cells are long so they have space to contracts and contain a lot of mitochondria to generate the energy needed for contraction
Nerve cells as specialised cells
-Their function is to carry electrical signals from one part of the body to another
-These cells are long to cover more distance and have branched connections at their ends to connect to other nerve cells and form a network throughout the body
What is mitosis
When cells divide in the cell cycle
What do multicellular organisms use mitosis for
To grow or replace cells that have been damaged
What do the cells end up resulting in after mitosis
-Two new cells identical to the original cell with the number of chromosomes
outline Stage 1 of the cell cycle: Growth and DNA replication
-In a cell that isn’t dividing the DNA is spread out in long strings
-Before it divides a cell have to grow and increase the amount of sub cellular structures such as mitochondria and ribosomes
-Then duplicates it’s DNA so there’s one copy for each new cell the DNA forms X-shaped chromosomes
outline stage 2 of cell division : mitosis
-The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite end of the cell
-Membranes form around each of the sets of chromosomes and they become the nuclei of the two new cells - the nucleus has divided
-Lastly the cytoplasm and cell membrane divide
How can dissolved substances move in and out of cells
Through cell membrane, however only very small molecules can do this though such as oxygen for respiration, glucose, amino acids and water
What is osmosis
The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
-It is a type of diffusion
What do water molecules do during osmosis
They pass both ways through the membrane during osmosis because the molecules move about randomly all the time and because there are more on one side there’s a steady net flow of water into the region with fewer water molecules
-It tries to even up the concentration on either side of the membrane
Outline the potato cylinder and sugar solution experiment
-Cut up a potato into identical cylinders and get some beakers with different sugar solution, one with no sugar and one that is very concentrated with the sugar, then some other concentrations in between
-Measure the mass of the cylinders and leave one in each beaker overnight
-Then take them out and dry them with a paper towel and measure their masses again
What should the potato and sugar solution experiment show
-As the concentration of the sugar increases the mass of the potato should decrease
-This is because the water is trying to even up the concentration in both sides of the solution
-When the line on a graph is at zero it’s because the water is at the same concentration as both sides so no osmosis takes place
How do you reduce errors for the sugar solution and potato experiment
-Repeating the experiment and calculating a mean percentage change
Outline the process of binary fission
-The circular DNA and plasmid replicate
-The cell gets bigger and the DNA strands move to opposite poles of the cell
-The cytoplasm begins to divide and new cell walls form
-Cytoplasm divides and two daughter cells are produced and each cell has one copy of the DNA but can have a variable number of plasmid
How does the condition of the environment affect binary fission
-If they are in a warm environment and have lots of nutrients they divide very quickly
-However if they become unfavourable conditions the cells will stop dividing and eventually dir
How can you grow bacteria in a lab (out and inside of practical)
-Outside: Some bacteria are grown in a culture medium which contains the carbohydrates, minerals, proteins and vitamins they need to grow. It can be this or agar jelly
-Inside: An agar plate is made by hot agar jelly being poured into a petri dish
-When it cools inoculating loops transfer microorganisms onto the culture medium
-They then multiply
What temperature must microorganism be kept at when growing in schools and why
-Under 25°C as harmful pathogens are more likely to grow above this temperature
Outline how to investigate the effect of antibiotics on bacterial growth
-Place paper discs soaked in different types of antibiotics on an agar plate that has an even covering of bacteria and leave some space between the discs
-The antibiotic should diffuse into the agar jelly.
-Any antibiotic resistant bacteria will continue to grow, but non-resistant strains will die
-A clear area will be left where the bacteria have died
what is the clear area will be left where the bacteria have died called in an antibiotic experiment
Inhibition zone
Why should you use a control for the antibiotic and bacteria in agar jelly experiment
-Use a paper disc that hadn’t been soaked in antibiotic and instead with sterile water to ensure any difference between the growth of the bacteria around the control disc and one of the antibiotic discs is due to the effect of the antibiotic alone (and not something weird in the paper etc,)
Why should you use uncontaminated cultures
-It may affect your results and may potentially result in the growth of pathogens
How should you avoid contaminating your cultures
-Petri dishes and culture medium should be sterilised by heating to kill any unwanted microorganisms
-Sterilise inoculating loops if using them by passing them through a hot flame
- After transferring the bacteria the lid of the petri dish should be lightly taped on to stop microorganisms from the air getting
-Petri dishes should be stored upside down to stop drops of condensation falling onto the agar surface
How can stem cells from bone marrow be used to cure disease
They can replace faulty blood cells in the patient who receives them
How can embryonic cells cure disease
-Can replace faulty cells in sick people such as insulin producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries etc.
What is therapeutic cloning and what type of stem cells are used for it
-An embryo cell can be used
-Made to have same genetic information as the patient so stem cells from it would contain the same genes and wouldn’t be rejected by the patients body if used to replace faulty cells
What is a possible risk with the use of stem cells
If the cells grown in a lab become contaminated with a virus it could be passed onto the patient and make them sicker
Where are stem cells found in plants
-Found in the meristems (part of the plant where growth occurs)
What can plant stem cells differentiate into
-Produce clones of whole plants quickly and cheaply
-They can be used to grow more plants of rare species
-Can be used to grow crops of identical plants that have desired features for farmers for example disease resistance.
What is active transport
When substances need to be absorbed against a concentration gradient (e.g. from a lower to a higher concentration)
What can root hair cells use diffuse ion to take up minerals from the soil
The concentration of minerals is usually higher in the root hair cells than in the soil around them
What gives plants large surface areas
Each branch of a root is covered in millions of microscopic hairs that stick out into the soil
Why do plants need a large surface area
For absorbing water and mineral ions from the soil, plants need these ions for healthy growth
How do root hair cells take in minerals using active transport
Active transport allows the plant to absorb mineral from a very dilute solution, against a concentration gradients
What does active transport need to make it work
energy from respiration
Where does active transport happen in humans
Taking in glucose from the gut and from kidney tubes
Outline active transport between stomach and blood
-When there’s a higher concentration of amino acids and nutrients in the gut they naturally diffuse into the blood
-But when there’s a lower concentration it means the concentration gradient is the wrong way
-Active transport allows nutrients to be taken into the blood despite the fact the concentration gradient is the wrong way
-This means glucose can be taken into bloodstream where it can be transported to be cells and used for respirstion
Why do single-celled organisms having a large surface area to volume ratio help diffusion into or out of the cell across the cell membrane
Enough substances can be exchanged across the membrane to supply the volume of the cell
Why do multicellular organisms having a smaller surface area to volume ratio not help diffusion into or out of the cell across the cell membrane
Not enough substances can diffuse from their outside surface to supply their entire volume
What are exchange surfaces
surfaces that are structured to allow enough of the substances to pass through
How are exchange substances adapted
-thin membrane so substances only have a short distance to diffuse
-Large surface area so a lot of substance can diffuse
-Exchange surfaces in animals have lots of blood vessels to get things into and out of the blood quickly
-Gas exchange surfaces in animals (e.g. alveoli) are often ventilated too - air moves in and out
Gas exchange in the lungs
-Lungs job is to transfer oxygen > blood and to remove carbon dioxide from it. So lungs contain millions of little air sacs called alveoli where gas exchange takes place.
How are alveoli specialised
To maximise the diffusion of O2 and CO2 they have :
- An enormous surface area
-A moist lining for dissolving gases
-Very thin walls
-A good blood supply
How do villi help with exchanging substances
-The inside of the small intestine covered in millions of little projections called villi so surface area increases largely so digested food is absorbed quicker into the blood
-They have a single layer of surface cells and a very good blood supply that assists quick absorption
What part of a leaf is an exchange surface and how is it one
The underside of a leaf is covered in little holes called stomata. This is where the carbon dioxide diffuses in through
Where and why does carbon dioxide diffuse into a leaf
Into the air spaces within the leaf, then it diffuses into the cells where photosynthesis happens
What two substances diffuse out of the stomata
-Oxygen which is produced in photosynthesis
-Water vapour (is lost from from all over the leaf surface but most from stomata)
What do guard cells do
They control the size of stomata and close them if the plant is losing water faster than it is being replaced by the roots
Without these cells the plant would soon wilt
Two more adaptations of plants for gas exchange
-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 and the air spaces inside the leaf increase the area of this surface so there’s a higher chance for carbon dioxide to get into the cells
What are the gas exchange in fish
the gills
How does gas exchange happen in fish
-Water enters the fish through its mouth and passes out through the gills as this happens oxygen diffuses from the water into the blood
-and carbon dioxide diffuses from blood into the water
How are gills adapted for gas exchange
-Each gill is made of thin plates called gill filaments which give a big surface area for gas exchange
-the gill filaments are covered in tiny structures called lamellae which increase the surface area even more
-Lamellae have lots of blood capillaries to speed up diffusion and they have thin surface layers of cells to minimise the distance that gases have to diffuse
How is a large concentration gradient between blood and water maintained in fish gas exchange
Blood flows over Lamellae in one direction whereas water flows over in the opposite direction
Is the concentration of oxygen higher in water or blood and what affect does this have (fish)
Higher in the water so as much oxygen as possible diffuses from the water into the blood
