B1: cell biology Flashcards
Nucleus
In animal and plant cell
Contains genetic material that controls the activities of the cell
Cytoplasm
In animal and plant cell
Gel- like substance where most chemical reactions happen
Contains enzymes that control these chemical reactions
Cell membrane
In animal and plant cell
Holds the cell together and controls what goes in and out
Mitochondria
In animal and plant cells
Where most of the reactions for aerobic respiration take place
Ribosomes
In animal and plant cells
Where proteins are made in the cell
Cell wall
Plant only
Made of cellulose
Supports the cell and strengths it
Vacuole
Plant only
Contains cell sap a weak diluting of sugar and salts
Chloroplasts
Plant only
Photosynthesis occurs, which makes food for the plant
Contains a green substance called chlorophyll which absorbs the light needed for photosynthesis
Bacterial cells
Much smaller
Have cell membranes, cell wall , cytoplasm
Don’t have chloroplasts or mitochondria , don’t have a true nucleus instead they have a singular strand of DNA that floats freely in the cytoplasm
They contain one or more small rings of DNA called plasmids
Formula for magnification
Magnification = image size/ real size
Formula for image size
Image size = magnification * real size
Formula for real size
Real size = image size / magnification
How to prepare a slide to view a onion cell
- Add a drop of water to the middle of a clean slide
- cut up an onion and separate it out into layers . Use tweezers to peel off some epidermal tissue from the bottom of the layers
- Using the tweezers place the epidermal tissue into the water in the slide
- Add a drop of iodine solution (stains are used to highlight objects in a cell by adding colour)
- Place a cover slip on top - make sure there are no bubbles as they will obstruct your view of the specimen
Differentiation in cells
Differentiation is the process by which a cell changes to become specialised for its Job
Function of Sperm cells specialised cells)
Specialised for reproduction
Function:
- is to get male DNA to the female DNA
Structure of sperm cell (specialised cell)
Has a long tail and a streamlined head to help it swim to the egg
A lot of mitochondria in the cell to provide the energy needed
Carried enzymes in its head to digest through the egg cell membrane
Function of Nerve cells ( specialised cells)
Specialised for rapid signalling
function:
-To carry electrical signals from one part of the body to another
Structure of the nerve cell ( specialised cells)
Long to cover more distance and have branched connections at their ends to connect to another nerve cells and form a network throughout the body
Function of the muscle cells (specialised cell)
Specialised for contraction
Function:
- is to contract quickly
Structure of muscle cells ( specialised for contraction)
Long so they have space to contract
contain lots of mitochondria to generate the energy needed for contraction
Function of root hair cells (specialised cell)
Specialised for absorbing water and minerals
Function:
-cells on the surface of the plan roots
- Grow into long microscopic “hairs” that stick out into the soil which gives plants a big surface area for absorbing water and mineral ions from the soil
Plants need these mineral ions for healthy growth
Function of phloem and xylem cells (specialised cells)
Specialised for transporting substance
Function:
-Form tubes which transports substances such as food and water around the plants
Structure of phloem and xylem cells (specialised cells)
To form tubes the cells are long and joined end to end.
Xylem cells: hollow in the centre
Phloem cells: have very few sub-cellular structures so that stuff can flow through them
Growth and DNA replication
- In a cell that’s not dividing, the DNA is all spread out in long strings.
- The cell grows and increases the amount of subcellular structures such as mitochondria and ribosomes.
- Then is duplicates it’s DNA.
- copped and forms x- shaped chromosomes
Growth and dna replication -> Mitosis
Once it’s content and dna have been copied the cell is ready for mitosis
4. Chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each go to opposite ends of the cell
5 membranes form around each of the sets of chromosomes. Becoming the nuclei go the two cells - nucleus had divided
6) cytoplasm and cell membrane divide
The cell had produced daughter cells - identical to the dna and to the parent cell
Embryonic stem cells
- Can turn into any type of cell
- Stem cells are Found in early human embryos
- all cells in the human being have to come from those few cells in the early embryos
- can be used to replace faulty cells in sick people
- can create insulin- produced cells
Differentiation
Is the process where cells change to become specialised for its job
Undifferentiated Cells (stem cells)
- can divide to produce lots more undifferentiated cells
* they can differentiate into different type of cells depending on what instructions they’re given
Stem cells in adults
- Only found in places like bone marrow
* Can’t turn into any cell type at all only certain ones like blood cells
Lab grown stem cells
Stem cells from embryos and bone marrow can be grown is a lab to produce clones (genetically identical cells) and made to differentiate into specialised cells to use in medicine or research
Against stem cell research
- an embryonic stem cell is a potential human life
- others think that curing existing patients who are suffering is more important than the riches of embryos
- banned in some countries
- favouring for embryonic stem cells is that embryos used in research are usually unwanted ones from fertility clinics and if they are not used they are destroyed
Stem cells producing identical plants
- in plants stem cells are going in the meristems
- throughout the plants entire life cells in the meristem tissue can differentiate into any type of plant cell
- stem cells can be used to produce clones - quickly and cheaply
- used to grow more plants of rare species
- stem cells can also be used to grow crops of identical plants - diseases resistance
Diffusion
Is the spreading out of particles from an area of higher concentration to an area of lower concentration
Where does diffusion occur?
In solutions and gases - particles in these substances are free to move about randomly
Concentration gradient -diffusion
The bigger the concentration gradient the faster the diffusion rate
Temperature- diffusion
The higher the temperature the faster the diffusion rate because the particles have more energy so they move around faster
Cell membranes function
- They hold the cell together and left stuff inside and out
- Dissolved substances move in and out by diffusion
- Only very small molecules can move through cell membranes
- flow through the membranes from where there is high concentration to whet there is low concentration
- The larger the surface are the faster the diffusion rate
Osmosis
Is the movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower concentration
Partially permeable membrane
- A partially permeable membrane is a membrane with very small holes in it
- so small only tiny molecules can pass through them, and bigger molecules Can’t
How osmosis works
- The water molecules actually pass both ways through the membrane during osmosis. This happens because water molecules mice about randomly all the time
- Because there are more water molecules on one side than in the other, There’s a steady net flow of water into the region with fewer water molecules
- Means strong sugar solution gets more dilute.
- osmosis is a type of diffusion
Why root hair cells can’t use diffusion
The concentration of minerals is usually higher in the root hair cells then in the soil around them
How do root hair cells take in mineral using active transport
- Root hair cells can’t use diffusion so they use active transport
- Active transport allows the plant to absorb minerals from a very dilute solution, against a concentration gradient.
Essential for growth
Active transport needs energy from respiration
Go make it work - Active transport also happens in humans
How does Active transport to stop us starving
Used in the gut when there is a lower concentration of nutrients in the gut, but a higher concentration of nutrients in the blood
- When there’s a higher concentration of glucose and amino acids in the gut they diffuse naturally into the blood
- but when there’s a lower concentration of nutrients in the gut than there is in the blood meaning the concentration gradient is the wrong way
- Active transport allows nutrients to be taken into the blood despite the concentration gradient is the wrong way - glucose can be taken into the blood when it’s concentration in the blood is higher than the gut
Calculating surface area to volume ratio
Surface area = length * width
The volume of a block is found me the equation = length * width * height
Ratio:
Surface area : volume
Single- celled organisms
•Gases and dissolved substances can diffuse directly into the cell across the cell membrane because they have a large surface area compared to their volume so enough substances can be exchanged across the membrane to supply the volume of the cell
Multicellular organisms
- have a smaller surface area compared to their volume so not enough substances can diffuse from their outside surface to supply their entire volume
- need some sort of exchange surface for efficient diffusion
Exchange surface adaptions in multicellular organisms
- have thin membrane so substances only have a short distance to diffuse
- have a large surface area so lots of a substance can diffuse at once
- exchange surfaces in animals have lots of blood vessels to get stuff in and out of the blood quick
- gas exchange surfaces in animals are often ventilated too
Job of the lungs
To transfer oxygen to the blood and to remove waste carbon dioxide from it
What does Alveoli do
For lungs to transfer oxygen in to the blood lungs contain millions of alveoli (little air sacs) where gas exchange takes place
What does Alveoli have to maximise the diffusion if O2 and CO2 ?
They have • an enormous surface area • moist lining for dissolving gases • very thin walls • good blood supply
Villi
- Inside of the small intestine is covered in millions of villi
- Increase surface are so that digested food can be absorbed more quickly into the blood
- They have a single layer of surface cells and a very good blood supply to assist quick absorption
Structure of leaves allowing gases to diffuse in and out of cells
- Carbon dioxide diffuses into the air spaces within the leaf , then diffuses into the cells
- The underneath of the leaf is an exchange surface covered in stomata where CO2 diffuse through and Oxygen and water vapour diffuses out of the stomata
- Guard cells close the stomata of the plant if it’s losing water faster than it being replaced by the roots
- The flattened shape of the leaf increase the area exchange- more efficient
- walls of the cells inside the leaf form another exchange surface the air space increases the area if the surface is there is more chance for CO2 to get into the cells
