Flashcards in Cell Biology Deck (58):
What is the difference between a eukaryotic and a prokaryotic cell?
Eukaryotic-complex and include all animal and plant cells
Prokaryotic-smaller and simpler eg bacteria
What are the parts of a cell called?
Sub cellular structures
What is the role of the nucleus?
Contains genetic information that control the activities of the cell
What is the role of mitochondria?
Where the reactions for aerobic respiration take place. Respiration transfers energy that the cell needs to work.
What is the role of the ribosomes?
These are where proteins are made in the cell.
What is the role of the cell membrane?
Holds the cell together and controls what goes in and out.
What is the role of the cytoplasm?
Gel-like substance where most of the chemical reactions happen. It contains enzymes that control these chemical reactions.
What is the role of the cell wall?
It is made of cellulose and supports the cell and strengthens it.
What is the role of the permanent vacuole?
Contains cell sap, a weak solution of sugar and salts.
What are the role of the chloroplasts?
These are where photosynthesis occurs, which makes food for the plant. They contain chlorophyll, which absorbs light needed for photosynthesis.
What is the structure of a bacteria cell like?
-have a single circular strand of DNA that floats freely in cytoplasm
-contain one or more small rings of DNA called plasmids
What is the equation for magnification?
=image size / object height
What are light microscopes used for?
Use light and lenses to form an image of a specimen and magnify it. They let us see individual cells and large sub cellular structures, like nuclei.
What are electron microscopes used for?
Use electrons instead of light to form an image. They have a much higher magnification than light microscopes.
How do you prepare a specimen on a slide?
-add a drop of water to middle of clean slide
-cut up an onion and separate it into layers. Use tweezers to peel off some epidermal tissue from bottom.
-place epidermal tissue using tweezers into water
-add a drop of iodine solution which will stain object by adding colour to it
-place a cover slip on top
What is cell differentiation?
The process by which a cell changes to become specialised for its function.
How do cells change?
They develop different subcellular structures and turn into different types of cells. It occurs as an organisms develops.
Why do cells differentiate in mature animals?
Used for repairing and replacing cells, such as skin or blood cells
How are sperm cells specialised?
-has a long tail and streamlined head to help it swim to egg
-a lot of mitochondria in the cell to provide energy needed
-carries enzymes in its head to digest through egg cell membrane
How are nerve cells specialised?
-they carry electrical signals from one part of the body to another
-they 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
How are muscle cells specialised?
-the function is to contract quickly
-they are long and contain lots of mitochondria to generate energy needed for contraction
How are root hair cells specialised?
-cells on the surface of plant roots, which grow into long “hairs” that stick out into the spill
-gives the plant a big surface area for absorbing water and mineral ions from the soil
How are the phloem and xylem cells specialised?
-made from phloem and xylem tubes which transport substances such as food and water around plants
-the cells are long and joined end to end to form the tubes
-xylem cells are hollow in the centre and phloem cells have very few subcellular structures so that stuff can flow through them
What are undifferentiated cells called?
Stem cells, which can divide to produce lots more undifferentiated cells
What are the use of stem cells found in early human embryos? (Embryonic stem cells)
-they have potential to differentiate into any kind of cell at all
-al the different types of cells found in a human being have come from these few cells in the early embryo
What is the use of adult stem cells?
They’re only found in certain places, like bone marrow.
-they can’t turn into any cell type at all, only certain ones such as blood cells
How can adult stem cells be used?
-used to cure disease
-stem cells can be transferred from the bone marrow of a healthy person to replace faulty bloody cells in the patient who receives them
What can embryonic stem cells be used for?
-to replace faulty cells in sick people
-you could make insulin-producing cells for people with diabetes
-or nerve cells for people paralysed by spinal injuries
What is a risk with using stem cells in medicine?
Stem cells grown in the lab could become contaminated with a virus which could be passed on to the patient which will make them sicker
Why are some people against stem cell research?
-feel human embryos shouldn’t be used for experiments as it is potential human life
-curing patients who already exist is more important
-can cause prejudice
How are stem cells used to create identical plants?
-in plants, stem cells are found in the meristems
-these stem cells can be used to produce clones of whole plants quickly and cheaply
-they can be used to grow more plants out of rare species to prevent them being wiped out
-used to grow identical plants with desired features eg disease resistance
What is a chromosome?
-coiled up lengths of DNA molecules
-carries a large number of genes
-23 pairs of chromosomes in a human cell
Why do multicellular organisms use mitosis?
They use it to grow or replace cells that have been damaged
What happens in growth and DNA replication?
-when a cell is not dividing, the DNA is all spread out in long strings
-before it divides, the cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes
-it then duplicates DNA and DNA is copied and forms X shaped chromosomes
What happens in mitosis?
-chromosomes line up at centre of cell and cell fibres pull them apart
-two arms of each chromosome go to opposite ends of cell
-membranes form around each sets of the chromosomes. These become the nuclei of the two new cells as the nucleus has divided
-cytoplasm and cell membrane divide
-two new daughter cells are produced and are identical
What happens in binary fission?
-circular DNA and plasmids replicate
-cell gets bigger and circular DNA strands move to opposite ‘poles’
-cytoplasm begins to divide and new cell walls begin to form
-cytoplasm divides and two new daughter cells are produced
-each new daughter cell has one copy of the circular DNA Bur can have a different number of plasmids
What conditions are required for bacteria to divide?
Warm environment and lots of nutrients available
What is diffusion?
The spreading out of particles from an area of a higher concentration to an area of lower concentration
Where does the diffusion happen?
Happens in both solutions and gases as particles in these substances are free to move about randomly
-simplest type is when gases diffuse through each other eg perfume in a room
How do cell membranes allow dissolved substances to move in?
By diffusion and a higher temp (more energy)
-particles flow through cell membrane where there’s a higher conc to where there’s a lower conc
-the larger the SA of the membrane, the faster the diffusion rate because more particles can pass through at once
What is osmosis?
The movement of water molecules across a partially permeable membrane from a region of higher water conc to a region of lower water conc
-a type of diffusion
What is a partially permeable membrane?
One that has very small holes in it.
Only tiny molecules (like water) can pass through them and bigger molecules (like sucrose) can’t fit through
What is active transport?
When substances are absorbed against a concentration gradient, from a low to high conc.
-requires energy and respiration to work
How does a root hair cell take in minerals and water?
-has a large SA due to microscopic hairs which means it can absorb mineral ions and water from soil
-active transport allows plant to absorb minerals against a conc gradient
When is active transport used in the body?
Used in the gut when there is a lower conc of Nutrients in the gut, but a higher conc of nutrients in blood
What happens in gas exchange?
Where oxygen and CO2 is transferred between cells and environment
How do substances diffuse into single-celled organisms?
Substances and gases can diffuse directly into the cell across the cell membrane as they have a large SA compared to their volume
How do substances diffuse into multicellular organisms?
Have a smaller SA compared to volume, not enough substances can diffuse from their outside surface to supply their entire volume
How are exchange surfaces adapted to maximise effectiveness?
-have a thin membrane so substances have a short distances to diffuse
-have a large SA so lots of substance can diffuse at once
-exchange surfaces in animals have lots of blood vessels to get stuff in and out of blood quickly
-gas exchange surfaces in animals are often ventilated-air moves in and out
What is the function of the lungs?
To transfer oxygen to the blood and remove waste CO2 from it
-lungs contain millions of little air sacs called alveoli where gas exchange takes place
How are the alveoli specialised to maximise the diffusion of oxygen and CO2?
-have a huge SA
-a moist lining for dissolving gases
-very thin walls
-a good blood supply
What is the role of the villi?
Found in the small intestine
-increase the SA so that digested food is absorbed more quickly into blood
How is the villi specialised?
-a single layer of surface cells
-a very good blood supply to assist quick absorption
Where is the exchange surface in a plant?
Underneath the leaf, covered in tiny holes called the stomata where carbon dioxide diffuses in through for photosynthesis
Where does the oxygen and water vapour go in photosynthesis?
They diffuse out through the stomata
-size of stomata is controlled by guard cells which close stomata if plant losing water faster than it is being replaced by roots
How is the structure of the leaves adapted to let gases diffuse in and out of cells?
-flattened shape of leaf increases are of exchange surface so it’s more effective
-walls of the cells inside the leaf form another exchange surface. The air spaces inside the leaf increase the area of the surfaces do there more chance of CO2 to get into cells
What happens in gas exchange of a fish?
Water enters fish through mouth and passes out through gills and oxygen diffuses from water into blood in the gills and CO2 diffuses from the blood into water