Flashcards in Cell Biology Deck (68):
What's another name for plant and animal cells?
What's another name for bacterial cells?
What do plant cells have?
Nucleus, cell membrane, cell wall, cytoplasm, chloroplasts and a vacuole
What do animal cells have?
Nucleus, cell membrane, cytoplasm, mitochondria and ribosomes
What do bacterial cells have?
A lot smaller in comparison. Cytoplasm and a cell membrane surrounded by a cell wall. Genetic material is not enclosed in a nucleus. It is a single DNA loop and there may be one or more small rings of DNA called plasmids
Function of nucleus
Controls the activities of the cell and contains genetic material
Function in cytoplasm
Where most chemical reactions take place. Contains enzymes that control these chemical reactions
Function of cell membrane
Controls the passage of substances into and out of the cell
Functions of mitochondria
Where aerobic respiration takes place. Respiration transfers energy that the cell needs to work
Function of ribosomes
Where proteins are made in the cell
Function of chloroplasts
Absorb light to make food by photosynthesis. They contain chlorophyll which absorbs the light needed for photosynthesis
Function of vacuole
Filled with cell sap
Function of cell wall
Made of cellulose, which strengthens the cell
What is a specialised cell?
A cell that has become differentiated to carry out a particular function
Name some specialised animal cells
Sperm cells, nerve cells and muscle cells
Name some specialised plant cells
Root hair cells, xylem and phloem cells
Uses light and lenses to form an image of a specimen and magnify is. Let us see individual cells and large subcellular structures like nuclei
Used electrons instead of light to form an image. They have much higher magnification than light microscopes. Let us see even tinier things like ribosomes
How to calculate magnification
Magnification = image size
μm into mm
Divide by 1000. 5000 μm divided by 1000 = 5mm
Write 0.0025 in standard form
-the first number needs to be between 1 and 10 so the decimal point needs to move after the 2
-count how many places the dp has moved, this is the power of 10.
= 2.5 x 10^-3
What is resolution
Is the ability to distinguish between two points, so a higher resolution gives a sharper image
How to prepare a slide to view onion cells
1) add a drop of water into the middle of a clean slide
2) cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers.
3) place the epidermal tissue into the water on the slide
4) add a drop of iodine solution , this highlights objects in a cell.
5) place a cover slip on top without trapping any air bubbles
How to use a light microscope
1) clip the slide into the stage and select the lowest-powered objective lens
2) use the coarse adjustment knob to move the stage up to just below the objective lens
3) look down the eye piece and use the coarse adjustment knob to move the stage downwards until the image is in rough focus
4) adjust the focus with the fine adjustment knob until a clear image of the cells is visible
Function is to get the male DNA to the female DNA.
It has a long tail and a streamlines head to help it swim to the egg.
Lot of mitochondria in the cell to provide the energy needed.
Also carries enzymes in its head to digest through the egg cell membrane
Function is to carry electrical signals from one part of the body to another.
These cells are long and have branched connections at their ends to connect to other nerve cells and form a network throughout the body.
Function is to contract quickly.
These cells are long and contain lots of mitochondria to generate the energy needed for contraction
Root hair cell
Absorbing water and minerals
Root hair cells are on the surface of plant roots which grow into long "hairs" that stick out into the soil.
This gives the plant a big surface area for absorbing water and mineral ions from the soil
Phloem and xylem cells
For phloem and xylem 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 is cell differentiation
It's the process by which a cell changes to become specialised for its job
Info about cell differentiation
As an organism develops, cells differentiate to form different types of cells.
Most types of animal cell differentiate at an early stage whereas many types of plant cells retain the ability to differentiate throughout life.
As a cell differentiates it acquires different sub-cellular structures to enable it to carry out a certain function. It has become a specialised cell
What is a stem cell
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
Function of stem cells in embryos
They can be cloned and made to differentiate into most different types of human cells
Function of stem cells in adult animals
Stem cells from adult mine marrow can form many types of cells including blood cells
Function of stem cells in the meristems in plants
Meristem tissue in plants can differentiate into any type of plant cell, throughout the life of the plant
Adult stem cells for medicine
Used to cure diseases. For example stem cells transferred from bone marrow of a healthy person can replace faulty blood cells in the patient who receives them
Embryonic stem cells for medicine
Can be used to replace faulty cells in sick people- you could make insulin-producing cells for people with diabetes, never cells for people paralysed by spinal injuries.
What's therapeutic cloning
A type of cloning where an embryo could be made to have the same genetic information as the patient, so the stem cells produced wouldn't be rejected by the patient's body if used to replace faulty cells
What's the risk involved in using stem cells in medicine
Stem cells grown in the lab may become contaminated with a virus which could be passed on to the patient and so make them sicker
Why are some people against stem cell research?
-human embryos shouldn't be used for experiments since each one is a potential human life
Why are some people for stem cell research
-curing patients who already exist and who are suffering is more important than the rights of embryos
-embryos used in the research are usually unwanted ones from fertility clinics which would probably would of just been destroyed.
Stem cells in plants in meristems
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
The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of genes.
Pairs of chromosomes
Body cells normally have two copies of each chromosome- one from the organism's 'mother' and one from its 'father'.
Body cells in multicellular organisms divide to produce new cells as part of stages called the cell cycle
Multicellular organisms use mitosis to grow or replace cells that have been damaged.
What are the two main stages of the cell cycle
Growth and DNA replica
Growth and DNA replication
In a cell that's 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 its DNA- so there's one copy for each new cell.
Growth and DNA replication
In a cell that's not dividing, the DNA is all spread out in long strings
Once the cells contents and DNA have been copied, the cell is ready for mitosis
The chromosomes line up at the centre of the cell and cell fibres pull them apart. Two arms of each chromosome go to opposite ends of the cell.
Membranes form around each of the sets of chromosomes. These become the nuclei of the two new cells.
Lastly the cytoplasm and cell membrane divide.
The cell has now produced two new identical daughter cells.
What is diffusion
The 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
What does diffusion happen in
Both solutions and gases as the particles are free to move about randomly
What factors affect the are of diffusion
The difference in concentrations (concentration gradient)- the bigger the difference the faster the diffusion rate.
The temperature- the higher the faster as the particles have more energy so move faster.
The surface area of the membrane- the larger the faster
What's a partially permeable membrane
A membrane with small holes to let tiny molecules pass through
Give examples of substances transported in and out of cells by diffusion
Oxygen and carbon dioxide for gas exchange
Waste product urea from cells into the blood plasma for excretion in the kidney
What is osmosis
The movement of water molecules across a partially permeable membrane from a region of higher water concentration to one of lower concentration. Water in lower concentrated solution goes into higher
Distilled water- potato grows as there is less water in potato so the higher concentration of water goes into the lower concentration
Salt solutions- potato shrinks as water ALWAYS moves into the more concentrated solution
How to work out the percentage change in mass
Initial mass- 3.5
Final mass- 3.9
Change in mass- 0.4
Moves substances from a more dilute solution to a concentrated solution (against the concentration gradient). This requires energy from respiration
Active transport in root hair cells
Plants need mineral ions for healthy growth.
The concentration of minerals is usually higher in the root hair cells than in the soil around them. So the root hair cells can't use diffusion to take up minerals from the soil
Active transport in the gut
It allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has higher sugar concentration.
Surface area to volume ratio
Single called organism
Has a relatively large surface area to volume ratio
Multi cellular organisms
Have a smaller surface area to volume ratio
Why do multicellular organisms need exchange surfaces
They have a small surface area to volume ratio so not enough substances can diffuse from their outside surface to supply their entire volume.
Diffusion in small intestine
Inside of small intestine is thin with a large surface area, allowing absorption to happen quickly. To get a big surface area the inside wall is lined with villi
Diffusion in lungs
They have a huge surface area and moist lining for dissolving gases
Diffusion in gills
Have large surface area for gas exchange