Cell Biology Flashcards
What are eukaryotic cells?
have a cell membrane, cytoplasm and genetic material enclosed in a nucleus
example of eukaryotic cells:
animal cells and plant cells
What are prokaryotic cells?
They have cytoplasm and a cell membrane surrounded by a cell wall. The 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.
examples of prokaryotic cells:
bacterial cells
what does the nucleus do?
this contains the genetic material (DNA) of the organism and controls the cell’s activities.
what is cytoplasm?
the liquid that makes up most of the cell in which chemical reactions happen. This is mainly water.
What is the cell membrane?
a flexible outer layer that surrounds the cell and controls which substances can pass into and out from it.
What is mitochondria?
tiny parts of cells floating in the cytoplasm where energy is released from glucose from food. The mitochondria, found in the cell cytoplasm, are where most respiration happens.
What is the cell wall?
a tough outer layer of the cell, which contains cellulose to provide strength and support to the plant.
What is the vacuole?
a space inside the cytoplasm that contains a watery liquid called cell sap. It keeps the cell firm.
What is the chloroplasts?
structures found in the cells of green parts of plants only (leaves and stems) which contain a green pigment called chlorophyll in which photosynthesis occurs.
How are Nerve cells specialised?
They are thin, and can be more than 1 metre long. This means they can carry messages up and down the body over large distances.
Nerve cells have branched connections at each end. These join to other nerve cells, allowing them to pass messages around the body.
They have a fatty (myelin) sheath that surrounds them. The fatty sheath increases the speed at which the message can travel.
How are muscle cells specialised?
Muscle cells are held together in bundles, which pull together to make muscles contract (get shorter and fatter).
how are cardiac cells specialised?
Cardiac (heart) muscle cells are branched, and they join together to make a net. Cardiac muscle cells contract rhythmically, even outside the body. They never get tired.
how are skeletal muscle cells specialised?
Skeletal muscle is joined to bones. Its cells contract to make bones move and joints bend.
how are smooth muscle cells specialised?
Smooth muscle cells make up thin sheets of muscle, such as the stomach lining. They can also be arranged in bundles, or rings, like that in the anus.
How are sperm cells specialised?
the head contains the nucleus with the DNA. The head contains enzymes so the sperm can penetrate the egg. It has mitochondria to release energy needed to swim and fertilise the egg. The tail enables the sperm to swim.
How are root hair cells specialised?
They are long and thin so they can penetrate between soil particles and they have a large surface area for absorption of water.
How are xylem cells specialised?
xylem are specialised cells called vessels.
Vessels: Lose their end walls so the xylem forms a continuous, hollow tube. Become strengthened by a chemical called lignin. The cells are no longer alive. Lignin gives strength and support to the plant. We call lignified cells wood. Transport in the xylem is a physical process. It does not require energy.
how are phloem cells specialised?
Sieve tubes – specialised for transport and have no nuclei. Each sieve tube has a perforated end so its cytoplasm connects one cell to the next. Companion cells – transport of substances in the phloem requires energy. One or more companion cells attached to each sieve tube provide this energy. A sieve tube is completely dependent on its companion cell(s).
what is cell division for?
cell division is mainly restricted to repair and
replacement. Cell division by mitosis is important in the growth and development of multicellular organisms
what is cell differentiation?
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 difference between an electron microscope and microscope?
An electron microscope has much higher magnification and resolving power than a light microscope. This means that it can be used to study cells in much finer detail. This has enabled biologists to see and understand many more sub-cellular structures.
what is an equation for size of image (magnification)?
size of image = magnification x size of real object