Topic 1 - Cell Biology Flashcards
What are the 2 types of cell?
Eukaryotes and Prokayotes
all living things are made up of…
cells
Eukaryotes are…
complex. Animal and plant cells are eukaryotes
they are organisms that are made up of eukaryotic cells.
Prokaryotic cells are…
smaller and simpler e.g. bacteria. a prokaryote is a prokaryotic cell(single-celled organism)
what is the collective name for the different parts of a cell?
subcellular structures
subcellular structures of animal cells?
nucleus cytoplasm cell membrane mitochondria ribosomes
subcellular structures of plant cells?
everything an animal cell has
rigid cell wall
permanent vacuole
chloroplasts
Purpose of nucleus
contains genetic material that controls the activities of the cell
Purpose of cytoplasm
gel-like substance where most of the chemical reactions happen. it contains enzymes that control these chemical reactions.
Purpose of cell membrane
holds the cell together and controls what goes in and out
Purpose of mitochondria
these are where most of the chemical reactions for aerobic respiration take place. respiration transfers energy that the cell needs to work.
Purpose of ribosomes
these are where proteins are made in the cell
Purpose of rigid cell wall
made of cellulose. it supports the cell and strengthens it
Purpose of permanent vacuole
contains cell sap, a weak solution of sugar and salts
Purpose of chloroplasts
these are where photosynthesis occurs, which makes food for the plant. they contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis
bacteria are…
prokaryotes
what subcellular structures do bacteria have?
cytoplasm
cell membrane
cell wall
what subcellular structures do bacteria not have?
chloroplasts
mitochondria
nucleus
what substitutes the nucleus in a bacteria cell?
they don’t have a “true” nucleus - instead they have a singular circular strand of DNA that floats freely in the cytoplasm
they also contain 1 or more small rings of DNA called plasmids
microscopes
they let us see things that we can’t see with the naked eye. the microscopy techniques we can use have developed over the years as technology and knowledge have improved
light microscopes
they use light and lenses to form an image of a specimen and magnify it. they let us see individual cells and large subcellular structures. like nuclei
electron microscopes
use electrons instead of light to form an image. have a much higher magnification than light microscopes. have a higher resolution (the ability to distinguish between 2 points, so a higher resolution gives a sharper image)
let us see much smaller things in more detail, like the internal structure of mitochondria and chloroplasts and even tinier like ribosomes and plasmids
what is the formula for magnification?
magnification= image size/real size
the image and real size have to have the same units
steps to prepare a slide for an onion:
- add drop of water to centre of clean slide
- cut up onion and separate layers. use teasers to peel off some epidermal tissue from bottom of 1 of the layers
- using tweezers place tissue in water on slide
- add drop of iodine solution, iodine solution is a stain. stains are used to highlight objects in a cell by adding colour to them.
- place cover slip on top. do this by standing it next to water droplet and slowly lowering it so it covers specimen. air bubbles obstruct view from specimen
how to record cells under a microscope?
fill up at least half the page
drawn in proportion
title for what is being observed and magnification
label important features (nucleus, chloroplasts)
differentiation
the process where a cell changes to become specialised for its job.
as cells change, they develop different sub-cellular structures and turn into different types of cells.this allows them to carry out specific functions.
when is differentiation lost?
most differentiation occurs as an organism develops.
in most animal cells, the ability to differentiate is then lost at an early stage, after they become specialised. however, lots of plant cells don’t ever lose this ability.
what are differentiated cells used for?
cells that differentiate in mature animals are mainly used for repairing and replacing cells, such as skin and blood cells.
what are undifferentiated cells called
stem cells
examples of specialised cells?
sperm cells - reproduction
nerve cells - rapid signalling
muscle cells - contraction
root hair cells - absorbing water and minerals
phloem and xylem cells - transporting substances
function of sperm cell
to get the male DNA to the female DNA. it has a long tail and a streamlined head to help it swim to the egg.
there are lots of mitochondria in the cell to provide the energy needed. it also carries enzymes in its head to digest through the egg cell membrane
function of nerve cell
to carry electrical signals from 1 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.
function of muscle cell
to contract quickly. they are long(to have space to contract) and contain lots of mitochondria to generate the energy needed for contraction.
function of root hair cell
they’re cells on the surface of plant roots, which grow into long “hairs” that stick out into the soil. gives the plant a bigger surface area for absorbing water and mineral ions from soil.
function of phloem cells
they form phloem tubes, which transport things such as food and water around plants. to form the tubes, the cells are long and joined end to end. they have very few sub-cellular structures, so that stuff can flow through them
function of xylem cells
they form xylem tubes, which transport things such as food and water around plants. to form the tubes, the cells are long and joined end to end. they are hollow in the centre
how does the nucleus store DNA?
the nucleus stores genetic material in the form of chromosomes
What are chromosomes
they are coiled lengths of DNA molecules. each chromosome carries a large number of genes. different genes control the development of different characteristics e.g. hair colour.
how many chromosomes do our cells have?
body cells normally have 2 copies of each chromosome - 1 from the organisms mother and 1 from its father. so humans have 2 copies of chromosome 1, 2, etc. 23 pairs of chromosomes for a human cell.
cells divide as part of?
body cells in multi cellular organisms divide to produce new cells as part of a series of stages called the cell cycle
what is mitosis?
the stage of the cell cycle when the cell divides. multi-cellular organisms use mitosis to grow or replace cells that have been damaged.
what does the end of the cell cycle result in?
2 new cells identical to the original cell, with the same number of chromosomes
what are the 2 main stages of the cell cycle?
growth and DNA replication
mitosis
steps of growth and DNA replication
- in a cell thats not dividing,the DNA is spread out in long strings
- before it divides, cell has to grow and increase amount of subcellular structures like mitochondria and ribosomes
- it then duplicates its DNA - so 1 copy for eah new cell. the DNAs copied and forms x-shaped chromosomes. each ‘arm’ of chromosome is exact duplicate of other.
steps of mitosis
after contents and DNA copied:
- chromosomes line up at centre of cell and cell fibres pull them apart. the 2 arms of each chromosome go to opposite ends of cell
- membranes form around each of the sets of chromosomes. these become the nuclei of the 2 new cells - nucleus has divided
- cytoplasm and cell membrane divide. cell has now produced 2 new daughter cells. these cells contain exactly the same DNA- identical to each other and parent cell
how do prokaryotic cells replicate?
by binary fission
binary fission
- circular DNA + plasmids replicate.
- cell gets bigger, circular DNA strands move to opposite ends of the cell
- cytoplasm begins to divide, new cell walls begin to form.
- cytoplasm divides, 2 daughter cells produced. each 1 has 1 copy of circular DNA, but can have a variable number of copies of plasmids
how do bacteria divide in different conditions?
divide quickly in right conditions (warm environment, lots of nutrients)
some bacteria like E coli only take 20 mins to replicate on right environment.
unfavourable conditions - cells can stop dividing, eventually begin to die