Studied by 4 peoplewhat do cells make up?
all living things
what does prokaryotic mean?
genetic material in cytoplasm. smaller and simpler
what does eukaryotic mean?
has a membrane bound nucleus and organelles. more complex
what is the job of the nucleus?
contains genetic material that controls the activities of the cell
what is the job of a cell membrane?
holds the cell together and controls what goes in and out
what is the job of a cytoplasm?
gel like substance where most of the chemical reactions happen . enzymes control these reactions.
what is the job of a mitochondria?
where the reactions for aerobic respiration takes place. respiration transfers energy that the cell needs to work
what is the job of a rigid cell wall?
made of cellulose. It supports the cell and strengthens it
what is the job of ribosomes?
where proteins are made in the cell
what is the job of chloroplasts?
where photosynthesis occurs, which makes food for the plant. They contain a green substance called chlorophyll, which absorbs the light needed for photosynthesis.
what is the job of a permanent vacuole?
contains cell sap, a weak solution of sugar and salts.
what is a bacterial cell?
has a cytoplasm and a cell membrane surrounded by a cell wall. doesnt have a true nucleus - instead a single circular strand of DNA that floats freely in the cytoplasm.
are bacterial cells eukaryotes or prokaryotes?
prokaryotes
what dont bacterial cells have?
mitochondria or chloroplasts
what are plasmids?
small rings of DNA
what is the job of a strand of DNA?
allows the cell to divide or reproduce
what do light microscopes do?
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
what do electron microscopes do?
use electrons to form an image. they have a much higher magnification than light microscopes and a higher resolution. They let us see much smaller things in more detail, like the internal structure of mitochondria
what is resolution?
how clearly something can be seen
what is magnification?
how zoomed in something is
total magnification = ?
objective lens x eyepiece lens
magnification = ?
image size / real size
what is a brief explanation of how to do a microscopy practical?
drop some water onto slide and place your object on slide. add iodine solution and put a cover slip on. put under microscope and adjust the magnification until focused, then draw observations
how do you want to write numbers in biology?
in standard form
what can prokaryotic cells do?
reproduce using a type of simple cell division called binary fission
what happens in binary fission?
the cell splits into 2
what is step 1 of binary fission?
plasmids and the circular strands of dna replicate
what is step 2 of binary fission?
the cell gets bigger and the circular dna strands move to opposite ends of the cell
what is step 3 of binary fission?
the cytoplasm begins to divide and new cell walls begin to form
what is step 4 of binary fission?
the cytoplasm divides and 2 daughter cells are produced. each daughter cell has 1 copy of the circular dna, but can have a variable number of copies of the plasmid (s)
what conditions are needed for bacteria to divide quickly?
warm environment
what can some bacteria, such as E. coli do?
they can take as little as 20 mins to replicate in the right environment
what happens if conditions for bacteria become unfavorable?
the cells will stop dividing and eventually begin to die
what is the mean division time?
the amount of time it takes for 1 bacterial cell to divide into 2
what can you work out if you know the mean division time?
how many times it has divided in a certain amount of time, and the number of cells it has produced in that time
what is the equation to work out the number of divisions?
total time / mean division time
what is diffusion?
the spreading out of particles from an area of higher concentration to an area of lower concentration
where does diffusion happen?
in solutions and gases, because the particles are free to move about randomly
what is the simplest type of diffusion?
when different gases diffuse through each other
what makes the diffusion rate go faster?
a bigger concentration gradient, and a higher temperature, because it gives particles more energy
what is a concentration gradient?
the difference in concentration
what goes through the cell membrane?
dissolved substances
what molecules can diffuse through the cell membrane?
small molecules eg. oxygen, water, amino acids, glucose
what concentration do particles flow through the cell membrane?
from a higher to a lower concentration
if there are a lot of particles on one side of the cell, what is on that side?
a net (overall) movement
what makes the diffusion rate faster (2)
the larger the surface area of the membrane, 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 concentration to a region of lower water concentration
what is a partially permeable membrane?
a membrane with very small holes in it. Smaller molecules eg. water, can pass through, but larger ones eg. sucrose, cant
where do the water molecules pass through?
they pass through both ways through the membrane during osmosis. This happens because water molecules move about randomly all the time
why do the water molecules pass through both ways of the membrane?
because there are more water molecules on one side than on the other, theres a steady net flow of water into the region with fewer water molecules eg. into the stronger sugar solution
what does the water molecules in the membrane mean?
means that the sugar solution gets more diluted. the water acts like its trying to even up the concentration, either side of the membrane
what is osmosis (compared to diffusion)?
is a different type of diffusion - the passive movement of water particles from an area of higher water concentration to an area of lower water concentration
what is a brief explanation of the osmosis experiment?
cut identical potato cylinders and get beakers with diff sugar solutions. measure mass of cylinders, and leave them for 24hrs in the solution. take them out, dry them, and remeasure mass
what is the dependent variable of the osmosis experiment?
the chip mass
what is the independent variable of the osmosis experiment?
the concentration of sugar solution
what is the control variable of the osmosis experiment?
the temp, time, and type of sugar
what are some errors that could occur for the osmosis experiment
potatoes werent fully dried, water evapouration would change the sugar solution concentration
how do you reduce errors for the osmosis experiment?
do the experiment multiple times and calculate the mean percentage change
what is active transport?
the movement of particles against a concentration gradient using energy transferred during respiration
how does active transport take place in root hairs? (brief)
there are hairs that stick out of the soil from roots, which absorb mineral ions, which are needed. they use active transport for this, because diffusion wouldnt work. active transport allows the plant to absorb minerals from a very dilute solution against a concentration gradient, which is essential for its growth
why doesnt diffusion work in root hairs?
because the concentration of minerals is usually higher in the root hair cells than in the soil around them, so the root hair cells cant use diffusion to take up minerals from the soil
what is an example of active transport happening in humans?
taking glucose from the gut and from the kidney tubules
how can active transport be used to stop starvation?
active transport is used in the gut where there is a lower concentration of nutrients, but a higher concentration in the blood
what happens when theres a higher concentration of glucose and amino acids in the gut?
they diffuse naturally into the blood
what happens if theres a lower concentration of nutrients in the gut than there is in the blood?
the concentration is the wrong way
when can glucose be taken into the bloodstream?
when its concentration in the blood is already higher than in the gut. it can then be transported to cells, where it is used for respiration
what are stem cells?
undifferentiated cells, which can divide to produce lots more undifferentiated cells. these can differentiate into different types of cell, depending on the instructions given
where are stem cells found?
in early human embryos, which have the potential to turn into any kind of cells, and bone marrow in adults, which can only turn into certain cells
where can stem cells be grown?
in a lab to produce clones (genetically identical cells) and made to differentiate into specialised cells for medicine or research
how can stem cells cure diabetics?
can make insulin producing cells for diabetics
how can stem cells cure blood cells?
stem cells transferred from the bone marrow of a healthy human can replace faulty blood cells in another human
how can stem cells cure paralysed people?
embryonic stem cells can make nerve cells for paralysed people
what is therapeutic cloning?
where an embryo can be made to have the same genetic information as the patient. this means that the stem cells produced from it would also contain the same genes and so wouldnt be rejected by the patients body if used to replace faulty cells
what are the risks of stem cells in medicine?
could get contaminated with a virus and make a patient sicker
why are people against stem cells?
people think embryos shouldnt be used because its a humans life, and they think scientists should concentrate on developing other sources of stem cells
where are stem cells found in a plant?
in the meristems
what happens throughout a plants life?
the stem cells can differentiate into any type of plant cell
what happens to the stem cells in plants?
they can be used to produce clones quickly and cheaply, and can be used to grow more rare species to prevent them from being wiped out, and crops of identical plants, for desired features
why do cells have different structures?
to suit their functions
what is differentiation?
the process by which a cell changes to become specialised for its jobs
what happens as a cell changes?
they develop different subcellular structures and turn into different types of cells. this allows them to carry out specific functions
when does most differentiation occur?
as an organism develops
what happens in most animal cells and plant cells?
the ability to differentiate is then lost at an early stage, after they become specialised. plant cells dont lose this ability
what are the cells that differentiate used for?
repairing and replacing cells
what are sperm cells for?
reproduction, used to get the male dna to the female dna
what are some sperm cell functions?
long tail for swimming, mitochondria for energy, enzymes to digest through the egg cell membrane
what are nerve cells used for?
for rapid signaling, it carries the electrical signals from 1 part of the body to another
what are some nerve cells functions?
long to cover distance, branched connections to connect to other nerve cells and form a network throughout the body
what are muscle cells used for?
for contraction, to contract quickly
what are muscle cells functions?
long for space to contract, mitochondria for energy
what are phloem and xylem cells used for?
for transporting substances
what are phloem and xylem cell functions?
joined end to end to form tubes which transports substances around plants, hollow in the centre and have very few subcellular structures so that substances can flow through them
what are root hair cells used for? (to do with specialised cells)
for absorbing water and minerals
what are root hair cells functions? (to do with specialised cells)
on the surface of plant roots, gives a big surface area to absorb water and mineral ions from the soil, grow into long hairs that stick out into the soil
what do most cells in the body have?
a nucleus which contains your genetic material in the form of chromosones
what are chromosones?
coiled up lengths of dna molecules
what does each chromosome have?
a large number of genes and the different genes control the development of different characteristics
how many pair of chromosomes do body cells have?
23
what do body cells in multicellular organisms do?
they divide to produce new cells called a cell cycle. the stage where the cell divides is called mitosis
what do multicellular organisms use?
they use mitosis to grow or replace cells that have been damaged
Note 
Flashcard (109)