Biology- cells

Different parts of a cell is called...

subcellular structures

What do cells make...

everything

Which cell is bigger? Prokaryotic or eukaryotic?

Eukaryotic

What does the cell membrane do?

controls what goes in and out of the cell

What does the nucleus do?

It contains genetic material and controls the activities of the cell

What does the ribosome do?

protein synthesis

What does the mitochondria do?

aerobic respiration

What does the cytoplasm do?

Where most chemical reactions take place

Cellulose cell wall

Gives support and strength

Chloroplasts

photosynthesis, contains chlorophyll

Permanent vacuole

Contains cell sap

Bacteria cells contain...

no nucleus

no chloroplasts or mitochondria

cytoplasm

cell wall (murein)+ membrane

plasmids

What does a nucleoid DNA do?

Holds DNA and genetic information

What is pili?

Short hair-like structures that helps movement

What is a flagellum?

Long tail that enables movement

1mm to um

1000um

1um in nm

1000nm

1cm to um

10000um

light microscope

uses light and lenses to form an image of a specimen and magnify it

electron microscope

-uses electrons to form an image of a specimen and can magnify it to a much higher resolution and magnification

- can be used to study cells in finer detail

- see/ understand many more subcellular structures

Formula for magnification

Magnification = image size / real size

Magnification

How many times bigger the image is than the actual specimen

Resolution

The ability to distinguish between two separate points/how much detail it shows

Why do cells have different structure?

To suit their different functions

Differentiation

-The process by which a cell changes to become specialised

- as an organism develops, cells differentiate to form different types of cells

- animal cells differentiate at an early stage

- plant cells retain the ability to differentiate throughout life

- acquires different subcellular structures to carry out a certain function

Specialisation

The adaption of an organism/cell to a special function or environment

Growth

- a permanent increase in size of an organism because of cell division or enlargement

- little to no growth in mature animals

- growth occurs in plants throughout their lifetime

- restricted in meristems

sperm cell- a long tin tail

helps with movement to swim fast to the egg

sperm cell-streamlined head

aerodynamic helps it swim to the egg

Sperm cell - lots of mitochondria

provides energy for movement

Sperm cell- special lysosome(acrosome)

releases enzymes for breaking through the membrane

Sperm cell- large nucleus

carries half of the genetic material

Nerve cells function

carries electrical signals from one play to the other

Nerve cell- lots of dendrities

allows connection with other nerve cells

Nerve cells axon

carries impulse from one place to other

Nerve cell lots of mitochondria

Makes the transmitter chemical

Nerve cell: Synapse(nerve ending)

passes the impulse to other cells

muscle cell function

to contrast and relax

muscle cell special proteins

slide over one another, allowing contraction

muscle cell lots of mitochondria

energy for contraction

Root hair cells function

Absorbing water and minerals ions from soil

root hair large surface area

can absorb the most out of the soil

root hair large vacuole

speeds up osmosis

Root hair lots of mitochondria

provides energy for active transport

Phloem and xylem cells function

Transporting substances

Phloem and xylem hollow tubes

substances can flow through them easily

Culturing Bacteria

- bacteria multiple by cell division (binary fission) every 20 mins if they have enough nutrients and suitable temperature

- can be grown in a nutrient broth solution

- or as colonies on an agar gel plate

uncontaminated cultures

- required to investigate action of disinfectants and antibiotics

- To sterilize petri dishes and culture medium heat at high temperature.

- Pass inoculating loop through hot flame.

- Lid stored upside down to stop condensation from falling onto the agar, secured with adhesive tape

- cultures incubated at 25 C

Chromosomes

- contained in the nucleus

- made of DNA molecules

- each carries a large number of genes

- found in pairs (body)

What is the cell cycle?

series of stages where cells divide

cell cycle stage 1

- grows/increases number of subcellular structures (ribosomes/ mitochondria)

- DNA replicates to form two copies of each chromosome

cell cycle stage 2

-mitosis

- one set of chromosomes is pulled to each end of the cell

- the nucleus divides

Why/ when is mitosis important?

- growth

- repair damaged tissue

- asexual reproduction

- replaces worn out cells

- development of multicellular organisms

cell cycle stage 3

cytoplasm and cell membranes divide to form two identical cells

stem cells

an undifferentiated cell of an organism which is capable of division to produce many more cells of the same type

- from which certain other cells can be produced by differentiation

embryonic stem cells

- found in embryos

- cloned and made to differentiate into most different types of human cells

adult stem cells

- remaining stem cells in the adult

- can form many types of cells

- e.g bone marrow- blood cells

meristem tissue in plants

- can differentiate into any type of plant cell

throughout the life of the plant

treatment with stem cells

- helps with conditions such as diabetes and paralysis

therapeutic cloning

- an embryo is produced with the same genes as the patient

- stem cells from the embryo aren't rejected by the patient's body

- may be used for medical treatment

cloning plants

- production fo genetically identical plants

- tiny piece of plant tissue taken and with the right conditions

- cells become unspecialised and undergo rapid cell division involving mitosis to produce a ball of cells

- quickly and economically

- rare species can be cloned to protect from exxtinction

- crop plants w/ special features can be cloned to produce larger number of identical plans for farmers

- e.g disease resistance

advantages of stem cells

- plentiful supply

- painless technique

- can treat many diseases e.g cancer, diabetes

- adult stem cell can become any type of cell

disadvantages of stem cells

- unethical can cause harm to embryo

- embryo has no consent/ right to life

- unreliable

- cells might transfer a virus

- may be rejected

- patient has to take immunosuppressant drugs

advantages of adult stem cells

- adult can give permission

- can treat some diseases

- less chance of rejection

- technique is reliable

disadvantages of adult stem cells

- risk of infection

- can only treat a few diseases

- procedure to remove can be painful

Diffusion

- spreading out of the particles of any substance in solution/ particles of a gas

- net movement from an area of higher concentration to an area of lower concentration

what are some substance transported by diffusion?

- oxygen

- carbon dioxide in gas exchange

- the waste product urea from cells into the blood plasma for excretion in kidney

Where does diffusion happen?

Solutions and gases because they are free to move about randomly

Dissolved substances can...

Move in and out of cells by diffusion

What can move through the Cell membrane?

very small molecules- oxygen, amino acids and water

What can't move through the cell membrane

Bigger molecules like starch and protein

Molecules move randomly so...

they go both ways but if theres a lot more particles on one side then theres a net movement from that side

Affects the rate of diffusion- difference in concentration

The larger the concentration gradient the faster the rate of diffusion down a concentration gradient

Affects the rate of diffusion- temperature

Higher the temperature, faster the rate of diffusion

affects rate of diffusion- surface are of membrane

Larger the surface area, the faster the diffusion

affects rate of diffusion- diffusion distance

Shorter the distance, faster the rate of diffusion

e.g single celled organism

- relatively large surface area to volume ratio

- allows sufficient transport of molecules into and out of the cell to meet the needs of the organism

exchange surfaces

- increasing size = smaller surface area:volume ratio

- cells no longer reach every cell by simple diffusion

- sufficient molecules to be transported into and out of cells for the organism's needs

exchange surface adaptions

- effectiveness increased

- larger surface area

- thin membrane to provide short diffusion path

- (animals) efficient blood supply to move diffusing substances awat and maintain a concentration gradient

- (animals, for gaseous exchange) being ventilated to maintain steep concentration gradient

exchange in the gut-villi = exchange surface

- food molecules like glucose, amino acids, fatty acids and glycerol must be moved from inside your small intestine into your bloodstream- absorption

- diffusion and active transport

-small intestine covered in millions of villi

-they provide large surface area so digested food absorbed quickly into blood

-have single layer of surface cells- short path

-good blood supply to maintain conc gradient- blood capillaries

Osmosis

- movement/ diffusion of water from an area of high concentration of water (dilute) to an area of low concentration of water (concentrated) through a partially permeable membrane that allows the passage of water molecules

Examples of osmosis

red blood cells

dilute

high water concentration

if a plant cell is too dilute

it becomes turgid

if a plant cell is too concentrated

it becomes plasmolysed

active transport

movement of substances into cells from a low concentration to a high concentrated solution against a concentration gradient, requires a protein pump and energy from respiration across a membrane

active transport- root hairs

- allows mineral ions to be absorbed into plant root hairs from very dilute solutions in the soil

- plants require ions for healthy growth

active transport- sugar

- allows sugar molecules to be absorbed from lower concentrations in the gut into the blood which has a higher sugar concentration

- sugar molecules are used for cell respiration