Biology- cells

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1

Different parts of a cell is called...

subcellular structures

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2

What do cells make...

everything

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3

Which cell is bigger? Prokaryotic or eukaryotic?

Eukaryotic

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4

What does the cell membrane do?

controls what goes in and out of the cell

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5

What does the nucleus do?

It contains genetic material and controls the activities of the cell

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What does the ribosome do?

protein synthesis

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7

What does the mitochondria do?

aerobic respiration

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8

What does the cytoplasm do?

Where most chemical reactions take place

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9

Cellulose cell wall

Gives support and strength

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10

Chloroplasts

photosynthesis, contains chlorophyll

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Permanent vacuole

Contains cell sap

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12

Bacteria cells contain...

no nucleus

no chloroplasts or mitochondria

cytoplasm

cell wall (murein)+ membrane

plasmids

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13

What does a nucleoid DNA do?

Holds DNA and genetic information

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14

What is pili?

Short hair-like structures that helps movement

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15

What is a flagellum?

Long tail that enables movement

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16

1mm to um

1000um

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1um in nm

1000nm

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1cm to um

10000um

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light microscope

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

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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

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Formula for magnification

Magnification = image size / real size

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Magnification

How many times bigger the image is than the actual specimen

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Resolution

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

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Why do cells have different structure?

To suit their different functions

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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

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Specialisation

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

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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

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sperm cell- a long tin tail

helps with movement to swim fast to the egg

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sperm cell-streamlined head

aerodynamic helps it swim to the egg

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Sperm cell - lots of mitochondria

provides energy for movement

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Sperm cell- special lysosome(acrosome)

releases enzymes for breaking through the membrane

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Sperm cell- large nucleus

carries half of the genetic material

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Nerve cells function

carries electrical signals from one play to the other

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Nerve cell- lots of dendrities

allows connection with other nerve cells

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Nerve cells axon

carries impulse from one place to other

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Nerve cell lots of mitochondria

Makes the transmitter chemical

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Nerve cell: Synapse(nerve ending)

passes the impulse to other cells

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muscle cell function

to contrast and relax

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muscle cell special proteins

slide over one another, allowing contraction

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muscle cell lots of mitochondria

energy for contraction

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41

Root hair cells function

Absorbing water and minerals ions from soil

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root hair large surface area

can absorb the most out of the soil

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root hair large vacuole

speeds up osmosis

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Root hair lots of mitochondria

provides energy for active transport

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45

Phloem and xylem cells function

Transporting substances

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Phloem and xylem hollow tubes

substances can flow through them easily

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47

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

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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

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49

Chromosomes

- contained in the nucleus

- made of DNA molecules

- each carries a large number of genes

- found in pairs (body)

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50

What is the cell cycle?

series of stages where cells divide

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51

cell cycle stage 1

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

- DNA replicates to form two copies of each chromosome

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52

cell cycle stage 2

-mitosis

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

- the nucleus divides

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Why/ when is mitosis important?

- growth

- repair damaged tissue

- asexual reproduction

- replaces worn out cells

- development of multicellular organisms

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cell cycle stage 3

cytoplasm and cell membranes divide to form two identical cells

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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

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embryonic stem cells

- found in embryos

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

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adult stem cells

- remaining stem cells in the adult

- can form many types of cells

- e.g bone marrow- blood cells

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meristem tissue in plants

- can differentiate into any type of plant cell

throughout the life of the plant

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treatment with stem cells

- helps with conditions such as diabetes and paralysis

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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

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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

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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

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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

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advantages of adult stem cells

- adult can give permission

- can treat some diseases

- less chance of rejection

- technique is reliable

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disadvantages of adult stem cells

- risk of infection

- can only treat a few diseases

- procedure to remove can be painful

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66

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

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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

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Where does diffusion happen?

Solutions and gases because they are free to move about randomly

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Dissolved substances can...

Move in and out of cells by diffusion

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What can move through the Cell membrane?

very small molecules- oxygen, amino acids and water

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What can't move through the cell membrane

Bigger molecules like starch and protein

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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

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Affects the rate of diffusion- difference in concentration

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

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Affects the rate of diffusion- temperature

Higher the temperature, faster the rate of diffusion

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affects rate of diffusion- surface are of membrane

Larger the surface area, the faster the diffusion

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affects rate of diffusion- diffusion distance

Shorter the distance, faster the rate of diffusion

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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

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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

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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

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80

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

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81

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

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Examples of osmosis

red blood cells

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83

dilute

high water concentration

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if a plant cell is too dilute

it becomes turgid

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85

if a plant cell is too concentrated

it becomes plasmolysed

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86

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

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87

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

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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

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