B1-Cell Biology

Prokaryote vs. Eukaryote cells

Eukaryotic: Plant, Animal

Prokaryotic: Bacteria

(no nucleus)

animal cell subcellular structures

Cell membrane

Cytoplasm

Nucleus

Mitochondria

Ribosomes

What do plant cells have that animal cells don't?

cell wall, chloroplasts, vacuole

cell membrane

controls the movement of substances in and out of a cell

(a , p , pr)

nucleus

contains DNA

controls cell activities

(a, p)

mitochondria

'powerhouse of the cell', releases energy through respiration

(a, p)

ribosomes

site of protein synthesis

(a, p)

cytoplasm

jelly like substance where chemical reactions happen

(a, p, pr)

Permanent vacuole

Contains cell sap, a weak solution of sugar and salts

(p)

chloroplasts

Site of photosynthesis; contains chlorophyll to absorb light energy for it

(p)

cell wall

made of cellulose

strengthens and structures cell

(p, pr)

bacterial cells are/have...

prokaryotic

single celled

dna loops in cytoplasm

dna rings ( 'plasmids' )

Magnification equation

magnification = image size/actual size

Light electroscope

-uses light to form images

-can see individual cells and large subcellular structures

electron microscope

-uses electrons to form images

-higher magnification and resolution than light ones

-can see internal structure of mitochondria and chloroplasts

RP: Microscopy

1. Add drop of water to clean slide

2. Use tweezers to peel the epidermal tissue from a layer of onion and place it onto drop

3. Add drops of iodine solution (a stain that highlights objects in a cell by adding colour)

4. Place cover slip ontop by lowering it from the side.

5. Clip slide onto stage, select lowest powered objective lens, use coarse adjustment knob to rise stage

6. Look in eyepiece and use coarse adjustment knob to move stage down until focuses.

7. Adjust focus with fine adjustment knob.

8. Draw with pencil.

Why do cells differentiate?

To become specialised for its job

What are undifferentiated cells called?

stem cells

Sperm cell adaptations and function

For reproduction

-long tail helps it swim to egg

-streamlined head helps it swim to egg

-lots of mitochondria to provide energy needed to swim

-enzymes in head to digest egg cell membrane

Nerve cell adaptations and function

to send rapid, electric signals

-long to connect to other cells

-branched connections to connect to other cells and form a network

Muscle cells adaptations and functions

for contraction

-long to have space to contract

-lots of mitochondria for energy needed when contracting

Root Hair Cells adaptations and functions

to absorb water and minerals

-hairs grow from roots to absorb from soil so larger surface area (which supports active transport)

Xylem adaptations and function

to transport water

-hollow in centre to enable efficient flow

Phloem adaptations and function

to transport food

-few subcellular structures so things can flow through

How many chromosomes do humans have?

46 (23 pairs)

What is mitosis?

Cell division that generates new cells for growth and repair. The division of one cell into two genetically identical daughter cells

Steps of the cell cycle

1. Cell grows and increases subcellular structures

2. Duplicates DNA in X shaped chromosome form

3. Mitosis

-chromosome pairs align in centre. cell fibres pull them apart so two arms go to opposite sides

-membranes form around each set of chromosomes and become the nuclei of the two new cells, so nucleus has divided

-cytoplasm and cell membrane divide

-now have two new daughter cells with identical DNA to eachother and parent cell

Diffusion

The movement of particles from an area of high concentration to an area of low concentration.

big particles cannot diffuse such as starch or protein

How to speed up diffusion

bigger concentration gradient

higher temperature

Osmosis

net movement of water molecules across a partially permeable membrane from an area of high concentration to an area of low concentration

Active Transport

movement of particles from an area of low concentration to an area of high concentration

against concentration gradient so requires energy, unlike osmosis and diffusion

RP- Osmosis

1. cut potato into identical cylinders

2. get two beakers: one with pure water, other with highly concentrated sugar solution

3. measure potato cylinder mass before you do anything

4. leave 1 potato cylinder in each beaker for hours, then dry and measure. if it took in water via osmosis, itll increase noticeably

example of active transport

root hair cells which have a larger surface area to support A.T.

it's A.T. because the concentration of minerals is usually higher within the cell than the soil.

How do you determine how easily an organism can exchange substances?

surface area : volume ratio

what are exchange surfaces for/why can't everything be done via cell membrane?

single-celled organisms can diffuse things in and out of cell membrane because surface area > volume

multicellular organisms can't as they're too large so there'd be too much distance. therefore, they have exchange surfaces.

How are exchange surfaces adapted to maximise effectiveness?

Thin membrane (short distance to diffuse)

Large surface area

Lots of blood vessels and often ventilated (in animals)

Exchange surface in the lungs and adaptations

Alveoli, in which oxygen diffuses into the blood and CO2 out

-enormous surface area (more contact points so increases rate things can diffuse)

-moist to disolve gases (water acts as a medium, allowing it to happen more steadily)

-thin walls (shorter distance->faster diffusion rate)

-good blood supply (constantly delivering nutrients and oxygen to enhance efficiency)

Exchange surface in the small intestines and adaptations

Villi

-millions, so big surface area for more contact points

-single layer of cells on surface so shorter distance

-good blood supply

Exchange surface of leaves and adaptations

stomata, CO2 in, O2 and water vapour out

-flat shape increases surface area, as well as cell walls

exchange surface of fish

gills

-made of lots of thin filaments and a lot of lamallae increases surface area

-lamallae have blood capillaries

-thin surface area of cells