B1 : Cell structure and transport 🧬

Are plant and animal cells prokaryotic or eukaryotic?

Eukaryotic

What does a nucleus do

Controls the activities of the cell / has its DNA

what does the cytoplasm do

controls chemical reactions / has enzymes

what does the cell membrane do

controls what goes in and out of the cell

What does the mitochondria do?

most of the energy for respiration is released

what do ribosomes do

protein synthesis

what does the cell wall do

strengthens the cell / made of a cellulose

What do chloroplasts do?

photosynthesis

What does the permanent vacuole do

Filled with cell sap / keeps cell shape

What does the bacterial DNA

Loop of DNA, not in the nucleus

what do the plasmids do

Used as a vector in genetic modification

Does an animal cell have a cell membrane or cell wall

Cell membrane

What is diffusion?

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

Name 3 examples of diffusion

alveoli in the lungs / villi in the small intestine for glucose / the stomata of a plant

What are 4 ways cells are adapted to increase the rate of diffusion

Inc sa:v ration / moist surfaces allow molecules to dissolve / thin / good blood supply allows gradient to remain high

What is a hypotonic solution

Too much water diffuses in / more dilute than cell contents

hypertonic solution

Too much water is taken / more concentrated than cell contents

Isotonic

when the concentration of two solutions is the same

Explain the adaptations of rbc

Haemoglobin to let 02 bind to C02 / no nucleus for more 02 space / concave shape

Explain the adaptations of nerve cells

Long structure to transmit electrical signals / Insulating material reduces signal loss / dendrites spread charge

Explain the adaptations of a sperm cell

streamlined / enzymes in head to digest ovum wall / many mitochondria for energy / flagellum tail to propel

How o you calculate the size of a real object

size of image / magnification

Describe light microscopes

light energy to form image / invented 1700s / low mag x2000 / low res 200nm / cheap / dead or alive specimen

Describe electron microscopes

electron beams form image / made 1900s high mag xx2000000 / High resolution (0.2nm) / expensive / dead specimens only

What is osmosis

diffusion of water across a selectively permeable membrane

Features of a eukaryotic cell

Cell membrane / cytoplasm / nucleus / genetic material is in DNA / animals plants fungi protista

What are Protista

Eukaryotes that are neither plants, nor fungi, nor animals.

Features of a prokaryotic cell

cell membrane and wall / cytoplasm / no distinct nucleus / bacteria / DNA or RNA forms circular plasmids / some have protein strands that lash around and enable movement

Required Practical : Microscopes

- place the slide on the stage and use the clips to hold it in place

- select the lowest power objective lens (x4)

- slowly turn the coarse focusing dial so the objective lens nearly touches the slide

- slowly turn the coarse focussing dial again to bring distance between the slide / lens, do this until the cells come into focus

- use the fine focusing dial to bring it into clear focus

How do we calculate Magnification

Eyepiece lens x objective lens

Where is the genetic material in a prokaryotic cell

Bacterial DNA loop / maybe be one or more plasmid rings

Adaptations of muscle cells

many mitochondria to produce ATP /
long protein fibres to aid with contraction

Adaptations of root hair cells

Hair like projections to increase sa:v ratio to help with absorption / no chloroplasts

Adaptations of xylem

Long cell walls toughened by lignin / one way flow of H20 and minerals (transpiration) / hollow tubes made of dead tissue

Adaptations of a phloem

Companion cells have mitochondria to produce energy for loading of sugars into the phloem sieve tubes / end plates with holes in them so sugars can leave

Why are electron microscopes better than light microscopes

Let's us see internal structures of chloroplasts and mitochondria etc / scientist can see more sub-cellular structures / higher mag and res

Required practical : effects of osmosis on plant tissue

- peel a potato skin and use a cork borer to make three cylinders of potato of the same diameter

- use scalpel to trim all cylinders to around 3cm length / measure the length and mass of each cylinder

- place one cylinder into a test tube with 10cm cubed of 0.5 molar sugar solution / one with 10cm cubed 0.25 m sugar solution / one with just 10cm cubed distilled water

- leave overnight for osmosis to happen

- dry with paper towel and measure length and mass again / calculate percentage change

How do we calculate percentage change

( Change in value / original value ) x 100

turgid (plant)

swollen / vacuole swells and cytoplasm presses against wall

flaccid cell

water lost from cell, vacuole shrinks, cell loses shape / hypertonic

Plasmolysed plant cell

The cell looses water / cytoplasm shrinks / the membrane pulls away from cell wall