Edexcel GCSE Combined Science CB1 Key concepts in biology overview quiz quiz

A cell surface membrane around the outside

Cytoplasm filling the inside of the cell

A nucleus enclosed in a membrane

Ribosomes for making proteins

Nucleus, ribosomes and energy-releasing mitochondria

Cell membrane, watery cytoplasm and a true nucleus

Plasmids, whip-like flagella and green chloroplasts

Cellulose cell wall, chloroplasts, permanent vacuole

The mitochondria

The nucleus of the cell

The ribosomes on the membrane

The cell wall outside

Any substrate can fit any enzyme because every active site has exactly the same overall shape and charge

Only a substrate with a shape complementary to the active site can bind to the enzyme

Enzymes supply heat that raises the temperature of the reaction mixture so the particles collide

Enzymes physically push substances against a concentration gradient using stored energy

It is a living thing that is killed off by the high temperature inside the cell

It quickly runs out of substrate molecules to bind to and convert into products

Its active site changes shape (it denatures) so the substrate no longer fits

It is permanently used up and destroyed during the reaction it catalyses

The net movement of any dissolved particle down its own concentration gradient through gaps in the cell membrane

The movement of substances against a concentration gradient that uses energy released by aerobic respiration

The active uptake of dissolved mineral ions by root hair cells against a steep concentration gradient

The diffusion of water across a partially permeable membrane from a dilute to a more concentrated solution

Because it moves substances against the concentration gradient

Because it moves substances passively down the concentration gradient like ordinary diffusion does

Because it can only ever take place inside the cells of green plants and never in animal cells

Because water molecules are too large to cross the membrane without an input of energy

6 $\mu m$

60 $\mu m$

600 $\mu m$

0.06 $\mu m$

It is much cheaper to buy and far more portable for fieldwork

It can be used to view living cells and watch processes happen

It has much higher magnification and resolution

It uses ordinary visible light rather than electrons to form the image

A cell wall

Cytoplasm

A cell membrane

A plasmid

A steeper concentration gradient

A smaller surface area of the membrane for particles to cross

A lower temperature that slows the random movement of particles

A longer diffusion distance for the particles to travel across

It loses mass because water leaves the cells by osmosis

It gains mass because water enters the cells by osmosis

It stays the same because no water moves

It gains mass because salt enters the cells by active transport